04-02
Turning and Related Operations
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Material Removal Processes
• The starting material is solid metal
• Excess material is removed from the starting metal
that the resulting part has the desired geometry
so
• Most common in this category are machining operations
such as turning, drilling and milling, accomplished using
cutting tools that are harder and stronger than the work
metal
• In grinding abrasive grinding wheel is used to remove
material
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What is a Machine Tool?
• A machine tool is a non-portable, power operated
device or system of devices in which energy is
expended to produce jobs of desired size, shape and
surface finish by removing excess material from the
preformed blanks in the form of chips with the help of
cutting tools moved past the work surface(s).
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Lathe Cutting
Operations
Miscellaneous cutting operations
that can be performed on a lathe.
Note that all parts are circular – a
property known as axisymmetry.
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What is Common in Machine Tools?
•
•
•
•
•
•
•
Electric Motor
Transmission Mechanism
Spindle
Base or Bed
Slides or Ways
Cutting Tool
Mechanisms for different
movements
• Different Levers,
Handwheels & Gauges
• Workpiece holding
device
• Accessories
• Cutting Speed
• Feed Rate
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The Lathe
• The forerunner or mother of all machine tools
• The work is held and rotated on its axis while the
cutting tool is advanced along the lines of a desired cut
main purpose of a lathe is to machine round
work
• The engine lathe is the most common lathe found in a
machine shop
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Parts of the Lathe
• The main parts of the lathe are
– The bed (and ways)
– Headstock
– Quick-change gear box
– Carriage
– Tailstock
Bed:
• The bed is a heavy casting made to support the
working parts of the lathe
• On its top section are machined ways that guide and
align the major parts of the lathe
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Parts of the Lathe…
Headstock:
• The headstock is clamped on the left-hand side of the
bed
• The headstock spindle, a hollow cylindrical shaft provides
a drive through gears from motor to work-holding
devices
• A live center, a faceplate, or a chuck can be fitted to the
spindle nose to hold and drive the work
• The live center has a 60° point that provides a bearing for
the work to turn between centers
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Parts of the Lathe…
Quick-change Gearbox:
• The quick-change gearbox, containing a number of
different-size gears, provides the feed rod and lead
screw with various speeds for turning and thread
cutting operations
• The feed rod advances the carriage for turning
operations when the automatic feed lever is engaged
• The lead screw advances the carriage for thread
cutting when the split-nut lever is engaged
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Parts of the Lathe…
Carriage:
• Used to move the cutting tool along the lathe bed
• The saddle, an H-shaped casting mounted on the top
of the lathe ways, provides a means of mounting the
cross-slide and the apron
• The cross-slide, mounted on the top of the saddle,
provides a manual or an automatic cross movement
for the cutting tool
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Parts of the Lathe…
• The compound rest, fitted on top of the cross-slide, is
used to support the cutting tool
• It can be swiveled to any angle for taper-turning
operations
• The cross-slide and compound rest both have graduated
collars
• The apron, fastened to the saddle, houses the gears and
the mechanism required to move the carriage or crossslide automatically
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Parts of the Lathe…
• The apron handwheel can be turned manually to
move the carriage along the bed
• This handwheel is connected to a gear that meshes
in a rack fastened to the lathe bed
• The automatic feed lever engages a clutch that
provides automatic feed to the carriage
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Parts of the Lathe…
• The feed-change lever can be set for longitudinal feed or for
crossfeed
• When in neutral position , the feed-change lever permits the
split-nut lever to be engaged for thread cutting
• For thread cutting, the carriage is moved automatically
when the split-nut lever is engaged
• This causes the threads of the split-nut to engage into the
threads of the revolving lead screw and move the carriage at
a predetermined rate.
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Parts of the Lathe…
Tailstock:
• The tailstock can be adjusted for taper or parallel turning
by two screws set in the base
• The tailstock spindle has an internal taper to receive the
dead center, which provides support for the right-hand
end of the work
•
Other standard tapered-shank tools, such as reamers and
drills, can be held in the tailstock spindle
•
A spindle clamp is used to hold the tailstock spindle in a
• fixed position
The tailstock handwheel moves the tailstock spindle in
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Schematic view of a center lathe
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General view of a typical lathe, showing various components
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Movement of different parts of Lathe in different axes
The Carriage
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Turret Lathe
Schematic illustration of the components of a turret lathe. Note the two
turrets: square and hexagonal (main).
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Turret Lathe in Action Video
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Numerical Control Lathe and Turret
(a) A computer numerical-control lathe. Note the two turrets on this machine. These
machines have higher power and spindle speed than other lathes in order to take
advantage of new cutting tools with enhanced properties. (b) A typical turret equipped
with ten tools, some of which are powered.
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Boring and Boring Mill
(a) Schematic illustration of a steel
boring bar with a carbide insert.
Note the passageway in the bar for
(b)
cutting fluid application.
Schematic illustration of a boring
bar with tungsten-alloy “inertia
disks” sealed in the bar to
counteract vibration and chatter
during boring.
This system is
effective for boring bar length-todiameter ratios of up to 6.
Schematic illustration of a vertical boring mill. Such a
machine can accommodate workpiece sizes as large as
2.5m (98 in.) in diameter.
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Lathe Workholding Devices
Lathe Centers:
• Most turning operations can be performed between centers
on a lathe
• Work to be turned between centers must have a center hole
drilled in each end to provide a bearing surface
• A lathe dog, fitted into a driving plate, provides a drive for the
work
• The lathe dog has an opening to receive the work and a
setscrew to fasten the dog to the work
• The tail of the dog fits into a slot on the driveplate and
provides a drive to the workpiece
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Lathe centers and lathe dogs
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Lathe centers and lathe dogs
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Lathe Workholding Devices
Chucks:
The most common are three-jaw universal, four-jaw
independent, and collet chuck
The three-jaw universal chuck:
• Holds round and hexagonal work
• Three jaws move simultaneously when adjusted by
the chuck wrench
• Usually provided with two sets of jaws, one for
outside chucking and the other for inside chucking
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Three-jaw universal chuck
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Lathe Workholding Devices
Four-jaw Independent Chucks:
• 4-jaw chucks are usually non-self-centering
• Each jaw can be moved independently
• Ideal for gripping round, square, hexagonal and
irregularly shaped workpieces
• The jaws can be reversed to hold work by inside
diameter
• Multi-jaw chucks (6 or 8 jaws) for special purpose
and high standards of accuracy
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Four-jaw and six-jaw chucks
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Lathe Workholding Devices
Magnetic Chuck:
• It has the advantage of holding iron or steel parts
• The parts that are too thin or that may be damaged if
held in a conventional chuck
• Suitable only for light operations
• A magnetic chuck consists of an accurately centered
permanent magnet face
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Magnetic chuck
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Lathe Workholding Devices
Faceplates:
• Circular metal plate fixed to the end of spindle
• Used to hold work that is too large or of such a shape
that it cannot be held in a chuck or between centers
• It has slots or threaded holes
• W.piece is clamped using T-bolts in the slots or
threaded holes
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Faceplate and T-bolts
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Lathe Workholding Devices
Collet Chucks:
• Used for small parts that cannot be held in a jawchuck
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Lathe Workholding Devices
Collet Chucks:
Workpiece held in collet chuck
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Lathe Workholding Devices
Mandrels:
• Mandrels are shafts specially made to hold work to be
machined concentrically around a previously bored or
drilled hole
• There are two general types, plain and expanding
• Plain mandrels have a 0.006-in. taper per foot
• There must be a mandrel for each hole size
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Lathe Workholding Devices
Plain Mandrels:
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Lathe Workholding Devices
Sleeve-type Expanding Mandrels:
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Lathe Workholding Devices
Steadyrest:
• Used to support long or slender work held in a chuck or
between lathe centers
• It is located on, and aligned by, the ways of the lathe
•
It may be positioned at any point along the lathe bed,
provided it clears the carriage travel
• Its three jaws my be adjusted to support any work
diameter within the steadyrest capacity
• It also supports the center of long work to prevent
springing when the work is machined between centers
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Steadyrest
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Lathe Workholding Devices
Follower Rest:
• Often used to support a long, slender workpiece
during machining
• Mounted on the saddle, travels with the carriage to
prevent work from springing up and away from the
cutting tool
• The cutting tool is generally positioned just ahead of
the follower rest to provide a smooth bearing surface
for the two jaws of the follower rest
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Follower Rest
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Lathe Machine Types
Multispindle Lathe Machine
https://www.youtube.com/watch?v=y2dd_G_v
jGE
CNC Lathe, Conventional Lathe, Lathe
Accessories
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Cutting Speed, Feed and Depth of Cut
• Lathe work cutting speed (CS) : the rate at which a point
on the work circumference travels past the cutting tool
• Expressed as ft / min or m / min
• r / min = CS x 12 / π D ≈ CS x 4 / D
• Example: Calculate the r/min required to turn a 2-in.
diameter piece of machine steel (CS 90).
• For metric calculations: r/min =
CS (m) x 1000/π x D (mm) ≈ CS (m) x 320/D (mm)
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Cutting Speed, Feed and Depth of Cut
• The feed of a lathe may be defined as the distance the
cutting tool advances along the length of the work for
every revolution of the spindle
• For example, if the lathe is set for a 0.015-in. feed, the
cutting tool will travel along the length of the work 0.015
in. for every complete turn of the workpiece
• The depth of cut is the depth of the chip taken by the
cutting tool and is one-half the total amount removed
from the workpiece in one cut
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Lathe cutting speeds in feet and meters per minute
using a high-speed steel toolbit (rough cut turning and
boring)
Material
ft/min
m/min
Machine steel
90
27
Tool steel
70
21
Cast iron
60
18
Bronze
90
27
Aluminum
200
61
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Feed for various materials using high-speed steel cutting
tool (rough cut turning and boring)
Material
in.
mm
Machine steel
0.010-0.020
0.25-0.50
Tool steel
0.010-0.020
0.25-0.50
Cast iron
0.015-0.025
0.4-0.65
Bronze
0.015-0.025
0.4-0.65
Aluminum
0.015-0.030
0.4-0.75
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Lathe Cutting Tools
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Taper Turning Methods
1.
2.
3.
4.
5.
Offsetting the tailstock
Swiveling the compound slide
Using form tool
Using taper turning attachment
Giving longitudinal and cross feed
simultaneously
– Very rare and risky
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Brief Review on Lathe
Intro to Lathe Operations Video
Lathe Workholding Video
Lathe Cutting Tools Video
Lathe Controls Video
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Center Lathe Specifications
• Maximum diameter and length of job that can be
accommodated
• Power of the main drive (motor)
• Range of spindle speeds
• Range of feeds
• Space occupied by the machine
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Questions??
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N = v/(πD)
Homework
Problem related to turning from 22.1-22.5
References
• Technology of Machine Tools, 6th Ed. by S. F. Krar, A. R. Gill, P.
Smid; McGraw Hill Higher Education
• Degarmo’s Materials And Processes In Manufacturing, 10th Ed.
By J.T Black, R. A. Kohser; John Wiley And Sons
• Manufacturing Engineering And Technology, 5th Ed. By S.
Kalpakjian, S. R. Schmid; Pearson Education
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