Machinetool reconditioning chockalingam

DETAILED SYLLABUS
Unit-I: RECONDITIONING OF MACHINE TOOLS:
a) Sequence of maintenance operation:
Procedure- disassembly of machine tools, preparation of disassembly- disassembly sequence and rules- examples of
disassembly- washing of parts- fault finding- preparation for assembly- fitting in- balance of parts- assembly of
mechanisms and machines.
b) Scraping:
Importance of scraping- techniques of scraping- tools used for scraping- accuracy, tolerances and finish.
c) Reconditioning of machining parts:
Methods of determining wear of guides, Selection of repair method and sequence – Method of checking – Non –
linear – twist – parallelism of bed way – universal bridge – use and importance
Repairing parts with flat conjugate- surfaces- general- restoring parts like: bed ways of lathe- column way of a plain
milling machine- saddle ways of lathe- table saddle ways of a milling machine- knee ways of a milling machine-
table ways of a milling machine- ways of press slides- anvil blocks of hammers- clamping blocks and wedges.
Unit-II: MAINTENANCE ACTIVITY AND MAJOR OVERHAUL OF A MACHINE TOOLS:
a) Maintenance:
Maintenance – Definition – types – Preventive maintenance – advantages – procedure – break down maintenance.
b) Examples of Maintenance:
Example of an engine lathe overhaul. Inspecting and checking before repair- Disassembly- mounting and aligning
the feed gear box-apron, lead screw and feed rod bracket- repairing the tailstock – head stock spindle – three jaw
chuck – lead screw and nut – cracks in a cast iron body - technical requirements for the repaired lathe –standard
chart for major overhaul of an engine lathe.
Unit-III: PRINCIPLES OF ACCEPTANCE TEST:
a) Acceptance Test:
Acceptance test- reason for test- principles of acceptance test- machine tool under load – test charts- execution of
acceptance test – measuring equipments and methods.
b) Dial Gauges:
Dial gauges – test mandrels – straight edges - squares- spirit levels- level measurement by water level- alignment
by wire and measuring microscope.
c) Alignment by Telescope:
Alignment by telescope and target- magnitudes and direction of tolerances- straightness of slide ways and flatness
of tables- alignment and true running of shafts- lead or pitch error of lead screws- pitch errors of gears and dividing
errors of dividing heads.

Unit-IV: DETAILS FOR TESTING VARIOUS MACHINE TOOLS:
a) Milling and Gear cutting machines:
Milling and gear cutting machines – lathes - capstan and turret lathes, automatic lathes and vertical boring
machines.
b) Grinding Machines:
Grinding machines - drilling and boring machines - Acceptance tests and maintenance of machine tools. Test
specification - the accuracy with which the machine has been manufactured - installation and leveling of the
machines - testing the quality of slide ways and locating surfaces - testing the accuracy of the main spindle and of
its alignment relative to other important parts of the machine
c) Accuracy of the work Produced:
Accuracy of the work piece produced on then machine – power requirements - ISI test charts and detailed
procedure – lathe, milling machine, grinding machine - drilling machines.
Unit-V: CONDITION BASED MAINTENANCE:
a) Condition monitoring: Categories of condition monitoring- methods- on load monitoring techniques- temperature
monitoring – lubricating monitoring – leak detection – vibrating monitoring – noise monitoring – corrosion
monitoring.
b) Off- load monitoring:
Crack detection – leak detection - vibration testing - corrosion monitoring - general purpose monitoring techniques
- the systematic application of C.M.
c) Lubricating monitoring:
Debris deposited- debris in suspension- condition of used oil- ferrography.
d) Thermal monitoring:
Location of temperature measurement – temperature monitoring devices- contact sensors, liquid expansion sensors,
bimetallic expansion sensors, thermocouple sensors, resistance sensors - temperature paints, Crayons and pellets-
non contact sensors- optical pyrometer, radiation pyrometer. The scanning DR camera. Malfunction that can be
monitored thermally.
e) Vibration and noise monitoring:
The cause of vibration and noise – measurement – equipment. The vibration or noise signals - vibration monitoring
techniques- total signal monitoring – peak signal monitoring figure of merit- shock pulse monitoring.
Text Book:
1. Industrial maintenance by HP Garg &Co
2. Management of industrial maintenance by A. Kelley & M.J.Harris
Reference book:
Testing of machines Tools by DR.Georg schlesinger pergamon press

UNIT 1
SYLLABUS;
a)Sequence of maintenance operation:
Procedure- disassembly of machine tools, preparation of disassembly- disassembly sequence and rules- examples of
disassembly- washing of parts- fault finding- preparation for assembly- fitting in- balance of parts- assembly of
mechanisms and machines.
d) Scraping:
Importance of scraping- techniques of scraping- tools used for scraping- accuracy, tolerances and finish.
e) Reconditioning of machining parts:
Methods of determining wear of guides, Selection of repair method and sequence – Method of checking – Non –
linear – twist – parallelism of bed way – universal bridge – use and importance
Repairing parts with flat conjugate- surfaces- general- restoring parts like: bed ways of lathe- column way of a plain
milling machine- saddle ways of lathe- table saddle ways of a milling machine- knee ways of a milling machine-
table ways of a milling machine- ways of press slides- anvil blocks of hammers- clamping blocks and wedges.
SCRAPING PROCESS FOR MACHINE RECONDITIONING
There are certain machines which gives very fine accuracy in dimensions. These
machines are also useful to generate the smooth surface. For example Plano grinding
machines control the surface accuracy within 0.002 mm/meter. So it‟s a question why we
use scraper? We have seen about friction. To reduce the friction first attempt is to
produce the smooth surfaces for the contacting bodies. If we produce very fine smooth
surface of both the bodies then the another question will arise i.e „adhesion‟, Adhesion is
more critical than friction. If the mating sliding surfaces get adhesion between them then
it will take very high force to separate them. Scraping solve this problem. It is useful for
preparing good bearing surface and same time it provides oil pockets. These oil pockets
avoid the adhesion. Maintenance persons should know the skills of scraping.
SCRAPER
Scraper is a cutting tool used for removing / cutting material in minute particles to
reduce the surface asperities or high spots by flakes by flakes and produce good surface

finish and produce bearing into the surface with reference to another mating surface to
avoid adhesion.
The operation done by scraper is known as scraping.
OBJECTIVES OF SCRAPING
1. To remove the high spots from the surface
2. To rectify the surface irregularities
3. To introduce bearing with the mating components.
4. To establish very good surface finish.
5. To provide oil pockets in a surface to have efficient lubrication, to avoid
adhesion
6. To close the grains after machines
Scrapers are made of following materials
1. High carbon steel/ high carbon tool steel.
2. High speed tipped.
3. Cemented carbide tipped.
It is hardened & tempered – HRC 58 to HRC 62. Carbide tipped scrappers are
available with brazed tip or clamp – on type.
TYPES OF SCRAPERS
1. Flat Scrapers
1.1) HCS – flat scraper
1.2) Brazed tip scraper
1.3) Clamp on type
2. Half round scraper
3. Triangular Scraper
4. Hook type scraper
5. Bull nose scraper
6. Two handles scrapers
1. FLAT SCRAPERS
Flat scrapers are used for scraping the flat surfaces of surface plates (C.I.), slides
machine beds, wedges of slides and other so many flat surfaces. Mainly three types of
flat scrapers are used.
1.1 Flat scrapers HCS :- these scrapers are made of high carbon steel. Some
times it is economically prepared from old smooth hand file, after grinding the
file teeth. It is about 25 cm to 50 cm length, 2 cm to 3 cm width and 5 mm to 8
mm thick.Its cutting face is about 90º to the flat surface.Cutting edge,upto 1-2

cm is hardened & tempered.Hardness about HRC 58 to 60;Cutting face is
slightly rounded so that outercorners may not score the surface.
1.2 Brazed tip flat scraper;-In this scraper a carbide tip is brazed to the end and
ground at 85° to 90°. Cutting face should have a flatter curvature to get better
efficiency.It is longer than simple scraper,to provide little spring action.
1.3 Clamp-on scraper;-A carbide tip is well ground and mounted in the scraper
holder by means of plate-clamp and screws.A warnout tip can be replaced.
Now a days these scrapers are widely used as they are capable for jerky
strokes,suitable for scraping hard material,and having long life.
2.HALF ROUND SCRAPER;-
Half round scrapers are used to scrape the curve surfaces like split
bushes.These are mostly made of high carbon tool steel.Its cutting edges are
ground at 60° to 65°

3.TRIANGULAR SCRAPER;-Triangular Scraper are also called as three corner
scraper. Its cross section is triangular. Front side is pointed. Its three faces are
ground with slight curve. So the curved cutting edge while scraping can touch the
particular point to be scraping and avoid the line contact.so it is very useful to
scrape the bearing halves observe the figure (I-041).The triangular scraper from its
point to handle end is straight. So while using it a simple circular movement is
applied. The half round scraper is bent touts front side, so while using it,a
combined movement is used. It is not so simple.it requires more skill. Hence most
of the persons prefer to use a triangular scraper for bearing scraping instead of half
round scraper.
4.HOOK TYPE SCRAPER;-Hook type scraper is bent at the front in 90°.Instead
of pushing, it is pulled. It is used for scraping at the congested places where
movement of flat scraper is inconvenient.
5.BULL NOSE SCRAPER;-According to its name its nose is like bull nose. It
has a half round curve face at the front side. It can be used suitably on flatter
surfaces, flatter curve surfaces.
6.TWO HANDLE SCRAPER;-It is a robust form of scraper. It may be used for
rough scraping. As it has two handles, it can hold by both handles.
POWER SCRAPER;-Power scraping machines are driven by electrically or
pneumatically. These are supplied with a belt. This belt is hanged on the operators

shoulder and the handle is Holden by hands. While using these power scrapers
first hold the machine at lower angle to the surface and then increasing the angle
as per requirement of the depth of cut. If it is started by large angle then it may gin
a heavy retarding jerk. Hence handle such machine carefully. Power scraping is
useful for large area and tore move more material. It is better to use it for initial
roughing work and then use hand scrapers for finishing work.
SCRAPING
Scraping operation requires a lot of skill. In every type of scraping, first, the
surfaces are checked. The high spots are traced carefully. Mostly when it reaches to final
stage the operator should take more care, otherwise a little carelessness may spoil the
whole surface and again it will take too much time to rectify it.
SCRAPING FLAT SURFACES
Scraping may be done by various ways. Now a- days the centered carbide
tipped scrapers are generally used. This material withstands on jerky motion and
can cut the material at various holding angles. This advantage (of carbide tips) has
affected the original scraping operation and hence different people do this job in different
ways. Anyway we have to achieve the aim of maintenance of surface accuracy only.
HIGH SPOTS
Main object of scraping is to remove the high spots which influences the accuracy
of the surface. Hence to find out the high spots is the important operation in scraping.
High spot means such an elevated area or asperities or ridged in the surface which are in
higher plane than the surrounding surface or reference surface. Different marking
compounds/media are used to find out the high spots. The Prussian blue, car-bon
black, red lead mixed with oil are the marking compound usually used.

The marking media is smeared over the surface plate or master plate, so there
should be no pigment remained on the surface. A fine layer say without thickness will
give a fine result. Now take the plate (to be scraped ) and put on the surface plate very
slowly in such a way that its maximum surface will touch. Move the upper plate on
surface plate just for two three strokes or rounds. Take off the upper plate gently and find
the more deep color spots. These color are the high spots. Scrape these spots your
selected methods (any of above four methods.)
For next time take the oil stone or hone and move it on the flat surface just
scraped. The burns will be removed.
b) Again repeat the operation – smearing over the Prussian blue or red – lead oil
paste – putting the plate on it – taking stroke or rounding – lifting the plate straightly –
finding the spot and scraping.
After repeating the operation for several times we will find the area of high spot is
reducing it means the rough scraping is just finished for further fine work, now it is
necessary to take more care.
c) For fine scraping we have to decide or judge where the flat scraping should be
done or should be avoided. Suppose there is a line of little width to one side and broad
belt of colour on the second side end. Here you will find that instead of scraping the
broad belt. First scrape the colour of the broad belt colour. Thus analysis of the spot is
more important.
d) Thus rough scraping is a laborious job but same time it is simple. The fine
scraping is very tidiness job. It requires more peshions for deciding the real spot to be
scraped Rough scraping strokes are more longer and fine scraping strokes are lesser in
length.

Scraping operation is followed by pre – filing turning, milling, shaping, planning
operation. It remains some roughness.
At initial stage the surfaces are observed with uneven high spots. These high spots
may have different minute height and form, but after starting the scraping operation it
gradually comes in regular form with negligible height.
Grade of
operation
Length of stroke
in mm
Number of
impression in 25 x
25 mm
Depth of cut in
mm
Rough Operation 15 to 20 3 to 4 0.05 to 0.15
Fine Scraping 5 to 8 6 to 18 0.01 to 0.02
Super Fine
Scraping
3 to 5 20 onwards 0.005 to 0.01
Flat Plate, Early Stage
Flat Plate, After Several Cycles

Flat Plate After More Cycles
After removing the highspots repeatedly the scraped marks comes nearer and the sopt
turns in the Bearing spot while scraping a stroke is not taken in a straight line like
shaping filling but it is a just curved stroke which causes to meet in a bearing spot and
the surrounding has hollow shaped cut called Cavities. These cavities are useful to keep
the oil drops and supply the lubricant while sliding.
Some persons prefer to apply the marking media or colours on the job to be
scraped and to rub it on master plate / reference plate. The rubbing action cleans the
colour of high spot. It may be more useful at final stags.
There is no hard and fast rule to adopt the “this or that system”. Any way one has
to fulfill the requirement of accuracy. Still the beginner should follow the only one
system as instructed. Otherwise he will learn nothing.
PREVENT CHATTER MARKS
If scraping is done continuously in one direction only, then it forms a surface
harder and smooth. So further scraping produces chatter marks. These chatter marks can
be avoided by change the direction of scraping in suitable angles i.e. 45 to 90 after two
three cycles. Change of direction of scraping will also give nice frostily appearance.
OIL POCKETING
In fine scraping the depth of cut is very negligible. So the cavity formed during
fine scraping not be sufficient for oil pockets. Hence mist when flat surfaces are scraped
successfully and full bearing seat is achieved then the oil pockets is done, it also reduces
the contacting area, on pocketing is done by various way.
Methods of oil pocketing

1. Ideal scraping with keeping particular distance between tow marks. Do it in one
direction and then in another direction i.e. 45 and 90 see fig. 1-048 A.
2. Mark and squares like square designed mat and scrape the squares leaving one
afterone in different direction. It is also called as Frosting or Flowering. It gives
pleasant look. So fig. 1-048 B.
3. Hold the scraper vertical to the surface with slight tilted and apply the flat
scraping method 4. The stroke should be very small and in different directions.
It also gives very nice appearance.
CARE :
1. After oil pocketing operation do not furgate to clean the job and remove the burrs by apply
the oil stone lightly.
2. Do not gather closely the oil pocketing other wise your original accuracy may loss.

The general defects that may arise in guide surface are;
i) Non linearity
ii) Spiral / twist
iii) Parallelism of guide surfaces along the horizontal and vertical
plane.
i) Checking Non linearity (straightness) :-
Wear of guide ways is estimated with the aid of a straight edge and thickness gauges
(Fig.a). The length of the straightedge should be At least 2/3 that of the surface being
checked.
First of all, clean the surfaces of the bedways to eliminate dents and large scores.
Then apply straightedge 1 and measure the clearance between it and bedway 2 with a set
of thickness gauges 3 at 300-500 mm intervals. The maximum wear and, hence, out-of-
straightness of the bed ways, occurs where the clearance is the largest.

ii)Checking Spiral / Twist:
Spiral or twist of a guide surface is measured by placing the level on the bridge across
the guide length. The bridge is traversed along the guide length and level readings are
taken.

iii)Checking Parallelism of guide surfaces along the horizontal and
vertical plane:

Deciding The Method For Repairing The Guide Surface;
1.
Method of measuring value of wear on guide surfaces.
WEAR ON GUIDE SURFACES AND METHODS OF DETERMINING THE
VALUE OF WEAR:
There are 4 methods most commonly employed for determining the value of wear of
guide surfaces and are described below. Method (1) is applicable only for short bed
lengths upto three metres. Methods (2, 3 & 4) are used for longer beds. 3 & 4 are the
hydraulic level methods, in which method (4) gives most accurate results.
METHOD (1) FOR SHORT GUIDES: (Fig a, b)
S.No. Amount of wear Repairs Needed
01. Upto 0.02mm Scraping method
02. 0.02 to 0.03mm Grinding and Scraping
03. More than 0.03mm Planning & Scraping

Value of wear on narrow guide surfaces (Fig a) is measured by placing a straight edge
along the guide surface 2, and measuring the gap 3 with a feeler gauge, at every 500 mm
along the entire guide length.
Fig (b) shows the method of determining the wear on wide guide surfaces and is
measured by placing the straight edge 1 on two accurate equal-thickness pieces 2 & 3.
The gap is measured at several places between the straight edge 1 and the guide surface
4. This is repeated in several directions as shown a1, a2, a3, a4 & a5.

METHOD (2) FOR FLAT / PRISM LONG GUIDES: (Fig. c)
Fig. (c) shows the method of determining the wear on longer guide
surfaces.
1. The guide length is divided in 500 mm distances and marked with a chalk.
2. Suitable bridge (i.e. 2 equal-thickness pieces and a straight edge for flat guides
or the guide length and the level read, say L1 divisions. The bridge is moved to

the next position and level read, say L2 divisions. The bridge is moved to the
next position and level read, say L2 divisions. This is repeated for the entire
bed length, and the levels are L3, L4, L5 (say) divisions etc.
3. If the level used has a least count of L mm / meter, the level difference as
measured (at 2) on every 500 mm will be
L1 x L L2 x L L3 x L and so on
2 2 2
4. This is plotted on a graph and the value of maximum wear is noted from there.

METHOD (3) FOR LONG GUIDES, BEDS OR PLATES (JOBBING,
MARKING, SURFACE).
1. The measuring device consists of two cups joined together with flexible pipe
(polythene) and the system filled with kerosene oil.
2. The position of one cup is fixed up near the middle of the guide surface / bed
and the other cup placed adjacent to it. The reading of this second cup is noted
say x mm. This cup is now moved all along the guides w.r.t the fixed cup.
3. The readings are noted at every 500 mm distance, along the entire bed length
(and width), say x1, x2, x3 etc. The level differences with respect to the
position of the fixed cup will be 2 (x1 – x), 2 (x2 – x), 2 (x3 – x), etc. From
this, the value of maximum wear 9i.e. maximum difference of level between
any two points) is known.

2. Explain the method of repairing the lathe bed guide ways by scraping?
CONTROL CHARACTERISTICS:
1. Non linearity of all guide surfaces within 0.02 / 1000 mm
2. Parallelity of guides 2, 7, 8 and guides 6, 3, 4 within 0.02 / 1000 mm
3. Twist of guides 2, 7, 8 and guides 6, 3, 4 within 0.02 / 1000 mm
4. Guides 7, 8 must be parallel to guides 11, 12
5. Relative parallelity of guides 3, 4 to guides 7, 8 within 0.03 mm along the
whole bed length
6. Guides 1, 10 must be parallel to guides 2, 7, 8 within 0.03 mm along the whole
bed length
REPAIR METHODS:
Before the repair commences, it is important to select out the base guides which
serve as a base for controlling and starting the repair work. Tail-stock guides 3, 4
& 6 are usually taken as the base guides.
Repair by Scraping – wear up to 0.2mm:
If the wear of the guide surface is within 0.2mm, guide can be repaired by direct
scraping:
1. Bed levelling:
The bed is levelled on its foundation along the tailstock guides by means of
levelling screws / wedges etc. Provided for the purpose (Fig). The level is
placed on the tail-stock base (or on the universal bridge installed on the

tailstock guides as shown in Fig) and the level checked in the longitudinal as
well as in the transverse plane.
2. Preparing of base guides:
Tail-stock guides 3, 4 & 6 are taken as the base guides. It is advisable to
check these base guides and scrape, if necessary against the rack guide surfaces
11 & 12. The base of the dial indicator is placed on the tail-stock base (or on
the universal bridge installed on the tail-stock guides) and its finger point is
made to touch first the surface 11 and then the surface 12. The tail-stock base
(or the universal bridge) is now traversed along the guides length and the
readings taken, which should be within 0.03 mm on the whole bed length.
The twist of the tail-stock guides should also be checked with a level placed
on the bridge / tail-stock base as shown in Fig. And should be within 0.02 /
1000 mm.
3. The flat guide (main) 2 is now scraped against a straight edge of class II
accuracy within an accuracy of 15 – 18 points / 1000 sq.mm and its
parallellality with the base guides 3, 4 & 6 is checked with an indicator placed
on the tail-stock base or on the universal bridge installed on the base guides.
The parallelity should be within 0.02 / 1000 mm.
4. The prism guides (main) 7 & 8 are also similarly scraped and the parallelity &
twist of guides 2, 7 & 8 are checked with a level and the universal bridge
installed on guides 2, 7 & 8. The parallelity and twist should be within 0.02 /
1000 mm.
5. Parallelity of guides 7 & 8 relative to the base guides 3, 4 & 6 is checked by
placing a dial-indicator on the tail-stock base / or on the universal bridge
installed on guides 2, 7 & 8. The indicator finger point touching either of the
guides 3, 4 & 6, the tail-stock base / bridge is traversed along the whole bed
length. The parallelity should be within 0.02 / 1000 mm.
6. Oil pockets are now made with the scraper on all thye guide surfaces.
7. About a meter length of the bed towards the head-stock is mostly used and is
kept about 0.02mm higher than the remaining guides. This increases the
working life of the guides without repairs as it takes into account the fast wear
on the guides near the head-stock.

Explain the method of repairing the guide surface on lathe by Machining on planer.
This method is briefly described here with a detailed description is given:
1. Template is prepared at the un-used portion of the guide surface counter template
is prepared against this template.
2. The bed is fixed near the table center of the planer or or Plano-miller paper pieces
are placed between the table and the bed so as to check for equal distribution of
load.

3. Dial indicator is fixed on the tool post and traversed along the base guides (usually
the surface under the rack) and set horizontally and vertically within an accuracy
of 0.05mm on whole length. The bed is now reliably clamped on the table.
4. The dial indicator is now traversed on all the guide surfaces (flat and prism) and
max wear is no certained let a x wear is x mm.
5. The flat guide is machined first of all to a depth of x mm. XI mm = x + 0.05mm
6. Center template (refer 1) is temporarily installed on the approach oend of the bed
guide so that the machined flat guide so that the to its corresponding face on to the
template.
7. For machining prism guides the tool is set as long its corresponding face on the
counter template the depth of cut taken with be x1, cos x where x is the angle of
the guide surface with the horizontal.

3. Explain the method of repairing the bed ways of lathe by grinding on planer?
Grinding of guide surfaces grinding attachment on planer sorter bed length
up to 2.5 meters are usually ground on planer with grinding attachment installed in
place of the too head the attachment consist or an electric motor (about 4 kW &

3000 rpm suitable for use in vertical position) suitably fixed on a base plane and
mountable in place of the tool head. The grinding wheel is matched on the motor
shaft and the grinding operation is carried out with the force of the cap wheel of
dia 100 to 175 mm. The attachment can be used for grinding flat guides as well as
prism guides by rotating the tool head at the desire long.
The preliminary rough grinding is carried out by inclining the grinding
spindle axis 30 – 40 as shown grinding for final is carried out with the spindle
perfectly vertical and depth of cut not exceeding 0.01mm. Table feed of the planer
should preferably be kept equator the forward and the return strokes.
Explain the procedure for repairing the column guides of horizontal
milling machine by scraping.
CONTROL CHARACTERISTICS:
The followings are the main characteristics that should be restored during the
repair:
1. Guides linearity should be within 0.02 / 1000 mm.
2. Guides parallelity should be within 0.02 / 1000 mm.

3. Perpendicularity of the flat guides relative to the spindle axis should be within
0.02 / 300 mm.
REPAIR PROCEDURE:
Dovetail type guides of the column of the horizontal milling machines are repaired
in the following steps
(a) Flat Guide 1:
To achieve the perpendicularity of the flat guide 1 relative to the spindle axis,
the following sequence of scraping is followed.
1. Before the machine is dis-assembled, a dial-indictor is installed on the
spindle at a radius R (Fig) equal to the maximum possible setting. The
spindle is given one complete rotation and the lowest section of the guide as
shown by the indicator is marked.
2. With this lowest section as base, three more sections (about 20 x 10 mm size
at about 90° from the lowest section) are scraped as shown in Fig. So that
the indicator readings of the lowest section and the formed three sections are
equal. These sections serve as a control during scraping.
3. The bed is removed from the foundation and placed with guide 1 in the
horizontal plane.

4. Suitable size straight edge or surface plate of class II accuracy is taken, blue
paste applied on it and rubbed against the guide surface 1 so as to leave blue
markings there. These blue marking are scraped. This is repeated till we
just start getting blue markings on the four sections mentioned at 2.
5. The scraping accuracy should be 15-18 points / 1000 sq.mm.
6. The twist of guide 1 is checked by installing a level on the straight edge
(level placed across the guide length) and traversing it along the guide
length.
The flat guide 1 having been scraped, the guides 2 & 4 are then scraped.
(b)Dove tail guides 2 and 4:
The guide 2 is scraped first and then the guide 4.
1. The guide 2 is scraped against a 55° angular straight edge of class II
accuracy, to an accuracy of 15-18 points / 1000 sq.mm.
2. The guide 4 is then also scraped against a 55° angular straight edge of class
II accuracy, to an accuracy of 15-18 points / 1000 sq.mm., but at the same
time, the guide 4 should be parallel to guide 2. This relative parallity of
guide 2 and 4 is checked by the universal bridge for dove-tail guides.

4. Explain the procedure for repairing the table surface of milling machine
REPAIR PROCEDURE:
(a) Table Surface:
1. Any damaged section of the table surface is repaired by machining the
section to a depth of not less than 2 mm and pasting (With Araldite
compound) the packing of the same material as that of the table. The
section after pasting of the packing is suitably machined.
2. Any damage on the T-slots is repaired by fixing a suitable size oacking
(material will be the same as that of the tabnle) on the damaged section, as
shown in Fig (a). the packing can be fixed by pasting with Araldite
compound or more reliably, by bolting in which case the packing thickness
should not be less than 5 mm.
Fig (b) shows the bolting method with special bolts. The shank
diameter of the bolt is kept approximately 4/5th
of the bolt dia at the thread
depth. Such bolts are screwed in position till the shank gets sheared off. the
screw heads after this process are machined along with the packings to the
required accuracy.
(b)Table Guides;
1. If necessary, thye guides 1 & 23 are machined after the table surface 6 has
been repaired.

2. The guides are scraped against their corresponding guides to an accuracy of
8-10 points / sq. inch in a similar way as explained at C2-2 for vertical
guides.
(c) Final Machining / Grinding of Table surface:
It is recommended to machine or grind the table surface 6 after the final
assembly. In the absence of proper facilities formachining / grinding, the table
surface can be scraped against a surface plate and checked by installing an
indicator on the spindle.
Explain the procedure for repairing the regulating and non-regulating type of
clamping plates.
1. Clamping Plate
2&3 Wearing Surfaces
4. Fastening Screws
5. Regulating Screws
6. „X‟ permissible gap
REPAIR METHODS:

(I) Non-regulating type (Fig)
The bolting face of the clamping plate is machined or ground so that the gap
between the guide surfaces is practically nil. The clamping plate guide is then
scraped against its corresponding face to an accuracy of 6 to 8 points / 1000
sq.mm so that a gap of 0.03 – 0.04mm is achieved.
1. Bolt the clamping plate 1 in position with the table, as shown.
2. Measure the gap between the guide surface of the clamping plate 1 and the
bed 2. Let it be g mm.
3. The bolting face of the clamping plate 1 is machined by g .mm.
4. Blue paste is applied on the bed guide (for clamping plate) and the clamping
plate boles in position with the table.
5. The table is traversed so as to obtain blue shining marks on the clamping
plate guide surface. The clamping plate is removed and blue marks scraped.
6. The above process is repeated till the desired control characteristics are
achieved.
(II) Regulating Type (Fig) (b)

Fig (b) shows the
regulating type of clamping plates. The gap is regulated by unscrewing the bolt 5.
When the gap „K‟ exceeds 2 mm, the clamping plate 1 is either replaced by new
one or the old one repaired by pasting a hylam packing on its face.
Bearing removal method;
Disassemble bearing in a clean environment.
Re-installation the bearing without damage in the same position and direction on the shaft.
Mark the relative position of each of the bearing, for example, which part is upward, and which
is facing inwardly.
If the bearing is damaged, it may be necessary to check and analysis bearings and other
components to identify the cause and take corrective measures. So you should remove as
careful as possible to keep bearing undisturbed.
Study the actual drawings and bearings arrangement.

During the demolition process, ensure that the appropriate support of shaft or bearing box.
Remove program
Remove bearing using the puller.
If possible, hold the bearing inner ring or adjacent components
(such as the labyrinth sealing ring) with puller. Pull the inner ring
with uniform force, until it is completely out of the axle.
Puller should be accurate on center in removal, or it easily damages the journal. Use the puller
in center automatically to prevent this situation.
Puller cannot grab the inner ring, seize the outer ring.
If bearings have to be used again or other reasons which prevent bearing damaged, but only
the outer ring loads, you must rotate the outer ring to remove.

Procedure Recommended For Repairing The Machine Tools;-
Each mechanism, and the more so s system of mechanisms, should be repaired in a
definite sequence to obtain the best results. The following procedure is recommended:
1. Find the faults
2. Establish the sequence of dismantling;
3. Disassemble the mechanism into units and parts and wash them.
4. Determine the nature and amount of wear;
5. Repair the components;
What are the preparation for disassembly of machines?
Successful repair of a machine largely depends upon correct disassembly, which is a
highly important operation performed by methods specified for each particular unit.
Before disassembling a machine, study its design, purpose and interaction of its units and
components. If external inspection of the machine does not provide sufficient
information, consult instructions and drawings. Similarly unit-by-unit dismantling
should be proceeded by a thorough study of the design and ways of fastening individual
elements, and by the planning of the sequence and methods of disassembly.
Before and during disassembly of intricate and critical units it is advisable to draw
diagrams and sketches, especially if the maintenance man has never before dealt with
such units. During disassembly, mark the non-operative faces of parts with digits
facilitate the matching of parts during assembly.
When dismantling fastening elements, bear in mind that certain parts may lose their
balance after some of the fasteners are removed, and fall down. Therefore safety
measures should be taken. For example, when taking off a heavy bracket, provide a
reliable support for it as the upper bolt is being removed. When unfastening parts,
estimate the position of their centre of gravity and the direction in which the part will
move when a particular fastener is released.
Rules And Sequences During Disassembly;
Prior to being taken out of service for repair,
Equipment should be cleaned of chips, dirt, dust and coolant.
When assigning a piece of equipment to repair, a special certificate is compliant by the
representatives of the plant and shop maintenance services. The certificate sums up the
results of visual inspection and performance tests, and also the faults noticed by the
operator.

The units and mechanisms making up the piece of equipment to be repaired are visually
checked for completeness and faults, and their components, for evidence of nicks, dents,
cracks, deflections, broken portions, and other defects noticeable without the
disassembly of units; also the condition of lubricating and protective devices is
evaluated.
The operator is questioned about malfunctions of the machine under various operating
conditions, the state of units, mechanism, and even individual components. Suppose a
lathe operator reports that a great transmission spontaneously disengages at a certain
speed. This means that the teeth in the corresponding pair of gears are worn out; so,
these parts should be entered into the certificate.
By listening to the running machine, the presence of unusual noises, rattling, or
vibrations is checked.
All the faults put down in the certificate are taken into account when the final version of
the record of defects is complied.
Each mechanism and the more so a system of mechanism should be repaired in a definite
sequence to obtain the best result the following procedure is recommended.
1. Find the faults
2. Establish the sequence of dismantling
3. Disassembles the mechanism in units and pass and wash them.
4. Determine the nature and amount of wear
5. Repair the components
6. Assemble the mechanism and its elements together
7. Then adjust the assembled mechanism
WASHING THE DEMOUNTED PARTS;
Parts and units demounted from the machine should be cleaned and washed to better
reveal their defects and improve the sanitary conditions of repair.
Parts prepared for restoration or painting should likewise be cleaned and washed.
The methods of washing the demounted parts are:
1. Thermal method
2. Mechanical method
3. Abrasive method
4. Chemical method

.
With the thermal method the cleaning (removal of rust and old paint) is done with the
aid of flame.
In the mechanical method, old paint, rust and solidified oil are removed by brushes,
power-operated milling cutters, rotor machines or other portable mechanisms.
The abrasive method employs hydraulic and blasters.
With the chemical method old paint, grease, oil deposits etc. are removed with the aid of
special paste or solutions consisting of unslaked lime, chalk, caustic soda, mazut
(residual fuel oil) and other ingredients
FAULT FINDING;
Scratches, cracks and dents can be easily seen on the surfaces of washed parts.
It is customary to clean parts with scrubbers and cotton waste dipped in kerosene to
reveal the defects. Small parts are washed and degreased in baths or tanks filled with
kerosene, gasoline or alkali solution. Washed parts are dried in the air or wiped dry with
clean rags.
Washed and dried parts are inspected after being sorted out and grouped in units. At
first, inspect each part externally and then check its shape and size. To decide on its
repair or replacement, a part is sometimes tested for interaction with mating parts.
Parts are divided into three groups: usable parts, parts that have to be repaired or
restored and unusable parts that go for scrap. Corresponding notes are entered into
the record of defects.

Mark the parts during the fault finding procedure with the number of the record of
defects and the number of the machine to make subsequent maintenance operations
easier.
The marking is carried out with stamps, pigment, acid by means of an electrograph, or by
attaching tags. The stamping of designations is done on unhardened parts, and the other
methods are used for both hardened and unhardened parts. For instance, a rubber stamp
is wetted with a solution containing 40 per cent nitric acid, 20 per cent acetic acid and 40
per cent water to mark unhardened parts, or 10 per cent nitric acid, 30 per cent acetic
acid, 5 per cent alcohol and 55 per cent water, for hardened parts; the wetted stamp is
applied to an inoperative surface of the part and kept in place for 1-2 min; after that, the
surface is neutralized with a wag wetted with a soda ash solution.
Parts to be replaced are kept unit the mechanism is repaired, since they may be needed in
making drawings or manufacturing new parts.
The record of defects is the initial technical and financial document.
A correctly compiled and sufficiently detailed record of defects is a substantial addition
to the repair operational sheet. This important document is usually prepared by the
repair process engineer together with the maintenance foreman, chief of the maintenance
team, and representatives of the quality control department and the machine‟s user.
The specifying of wear limit values and their knowledge are essential in fault finding.
However, it is a very difficult task to correctly establish wear limits, basing on the
specific requirements for a wide variety of parts in equipment of different types used for
different purposes.
Wear limit values for some parts adopted in plant repair practice are given below by way
of example.
For precision machine tools and for those of normal accuracy class, the maximum
permissible wear of guideways over a length of 1,000 mm is taken to be 0.02 – 0.03 and
0.1 – 0.2 mm respectively.
Wear of shaft journals running in non-adjustable plain bearings in feed gear boxes, in
aprons and similar mechanisms is permissible within the range of 0.001 – 0.01 the shaft
diameter, depending on its tolerance.
The permissible wear of spindle journals (0.01 – 0.05 mm) depends on the machine
accuracy requirements. Wear of shaft journals supported by antifriction bearings should
not exceed 0.01 – 0.02mm, and that of splines, 0.1 – 0.15 mm over their width.
Static and Dynamic balancing

Flywheels, pulleys and other parts which rotate at high peripheral speeds should be well
balanced, for otherwise the machine will vibrate and the surface finish and the accuracy
of the parts will be impaired.
Two kinds of unbalance are known in maintenance practice – static and dynamic
Static Unbalance is characterized by the displacement of the centre of gravity of the part
relative to its axis of rotation and dynamic unbalance by the presence of unbalanced
centrifugal forces in different sections of a rapidly rotating long part, although its centre
of gravity may lie on the axis of rotation.
Accordingly, there exists Static and Dynamic balancing. The static balancing consists
in balancing a stationery part mounted on special fixtures such as knife-type guides,
rollers, etc. The second is intended to minimize vibration. The part is rapidly rotated on
special machines, the use of which is justified only when new equipment is manufactured
at machine tool works.
In most cases, parts are balanced by the static method. For balancing, knives 1 and 4
(Fig a) are aligned in a horizontal position with a straight edge and a spirit level to an
accuracy within 0.05 – 0.01 mm over a length of 1,000 mm. The working surfaces of the
knives should be well finished and hardened.
Part-3 to be balanced is secured on mandrel 2, the ends of which should be of small and
equal diameter to improve the sensitivity of balancing without impairing the rigidity of
the whole arrangement. Push the wheel gently to make it rotate, its heaviest portion will
always assume the lower most position after it stops.
To balance the part, either drill holes or cut surplus metal from the heavier portion to
make it lighter or attach some weight to the opposite side, seeing that it does not
interface with operation. Check the balance by rolling the part over the knives. A well
balanced part will stop in a new position each time.
Parts can be also balanced on a fixture with discs (Fig b) Discs 2 are mounted in ball
bearings on supports 1. The part is placed between the discs and balanced in the same
manner as on the knives.

UNIT II
SYLLABUS;
Unit-II: MAINTENANCE ACTIVITY AND MAJOR OVERHAUL OF A MACHINE TOOLS:
a)Maintenance:
Maintenance – Definition – types – Preventive maintenance – advantages – procedure – break down maintenance.
b)Examples of Maintenance:
Example of an engine lathe overhaul. Inspecting and checking before repair- Disassembly- mounting and aligning the feed
gear box-apron, lead screw and feed rod bracket- repairing the tailstock – head stock spindle – three jaw chuck – lead screw
and nut – cracks in a cast iron body - technical requirements for the repaired lathe –standard chart for major overhaul of an
engine lathe.
MAITENANCE ;
INTRODUCTION;
Maintaining the production capability of an organization is an important function
in any production system. Maintenance encompasses all those activities that relate
to keeping facilities and equipment in good working order and making necessary
repairs when breakdowns occur, so that the system can perform as intended.
Maintenance activities are often organized into two categories:
(1) Buildings And Grounds, And
(2) Equipment Maintenance.
Buildings and grounds is responsible for the appearance and functioning of buildings,
roads, parking lots, lawns, fences, and the like.
Equipment maintenance is responsible for maintaining machinery and equipment in
good working condition and making all necessary repairs.
The goal of maintenance is to keep the production system in good working order at
minimum cost.
There are several reasons for wanting to keep equipment and facilities in good operating
condition, such as to:
1. avoid production disruptions
2. not add to production costs
3. maintain high quality
4. avoid missed delivery dates
When breakdowns occur, there are a number of adverse consequences:
1. Production capacity is reduced, and orders are delayed.

2. There is no production, but overhead continues, increasing the cost per unit.
3. There are quality issues; product may be damaged.
4. There are safety issues; employees or customers may be injured.
Types of Maintenance:
Breakdown Maintenance – You wait until the machine completely fails, then you
repair it to working order. Usually assigned to machines with backups in place, or
machines which are of low importance to production.
Preventive Maintenance – You maintain the machine, while still in operation to
prolong or prevent the machines failure. This should be applied to machines of
importance and high value when compared to production.
Predictive Maintenance – You predict when the machine may require maintenance
based on analysing past history, and apply maintenance just before the machine has
failed in the past, extending its service life. Often applied in conjunction with
Preventative Maintenance.
Periodic Maintenance - A set schedule of maintenance routines assigned to prolong
the life of the machine.
Breakdown maintenance is usually applied on machines which are not the backbone of
the project. For example, in a factory, if a machine is of little importance to whether
production carries on, or there are backup procedures in place for said machine, it may
be cheaper and more efficient for the company to send a maintenance worker to the
machine when it actually breaks, as opposed to assigning a work order periodically on
the machine as it is still performing up to par. This cuts back in labour hours for the
company, as well as cost of operation.
You yourself probably perform breakdown maintenance on a routine basis in many
aspects of your life, disregarding, preventive, predictive, and periodic maintenance when
they could have prevented a problem, but just were not worth the time.
Functions of a maintenance department
Following are the major functions of a maintenance department [3-4]:
facilities
– Inspection and lubrication of existing equipment
– monitoring of faults and failures using appropriate techniques

01. Distinguish between the breakdown maintenance and preventive maintenance.
S. No. Break-down maintenance Preventive Maintenance
01 Maintenance is done only after
machine fails.
Maintenance is done before the
machine fails.
02 Maintenance is done after break-
down
Maintenance is done to prevent
break-down
03 The time of breakdown is
unexpected. So the maintenance
work cannot be planned.
Maintenance work is well planned
04 Not suitable for critical machineries
like cranes, hoists, boilers etc.
Suitable for all types of equipment
05 Cost due to downtime is more No down time
06 Production loss takes place. No production loss
Maintenance objective;

Different type of maintenance
Overhauling of engine lathe;
Maintenance
Planned
Maintenanc
e
Preventive
Maintenance
Running
maintenance
Shutdown
maintenance
Scheduled
maintenance
Corrective
Maintenance
Breakdown
maintenance
Shutdown
maintenancePredictive
Maintenance
Unplanned
maintenanc
e
Emergence
maintenance

List out the inspection to be carried out before repairing the engine lathe.
1. To externally inspect (with disassembly) the whole machine and each of its
for making the defect list about the condition and the operation of the machine. To
regulate, check durability and tightness of fixed / rigid joints i.e. Bed foundation,
bed sections between themselves, pulleys, flywoods, sprockets, gears, friction discs
etc.
2. To open out the cover of the units for inspection and check the condition of
mechanisms.
3. To regulate clearances between lead screws and their mating nuts of the
slides, saddles, traverses, carriages, etc.
4. To regulate spindle bearings.
5. To check proper engagement of speed and feed gears and the lever / handle
position.

6. To regulate smooth sliding of tables, slides, saddles, traverses, carriages,
slide blocks, slotter ram. To tighten wedges and clamping plates.
7. To check the condition of guides of the bed, carriages, traverses and other
friction surfaces. To clean scratches and any other damages.
Dismantling Procedure For Three Jaw Check.
To dismantle and assembly of the given three jaw chuck, the following tools are
required: Screw driver, Hammer, Chuck key, Piston gauge and cleaning brush.
Dismantling Procedure of three jaw chuck:
The dismantling procedure for three jaw chuck is as follows:

First the three jaw chuck is removed from the head stock spindle by means of a spanner.
First move the block plate in the chuck key by means of screw driver, the jaw is
removed. Simultaneously backward by means of chuck key.
The jaw are dismantled by unscrewing the bevel pinion back plate is dismantled after the
scroll disk jaw back plate is completely dismantled, keep the bolts, screws, studs and
other fasteners, away in a special case on comparity assembly the fasteners back into
rods. Thus the three jaw chuck is removed from lathe.
DISMANTLING AND ASSEMBLING OF TAILSTOCK
Tools And Equipment‟s Required For Dismantling And Assembly;:
Spanner sets, centre punch, hammer, screw driver, chisel, bearing puller, cutting plier,
nose plier and Allen keys etc.

Dismantling:
The tailstock clamping bolts are slackened and the tailstock is removed from the lathe
bed. Then the clamping plate at the bottom of the tailstock is removed. The tailstock
handle nut is unscrewed and hand wheel with the keys are removed. The end cover for
the spindle is removed. The screwed is take out by unscrewing it. Now remove the
spindle from the tailstock housing.
Cleaning And Inspection:
Clean all the parts of pump unit with the spindle oil or cleaning agents. Washed parts are
dried in the air or wiped dry with clean rags.
Inspect the washed and dried parts, group them and store separately. Then inspect each
part externally and then check for it shape and size.
Assembly:
The procedure for assembling the tailstock unit is as follows:Before assembling the
tailstock unit, all the parts are thoroughly cleaned and lubricated.
Method Of Repairing The Tailstock Housing By Poring Stellon Compound.
Pouring Stellon Compound:
1. The tail-stock housing is rough bored, 4-6 mm oversize in diameter.
2. A few holes are drilled in the housing so as to reliably hold the compound.
3. The tail-stock spindle (old) is now installed on the mandrel, fixed in the head-stock as shown
in Fig.
4. Both the ends are sealed with paper and wax so as to prevent the outflow of the compound,
when poured.
5. The compound is now poured and allowed to set for 12 hours.
6. Describe the method of repairing the tailstock housing by boring.

Boring of tail-stock housing:
1. After the tail-stock guides have been scraped, the tail-stock housing (without the spindle) is
fixed in-between the head-stock and the carriage 4 and clamped.
2. Boring spindle 5 is placed in the head-stock spindle 2 and supported at the other end on the
steady 6 secured on the bed guides 7, as shown in Fig.
3. The tool is now fixed in the boring spindle, in the position marked in the Fig.
4. The tail-stock housing is now bored at a speed of about 100 – 120 rpm and a feed of about 0.1
mm / revolution. Permissible taper is of the order of 0.02 mm along the whole length and the
ovality of 0.01 mm.
5. The tail-stock spindle is now made new and ground to size corresponding to the new bore of
the tail-stock housing.

EXAMPLE FOR DISMANTLING ;
List out any two defects that may occur in the spindle and how it can be rectified?
Defect Cause Repair Steps
1. Spindle underload
vibrates radially /
axially causing general
vibrations in the
machine itself.
Radial / thrust bearings
need regulation
Regulate the bearings
2. Spindle HEATS up
(over 50°C) and
sometimes jammed up
Bearing regulated too
light.
Regulate the bearing to
increase the gap
slightly.Scratches on the surface
of bush bearing due to the
Metal chips fallen there.
Clean and scrape the
bush bearing
Scratches on the running
race of the ball / roller
bearing.
Replace the bearing.
Insufficient lubrication Check the lubricating
arrangement
Oil seal too tight on the
shaft
Rectify / replace the
seal.3. NOISE during
operation at the
bearing set
Ball / roller bearing
damaged or running dry.
Replace the bearing /
check the lubrication

Eliminate The Play In The Lead Screw;
Elimination of Play: After a certain period of use, the threads of the lead
screw and that of the nut wear-out, resulting in play. In modern machine tools,
play eliminating arrangements is provided on the nut so that the play is regulated
and nut is not required to be replaced / repaired very often. If consists of two nuts,
one fixed to the housing as usual and the other freely screwed on the lead screw.
Fig (a) shows the self play eliminating arrangement and Fig. (b) shows the hand
regulating arrangement. The regulation is done by screwing-in the play adjusting
screw which pulls apart the two nuts thereby eliminating the play.
Thread wear up to 0.3 mm: If the thread wear is within 0.3mm the following three methods of
repair are recommended.
1. Both sides of the lead screw threads are cleaned on a lathe by taking small cuts along the
whole length so that the tool starts taking a uniform cut. This method is applicable for lead
screws with trapezoidal threads only.
2. Reduce the lead screw O.D. by 2x/Cos α („x‟ being the thread wear in mm and „α‟ the half
angle of the trapezoidal thread with the horizontal, usually 15°) and cut new threads.
3. Reverse the lead screw so that the end of the lead screw which is worn-out less, now falls
within the working zone.
Thread wear exceeding 0.3 mm: If the thread wear exceeds 0.3 mm, the lead screw is either
replaced completely or partly. In the latter case, the worn out section is cut off and replaced by new
one.
Two sections should be joined as per template and then pinned together. If the threads do not fall in line
with the template, the joining end faces may have to be machined / files so as to match the template.
Describe the method of mounting and aligning the lead screw and half nut.
As the individual components of a lathe are repaired, align the feed gear box, apron and the
bracket supporting the lead screw and feed rod so that the holes through which the lead screw
passes are strictly concentric as are the holes accommodating the feed rod. The maximum
permissible error is 0.07 – 0.1 mm.

Alignment is done after all the units, including slide 4, are installed in the required
sequence and firmly secured.
The checking is made at three points (Fig) at closed split nut 1 in the apron and near both
bearings of lead screw 4. The misalignment of the axes must be corrected if the non-parallelism
of the axes of bearings 3 and 5 to bedways 6 exceeds 0.1 mm. and the out of coincidence of the
axis of nut 1 with the axes of the bearings exceeds 0.15 mm.
Errors can be eliminated by:
Placing compensating linings on the woprn saddle ways to correct the position of the nut
axis.
Fitting the surfaces of the feed gear box and the bracket conjugage with the bed by
scraping in order to correct the position of axes of the bearings.
When the above mentioned units are mounted and properly adjusted, continue assembling the lathe.
Install the main drive electric motor in the left hand led and adjust the belt drive. mount the carriage
rapid traverse electric motor. Fill the reservoirs of the speed and feed gear boxes and the apron with
machine oil. Fasten the fittings of the cooling system, protective housings and guards. Restore the
electric
Aligning The Hole Axes For The Lead Screw And Feed Rod In The Apron And Feed
Gear Box.
The alignment of the hole axes for the lead screw and the feed rod in the apron and the
feed gear box, respectively, and also the parallelism of the screw and he rod axes to the
guideways are determined by means of fixture 8 (Fig). This fixture contains tubular rod
3 carrying shoes 5 in which dial indicators 1 and 2 are placed. Shoes 5 are secured in
clamps fastened by screws 4. The measuring plungers of the dial indicators are in

contact with the end faces of spring loaded inserts 7. One of the indicators is fitted with
pivot-table bell-crank lever 6. The fixture is secured to a universal bridge, the tail-stock
base, or other machine elements.
As shown in Fig. the checking is done in the vertical and horizontal planes
simultaneously. The bell crank lever interacting with the upper dial indicator contacts
with its respective arm ends the shaft or the lead screw being checked and the end face of
insert 7. The insert which engages the measuring plunger of the bottom indicator also
touches the shaft checked.
The clamps with the dial indicators are arranged in such a way that the bell-crank lever
contacts the lead screw or the feed rod at its upper generator, and the bottom clamp‟s
insert contacts its side generator. The pressure of the indicators‟ measuring springs is set
up by adjusting the projection of the shoes.
The non-parallelism is determined from the readings of the dial indicators, moving the
fixture along the bedways. The diameter of the insert‟s contact anvil should not be
smaller than 1.5 the lead screw pitch. Otherwise, the insert will get between the thread
ridges during its movement along the lead screw.

Row checking for parallelism is done at three points (Fig.) nearby nut 1 in the apron, and
at both bearings of lead screw 4. The misalignment of the axes should be corrected if the
axes of bearings 3 and 5 and bedways 6 are out of parallel for more than 0.1 mm, and the
axes of nut 1 and bearings are out of coincidence in excess of 0.15 mm.
Main Technical Requirements For The Repaired Lathe.
Machine tools and other equipment must meet the requirements for reliability, accuracy
and productive output laid down in their specifications in accordance with the respective
State Standards.
Quoted below are some machine-tool technical requirements.
Guide ways must be straight and parallel to within 0.02 mm over a length of 1000 mm
and tightly fit to the mating parts over the whole surface. The matching is checked with
a marking compound or with a 0.04 mm thick feeler gauge. The latter is allowed to
enter between the mating parts to a depth of not more than 10 mm, this being valid only
for large size parts and the feeler gauge inserted from the end faces of the parts. As for
small size mating parts, a 0.03 mm feeler gauge must not enter between them at all.
Clearance and wear compensating wedges for guideways and straps for slides and
carriages must also tightly fit their mating parts. Choose screws for fastening the straps
and adjusting the wedges so that the set clearances are reliably maintained during
operation and the respective units are displaced smoothly, without jerks.
Provide for adequate adjustment range for the wedges and other compensating elements
to tighten them as they wear down and also after repair scraping. Identical adjustment
range is necessary for adjustable bearings to make up for wear.
Carefully adjust friction clutches so as to ensure the engagement of friction surfaces
without slipping under maximum load.
The maximum backlash i.e. axial play, of the lead screw must not exceed 0.01 mm.
The lead screw for moving slides must rotate smoothly in their bearings and in nuts over
the whole length of their thread.

Backlash in the hand wheels mounted on the saddle and the slide lead screws, and also in
the hand wheel for moving the apron manually must not exceed 1/40 and 1/20 of a full
revolution, respectively.

UNIT III
Testing Of Machinetools

ACCEPTANCE TESTS AND MAINTENANCE OF MACHINE TOOLS
1- INTRODUCTION
The basic function of a machine tool is to produce a workpiece of the required geometric
form with an acceptable surface finish at, as a high rate of production as is economically
possible. In order, therefore, to evaluate the relative merits of machine tools it is essential
to perform the acceptance tests, i.e. to measure the geometric accuracy, the surface finish
and the maximum metal removal rate (Dynamic performance test).
Experienced fitters and inspectors carry out the acceptance test of a new machine tool in
the manufacture's works. These men know how to use measuring instruments and how
to assemble the machine in such a manner that manufacturing tolerances of individual
components have a compensating and a cumulative effect as far as the accuracy of the
whole is concerned.
Machine tools, which satisfy the specified accuracies in the standards of
machine tool acceptance tests, will produce components that will meet the
requirements of modern production in accordance with standard limits and
fits. However, if closer tolerances are needed, an expensive additional
operations and tedious selective assembly have to be carried out. For the
manufacture of components to medium or coarse tolerances, wide tolerances
may be permissible.
When the machine tool is under load, deformations and vibrations are
created in the frames and other parts of machine tool during machining
operations. Tests that cover the vibration behavior of any machine tool are
difficult.
With regard to vibrations, various investigations concerning the causing and
elimination of chatter on different machine tools have carried out. Some of

them serve for determining the conditions under which a machine tool can
be used without the danger of chatter, others serve for the testing and
improving of newly designed and prototype machines.
As far as acceptance tests for standard machines rather than prototypes are
concerned, finishing cuts be still taken for determining the performance of
the machine.
INTRODUCTION:
The surface components produced by machining processes are mostly by generation.
As a result, the quality of surface produced depends upon the accuracy of the various
movements of the machine tool concerned. It therefore becomes important to know the
capability of the machine tool by evaluating the accuracy of the various mechanisms that are
directly responsible for generating the surface. For this purpose a large variety of tests have
been designed.
MEASURING INSTRUMENTS USED FOR TESTING:
The accuracy of the machine tools employed should be higher than the accuracy of the
components that it produces. Similarly the quality of the measuring equipment used for
machine tool testing should be commensurate with the quality expected from such testing. A
few commonly used equipments are
 Dial Indicators
 Test mandrels
 Straight edges
 Spirit levels
 Feeler gauge
 Depth gauge micrometer
2 - GEOMETRICAL TEST
Measuring Equipment and Methods
Any type of equipment may be used as long as the specified measurement can be carried
out with the required degree of accuracy.
(a) Dial Gauges
1. The graduation must be clear and normally need not be finer than 0.01 millimeter.

Finer graduations that are required in special case graduation down to 1  m may
be used.
2. The initial plunger pressure should vary between 40 and 100 grams; for very fine
measurements a pressure as low as 20 grams is desirable.
3. The dial gauge must be fixed to robust and stiff bases and bars in order to avoid
displacements due to shock or vibration.
Dial indicator is a handheld control device that looks like a clock in appearance. It is used to
check the parallelism of the surfaces and to check the accuracy and misalignment of the precision
machine parts to check whether the axes are in the same direction.

(b) Test Mandrels
Mandrels are used in alignment tests to represent the axis and are of
two types :
(i) Test mandrels with taper shanks, (ii) Mandrels between centres.
(i) In construction the test mandrels with taper shank&wea conical shank for inserting in the
socket of the machine to be tested, and a cylindrical body which is used as a reference
surface for the measurements. In alignment tests, the cylindrical surface of the mandrel
represents the axis desired to be checked, either for out of true running or for position in
relation to other elements of the machine tool. These are made of hardened and stabilised
steel left either unplated or plated with hard chromium. The mandrels of such type having
relatively slow, and steep tapers are shown in Fig. 16.24 (a) and (b) respectively.
The deflection of free ends of mandrels should be less than 0.65 um for those having working
length of 75 mm and than 5.8 um for those having working length of 505 mm. These should
be free from errors of roundness and the axes of the conical and cylindrical portions be
straight and coincident. The cylindricity should be perfect over the whole of the measuring
length.
(6) Test mandrel with steep taper shank. Fig. 16.24
Mandrels between centres are used to represent simply a straight line passing between two
points. Its axis is made straight and exterior surface truly cylindrical having an accuracy
of 3 microns over 300 mm length. It also has four reference marks located in two
perpendicular axial planes and centres recessed for protection. Mandrels of large diameter
are made tubular to reduce weight, but should be rigid enough.
Fig. 16.25. Mandrel between centres.
The most widely used inspection tool during manufacture and acceptance tests of new
machine tools, and the repair of old ones, is the test mandrel, the quality of which
(especially as far as straightness and roundness are concerned) is of paramount importance
for accurate results. Two types of test mandrel are used:

a) Mandrels with a cylindrical measuring surface and a taper shank, which can be inserted
into the taper bore of the main spindle, as shown in Fig.15(b).
b) Cylindrical mandrel that can be held between centers Fig.15(c).
However, the “natural sag” i.e. the deflection caused by the weight of the mandrel should
be kept within permissible limits. Table below shows the permissible deflection of
cylindrical mandrels with 1000 mm in length and held between centers.
(d) Outside
diameter, mm
75 80 80 80 100 100 100 125 125 125
Bore diameter, mm solid solid 50 60 solid 60 80 solid 80 100
Deflection,  m 13.20 11.60 8.35 7.45 7.40 5.50 4.55 4.75 3.40 2.90
All mandrels must be hardened, stress-relieved and ground.
(c) Straight - edges and Squares
Straight - edges of cast iron or steel should be heavy, well ribbed and free of internal
stresses. Their bearing surfaces should be as wide as possible. The error at the top of a
standard square should be less than  0.01millimeter, and for a precision square less
than  0.005 millimeter.

triangular straight edge
(d) Spirit Levels
Spirit levels are used in the shape of a bubble tube, which is mounted on a cast-iron base.
The two main types are the horizontal, and the frame spirit level. Spirit levels used for high-
precision measurements (tolerances 0.02 to 0.04 millimeter per 1000 millimeters) should
have a sensitivity of about 0.03 to 0.05 millimeter per 1000 millimeters for each division.

1. Spirit levels which are too sensitive are difficult to bring to rest in a workshop in
which machines are running, while too low a sensitivity result in insufficient reading
accuracy.
2. It is often advisable to use a bridge piece, the feet of which are about 300 millimeters
apart. The spirit level can then be placed on the scraped surface of the bridge. This
method avoids errors which could be caused be irregular scarping of the surface to be
measured.
The sensitivity E of the spirit level is the movement of the bubble in millimeters, which
corresponds to a change in slope of 1 millimeter per 1000 millimeters.
The scale value „S’ indicates the change in slope (millimeter per meter) necessary for
producing a bubble movement of one division. If the distance between two divisions is
called „t’ then S = t/E.
The sensitivity of the level depends, only on the radius of curvature of the bubble tube „R‟,
and not on the length of its bearing surface, as shown in Fig2.

CHECKING SQUARENESS WITH SQUARE LEVEL
 Feeler gauge
A feeler gauge (also known as a thickness gauge) is an accurately manufactured strip of metal that is used to
determine the gap or clearance between two components.

Slip gauges are rectangular blocks of steel having a cross-section of about 30 by 10mm
Normal set
Special set

Depth gauge micrometers are used to measure the depth of blind holes, slots, key ways,
etc. •The spindle length can be changed to set the micrometer for the desired range of
measurement. •To read a depth gauge micrometer you must visualize the distance that
has been covered by the thimble.
2 - GEOMETRICAL TEST
Magnitude & Direction of Tolerances
In the test charts, the tolerances are given in three different ways, viz.:
a) As plus or minus tolerances (example: ± 0.03 millimeter per 1000 millimeters); With
plus or minus tolerances, the permissible error is allowed to occur in either direction
within the specified reference length. The total range of error is therefore double the
specified tolerance.
Example: A tolerance of ± 0.02 millimeter per 1000 millimeters means that, on a
reference length of 1000 millimeters, a deviation of 0.02 millimeter will be permissible
in both directions. The total range of error is double the amount of deviation, i.e. 0.04
millimeter per 1000 millimeters.
b) As tolerances without signs (example: 0.03 millimeters per 1000 millimeters);
Tolerances without signs include the total range of error measured on the reference
length, no matter in which direction the error appears.
c) As unilateral tolerances (example: 0 to 0.03 millimeter per 1000 millimeters); With
unilateral tolerances, the specified limits cover the total range of error across the total
reference length, the direction of error being of great importance and always stated in
the text of the respective test chart.
In detail, the tolerances are specified in the test charts and cover the following:
1- Straightness of Slideways and Flatness of Tables
These are tested by means of the spirit level. The tolerances are specified either: As plus
or minus tolerances, or as unilateral tolerances.
Example: Lathe bed straight or flat in the longitudinal direction (convex only) with
specified tolerance of 0 to 0.02 per 1000 millimeters.
The spirit level is allowed to deflect in one direction only, i.e. rising towards the
center (Fig.3) and within the limits of 0 to 0.02 as measured on a reference length of
1000 millimeters, with the result that the bed will be only convex.

The spirit level should be used on a bridge the feet of which are spaced about 300 mm.
The measurement is started at the center of the bed with zero reading as accurately as
possible. From this point the spirit level is moved to the right and to the left.
The slope has its largest permissible value if the spirit level indicates the maximum
reading 0.02 per 1000 millimeters (convex) along the left, and the opposite reading
along the right half of the bed. The largest permissible rise of a bed having a length of
1.5 meters, would be equal 0.75x0.02=0.015 millimeter.
2- Flatness of Slideways (Twist of Cross Rails and Arms)
These are tested by means of the spirit level. The tolerances are specified without signs.
In these cases, the spirit level is moved along the surface to be tested. Then, the range of
the largest readings taken in both directions indicates the error that must be within the
specified tolerance.
3- Alignment of Slideway and Axes, or Center Line Parallel or perpendicular to
each other
These are tested by means of the dial gauge or the spirit level. The tolerances are
specified in the form of either: tolerances without signs, or unilateral tolerances. In each
case the specified tolerance represents the total range within which the pointer is
allowed to deflect.
Example: Lathe spindle parallel with the bed in the vertical plane (spindle rising towards
the free end of test mandrel only) with specified tolerance of 0 to 0.02 millimeter per
300 millimeters (Fig.4) . When the dial gauge is being moved along the test mandrel, the
pointer is allowed to deviate in the stated direction only.
4- Alignment and True Running of Shafts
The tolerances for the true running of a shaft have to be taken as the admissible total
deviation (range of deviation) of the dial-gauge pointer.
Example: Testing lathe spindle for true running, with specified tolerance of 0.01
millimeter. Then, during one revolution of the spindle, the dial pointer is allowed to
deviate over range of 0.01 millimeter
5- Lead or Pitch Error of Lead-screws
The lead or pitch error is generally based on a reference length of 300 millimeters.
Beginning from any given initial position, the test nut is moved over a number of
threads corresponding to an accurate travel of 300 millimeters for metric or 12 inches for
Whitworth thread screws. The actual travel of the nut may be either lager or smaller than
300 millimeters and 12 inches, respectively, by not more than the specified permissible
lead error

Levelling of the Machine.
Before the various tests on any machine tool are carried out, it is very essential that it
should be installed in truly horizontal and vertical planes. In horizontal plane, both
longitudinal and transverse directions are equally important. If, say, any long lathe bed
is not installed truly horizontal the bed will undergo a deflection, thereby producing a
simple bend and undesirable stresses will be introduced. If the bed is not installed truly
horizontal in transverse direction, twist will be introduced. Thus the movement of the
saddal can‟t be in a straight line and true geometric cylinder can‟t be generated.
For proper installation and maintenance of its accuracy, a special concrete foundation
of considerable depth must be prepared. Also this must be insulated from the
surrounding floor by introducing some form of damping.
The level of the machine bed in longitudinal and transverse directions is generally
tested by a sensitive spirit level. The saddle is kept approximately in the centre of the
bed support
feet. The spirit level is then placed at a-a (Fig. 16.1), the ensure the level in the
longitudinal direction. It is then traversed along the length of bed and readings at
various places noted down. For test in transverse direction the level is placed on a
bridge piece to span the front and rear guideways and then reading is noted. It is

preferable to take two readings in lon-gitudinal and transverse directions
simultaneously so that the effect of adjustments in one direction may also be observed
in the other. The readings in transverse direction reveal any
Fig. 16.1
twist or wind in the bed. It may be noted that the two guideways may be perfectly
levelled in longitudinal direction, but might not be parallel to each other. This is
revealed by the test in transverse direction.
The straightness of bed in longitudinal direction for the long beds can also be
determined by other methods, e.g., using straight edges, autocollimators or by taut wire
method. But the test in transverse direction can be carried out only by spirit level.
It is desired that the front guideway should be convex only as the cutting forces and the
weight of carriage act downward on it. If the front guideways are concave, then the
effect will be comulative. The tendency of the carriage, under cutting forces is to lift
upwards from the rear and this is prevented by a gib placed underneath the guideways.
With the result, an upward force acts on the rear guideways ; which must, therefore, be
made concave.
Transverse level may be in any direction, but no twist can be tolerated.

3- DETAILS FOR TESTING CENTER LATHES
The geometrical test specifications of a machine tool are as follow;
A) The accuracy with which the machine has been manufactured.
A-1) Installation and leveling of the machine.
A-2) Tests the quality of slideways and locating surfaces.
A-3) Tests the accuracy of the main spindle and of its alignment relative to
other
important parts of the machine.
B) The accuracy of the workpieces produced on the machine.
C) Power requirements.
During the next sections, the test specifications of a center lathe are discussed.
A) The accuracy with which the machine has been manufactured
A-1) Installation and Leveling of the Lathe
Lathes are grouped in accordance with their uses, their sizes and the degree of
accuracy required from them. Experience shows that lathe beds wear more rapidly in
the center than at the ends. Moreover, the overhanging weights of the carriage and the
cutting resistance force the front shears (apron side) down and lift the rear shears.
Hence, the tolerance must be directed in opposition to this deformation. The front shears
are, therefore permitted to be arched or humped upwards (convex) only, while the rear
shears may be less convex or even slightly concave. To avoid the undesirable
combination of a maximum convex tolerance for the front shears and a maximum
concave tolerance for the rear shears, spirit level for twist in the transverse direction is

also carried out.
Measurements are carried out with the spirit level the sensitivity of which has to be in
accordance with the required accuracy.
A-1-1) Leveling the lathe Bed
1. Longitudinally.
2. Transversely.
During the test of short machine the carriage must be in the middle of the bed.
In the case of long beds with more than two legs it must be between two legs.
1. A spirit level (scale value 0.04/1000) is best put first on the rear slideway (i.e. the
slideway opposite the operators‟ side). This slideway is usually plane whilst the
front slideway may be intentionally convex. By checking positions „a‟ and „b‟ of
the rear slideway (Fig.5) and repeating the measurements for the front slideway
straightness of the beds can be determined.
2. It is advisable to check the leveling in the transverse direction simultaneously
with the previous step. This is done by means of a second spirit level alternatively
placed in position „c‟ and „d‟. A ± twist tolerance is not permissible because the
sliding surface of the carriage would not be properly supported by twisted
slideway.
TESTING OF CENTRE LATHE;
True Running of Locating Cylinder of Main Spindle.
Locating cylinder is provided to locate the chuck or face plate. However locating surface
can’t be threaded one as threads get worn out soon and thus introducing play in face
plate or chuck. Thus locating surface is cylindrical and this must run truly; for only then
the face plate etc., can run truly. The dial indicator is fixed to the carriage (or any other
fixed member) and the feeler of the indicator touches the locating surface. The surface
is then rotated on its axis and indictor should not show any movement of needle.

Fig. 16.2
16.3.3.
Axial Slip of Main Spindle and True Running of Shoulder Face of Spindle Nose.
Let us first distinguish between the axial play and the axial slip. Axial play means the
indispensable freedom of spindle movement in axial direction to prevent it from
seizing by heating. The spindle is supported between two bearings. Due to running of
spindle, there will be a rise in temperature and thermal expansion of spindle would be
there. If no axial play is allowed, it would try to bend. Thus there will be no adverse
effect of axial play if the direction of cutting forces remains same. If the direction of
cutting force changes, there would be some error introduced due to movement of
spindle axially in either direction. Under such conditions, therefore, it is advisable to cut
threads in one direction only.
Axial slip is defined as the axial spindle movement which
Fig. 16.3
follows the same pattern and is due to the manufacturing error. Actually this test is
meant to check this error. To test this the feeler of the dial gauge rests on the face of
the locating spindle shoulder and the dial gauge holder is clamped to the bed (Fig. 16.3).
The locating cylinder is then rotated and the change in reading noted down. The
readings are taken at two diametrically opposite points. The total error indicated by the
movement of the pointer includes three main sources of errors.
(i) Axial slip due to error in bearings supporting the locating shoulder, i.e., the bearings
are not perpendicular to the axis of rotation and due to it a point on the shoulder will
move axially in and out at diametrically opposite points.

(ii) Face of the locating shoulder not in a plane perpendicular to axis of rotation. (Hi)
Irregularities of front face.
Due to axial slip, in screw cutting, the pitch will not be uniform due to periodic
movement of the spindle. This, however, is not important while turning.
16.3.4.
True Running of Headstock Centre.
Headstock centre is live centre and the workpiece has to rotate with this centre. If it is
not true with the axis of movement of the spindle, eccentricity will be caused while
turning a work, as the job axis would not coincide with the axis of rotation of main
spindle. For testing this error, the feeler of the dial indicator is pressed perpendicular to
the taper surface of the centre (Fig. 16.4), and the spindle is rotated. The deviation
indicated by the dial gauge gives the trueness of the centre.
16.3.5.
Parallelism of the Main Spindle to Saddle Movement.
This has to be checked in both vertical and horizontal planes. In this we require the use
of mandrel. An important precaution in the use of mandrels and dial indicator is
mentioned here. The mandrel must be so proportioned that its overhang does not

produce appreciable sag, or else the sag must be calculated and accounted for. The
rigidity indicator set up is also very important and must be carefully watched. Otherwise
variations in readings are recorded by pointer may be solely due to deflection of the
indicator mounting in different positions and it becomes very difficult to detect and
isolate the spurious deflection from the true variations.
If axis of the spindle is not parallel to bed in horizontal direction, a tapered surface is
produced.
Any deviation from parallelism of spindle axis from bed in vertical axis will produce a
hyperboloid surface. For this test, a mandrel is fitted in the taper socket of the spindle.
Mandrel has a concentric taper shank which is close fit to the spindle nose taper. The
feeler of the dial indicator is pressed on the mandrel and the carriage is moved. The
indication in horizontal plane is given by dial (b) and in vertical plane by dial (a) (Fig.
16.5). In vertical plane the mandrel should be rising towards
Fig. 16.5
the free end in order to counteract the weight of mandrel and job. But for counter-
acting cutting forces, it should be lower towards free end. In horizontal plane, mandrel
should be inclined in a direction opposite to the direction of tool pressure.
16.3.6.
True running of taper socket in main spindle.
If the axis of tapered hole of the socket is not concentric with the main spindle axis,
eccentric and tapered jobs will be produced. To test it, a mandrel is fitted into the
tapered hole and readings at two extremes of the mandrel are taken by means of a dial
indicator as shown in Fie. 16.6.
Fig. 16.6
16.3.7.
Parallelism of tailstock guideways with the movement of carriage.

Sometimes the job is held between head-stock and tail stock centre for turning. In that
case the job axis must coincide with the tailstock centre. If the tailstock guideways are
not parallel with the carriage movement there will be some offset of the tailstock
centre and this results in taper turning.
To check the parallelism of tailstock mideways in both the planes i.e., horizontal and
vertical, a block is placed on the guideways as shown in Fig. 16.7 and the feeler of the
indicator is touched on the horizontal and vertical surfaces of the block. The dial
indicator is held in the carriage and carriage is moved. Any error is indicted by the
pointer of dial indicator.
16.3.8.
Movement of upper slide parallel with main spindle in vertical plane.
The dial indicator if fixed in the tool post. A mandrel is fitted in the spindle. The feeler
Fig. 16.7
of the dial gauge is pressed against the mandrel in vertical plane and the upper slide is
moved longitudinally. This error is not tested in horizontal plane because there is
swivelling arrangement for taper turning.
Parallelism of tailstock sleeve to saddle movement. If the tailstock sleeve is not parallel
to the saddle movement, the height of dead centre would vary as varying lengths of
sleeve are taken out. For the jobs held between two centres, it is necessary that the
central axis of the dead centre be coaxial with the job axis in both the planes. If it is not
so, the job
may be tilted up or down or in sideways due to the support of the dead centre. The test
is carried out by fixing the dial indicator on the tool post and pressing the plunger
against the sleeves first in vertical and then in horizontal plane (Fig. 16.9). The carriage
is moved along the full length of the sleeve and deviations as indicated by dial indicator
are noted down. Tailstock sleeve should be rising towards the free end in vertical plane
and should be inclined towards the tool pressure in horizontal plane.
16.3.10.
Parallelism of tailstock sleeve taper socket to saddle movement.

A mandrel is put in the sleeve socket. The dial gauge is fixed on the tool post and
plunger is pressed against the mandrel
and saddle is moved from one side to the other. This test is carried out in both the
horizontal and vertical planes.
16.3.11.
Alignment of both the centres in vertical plane.
Besides testing the parallelism of the axes individually (main spindle axis and tailstock
axis) it is-necessary to check the relative position of the axes also. Both the axes may be
parallel to carriage movement but they may not be coinciding. So when a job
Fig. 16.10
is fitted between the centres, the axis of the job will not be parallel to the carriage
movement. This test is to be carried out in vertical plane only. A mandrel is fitted
between the two centres and dial gauge on the carriage. The feeler of the dial gauge is
pressed against the mandrel in vertical plane as

Fig. 16.11
shown in Fig. 16.11 and the carriage is moved and the error noted down.
16.3.12.
Pitch accuracy of lead screw.
The accuracy of the threads cut on any machine depends upon the accuracy of its lead
screw. Thus it is very essential that pitch of the lead screw throughout its length be
uniform.
Test for this is performed by fixing a positive stop on the lathe bed. Against the stop,
the length bars and slip gauges can be located. An indicator is mounted on the carriage
and first it makes contact against the calculated length of slip gauges. The initial loading
of the dial gauge against the slip gauge is noted. The slip gauges are then removed and
the carriage is connected to the lead screw and lead screw is disconnected from the
gear train. An indexing arrangement is utilised for rotating the lead screw and lead
screw is given some revolutions so that distance travelled by carriage is equal to the
length of slip gauges. The reading of the dial indicator against the stop is noted down in
this position. It it is same as before, there is no error, otherwise it can be recorded. In
this method, care must be taken not to disturb the datum location when changing the
gauges for testing different pitch lengths.

A suitable method for recording the progressive and periodic errors is by using a
suitably divided scale, which is placed close to the line of centres. A microscope is rigidly
mounted on the carriage in a convenient position to note the readings on the scale.
16.3.13.
Alignment of lead screw bearings with respect to each other.
The alignment of the bearings decides the position of the lead screw. Misalignment of
lead screw i.e., it not being parallel to the bed in vertical plane or horizontal plane can
cause additional stresses due to bending, when carriage is moved. Due to it the lead
screw might get damaged and the precision of the machine is reduced :
Alignment of lead screw bearing with split nut in both the planes is also essential.
16.3.14.
Axial slip of lead screw.
The thrust face and the collars of the lead screw (or the abuttment collar and the thrust
bearing of the screw) must be exactly square to the screw axis, otherwise a cyclic
endwise movement is set up which is of the same nature as the axial slip in the main
spindle. Thus a periodic pitch error will be additional to any true periodic errors in the
pitch of the screw.
For testing the axial slip in lead screw, a ball is fitted in the end of lead screw and the
feeler of the dial gauge is pressed against the ball. The lead screw is rotated and
deviation, if any, in any direction is noted down (Fig. 16.12).
Fig. 16.12
16.3.15.
Practical tests.
These tests consist of the actual turning of some jobs on the machine. The job is made
under prescribed condition of cutting speed, feed and depth of cut. The test piece is
then measured for its geometry and surface finish and results compared with the
standards as prescribed by the manufacturer. These tests are designed to reveal the
combined effects of possible errors in alignment accuracy and the rigidity of machine.
The various jobs to be made as prescribed by M/s Hindustan Machine Tools are given
below.
(i) Working accuracy of machine of cylindrical turning (chucking). S’ should be as small
as possible.
Permissible error = 0.01 mm.
Swing over bed ‘mm* d mm / mm

upto 300 50 10
over 300 and upto 500 80 15
Over 500 120 20
(ii) Working accuracy of machine facing : Permissible error=0.02 mm over the diameter
of test workpiece, which is taken as 300 mm for swing over bed of upto 500 mm, and
400 mm for swing over 500 mm.
(Hi) Working accuracy of cylindrical turning, the job held between centres.
D = L/8 max.
L = half to full centre distance. Permissible error is 0.02 mm/300 mm
MILLING MACHINE:
The following tests can be conducted:
1. True running of the spindle:

2. Spindle alignment:
In this test dial indicator is mounted on one of the surfaces whose alignment is to be tested
with another surface. In case of a horizontal milling machine the testing of the alignment
between the spindle and the over arm support can be done as shown in fig.
The dial indicator is mounted on the spindle while a test mandrel is mounted in the over
arm support with the plunger of the dial indicator resting on the cylindrical surface of the
test mandrel. The spindle is rotated and readings are taken when it is at different positions
on the periphery of the test mandrel. The test may be conducted at two extreme ends of
the mandrel.
Parallelism between the table and the spindle axis shown in fig. A test mandrel 300mm
long is mounted in the spindle axis and the dial indicator is mounted on the table. The
reading of the dial indicator is taken at the two extreme positions with out the table
movement.

Other tests that can be conducted are:
 Parallelism between the spindle axis and the transverse movement of the table.
 Perpendicularity between the spindle and the vertical column ways.
RADIAL DRILLING MACHINE:
Tests that can be conducted on Drilling Machine are:
1. True running of the spindle.
2. Perpendicularity between the spindle and the base plate.

3. Perpendicularity between the feed movement and the base plate.

UNIT V
Condition Based Maintenance

CONDITIONAL BASED MAINTENANCE
1. What is conditional based maintenance? What are the different types of condition
based maintenance?
Condition Monitoring is the process of monitoring one or more specific Condition
Parameters in Machinery at regular intervals, such that a significant change becomes
indicative of a developing failure to identify impeding damages. It is a major activity of
Condition Based Predictive Maintenance.
The use of Condition Monitoring allows Maintenance to measure the deterioration of the
Machine Condition well in advance so that appropriate Correction Activity may be
scheduled to avoid the consequences of failure, before the failure occurs.
Types of condition based maintenance
Condition monitoring fills into two distinct classes
(a) Monitoring which can be carried out without interruptions to the operation of
the unit and (b) monitoring which requires the shut down the unit or at least the release
of the unit from its prime duty .

How does condition based maintenance differ from the other maintenance actions?
Preventative Maintenance Condition based maintenance
Preventative Maintenance occurs when
a machine or parts of a machine are
overhauled on a regular basis
regardless of the condition of the parts.
While better than run to failure
maintenance, preventive maintenance
results in excessive downtime due to
unnecessary overhauls and in excessive
costs due to replacing good parts along
with worn parts
Condition Monitoring is the process of
determining the condition of machinery
as it operates. If a problem is indicated,
condition-monitoring equipment
provides information useful in
determining what the problem is, and
more importantly what caused the
problem. This allows us to schedule
efficient repairs of specific problems
prior to machinery failure.
Benefits of condition Monitoring
Extend Bearing Service Life:
Condition monitoring is an essential element in detecting and identifying bearing
defects. Once a symptom is detected, the cause can be identified and corrected.
When found early enough, cost savings can be realized by repairing rather than
replacing a bearing impacted by misalignment, lubrication or other damage
conditions.
Maximise machine productivity:
Through effective condition monitoring one can virtually eliminate plant downtime
due to unexpected machine failure.
Minimise unscheduled downtime:
Allows you to plan repair during non peak production hours.
Safely extend overhaul intervals: Condition monitoring lets you schedule maintenance
on a needs only basis.
Minimise the numbers of open, inspect and repair if necessary overhaul routines:
Condition monitoring directs repair and overhaul actions at known problems.
Improve repair time: Because you can plan a machine's maintenance, the actual
repair/maintenance work is faster and smoother.
ON LOAD CONDITION MONITORING TECHNIQUES;
 Temperature monitoring

 Lubrication monitoring
 Leak detection
 Vibration monitoring
 Noise monitoring
 Corrosion monitoring
OFF LOAD CONDITION MONITORING TECHNIQUES;
 Crack detection
 Leak detection
 Corrosion monitoring
 Vibration monitoring
 Lubrication monitoring
 Thermal monitoring
How does Condition Monitoring Work;
Condition Monitoring is the process of measuring the physical characteristics of a
machine (e.g. vibration, bearing condition, temperature) while it is operating. A
change in a machine's physical characteristics indicates a change in its operating
condition. A wide range of hardware and software designed to assist an operator in
identifiing and quantifying these changes are available.
Hardware
To perform these measurements, sensors are placed at strategic points on the machinery
to monitor the machine's condition.
A sensor is a device which senses and converts energy (mechanical, thermal or
electromagnetic) into an electrical signal that can be measured, recorded, displayed
and analysed
Methodology;

Software
Measured machinery parameters can be uploaded from condition monitoring
equipment to condition monitorng software for long term storage and analysis of
data. Condition monitoring softwares most powerful feature is its ability to plot
measurement data.
Trend plots show how a machine's condition changes over a specific time period.
Trending a machine's condition allows you to easily compare its current measured value
to previous values, indicating a change in machine condition. These plots allow for early
detection of problems (before they become critical) and are used to schedule repair for
problem machinery or components.
Some condition monitoring software produces diagnostic plots (FFT spectra, time
waveforms) that indicate the cause of machinery problems. The way in which a
machine's operating parameters change can indicate what is causing the damage.

LUBRICATION MONITORING;
Oil analysis is a quick, nondestructive way to gauge the health of an engine by looking at
what's in the oil. It is as like as medical blood test, where we can know about our
diseases from our blood
Lubricant Monitoring:
It is not possible to examine the working a part of the complexed machines on load not
is converted to strip down the machine. However the oil which circulates through the
machine carries with it evidence of the condition of parts encountered examination of the
oil and any particles it has carried with it allow monitoring of the machine on load of it at
shut down. Numbers of techniques are applied.
Lubricant monitoring techniques:
Lubricant examination can over the debris in suspension or the condition of the oil.
Debris deposited: The larger particles carried along the lubricant can be collected on-
load in filters or magnetic collectors.
1)Filters: The rate of build up of debris on a filter ion readily monitored on load by
measuring the pressure drop across the filter removal of the filter which can be carried
out on-load if the machine is suitably designed, and subsequent examination of the debris
under the scope to establish size and shape or with a spectrograph to determine the
element of content provinces the more sophisticated method of detecting a significant
change in any component visited by the lubricant. It is good practice to store the debris
on an adhesive substrate the part of the routine condition records.
2)Magnetic debris collectors are a convention way of the capturing ferrous comforts
Magnetic plugs can be designed to be readily removed on-load and one prosperity
magnetic debris collector can be monitored without giving an indication of debris built-
up.
Debris in suspend: The smaller particle collected by the lubricant will remain in
the suspension gives the earliest warning of component damage quantities loss of
lubricant during the running and the dilute effect of tapping-up with demerits free fresh
oil.
Oil Analysis (Ferrography)

Monitoring oil condition warns of an increase in foreign substances, such as water,
which can degrade the lubricating properties of the oil and cause bearing failures.
It also detects the presence of metallic particles carried into the oil stream. These
metallic particles are analysed to determine which part of the machine is wearing
and how fast.
All Test of Your Oil
1.Elemental Analysis (Spectral Analysis)
 2.Particle count,
 3.Particle Shape Analysis
 4.Parts per million (PPM) distribution ,
 5.ISO codes and ASTM standard
 6.Ferrography
 7.Oil Chemistry ( Dielectric, TBN, TAN, Oxydation, Nitration, Sulfations,
Glycol, Soot etc.)
 8.Water-in-oil,
 9.Viscosity
 10.Wear Debris Analysis (WDA)
Particle Count and Shape Analysis

On load thermal monitoring;
Temperature measurement is a useful indicator of mechanical condition or the load
applied to a specific component such as a bearing.
As a bearing fails friction causes its temperature to rise . Installing thermocouple sensors
in the housing of a bearing and measuring temperature change within the bearing or
lubricant allows you to recognise problems early and to schedule maintenance before a
more serious and expensive failure occurs
The temperature sensors include contact thermometers, thermocouples,
thermostats and temperature chalks and paints and infrared detectors. Two examples
where temperature monitoring can give warning of mechanical trouble are lubricant
Temperature of bearing outlets and engine cooling water maintenance. This is a general
purpose technique.
Faults That can be detected by thermal monitoring.
1) Bearing damage
2) Failure of a coolant

3) Incorrect heat generation
4) Built-up of unwanted materials
5) Damaging to insulating materials
6) Faults in electrical components
THERMAL MONITORING DEVICES;
1. INFRARED THERMOMETER
Thermography
Infra Red Thermography is a technique for producing a visible image of invisible (to our
eyes). Infra red radiation emitted by objects due to their thermal conditions. The
amount of radiation emitted by an object increases with temperature; therefore,
thermography allows one to see variations in temperature.
Why Thermography?
• Non Contact
• Rapid Scanning
• Data can be recorded in differing formats
• Images produced are comprehensive & reliable
Advantages
• Non Contact
• Non Intrusive
• Can work at a distance

• Fast and Reliable
• Portable
• Convincing Results
Electrical
• Switch Gear
• Fuse boxes
• Cable runs
• Electrical connectors
• Insulation
• Transformers

•
Electric Motor Bearing
various types of contact sensors used for thermal monitoring
Devices, which take up the temperature of the body which they are in contact and
then transmit information on their own. Temperature are most commonly used they can
provided temperature indicator locally and remotely or control some function from the
temperature. Both accuracy and response time of contact sensors affected by attachment
Method. Good thermal contact is important. This is used provided for surface
measurement by embedding or welding the sensor to the body. Response times are
related to the volume of the sensor so the smaller devices are more suitable if
temperature very rapidly.

 Liquid expansion sensors
 Bimetallic expansion sensors
 Thermocouple sensors
 Resistance sensors
Liquid expansion sensors: Liquid expansion sensors are the most commonly used
devices mercury or alcohol in gals thermometers is accurate but fragile device liquid in
metal sensors. All these sensors are large (up to 9 *13 mm) and are therefore unreadable
for surface measurement.
various types of non-contact temperature sensors used for thermal monitoring;
Non-contact sensor energy radiation from body carries with the absolute
temperature of the body‟s‟ and the emissive o the radiation surface, „a‟ according to the
Stefan-bolt Mann law.
This enables surface temperature to be detected from the energy radiated without
any direct current.
The various types of non contact sensors are
 Optical pyrometer
 Radiation pyrometer
 The seaming infrared camera
on load leak detection monitoring;
A number of leave detecting techniques are available including the soap and water
method. The use of properties preparation can make this method leaks a lower 1ml./s.
one
Powerful technique is ultrasonic detection. When a fluid is forced through a leak under
internal or external pressure sound is generated in the frequencies range 40-80 kHz. The
ultrasonic leak detector identifies this very high frequency which easily separated from
the lower frequencies of ordinances machine noise a typical detector can sense the
pressure of 50mm dia hole in a unit containing a pressure of 0.1 bar at say 10m distance,
or expressed ina flow rate, 10m ½ halogen testing where a search gas e.g. Action 12,18
inserted into the system under the presence of the search gas outside the system indicates
a leak can be used to detect leakage test as low a 1 pl/m. unfortunately, it is common to
find sufficient halogens free around a plant to mask the effect of the leak.

Explain the following crack detection techniques?
(i) Ultrasonic testing (ii) Radiographic examination (iii) Flux testing of
magnetic materials.
Ultrasonic testing: Ultra sound generated the surface of the component will be reflected
at any surfaces in the two path of the sound whether they are manufactured or faults the
time delay between generation of the sound pulse and detection of the reflection is
displayed to give a measure of the distance the surface from the force. The generation
and propagation of ultra sound in the frequency range 0.25 – 10 MHz. is very directional
of so suitable orientation of the transmitter enables imperfections such as crack as be
displayed from out side of the surfaces of the component the technique has been
developed to high degree of sophistication. Cracks can be detected by examination from
one end and a suitable step the range of operation is 5 – 15 mm in steel.
Radio Graphic Examination: Imperfections can be photographed using either x-rays or
gamma rays from radio active source not special photographic material a change in
thickness of 2% can be detected member thickness normally limited to 50mm. The
method usually requires dismantling of the unit being examined and raised problems
associated with processes of personal.
Flux detection of magnetic materials: A crack as small as crosses the path of magnetic
field which is included locally into the surface of the material using U-type magnet
causes the magnetic fields and hence the crack is revealed using magnetic powder
VIBRATION MONITORING
OFF-LOAD VIBRATION MONITORING;
The response of a unit to vibration forcing can reveal much information. One of
th4 most common vibration tests for rotating machines is the run-down test, which takes
advantages of system resonance‟s to magnify vibrations.
ON LOAD VIBRATION MONITORING;
Vibration;
It is the response of a system to an internal or external force which causes the system to
oscillate.

Vibration can be used to detect a wide range of faults in machinery. This method
has wider application than any other monitoring technique. For example vibration
measurements made near the bearings of a machine can detect and distinguish between
in balance shaft misalignment, damaged bearings, damaged gears and other
transmissions components, mechanical looseness cavitations or stall and a number of
either faults. Although the basic methods of monitoring are straight forward of any case
very much more information can be extracted from the measurements if modern signal
processing techniques area plied. This is field which is currently receiving much
attention and Consequently understanding and practical experience are improving rapidly
vibration monitoring is examined in detail.
SKF MACHINE CONDITION ADVISOR
checking vibration using vibrometer

Monitoring an electric motor for temperature and vibration analysis
Procedure:
Monitoring an electric motor for temperature and vibrationanalysis
• Step 1: Mark the points of monitoring as shown in pictureabove
• Step 2: Using a condition advisor tool place the tool on thegreen mark-ups to
take reading of velocity(mm/s)
• Step 3: Using an infrared thermometer aim the red light from the tool to the
orange mark-up for readings of temperature in degrees (ºc)
Step 4: Capture the readings in table form in accordance to the colour sequence
• Step5 : Repeat step 1 to 5 until you have 3 tables for each machine monitoring.
• Step 6:Draw a temperature VS velocity graph to analyse the results.

Machinerysignaturesinunbalancedshaft;

Total Signal Monitoring In Vibration;
This is the most string forward method resulting in only location. The total signal,
product up by the transducer is employed time arranged and drop layer on a meter or
recorded for use the schematic of a typical act of equipment is show to gauge such
equipment is compact being typically contained in box of about 200mm cube and
weighing only 2.5 kg. brook describes the application of typical portable equipment to
signal monitoring. The vibration reading to obtain in potted on the machine record,
whole should be dearly laid out in tabular form or alternately in graphical farm. A change
is the Measurement between inspections indicates that some machines change may have
occurred untilled experience with the machine change may have accrued. Until
experience with the machine has been built up it is very difficult to provide whether a
particular change is signing ward.
peak signal monitoring in vibration;
Figure of merit some types of mauler migrated such as bearing failure cause
impulses to be transmitted to the transducer and pitted have in a roller bearing. For
example emits and impulse such time a ball comes in contact with pit. Though this
caused an increase in the vibration control, which is a measure of the amount of impulse
generating damage is called the figure of merit the normal vibration instruments. It is not
possible to register peak values of vibrations contain transients of duration less than
10ms. However this presents no significant restriction for vibration monitoring. This
measurement of peak vibration barrels is an additional means of detection damage.
shock pulse monitoring in vibration and noise;
Impulses emanating from impacts between damaged surface described in the
shock pulse monitoring method which was developed initially by S.P.M Instruments Ltd
of Sweden.
The impacts generate shock pulse waves through the machine body and they are
detected using a pies electric transducer similar to an accelerometer except that it is
termed mechanically and electrically to have a resonant frequency at 32 KHz. The
transducer resonant of this frequency in response in each pulse. The signal generated by
the transducer is filtered to separate the resonant frequency from the ground of vibrations
the magnitude of each resonance is held for an sufficient time for read on meter, by this
method and the peak amplitude of the signal from a transducer to the magnitude.
On Load Corrosion Monitoring;
Corrosion rate can be determined more accurately placing coupons. Ultrasonic
measurement will detect the change in dimensions due to corrosion a new technique for
remote measurement of corrosion thickness. Thickness can found by a pulsed laser to

drill. A fixed depth per pulse and a light detector to indicate when the hole has reached
the bright metal
Off Load Corrosion Monitoring;
Corrosion can be determined m0ore accurately by placing coupons is the plant and
removing them for weighing at intervals. Ultrasonic measurements will detect the change
in dimensions due to corrosion. A new technique for remote measurement of corrosion
thickness employee a pulsed laser to drill. A fixed depth per pulse and a light detector to
indicate when the hole has reached the bright metal.
10 MARK QUESTIONS
1. What are the different types of on load conditions based maintenance explain anyone of the
following?
2. Explain the on load vibration monitoring with example
3. Explain on load thermal heat monitoring with example
4. Explain on load lubricant monitoring with example
5. Explain on load leak detection monitoring with example
6. Explain on load vibration monitoring with example
7. Explain on load noise monitoring
8. Explain load corrosion monitoring with example
9. Explain the crack detection monitoring

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