METAL CUTTING, LATHE MACHINE,LATHE OPERATIONS, ALLIGNMENT TEST ON LATHE MACHINE, TYPES OF LATHE MACHINES

1. 2 Metal Cutting Lathe Machine
 Introduction
 Definition of Lathe
 Types of Lathe Machine
 Construction of Lathe Machine
 Accessories and Attachments of Lathe
 Specification of Lathe
 Lathe Operations
 Tapers and Taper Turning
 Thread Cutting
 Drilling on a Lathe
 Cutting Speed
Prof.MAYUR S. MODI
ASSISTANT
PROFESSOR,MED,SS
ASIT,SURAT

2.  Feed
 Machining Time Calculation
 Pre-Use Activities of Lathe
 Operating Precautions of Lathe
 Semiautomatic and Automatic Lathes
 Semiautomatic Lathes
 General Purpose Automatic Lathes
 Multi-spindle Automatic Lathes
 Process Planning and Tool Layout For Machining a
Product in Semi-Automatic and Automatic Lathes
 Combining Elementary Operations
 Alignment Test

3.  Definition of lathe
– The lathe can be defined as a machine tool which holds the work
between two rigid and strong supports, called centers, or in a
chuck or face plate while the later revolves.
– The chuck or face plate is mounted on the projected end of the
machine spindle.
– The cutting tool is rigidly held and supported in a tool post and is
made to move either parallel to or at an inclination with this axis
to cut the desired material.

4. Headstock
& Spindle
Lathe basics
Work Piece
Cutting
Tool Slide
Tail Stock
BodyQuill

5. Z Axis- +
Longitudinal Feed along Z- Axis

6. XAxis -
+
+
Cross Feed along X Axis

7. Types of lathe machine
Bench Lathe:
This is a small lathe usually mounted on a separately prepared bench. It
has practically all die parts of an engine lathe or speed lathe and it
performs almost all the operations. This is used for small and
precision work.
Speed Lathe:
Simplest of all types of lathes in construction and operation. The
important parts of lathe are following-
Bed
Headstock
Tailstock
Tool post mounted on an adjustable slide.

8. It has no feed box, lead screw, or conventional type of carriage. The tool
is mounted on the adjustable slide and is fed into the work by hand
control.
The speed lathe finds applications where cutting force is least such as
in wood working, spinning, centering, polishing, winding, buffing etc.
This lathe has been so named because of the very high speed of the
headstock spindle.
Wood working lathe
Spinning
Centering
Polishing
Centre or engine lathe:
The term "engine" is associated with this lathe due to the fact that in
the very early days of its development it was driven by steam engine.
This lathe is the important member of the lathe family and is the
most widely used. Similar to the speed lathe, the engine lathe has all
the basic parts, e.g., bed, headstock, and tailstock.

9. But its headstock is much more robust in construction and contains
additional mechanism for driving the lathe spindle at multiple
speeds.
Unlike the speed lathe, the engine lathe can feed the cutting
tool both in cross and longitudinal direction with reference to the
lathe axis with the help of a carriage, feed rod and lead screw. Centre
lathes or engine lathes are classified according to methods of
transmitting power to the machine. The power may be transmitted
by means of belt, electric motor or through gears.

10. Commonly used drives are:
(i) Cone Pulley/Belt drive
(ii) Individual motor drive
(iii) All Geared head lathe
Tool room Lathe:
This lathe has features similar to an engine lathe but it is much more
accurately built with some extra attachments to make it suitable
for a relatively more accurate and precision type of work carried
out in a tool room.
It has a wide range of spindle speeds ranging from a very low to a
quite high speed up to 2500 rpm. This lathe is mainly used for
precision work on tools, dies, gauges and in machining work
where accuracy is needed.

11. Capstan and Turret Lathe:
The development of these lathes results from the technological
advancement of the engine lathe and these are vastly used for
mass production work.
The distinguishing feature of this type of lathe is that the tailstock of
an engine lathe is replaced by a hexagonal turret, on the face of
which multiple tools may be fitted and fed into the work in
proper sequence.
Due to this arrangement, several different types of operations can
be done on a job without resetting of work or tools, and a
number of identical parts can be produced in the minimum time.

12. Special purpose lathe:
These lathes are constructed for special purposes and for
jobs, which cannot be accommodated or conveniently machined
on a standard lathe.
The wheel lathe is made for finishing the journals and
turning the tread on railroad car and locomotive wheels. The gap
bed lathe, in which a section of the bed adjacent to the headstock
is removable, is used to swing extra-large-diameter pieces.
The T-lathe is used for machining of rotors for jet engines.
The bed of this lathe has T-shape. Duplicating lathe is one for
duplicating the shape of a flat or round template on to the job.
• Wheel lathe
• Gap bed lathe
• Duplicating lathe
• T-lathe

13. Automatic lathe
These lathes are so designed that all the working and job handling
movements of the complete manufacturing process for a job are
done automatically. These are high speed, heavy duty, mass
production lathes with complete automatic control.

14. construction of lathe machine
A lathe comprises of a bed made of grey cast iron on which
headstock, tailstock, carriage and other components of lathe are
mounted
Head stock
Tailstock
Carriage
Feed mechanism
Thread cutting mechanism

17. Bed
The bed of a lathe machine is the base on which all other
parts of lathe are mounted. It is massive and rigid single piece
casting made to support other active parts of lathe.
On left end of the bed. headstock of lathe machine is located
while on right side tailstock is located.
The carriage of the machine rests over the bed and slides on
it. On the top of the bed there are two sets of guide ways-inner
ways and outer ways.
The inner ways provide sliding surfaces for the tailstock and
the outer ways for the carriage.
The guide ways of the lathe may be flat and inverted V
shape.
Generally cast iron alloyed with nickel and chromium
material is used for manufacturing of the lathe bed.

18. Head Stock
The main function of headstock is to transmit power to the
different parts of a lathe.
It comprises of the headstock casting to accommodate all the
parts within it including gear train arrangement.
The main spindle is adjusted in it. which possesses live centre to
which the work can be attached.
It supports the work and revolves with the work, fitted into the
main spindle of the headstock.
The cone pulley is also attached with this arrangement,
which is used to get various spindle speed through electric motor.
The back gear arrangement is used for obtaining a wide range of
slower speeds. Some gears called change wheels are
used to produce different velocity ratio required for thread cutting.

19. Use of Back gears
 The back geared headstock consists of a casing accommodating the
main spindle, the three or four step cone pulley and the back gears.
 In this, a step cone pulley is mounted on the main spindle, which
carries a spur gear G1 at its one end and a pinion P1 at the other.
Gear G1 is firmly keyed to the spindle so that it can never revolve
free of the same. [ See next fig. ]
 The spindle carries a sleeve over it which is a loose fit. The cone
pulley firmly secured to this sleeve. Also, the pinion P1 is firmly keyed
to this sleeve.
 This arrangement forces the pinion P1 to revolve with the cone
pulley under all conditions.
 A spring knob K engages the gear G1 with the cone pulley.
 The cone pulley is driven by means of a belt, through a
countershaft, by an electric motor. This enables four different speeds
of the spindle.

20. Use of back gears
The back gears are used for effecting
reduction in spindle speeds, thereby
facilitating a wider range of speeds.
The back gears are mounted on an
eccentric shaft which is operated by
means of a hand lever known as back
gear engaging lever (L).
The back gears consists of a spur gear G2 (Opposite pinion P1) and a pinion P2
(Opposite gear G1). When speed reduction is required, the knob is pulled out
to make the cone pulley free of gear G1 and hence of the spindle.
The back gears are put into mesh with the spindle gears by pulling in the
eccentric shaft.
Now, the sequence of transmission of the motion and power is such that the
cone pulley is driven by the motor through the belt.
With the result, the pinion P1 revolves. This, being in mesh with gear g2,
transfers the motion to the latter which, in turn, revolves the eccentric shaft
and hence the pinion P2. this, further being in mesh with gear G1, transmits
the motion to the later and hence to the spindle.

21. Tail Stock
The tail stock is commonly used for the objective of primarily giving an outer
bearing and support the circular job being turned on centers. Tail stock can be
easily set or adjusted for alignment or non-alignment with respect to the
spindle centre and carries a centre called dead centre for supporting one end
of the work. Both live and dead centers have 60° conical points to fit centre
holes in the circular job, the other end tapering to allow for good fitting into
the spindles. The dead centre can be mounted in ball bearing so that it rotates
with the job avoiding friction of the job with dead centre as it important to
hold heavy jobs

22. Carriage
Carriage is mounted on the outer guide ways of lathe bed and it can move in a
direction parallel to the spindle axis.
It comprises of important parts such as apron, cross-slide, saddle, compound
rest, and tool post. The lower part of the carriage is termed the apron in which
there are gears to constitute apron mechanism for adjusting the direction of
the feed using clutch mechanism and the split half nut for automatic feed.
The cross-slide is basically mounted on the carriage, which generally travels at
right angles to the spindle axis. On the cross-slide, a saddle is mounted in
which the compound rest is adjusted which can rotate and fix to any desired
angle. The compound rest slide is actuated by a screw, which rotates in a nut
fixed to the saddle.

23. Tool Post
The tool post is an important part of carriage, which fits in a tee-slot in the
compound rest and holds the tool holder in place by the tool post screw
As shown the tool post of centre lathe, fixed to the saddle.

24. Feed Mechanism
Feed mechanism is the combination of different units through which motion of
headstock spindle is transmitted to the carnage of lathe machine.
(i) End of bed gearing
(ii) Feed gear box
(iii) Lead screw and feed rod
(iv) Apron mechanism
The gearing at the end of bed transmits the rotary motion of headstock spindle
to the feed gear box. Through the feed gear box the motion is further
transmitted either to the feed shaft or lead screw, depending on whether the
lathe machine is being used for plain turning or screw cutting.
The feed gear box contains a number of different sizes of gears. The feed gear
box provides a means to alter the rate of feed, and the ration between
revolutions of the headstock spindle and the movement of carriage for thread
cutting by changing the speed of rotation of the feed rod or lead screw.
The apron is fitted to the saddle, it contains gears and clutches to transmit
motion from the feed rod to the carriage, and the half nut which engages with
the lead screw during cutting threads.

25. Tumbler Reversing Mechanism
•The gear mechanism operated by means of the feed reverse lever is called
the "Tumbler Reversing Mechanism". This is used for providing power feeds to
the carriage
•It will be seen that the motion from the spindle to the lead screw or feed rod
is transmitted through this mechanism
•Here, Gear G1 is mounted on the rear end of the spindle S. The feed
mechanism consists of gears G2, G3 and G4, and is operated by means of feed
reverse lever F.
•When the lever F is moved from the central position to either the top or the
bottom position, one of the gears G2 or G3 will mesh with gear G1, whereas
these two gears always mesh with each other mutually.
•Thus, it will be seen that in the top position of lever F motion is transmitted
from gear G1 to G4 through gear G3 and gear G2 plays no role. With the result,
the gear G4 will have the same direction of rotation as the spindle
•Against this, in the lower position of the lever F. motion from G1 is
transmitted to G4 through G2 and G3 respectively, as shown This will enable
G4 to rotate in a direction opposite to that of the spindle S.

27. ●it will be evident that when the lever F will be in its central position neither of
the gears G2 and G3 will be meshing with G1 and thus the feed mechanism will
be changed.
●The above mechanism is usually enclosed in the headstock except the lever F
which is kept projecting outside.
●Another set of gears called "Change gears" out side the headstock consists of
G5. G6. G7 and G8 etc. Gear G5 is mounted on the same spindle as G4 and
thus rotates at the same rpm as the latter.
●This transmits motion to gear G8 through G6 and G7, which further transmits
it to the lead screw or the feed rod.
●These four gears are known as "Change Gears" for the reason that they can
be removed and replaced by the other gears having different numbers of the
teeth

28. ●A desired speed of lead screw or the feed rod can be obtained by selecting
suitable change gears having proper number of teeth.
●Gears G6 and G7 are usually mounted on a stud and are known as "Stud
Gear".
●A quadrant is provided and the stud can be shifted along its straight slot to
enable proper meshing of change gears.
●Also, this quadrant can be swung vertically along the slot P to enable meshing
of gears G5 and G6.
●When proper meshing been acquired the quadrant is locked in position.
●Gear G8 is mounted directly on the lead screw on those lathes which do not
have a feed gear box, whereas it is mounted on the gear box driving shaft in
those lathes which carry the gear box.

29. Geared Headstock
A lathe spindle may be required to operate at various different speeds. For
this, the head stock may be equipped with either a cone pulley drive and back
gears, as discussed earlier or an all geared head stock.
The latter mechanism is very commonly used in all modern lathes. In this
method the desired speeds are obtained simply by sifting the positions of
sliding gears.
These gears are actuating by two or more speed change levers. The main
driving motor runs always at a constant speed and the desired variations in
spindle speeds are provided through the above shifting of gears.
The head stock has a rigid construction, compact design and incorporates a
number of sliding clutches and brakes etc.
some lathes sometimes are provided with a two speed motor in order to have
a wider range of spindle speeds from the same head stock.

31. The common method of designing such a gear box is to arrange the spindle
speeds in a geometrical progression, which means that each spindle speed
when multiplied by a constant number gives the next higher speed. For
example if S be the first or lowest speed and C the constant number, then:
2nd speed = S x C
3rd Speed =S x C x C = S x C2
nth speed= S x Cn-1
Now, if n be the total number of speeds and N be the maximum speed, then:
N =S x Cn-1
Cn-1 = N/S
Internationally the standard values of C have been fixed as
1.12,1.25,1.4,1.6, and 2.
A simple design of nine speed all geared head stock consists of a splined shaft
S1. an intermediate shaft S2 and the lathe spindle S3.
Shaft S1 carries the fast and loose pulleys on its outside end, through which it
receives power from the driving motor.
Gears G1. G2 and G3 are mounted on shaft S1, gear G4, G5 and G6 on shaft S2
and gear G7, G8 and G9 on the spindle S3.

32. ●The spindle body is also splined, as shown. Gear GT is called Translating Gear.
●It is fitted on the main spindle for transmitting motion to the lead screw and fed
shaft.
●The gear box shown in figure is said to have the sliding gear mechanism because
the changes in spindle speeds are obtained by sliding a set of gears over a splined
shaft to bring it in mesh with a cluster of gears mounted on the other shaft.
●In the above gear box. the power is transmitted to shaft S1 from the driving
motor through the fast pulley mounted on the shaft extension.
●Gears G1, G2 and G3 can be brought in mesh respectively with gears G4. G5 and
G6 by sliding the former over splined shaft S1 by means of a lever.
●Similarly another lever can be used to slide gears G7, G8 and G9 over spindle S3
to bring these gears in mesh respectively with gears G4, G5 and G6.
●The power is, thus, transmitted from S1 to S2 and then S3. Gears G4, G5 and G6
rotate freely on shaft S2 in their own positions, but they cannot be shifted axially.
●The above shifting of gears enables nine different gear combinations to give nine
different spindle speeds as follows:
(i) (G1/G4)x(G4/G7) (ii) (G1/G4) x (G5/G8) (iii) (G1/G4)x(G6/G9)
(iv) (G2/G5)x(G4/G7) (v) (G2/G5) x (G5/G8) (vi) (G2/G5) x (G6/G9)
(vii) (G3/G6) x (G4/G7) (viii) (G1/G4) x (G5/G8) (ix) (G1/G4)x (G6/G9)

33. Advantage of geared drive over the cone pulley drive
● It provide a more compact design and enables a wider range of spindle
speeds
● The power available at the tool is almost constant for all the speeds,
whereas in a cone pulley drive it varies with the speed
● The spindle speeds can be easily changed by simply moving a few levers,
which is relatively safer and much quicker than shifting of belt in a cone
pulley drive
● No line shaft or countershaft is required since the power is obtained from
an independent motor housed in the machine itself
● Less vibration are observed in the machine spindle since the driving pulley
is not mounted directly over it
The disadvantages of geared drives
● The lathes incorporating this drive are costlier
● There is some loss of power due to friction in gears, but can be minimized
with the use of suitable lubricant
● This being a positive drive, the chances of prevention of damage due to
overloading are very bleak.

34. Apron Mechanism
●It is hanging part in front of the carriage.
●It serves as a housing for a number of gear trains through which power feeds
can be given to the carriage and the cross slide.
●Also, it carries the clutch mechanism and the split half nut.
●Out of these two. the former (clutch mechanism) is used to transmit motion
from the feed rod whereas the latter, in conjunction with the lead screw,
moves the whole carnage in thread cutting.
●For efficient operation of the machine it is important to understand the apron
mechanism and its detail.

37. H is the hand wheel for providing the longitudinal hand feed to the carriage.
H1 is the hand wheel for providing hand feed to the cross-slide.
Lever L1 is for engaging or disengaging the power feed.
Star wheel S is operated when power feed is to be engaged.
Lever L2 operates the split half nut N to engage or disengage the same from
the lead screw L.
Chasing dial D used in thread cutting.
Inside the Apron there are 5 spindles S1, S2, S3, S4 and S5.
Spindle S1 carries gear G1 at its rear end and hand wheel H at the front.
G1 is in mesh with gear G2 mounted on spindle S2.
Spindle S2 carries another gear G7 at its rear end, out side the apron, which
meshes with the rack provided at the front of the lathe.
Spindle S3 carries gear G3 which is operated by lever LI. This lever has three
positions 1, 2 and 3.
In position 1, i.e. lowest, it engages gear G3 with G4 mounted on spindle S4.
In position 2, i.e. middle, gear G3 is free and does not mesh with any other
gear.
In position 3, i.e. top, gear G3 meshes with the gear G2. Spindle S4, in addition
to the gear G4, carries another gear G5 at its rear end.

38. ●It is always in mesh with gear G6, which is mounted on the screwed spindle
of the cross slide.
●Spindle S5 is just below the spindle S3 and it carries gears G8 and G9. G8 is in
mesh with G3 and G9 with the worm W.
●however, gear G9 is not rigidly secured to S5.
●Instead of this, a clutch T is provided at the rear end of this spindle which can
be drawn in or pushed out by rotating the spindle by means of the star wheel
S. on account of the same, whenever it is desired to transmit motion from the
lead screw to the spindle S5 the clutch is drawn in.
●this enables a temporary rigid fastening between S5 and S9. with the result
that S5 is driven by the lead screw through the worm W and gear G9.
Whenever we want to disengage the same, the star wheel is rotated in a
reverse direction to push the clutch out of G9 and the transmission is stopped.
●In operation, when hand feed is required to given, whether to the carriage or
the cross side, lever L1 is put in position 2 so that gear G3 is neither engaged
with G4 nor with G2.
●When power feed is to be given to the carriage, lever L1 is put in position 3
so that G3 meshes with G8 and G2 simultaneously.

39. ●Star wheel is tightened to connect G9 with S5. Motion is transmitted from
the lead screw to G9, through the worm, and hence to S5 and G8.
● It is further transmitted to G2 and hence to G7, they being on the same
spindle. G7 meshes with the fixed rack and. therefore, the carriage is moved.
●To give power feed to the cross-slide, lever L1 is put in position 1, so that gear
G3 meshes with G4.
●Now the transmission of motion from the lead screw is to the worm, then to
G2 and G8 and finally to G3 through G4 and G5.
●Note that the mechanism explained above is not capable of providing power
feeds both to carriage as well as the cross-slide simultaneously.

40. Half nut Mechanism
●The half nut or split nut is used for thread cutting in a lathe. It engages or
disengages the carriage with the lead screw so that the rotation of the lead
screw is used to traverse the tool along the work piece to cut screw threads..
●The nut is in two halves, each of these halves carries a pin at its back (P1 and P2)
●which engage into the cam
slots provided in the plate at
their back.
●When this plate is rotated by
means of the lever L it,
depending upon the direction
of the rotation of the lever,
engages or disengages the split
nut with the lead screw.
●Thus, the direction in which
the carriage moves depends
upon the position of the feed
reverse lever on the headstock

41. ACCESSORIES AND ATTACHMENTS OF LATHE
There are many lathe accessories provided by the lathe manufacturer along
with the lathe, which support the lathe operations. The important lathe
accessories include centers, catch plates and carriers, chucks, collets, face
plates, angle plates, mandrels, and rests. These are used either for holding and
supporting the work or for holding the tool. Attachments are additional
equipments provided by the lathe manufacturer along with the lathe, which
can be used for specific operations. The lathe attachment include stops, ball
turning rests, thread

42. Thank
you