Metrology lab manual for marine engineering

Metrology laboratory
SYLLABUS OF METROLOGYLAB PRESCRIBED BYJNTUK
Note: MINIMUM OF 8 EXPERIMENTS TO BE DONE
1. Measurement of lengths, heights, diameters by vernier calipers, micrometers etc.
2. Measurement of bores by internal micrometers and dial bore indicators.
3. Use of gear tooth vernier caliper for tooth thickness inspection and flange micro meter
for checking the chordal thickness of spur gear.
4. Machine tool alignment test on the lathe.
5. Machine tool alignment test on drilling machine.
6. Machine tool alignment test on milling machine.
7. Angle and taper measurements with bevel protractor, Sine bars, rollers and balls.
8. Use of spirit level in finding the straightness of a bed and flatness of a surface.
9. Thread inspection with two wire/ three wire method & tool makers microscope.
10. Surface roughness measurement with roughness measuring instrument.
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LIST OF EXPERIMENTS
1. Calibration of Precision Measuring Instruments & Measurement of lengths,
heights, diameters by vernier calipers, micrometers etc
2. Measurement of Bore Using Inside Micrometer & Dial Bore Indicator
3. Angle Measurement Using Bevel Protactor & Sine Bar
4. Measurement of Gear Tooth Thickness By Gear Tooth Vernier Calliper
5. Measurement of Screw & Gear Terminology Using Tool-Maker’s Microscope
6. Surface Roughness Measurement
7. Machine Tool Alignment Tests on Lathe
8. Use of spirit level in finding the straightness of a bed and flatness of a surface.
9. Vibration Measurement of Machines (Additional Experiment)
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CALIBRATION OF PRECISION MEASURING INSTRUMENTS
AIM:
To calibrate Vernier calipers, vernier height gauge & Micrometer and to measure
lengths, heights and diameters by these instruments.
APPARATUS :
Vernier callipers, vernier height gauge, Micrometer, Slip gauges & Surface plate,
OBJECTIVES:
1. To know about calibration, precision & accuracy
2. To know about least count of any precise instrument.
3. To know the difference between line standard and end standard
SPECIFICATION:
Vernier calipers: Range: L. C:
vernier height gauge: Range: L. C:
Micrometer: Range: L. C:
THEORY:
CALIBRATION:
It is the process of determining true values by comparison with an accurate standard. It is
the process of framing the scale of the instrument by applying some standards. Calibration is a
pre measurement process, generally carried out by manufacturers. During the course of use, due
to friction and lack of proper maintenance, errors enter into the instruments and these should be
properly accounted for when taking measurements. If the accuracy is to be maintained,
periodical calibration is essential.
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1) VERNIER CALIPER:
PRINCIPLE
The Vernier caliper has one ‘L’ shaped frame with a fixed jaw on which Vernier scale is
attached. The principle of Vernier is that when two scales or divisions slightly different in size
are used, the difference between them can be utilized to enhance the accuracy of measurement.
LEAST COUNT
Least Count is the smallest length that can be measured accurately and is equal to the
difference between a main scale division and a Vernier scale division.
LEAST COUNT = 1 MSD – 1 VSD (OR) = 1MSD/no of vernier scale divisons
Fig 1. Vernier Callipers
1. Outside jaws: used to measure external diameter or width of an object
2. Inside jaws: used to measure internal diameter of an object
3. Depth probe: used to measure depths of an object or a hole
4. Main scale: gives measurements of up to one decimal place (in cm).
5. Main scale: gives measurements in fraction(in inch)
6. Vernier gives measurements up to two decimal places(in cm)
7. Vernier gives measurements in fraction(in inch)
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USES:
It is used to measure the external diameter, the internal diameter and the length of the
given specimen.
2) MICROMETER:
PRINCIPLE
Micrometer works on the principle of screw and nut. A screw moves when it is rotated
through a nut. The relation between number of rotations and the distance moved is used for
measuring the dimensions.
LEAST COUNT
The micrometer essentially consists of U shaped frame. The component to be measured is
held between fixed anvil and movable spindle. The spindle can be moved with the help of
thimble. There are two scales on micrometer, a main scale and a circular scale. The barrel is
graduated in unit of 0.5 mm whereas thimble has got 50 divisions around its periphery. One
revolution of thimble moves 0.5 mm which is the lead of the screw and also the pitch.
Least Count = Pitch of the spindle screw ÷ Number of divisions on the thimble
Fig 2. Micrometer Screw Gauge
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USES:
1. Outside micrometer is used to measure the diameter of solid cylinder.
2. Inside micrometer is used to measure the internal diameters of hollow cylinders and
spheres.
3) VERNIER HEIGHT GAUGE
Vernier height gauge is similar to vernier caliper but in this instrument the
graduated bar is held in a vertical position and it is used in conjunction with a surface
plate.
The vernier height gauge is designed for accurate measurements and marking of
vertical heights above a surface plate datum. It can also be used to measure differences in
heights by taking the vernier scale readings at each height and determining the difference
by subtraction. The vernier height gauge is read in the same way as vernier calipers.
Fig 3. Vernier Height Gauge
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4) SLIP GAUGES:
They are rectangular blocks hardened and carefully stabilized. The surfaces are highly
polished to enhance wringing. It is used as a reference standard for transferring the dimensions of
unit of length from primary standard. It is generally made up of high carbon, high chromium
hardened steel.
USES:
These are accurate and used as comparator.
5) SURFACE PLATE:
The foundation of all geometric accuracy and indeed of all dimensional measurement
in workshop is surface plate. It is a flat smooth surface sometimes with leveling screws at the
bottom.
USES:
It is used as a base in all measurements.
PROCEDURE FOR CALIBRATION:
1.) The range of the instruments is noted down.
2.) Within that range, slip gauges are selected in steps of 2mm .
3.) The measuring instrument is placed on the surface plate and set for zero and the slip gauges are
placed one by one between the measuring points (jaws of the instruments.)
4.) The slip gauge (actual) readings and the corresponding (observed) readings in the measuring
instruments are noted down and tabulated.
CALIBRATION OF VERNIER CALLIPERS
S.No Slip M.S.R VC LC Measured Error
Gauge reading ( Measured
Reading MSR+(VCXL.C) reading- Actual)
(mm)
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MEASUREMENT OF LENGTH BY VERNIER CALLIPERS
S.No M.S.R VC LC Measured Error Final
reading Reading
MSR+(VCXL.C)
Average reading
CALIBRATION OF MICROMETER
S.No Slip M.S.R C.S.C LC Measured reading Error
Gauge MSR+(CSCXL.C) ( Measured
Reading reading- Actual)
(Actual)
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MEASUREMENT OF DIAMETER BY MICROMETER
S.No M.S.R CSC LC Measured Error Final Reading
reading
MSR+(CSCXL.C)
Average reading
CALIBRATION OF VERNIER HEIGHT GAUGE
S.No Slip M.S.R VC LC Measured Error
Gauge reading ( Measured
Reading MSR+(VCXL.C) reading- Actual)
(Actual)
Mm
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MEASUREMENT OF HEIGHT BY VERNIER HEIGHT GAUGE
S.No M.S.R VC LC Measured Error Final Reading
reading
MSR+(VCXL.C)
Average reading
GRAPHS:
Calibration graphs are then drawn for all measuring instruments between
1.) Actual value and Observed value.
ANALYSIS:
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RESULT:
CONCLUSION:
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VIVA-VOCE:
1. What is measurement?
2. Define the term calibration.
3. Define precision and accuracy.
4. List the various linear measuring instruments.
5. What is sensitivity?
6. What is meant by least count of an instrument?
7. Define Zero reading of a Micrometer?
8. Specify the term Backlash of a micrometer?
9. What is the principle of vernier calipers and Micrometer screw gauge?
10. What is the difference between line and end standard?
11. What is the function and principle of a ratchet drive in case of a micrometer?
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MEASUREMENTOF BORE USING INSIDE MICROMETER& DIAL
BORE INDICATOR
AIM:
To measure the bore diameter using inside micrometer and dial bore indicator
APPARATUS:
Inside micrometer , dial bore indicator, scale, vernier calipers
OBJECTIVES:
1. To know the working principle of inside micrometer
2. To know the working principle of dial bore gauge
3. To know about different types of gauges
THEORY:
INSIDE MICROMETER CALIPERS
The inside micrometer is intended for internal measurement to an accuracy of 0.01mm. In
principle, it is similar to an external micrometer and is used for measuring holes in the range of
5-30mm.
Fig 1. Inside Micrometer Calipers
The instrument shown in fig. 1 comprises measuring tips constituted by jaws. One of the
jaws is held stationary and the second one moves by the movement of thimble. A lock nut is
provided for locking of spindle. It is also provided with a ratchet stop for applying constant
force.
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DIAL BORE GAUGE
The instrument basically consists of a hollow tube into which is contained a lever pivoted
about its intermediate support. One end of the lever is linked to the movable contact point of the
instrument and the other end of the lever actuates the dial indicator. Interchangeable rods and
washers can be used in order to broaden the range of measurement.
Fig 2. Dial bore gauge
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Fig 3. Set of Interchangeable rods
PROCEDURE:
INSIDE MICROMETER CALIPERS
1. First the diameter of the bore is measured approximately by a scale.
2. The micrometer is then adjusted at a dimension slightly smaller than the diameter of the
bore.
3. One tip is held against the bore and the other is adjusted by moving the thimble till the
correct feel is sensed.
4. The micrometer is then removed and reading is taken.
S.No M.S.R(a) THIMBLE TOTAL READING
READING(b) a + (LC * b)
Average reading
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DIAL BORE GAUGE
1. For the required measuring dimension select the appropriate interchangeable rod and/or
washers and set them on the main unit.
2. Diameter is obtained automatically from the guide. To adjust the instrument to measure
diameter , search for a position where the bore gauge reading is maximized by tilting the
bore gauge back and forth .
3. The indicator reading is recorded to get the required diameter.
S.No BORE GAUGE READING
Average Bore Diameter =
PRECAUT IONS:
1. One contact surface must always be moved sideways in order to ensure that
diameter is being measured and not chord.
ANALYSIS:
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RESULT:
1. Bore diameter measured by using inside micrometer =
2. Bore diameter indicated by dial bore indicator =
CONCLUSION:
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VIVA-VOCE:
1. What is the working principle of inside micrometer?
2. What is the working principle of dial bore gauge?
3. What is a comparator?
4. What are the limitations of comparators?
5. Name the three materials commonly used for gauges.
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ANGLE MEASUREMENTUSING BEVEL PROTACTOR& SINE BAR
AIM:
To determine the angle of the given wedge using Since bar & Bevel Protractor
APPARATUS:
1. Sine bar 2. Dial Gauge 3. Slip gauges 4. Bevel Protractor. 5. Surface plate
OBJECTIVES:
1. To know the working principle of sine bar & bevel protractor
2. To know about the wringing of slip gauges
THEORY:
SINE BAR:
It is a simple instrument used for setting and measuring angles. It consists of a flat bar
and two rollers attached to the bar at each end. The axes of these rollers are parallel to each other
and also to the upper surface of the sine bar. The distance between the centres of the rollers is
fixed for a particular sine bar and the same is always written on the bar.
Fig 1. Sine Bar
The principle of the sine bar is shown in figure 2. The sine bar is always used in conjunction with
a true surface (surface plate). If ‘h’ is the height of the combination slip gauges and ‘l’ is the
distance between the roller centres , then the angle of the setting is given as,
θ =Sin-1(h/l)
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The angle to be measured is determined by an indirect method, as a function of sine. For this
reason, device is called as ‘sine bar’.
Fig 2. Measurement of parallelism of the upper surface of the workpiece using dial gauge
PROCEDURE:
1. For measuring unknown angle it is necessary to first find the angle approximately with
the help of a bevel protractor.
2. The sine bar is then set up at that nominal(approximate) angle on a surface plate by suitable
combination of slip gauges.
3. The component to be checked is placed over the surface of the sine bar.(if necessary the
component may be clamped with the angle plate)
4. The dial gauge is then set at one end of the work and moved along the upper surface of the
component.
5. If there is any variation in parallelism of the upper surface of the component and the surface
plate, it is indicated by the dial gauge.
6. The combination of the slip gauges is so adjusted that the upper surface is truly parallel
with the surface plate.
7. Than note down the height of the combination of slip gauges.
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8. Then angle of the component is Calculated by the relation , θ =Sin-1(h/l)
9. Repeat the procedure 3 or 4 times and take the average.
OBSERVATIONS:
S. No Height of Slip Gauge Length of The Sine Bar (l) Angle
Blocks (h)
Average Reading:
BEVEL PROTRACTOR:
The simple bevel protractor can be extended in its accuracy by the application of a
circular vernier scale and this instrument is known as vernier bevel protractor. It consists of a
base plate attached to the main body and an adjustable blade which is attached to the circular
plate containing vernier scale. The adjustable blade can be set at any angle with the base plate
and can be locked.
The main scale on the disc is graduated in degrees. The vernier scale has 12 divisons on
each side of the center zero. These are marked 0-60 minutes of arc, so that each divison equals
1/12 of 60, that is 5 minutes of arc. These 12 divisons occupy the same space as 23° on the main
scale. Therefore each divison of the vernier is equal to 1/12 of 23° or 5 minutes of arc. Thus the
least count of the instrument is 5 minutes.
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Fig 3. Bevel Protractor.
The graduations are read to the right and left on both the main scale and the vernier scale.
When the main scale is read to the right of the zero of the main scale, the vernier is also read to
the right of zero of the vernier scale.
Fig 4. Enlarged View of Vernier Scale of Bevel Protractor
The reading shown above gives
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a) The largest whole degree on the main scale indicated by the vernier zero divison ie
28°
b) The reading on the vernier scale in line with a main scale divison is 3*5ꞌ = 15ꞌ
c) Hence the vernier bevel protractor reads 28° + 15 ꞌ = 28°15 ꞌ
OBSERVATIONS:
Least count of Bevel Protractor =
S.No Main scale Vernier Coincidence(VC) Total Reading
reading(MSR) MSR + (VC*LC)
1
2
3
Average Reading:
PRECAUTIONS:
1. The sine bar should not be used for angle greater than 60° because any possible error
in construction is accentuated at this limit.
2. A compound angle should not be formed by mis-aligning of work piece with the sine bar.
This can be avoided by attaching the sine bar and work against an angle plate.
3. As far as possible longer sine bar should be used since using longer sine bars reduces many
errors.
ANALYSIS:
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RESULT:
The angle of the given specimen measured with the sine bar is…………….
The angle of the given specimen measured with the Bevel Protractor is………….
CONCLUSION:
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VIVA-VOCE:
1. List various angular measuring instruments.
2. What are the sources of errors in sine bars?
3. What is the working principle of sine bar & bevel protractor
4. What are the advantages of slip gauges?
5. Why sine bar is not preferred for generating angles larger than 45°.
6. What is least count of bevel protractor?
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MEASUREMENTOF GEAR TOOTHTHICKNESS BY GEAR TOOTH
VERNIER CALLIPER
AIM:
1. To determine the width of the tooth at pitch circle.
2. To determine the height of the tooth above pitch circle.
3. To check the width of the tooth at pitch circle using gear tooth vernier caliper
APPARATUS :
Gear tooth Vernier caliper, Spur gear of known module, Surface plate
OBJECTIVES:
1.To know about gear terminology
2. To find the chordal thickness of the gear tooth by theoretical methods
THEORY:
Brief description of different characteristics of measuring of tooth thickness by gear tooth
vernier is given. It consists of a horizontal and a vertical vernier scale. It is based on the principle
of vernier scale. The thickness of a tooth at pitch line and the addendum is measured by an
independent tongue each of which is adjusted independently by adjusting the slide screws on
graduated beams.
TERMINOLOGY OF GEAR TOOTH
(i) Pitch circle diameter (PCD): It is the diameter of a circle which by pure rolling action would
produce the same motion on the toothed gear wheel. It is equal to D = (T X OD)/ (T+2) where
OD = outside diameter T = number of teeth
(ii) MODULE: It is defined as the length of the pitch circle diameter per tooth. Module m=D/T
and is expressed in mm.
(iii) CIRCULAR PITCH (CP): It is the arc distance measured around the pitch circle from the
flank of one tooth to a similar flank in the next tooth and is given by CP==ΠD/T=Πm.
(iv) ADDENDUM: This is the radial distance from the pitch circle to the tip of the tooth. It is
equal to one module.
(v)Clearance: This is the radial distance from the tip of a tooth to the bottom of the mating tooth
space when the teeth are symmetrically engaged. Its standard value is 0.157m or 0.25m.
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(vi) DEDENDUM: This is the radial distance from the pitch circle to the bottom of tooth space.
Dedendum = Addendum +Clearance = m +0.157m =1 .157m.=1.25m (metric gearing system)
vii) TOOTH THICKNESS: This is the arc distance measured along the pitchcircle from the
intercepts with one flank to the intercepts with the other flank of the same tooth. It is given by
mT Sin(90/T)
Fig 1. Vernier Gear Tooth Callipers
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Fig 2. GEAR TOOTH DETAILS
PROCEDURE:
For finding PCD, module, addendum, dedendum and clearance:
1. First find the blank diameter, OD by a vernier calliper and also count the number of teeth T of
the spur gear.
2. Next calculate pitch circle diameter D=(TxOD)/(T+2)
3. Find addendum, clearance, pitch, module and dedendum as per the
formulae given in the theory.
FOR CHORDAL TOOTH THICKNESS (using gear tooth calliper):
1. Set the chordal depth (addendum) on the vertical slide of the gear tooth vernier and then
insert the jaws of the instrument on the tooth to be measured.
2. Adjust the horizontal vernier slide by the fine adjusting screw so that the jaws just touch
the tooth.
3. Read the horizontal vernier slide and note the reading. It gives the chordal thickness of tooth.
4. Repeat the observations for the different teeth.
5. Compare the values of different characteristics with the standard value and set the
percentage error.
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OBSERVATION:
1. Least count of caliper = mm
2. Number of teeth =
CHORDAL THICKNESS:
S.NO M.S.R V.S.R CHORDAL
THICKNESS
(M.S.R+V.S.R*L.C)
CALCULATIONS:
1. Pitch circle diameter, D=(TxOD)/(T+2) =
2. module, m=D/T mm =
3. Pitch(p) =m*π
4. depth = 0.7p
3. Addendum= 0.3p =
4. Dedendum= 0.4p =
5. Theoritical Chordal Thickness = mT Sin(90/T)= p/2
ANALYSIS:
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RESULT:
1. Theoritical Chordal Thickness =
2. Theoritical Chordal addendum =
3. Chordal thickness measured by gear tooth vernier calipers =
CONCLUSION:
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VIVA-VOCE:
1. Define chordal thickness of a gear.
2. Define the terms pitch circle and base circle of a gear.
3. Define module, addendum and dedundum.
4. What is pressure angle of a gear.
5. What is back lash.
6. What is helix angle.
7. What is lead angle.
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MEASUREMENTOF SCREW TERMINOLOGYUSING
TOOL-MAKER’S MICROSCOPE
AIM:
Measurement of screw thread parameters like pitch & flank angle using tool
maker's microscope.
APPARATUS:
Tool makers microscope & screw thread specimen
OBJECTIVES:
1.To know the working principle of Tool makers microscope
2. To know about the terminology of screw tread
THEORY:
Tool maker's microscope is based on principle of optics. A general view of the
toolmaker’s microscope giving its optical system is shown in fig 1. This is designed for
measurements on parts of complex forms e.g. profile of external threads, tools etc. It can also be
used to measure centre-to-centre distances of holes in any planes.
Basically it consists of the optical head, which can be adjusted vertically along the ways
of a supporting column. This optical head can be clamped in any position by a screw. The
working table on which the parts to be inspected are placed, is secured on a heavy hollow base.
The table has longitudinal and lateral movements. These movements are controlled by accurate
micrometer screws having thimble scales and verniers. A light source is arranged at the back of
the base. The source of light provides a horizontal beam of light, which is reflected from a mirror
by 90° upwards towards the table. This beam of light passes through a transparent glass on which
flat parts to be checked, are placed. A shadow image of the outline of contour of the part passes
through the objective of the optical head and is projected by a system of three prisms to a ground
glass screen. Observations are made through the eyepiece of the optical head.
Cross lines are engraved on the ground glass screen, which can be rotated through 360°,
and the measurements are made by these cross lines. The angle of rotation of screen can be read
through an auxiliary eyepiece provided on the optical head. The eyepiece field of view contains
an illuminated circular scale with a divison value of 1 minute. The optical head tube is adjusted
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in height for focusing purposes, till a sharp image of the projected contour is seen on the ground
glass screen.
Fig 1.Toolmaker’s Microscope
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PROCEDURE:
MEASUREMENT OF SCREW THREAD PITCH:
1) To measure the screw pitch, the screw is mounted on the table.
2) The microscope is focused (by adjusting the height of the optical head) until a sharp
image of the projected contour of the screw is seen of the ground glass screen.
3) The contour is set so that some point on the contour coincides with the cross line on the
screen. The reading on the thimble of the longitudinal micrometer screw is noted.
4) Then the table is moved by the same screw until a corresponding point on the contour
(profile) of the next thread coincides with the cross line. The reading is again noted and
the difference in two reading gives the screw pitch.
MEASUREMENT OF ANGLE OF THE THREAD:
1) To determine the thread angle, the screen is rotated until a line on the screen coincides
with one flank of the thread profile.
2) Then the angle of the screen rotation is noted.
3) The screen is further rotated until the same line coincides with the other flank of the
thread. The angle is noted again and the difference in two angular readings gives the
actual angle of the screw.
S. Description Initial Final Actual Theoritical % Error
No reading reading Experimental value
reading
1 Pitch of the
screw
2 Depth
3 thickness
4 Thread angle
CALCULATIONS:
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RESULTS:
1) Pitch of the screw =
2) depth of the screw =
3) thickness of the screw =
4) Angle of the thread =
PRECAUTIONS:
1) Obtain clean picture of cross line and the cross thread seen through the eyepiece.
2) For angular measurements lines must remain parallel to flank edge of the tooth.
ANALYSIS:
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CONCLUSIONS:
VIVA-VOCE:
1. What is pitch of a screw thread.
2. What is flank angle of a screw thread.
3. What are the applications of toolmaker's microscope?
4. What is the ‘best size’ wire?
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SURFACE ROUGHNESS MEASUREMENT
AIM:
To measure the surface roughness of a machined part using handysurf
APPARATUS:
HANDYSURF E-35A/B
OBJECTIVES:
1. To know about the terms like surface roughness, waviness, lay & profile
2. To know about the different methods of surface roughness measurement
3. To know about the working principle of Handysurf
SURFACE TEXTURE:
Surface topography is of great importance in specifying the function of a surface. A
significant proportion of component failure starts at the surface due to either an isolated
manufacturing discontinuity or gradual deterioration of the surface quality. Typical of the former
is the laps and folds which cause fatigue failures and of the latter is the grinding damage due to
the use of a worn wheel resulting in stress corrosion and fatigue failure. The most important
parameter describing surface integrity is surface roughness. In the manufacturing industry,
surface must be within certain limits of roughness. Therefore, measuring surface roughness is
vital to quality control of machining work piece. Below are the definition of surface roughness
and its main measurement methods. From a knowledge of the roughness amplitude and
wavelength values expected from the surface, it is possible to select the appropriate instrument
settings for a reliable roughness measurement.
Fig 1 Elements of surface character of a machined surface
DEFINITIONS:
SURFACE TEXTURE is the local deviations of a surface from its ideal shape e.g perfect flat
shape, perfect cylinderical shape, sherical shape etc. The measure of the surface texture is
generally determined in terms of its roughness, waviness and Form . In surface texture there are
many factors that, when combined, characterise a surface’s profile. For example:
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• the microstructure of the material
• the action of the cutting tool
• the instability of the cutting tool on the material
• errors in the machine tool guideways
• Mainly, what affects the surface texture could be summarized in the speed of the cutting tool,
feed rate & the depth of cut.
ROUGHNESS – a quantitative measure of the process marks produced during the creation of
the surface and other factors such as the structure of the material. The action of the cutting tool,
chemical action, polishing, lapping, and the structure of the material all contribute to the
roughness of the surface.
WAVINESS – a longer wavelength variation in surface away from its basic form (e.g. straight
line or arc). . It may result from such factors as machine or work deflection, vibration, chatter,
heat treatment, or warping strains
**Because both process and machine induced irregularities occur simultaneously, roughness is
superimposed over waviness.
LAY refers to the predominant direction of the surface texture. Ordinarily lay is determined by
the particular production method and geometry used.Turning, milling, drilling, grinding, and
other cutting tool machining processes usually produce a surface that has lay
PROFILE is, mathematically, the line of intersection of a surface with a sectioning plane which
is (ordinarily) perpendicular to the surface. It is a two-dimensional slice of the threedimensional
surface. Almost always profiles are measured across the surface in a direction perpendicular to
the lay of the surface. Shortly saying, it's the graphical representation of the surface.
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Fig 2. Profile generation by the intersection of sectioning plane with the surface
CENTER LINE (Mean line) : mathematically it's poisoned in such a way that within the
sampling length the sum of areas enclosed by the profile above & below the center line are equal.
FORM of a surface is the profile of the surface under consideration ignoring variations due to
roughness and waviness. Deviations from the desired form result from clamping marks or sliding
marks machining guide errors etc.
ARITHMETICAL MEAN ROUGHNESS (Ra)
Arithmetic mean deviation from the mean line of the profile (Ra) is defines as the average value
of the ordinates (y1, y2, y3……,yn) from the mean line.
Fig 3. Arithmetic mean deviation
Where l = Sampling length, f(x) indicates height of a point chosen from the profile with respect
to the center line .
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Ra readings serve well for surface finish control in most instances. It may be mentioned that Ra
provides an average reading and several different surfaces can have the same average. Thus,
more knowledge of the surface texture is required.
TEN-POINT MEAN ROUGHNESS (RZ)
A section of standard length is sampled from the mean line on the roughness chart. The
distance between the peaks and valleys of the sampled line is measured in the y direction. Then,
the average peak is obtained among 5 tallest peaks(Yp), as is the average valley between 5
lowest valleys(Yv). The sum of these two values is expressed in micrometer( µm).
Fig 4. Ten point height of irregularities
The R.M.S value (Rq) is defined as the square root of the mean of the squares of the
ordinates of the surface measured from the mean line
FILTERS are electronic or mathematical methods or algorithms which separate out different
wavelengths and allow us to see only the wavelengths we are interested in.
CUT-OFF is a filter and is used as a means of separating or filtering the wavelengths of a
component. Cut-offs have a numerical value that when selected will reduce or remove the
unwanted wavelengths on the surface. For example, a roughness filter cut-off with a numeric
value of 0.8mm will allow wavelengths below 0.8mm to be assessed with wavelengths above
0.8mm being reduced in amplitude; the greater the wavelength, the more severe the reduction.
For a waviness filter cut-off with a numeric value of 0.8mm, wavelengths above 0.8mm will be
assessed with wavelengths below 0.8mm being reduced in amplitude.
AVEV Page 40

SAMPLE LENGTH : after the data has been filtered with a cut –off, we then sample it.
Sampling is done by breaking the data into equal sample lengths. The sample lengths have the
same numeric value as the cut-off. In other words, if you use a 0.8mm cut-off, then the filtered
data will be broken down into 0.8mm sample lengths. These sample lengths are chosen in such a
way that a good statistical analysis can be made of the surface. In most cases, five sample lengths
are used for analysis.
Fig.5 : Sample of surface profile
Rsk –(it's an amplitude parameter which's a measure of the vertical characteristics of the surface
deviations). Rsk : is a measurement of skewness and will indicate whether the surface consists of
mainly peaks, valleys or an equal combination of both. It is the measure of the symmetry of the
profile about the mean line. A surface with predominant peaks will be considered as 'positive
skew' and a surface with predominant valleys will be considered as 'negative skew'
RSm (it's a spacing parameter- which's a measure of the horizontal characteristics of the surface
deviations). Rsm is the mean spacing between profile peaks as they pass through the mean line
(spacing is the distance between points that cross the mean line within a sample length in an
upward direction).
*note - almost all parameters are defined over 1 sample length, however in practice more than 1
sample length is assessed (usually 5) and the mean calculated. This provides a better statistical
estimate of the parameter's measured value
THE TRACER METHOD : Which uses a stylus that's dragged across the surface. This method
is the most common for obtaining quantitative results.
AVEV Page 41

HANDYSURF E-35A/B:
This equipment measures parameters of amplitude of surface profiles like Arithmetic
mean deviation of profile (Ra), Root mean square deviation of profile(Rq) & Maximum height
(Ry, Rmax, Rt, Rz, Rzmax, Pt) by scanning a mechanical stylus across the sample. A modern
typical surface measuring instrument will consist of a stylus with a small tip (diamond) a gauge
or transducer, a traverse datum and a processor. The surface is measured by moving the stylus
across the surface. As the stylus moves up and down along the surface, the transducer converts
this movement into a signal which is then exported to a processor which converts this into a
number and usually a visual profile. (The stylus must be moved in a straight line to give accurate
readings)
PROCEDURE:
1. Place the driving unit of handysurf on the workpiece in such a way that the bottom of the driving
unit is in contact with the workpiece for which the measurement will be made.
2. If the workpiece is smaller in size then set the adjuster to a groove at the rear side of the tracing
driver, and adjust the height of the tracing driver to become parallel between the workpiece
surface and the tracing driver. Then fix it with screw.
3. Press the ON• PRT•▼ button to turn the power of the amplification indicator on.
4. Press the SEL• ALT button shortly for about 0.5 second and select the cutoff value screen
5. Select the required cutoff value by pressing the ON• PRT•▼ button or MEAS•▲button.
6. Press the SEL•ALT button shortly for about 0.5 second and indicate the Ra screen.
7. Press the MEAS•▲ button and the measurement will start.

Fig 6 . Stylus operation
RESULTS:
S.No Type of workpiece Ra Rz Rq
1
2
3
ANALYSIS:

CONCLUSIONS:
AVEV Page 44

VIVA-VOCE:
1. What is surface finish (or) roughness?
2. Why surface finish is important in engineering applications?
3. What is the unit of surface roughness.
4. How do you classify geometrical irregularities.
5. What is the working principle of Talysurf.
AVEV Page 45

MACHINE TOOL ALIGNMENT TEST ON LATHE
AIM: To conduct alignment tests on lathe machine & To find straightness of a bed and flatness
of a surface using spirit level.
APPARATUS:
A lathe in good working condition with all standard accessories, i.e. live and dead
centers, sleeve etc, Dial indicator, Dial stand 'with magnetic base, Flexible dial stand, Parallel
blocks, Straight edge, Straight bar, Standard mandrel, Straight spirit level, Box type spirit level,
Alignment microscope, Taut wire, Set of spanners, Mandrel and centre draw bar.
OBJECTIVES:
1. To know about the different alignment tests of lathe
2. To know the use of spirit level & dial gauge in alignment tests
THEORY:
For metrology purposes the term alignment refers to two axes merged in each other or
where one axis extends beyond the other. Two lines or axes are said to be in alignment when
their distance apart at several points over a given length is measured and this distance does not
exceed a given standard tolerance. The dimensions of a gauge, its surface finish, geometry and
accurate production of components/parts depend upon the inherent quality and accuracy of the
machine tool used for its manufacture.
1. The alignment test is carried out to check the grade of manufacturing accuracy of the machine
tool. It consists of checking the relationship between various machine elements (such as bed,
table, spindle etc) when the machine tool is idle and unloaded.
2. The various tests applied to any machine tool could be grouped as below :
(a) Tests for the level of installation of machine in horizontal and vertical planes,
(b) Tests for flatness of machine bed and for straightness and parallelism of bed ways or bearing
surfaces,
(c) Tests for perpendicularity of guide ways to other guide ways or bearing surfaces,
(d) Tests for true running of the main spindle and its axial movements,
(e) Tests for parallelism of spindle axis to guideways or bearing surfaces.
AVEV Page 46

(f) Tests for the line of movement of various members, e.g., saddle and table cross slides etc.
along their ways,
(g) Performance tests in which some test pieces are machined and their accuracy and finish is
checked.
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 saddle 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. 1), to 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.
AVEV Page 47

Fig 1 level of installation
The readings in transverse direction reveal any 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.
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 (fig 2). The surface is then rotated on its axis and indictor
should not show any movement of needle.
AVEV Page 48

Fig 2 Fig 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 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 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
AVEV Page 49

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.
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. 4),
and the spindle is rotated. The deviation indicated by the dial gauge gives the trueness of the
centre.
Fig 4 Fig 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
AVEV Page 50

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. 5). In vertical plane the mandrel should be rising towards 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.
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 Fig.
6.
Fig 6 Fig 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
AVEV Page 51

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 guideways in both the planes i.e., horizontal and vertical, a
block is placed on the guideways as shown in Fig.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.
Movement of upper slide parallel with main spindle in vertical plane.
The dial indicator if fixed in the tool post as shown in fig 8. A mandrel is fitted in the spindle.
The feeler 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.
Fig 8 Fig 9
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. 9). The carriage is
moved along the full length of the sleeve and deviations as indicated by dial indicator are noted
AVEV Page 52

down. Tailstock sleeve should be rising towards the free end in vertical plane and should be
inclined towards the tool pressure in horizontal plane.
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.
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 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 shown in
Fig. 10 and the carriage is moved and the error noted down.
Fig 10
PROCEDURE:
1. Clean all surfaces perfectly on which alignment tests are to be performed,
2. Follow the following test chart for performing different alignment tests.
AVEV Page 53

ALIGNMENT TABLE:
S. OBJECT MEASURING PERMISSIBLE ERROR ACTUAL
No INSTRUMENT ERROR
1 Test for level of Spirit level, Front guide ways
installation Gauge block to 0.02mm/metre convex only.
a) In longitudinal suite the guide Rear guide ways 0.01 to
direction ways of the lathe 0.02mm/metre convexity.
b) In transverse bed Bed level in crosswise
direction direction ± 0.02mm/metres.
Tailstock guide ways
parallel with the movement
of carriage 0.02mm/m.
2 Straightness of saddle in Cylindrical test 0.02mm over 600mm length
horizontal plane mandril(600mm of mandrel.
long), Dial
gauge
3 Alignment of both the Cylindrical test 0.02mm over 600mm length
centres in vertical plane mandril(600mm of mandrel.
long), Dial
gauge
4 True running of taper Test mandrel Position A, 0.01mm,
socket in main spindle with taper shank position B 0.02mm.
& 300mm long
cylindrical
measuring part,
Dial gauge
5 Parallelism of main Test mandrel a) 0.02/300 mm
spindle to saddle with taper shank mandrel rising
movement & 300mm long towards free end
a) In vertical plane cylindrical only.
b) In horizontal measuring part, b) 0.02/300 mm
plane Dial gauge mandrel inclined at
free end towards tool
pressure only.
6 Movement of upper slide Test mandrel 0.02 mm over total
parallel with main spindle with taper shank movement of the slide
in vertical plane & 300mm long
cylindrical
measuring part,
Dial gauge
7 True running of loacating Dial gauge 0.01mm/revolution of the
cylinder of main spindle spindle.
AVEV Page 54

8 True running of head Dial gauge 0.01mm/revolution of the
stock centre spindle.
9 Parallelism of tail stock Dial gauge a) 0.01/100 mm( tail
sleeve to saddle stock sleeve inclined
movement towards tool pressure
a) In vertical plane only)
b) In horizontal b) 0.01/100mm
plane (Tailstock sleeve
rising towards free
end only)
10 Parallelism of tail stock Test mandrel a) 0.03/300 mm,
sleeve taper socket to with taper shank mandrel rising
saddle movement & 300mm long towards free end
a) In vertical plane cylindrical only.
b) In horizontal measuring part, b) 0.03/300 mm,
plane Dial gauge mandrel inclined at
free end towards tool
pressure only.
ANALYSIS:
AVEV Page 55

CONCLUSION:
VIVA-VOCE:
1. What is the need of machine alignment test?
2. What is the use of spirit level & dial gauge in alignment tests
3. Distinguish between alignment test and performance test of a machine tool.
AVEV Page 56

VIBRATION MEASUREMENT OF MACHINES
AIM:
To measure machine Vibration using single axis accelerometer
APPARATUS :
Accelerometer(10 mv/g), A/D Converter, Computer with Labview software
OBJECTIVES:
1 To know about different methods of condition monitoring
2 To know about sensitivity of sensor
3 To know the difference between time wave and frequency spectrum
SPECIFICATIONS:
1. Sampling frequency: 51.2 KHz
2. Frequency range: 0 – 25600 Hz
3. Sensitivity of ICP accelerometer: 10 mV/g
THEORY:
Vibration analysis one type of condition monitoring techniques being used in industries
for many years. Machines and engines contain components which has reciprocating and rotary
motions and hence it produce vibration. The causes for machine vibration are unbalance,
looseness, bearing faults, misalignment, gear tooth problem. Machine vibration is measured by
mounting the accelerometer on top of the component for which vibration is going to be
measured. Labview programming language is used to write the program for data acquisition in
the form of time waves and to convert them into frequency spectrums. Time wave forms are used
to find the overall vibration of the machine which measures the condition of a machine.
Frequency spectrums will be used to know the different sources of vibration and its
corresponding amplitudes.
DATA ACQUISITION SYSTEM & IT’S COMPONENTS
Data acquisition system (DAQ) consists of Vibration sensor, filter, amplifier, A/D
Converter & computer. Vibration sensor is connected to amplifier and A/D Converter to convert
the analog signal into digital signal which can be stored in a computer. The fundamental task of a
AVEV Page 57

DAQ system is the measurement or generation of real-world physical signals. Before a
computer-based system can measure a physical signal, a sensor or transducer must convert the
physical signal into an electrical signal such as voltage or current. Often, the plug-in DAQ board
is considered to
Fig 1. Diesel Engine with vibration measurement setup
be the entire DAQ system. However, the board is only one of the system components. Unlike
most stand-alone instruments, sometimes you cannot directly connect signals to a plug-in DAQ
board. A signal conditioning accessory must condition the signals before the plug-in DAQ board
converts them to digital information. Finally, software controls the DAQ system—acquiring the
rawdata, analyzing the data, and presenting the results.
Vibration severety chart
AVEV Page 58

DATA ACQUISITION PROCEDURE
Fig 1 displays the method of connection of the power supply, accelerometers, A/D converter and
computer. For acquiring vibration signals of the engine, general purpose ICP® accelerometer
with sensitivity of 10 mV/g is used. This accelerometer is used to measure frequencies from 0.5
to 26500 Hz. Accelerometer is connected to NI 9234 A/D converter with specifications (4-
channel, ±5V, 24-Bit Software –Selectable IEPE and AC/DC analog input module).
Accelerometer was used for measuring vibration of engine head in vertical direction and the
sampling frequency of converter is 51.2 kHz. The data acquisition system (DAQ) is shown in fig
1. Finally, collected data are transferred by a cable to the USB port of PC for recording. Data
acquisition duration for each test was 60s. A laptop was used for recording the data.
OBSERVATIONS:
S. No Position of the Overall vibration Overall Vibration
accelerometer level (RMS) or acceleration(m/s2)
vibration
velocity(mm/s)
AVEV Page 59

ANALYSIS:
CONCLUSION:
AVEV Page 60

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