Chapter 5

Upcoming Chapters

Metal Removal
Cutting-Tool Materials
Metal Removal Methods
Machinability of Metals

Single Point Machining

Turning Tools and Operations
Turning Methods and Machines
Grooving and Threading
Shaping and Planing
Turning Methods
& Machines
Hole Making Processes
Drills and Drilling Operations
Drilling Methods and Machines
Boring Operations and Machines
Reaming and Tapping

Multi Point Machining

Milling Cutters and Operations
Milling Methods and Machines 5.1 Introduction
Broaches and Broaching The basic engine lathe, which is one of the most widely used machine tools, is very ver-
Saws and Sawing satile when used by a skilled machinist. However, it is not particularly efficient when
many identical parts must be machined as rapidly as possible. As far back as 1850 there
Finishing Processes were efforts to develop variations of an engine lathe that could be operated by a relatively
Grinding Wheels and Operations unskilled person for mass producing machined parts. The cutting tools were preset, or
Grinding Methods and Machines “set up” by a skilled machinist, and usually several cutting tools were in operation at the
Lapping and Honing same time, reducing the time spent in machining each part. This is still the basic concept
on which mass- production type lathes are based.
The turret lathe and automatic screw machine in their various forms have been devel-
oped and improved with the objectives of producing machined parts more rapidly and
accurately at lower cost. On most machines of this type, the power available at the spin-
dle has been greatly increased to take advantage of better cutting tool material.
Mechanical power, in electrical, hydraulic, or pneumatic form, has replaced human mus-
cle power for such functions as feeding tools, operating chucks or collets, and feeding bar
stock in the machine.

5.2 Lathes and Lathe Components

Of the many standard and special types of turning machines that have been built, the most
important, most versatile, and most widely recognized is the engine lathe. The standard
engine lathe is not a high production machine, but it can be readily tooled up for many
one-piece or short-run jobs. It is also possible to modify the basic machine for many high-
er production applications. The modern engine lathe provides a wide range of speeds and
feeds which allow optimum settings for almost any operation. There have been advances
in headstock design to provide greater strength and rigidity. This allows the use of high-
horsepower motors so that heavy cuts with carbide tools are practical. To utilize this high
power without losing accuracy, new lathes incorporate heavier beds, wider hardened
George Schneider, Jr. CMfgE ways, and deeper-sectioned carriages.
Professor Emeritus A schematic illustration of the components of an engine lathe is shown and described
Engineering Technology
Lawrence Technological University in Figure 5.1.
Headstock: The headstock is the powered end and is always at the operator’s left.
Former Chairman
Detroit Chapter ONE This contains the speed changing gears and the revolving, driving spindle, to which any
Society of Manufacturing Engineers one of several types of work holders is attached. The center of the spindle is hollow so
Former President that long bars may be put through it for machining.
International Excutive Board Tailstock: The tailstock is non-rotating but on hardened ways, it can be moved, to the
Society of Carbide & Tool Engineers left or right, to adjust to the length of the work. It can also be offset for cutting small-
Lawrence Tech. Univ.: http://www.ltu.edu angle tapers.
Prentice Hall: http://www.prenhall.com Carriage: The carriage can be moved left or right either by handwheel or power feed.
This provides the motion along the Z-axis. During this travel turning cuts are made.
Apron: The apron attached to the front of the carriage, holds most of the control
levers. These include the levers which engage and reverse the feed lengthwise (Z-axis)

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 Chap. 5: Turning Methods & Machines
Headstock merely a slotted cylinder which can be
Spindle moved left or right in the T-slot in the
Spindle compound and clamped in place. It can
speed also be rotated so as to present the cut-
selector
Ways Cross slide ter to the work at whatever angle is best
Tool post for the job.
Carriage Bed: The bed of the lathe is its
Center ‘backbone’. It must be rigid enough to
Tailstock quill resist deflection in any direction under
Feed change load. The bed is made of cast iron or a
gear box Tailstock steel weldment, in a box or I-beam
shape, and is supported on legs, a cabi-
net, or a bench.
Ways: The ways of the lathe are the
Compound rest flat or V-shaped surfaces on which the
Apron Bed carriage and the tailstock are moved left
and right. Each has its separate pair of
Lead screw
ways, often one flat surface, for stabili-
Feed rod ty, and one V-way for guidance in a per-
fectly straight line. These ways are
hardened and scraped or ground to close
tolerances. The basic accuracy of
movement of the carriage depends on
FIGURE 5.1: Schematic illustration of the components of a standard engine lathe. the ways. A typical Toolroom Engine
Lathe is shown in Figure 5.2.
or crosswise (X-axis) and the lever ing. The cross slide can be moved by its Size: The size of a lathe is specified
which engages the threading gears. handwheel or by power feed. by two or three dimensions:
Cross Slide: The cross slide is Compound Rest: The compound • The largest diameter workpiece which
mounted on the carriage and can be rest, or compound for short, is mounted will clear the bed of the lathe. The cen-
moved in and out (X-axis) perpendicu- on the carriage. It can be moved in and ter is the headstock spindle center.
lar to the carriage motion. This is the out by its handwheel for facing or for • The largest diameter workpiece which
part that moves when facing cuts are setting the depth of cut. It can also be will clear the cross slide is sometimes
made with power feed, or at any time a rotated 360 degrees and fed by its hand- also specified.
cut must be made ‘square’ with the Z- wheel at any angle. The compound • The longest workpiece which can be
axis. This, or the compound, is also does not have any power feed but it held on centers between the headstock
used to set the depth of cut when turn- always moves longitudinally with the and the tailstock.
cross slide and the car- A larger, more sophisticated lathe is
riage. shown in Figure 5.3.
Tool Post: The tool A large 40” lathe with a steady rest is
post is mounted on the shown in Figure 5.4.
compound rest. This can
be any of several varieties 5.3 Turret Lathe
but in its simplest form is The standard engine lathe is versatile,

FIGURE 5.2: A typical toolroom engine lathe with face FIGURE 5.3: A more sophisticated 18-inch variable speed engine lathe
plate, square turrent, follower, and steady rest. (Courtesy permits optimal cutting speed selection. (Courtesy Clausing Industries,
Summit Machine Tool Manufacturing Corp.) Inc.)

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 Chap. 5: Turning Methods & Machines
movement of the tool by disengag-
ing the drive clutch.
Like the engine lathe, the mod-
ern turret lathe provides fast spin-
dle speeds, wide speed and feed
ranges, high power, and great rigid-
ity. The machine is operated in the
high end of its speed range more
than the engine lathe is, partly
because the tools placed in the tur-
FIGURE 5.4: 40 inch lathe with steady rest is used to machine large cylindrical parts.(Courtesy ret often work on small diameters
Summit Machine Tool Manufacturing Corporation) on the workpiece, but also because
the operator is more production
but it is not a high production machine. positive stops or feed trips. Likewise, conscious.
When production requirements are the longitudinal position of the entire 5.3.1 Horizontal Turret Lathes:
high, more automated turning machines assembly may be controlled by positive Horizontal turret lathes are made in two
must be used. stops on the left side of the apron. Cuts general designs and are known as the
The turret lathe represents the first may be taken with square turret tools ram and saddle types. The ram-type tur-
step from the engine lathe toward the and with tools mounted on the hexagon ret lathe shown in Figure 5.6a has the
high production turning machines. The turret simultaneously. turret mounted on a slide or ram which
turret lathe is similar to the engine lathe An outstanding feature is the turret in moves back and forth on a saddle
except that tool-holding turrets replace place of the tailstock. This turret clamped to the lathe bed. The saddle-
the tailstock and the tool post compound mounted on either the sliding ram or the type turret lathe shown in Figure 5.6b
assembly. These machines possess spe- saddle, or on the back of the structure, has the turret mounted directly on a sad-
cial features that adapt them to produc- carries anywhere from 4 to 18 tool sta- dle which moves back and forth with
tion. The ‘skill of the worker’ is built tions. The tools are preset for the vari- the turret.
into these machines, making it possible ous operations. The tools are mounted 5.3.2 Vertical Turret Lathes: A ver-
for inexperienced operators to repro- in proper sequence on the various faces tical turret lathe resembles a vertical
duce identical parts. In contrast, the of the turret so that as the turret indexes boring mill, but it has the characteristic
engine lathe requires a skilled operator between machining operations, the turret arrangement for holding the tools.
and requires more time to produce parts proper tools are engaged into position. It consists of a rotating chuck or table in
that are dimensionally the same. For each tool there is a stop screw or the horizontal position with the turret
The principal characteristic of turret electric/electronic transducer, which mounted above on a cross rail. In addi-
lathes is that the tools for consecutive controls the distance the tool will feed tion, there is at least one side head pro-
operations are set up for use in the prop- and cut. When this distance is reached, vided with a square turret for holding
er sequence. Although skill is required an automatic trip lever stops further tools. All tools mounted on the turret or
to set and adjust the tools prop-
erly, once they are correct, less
Spindle
skill is required to operate the speed selector Square
Hexagon
turret lathe. Many parts can be turret
turret Turret
produced before adjustments are stops
Ram
necessary. These machines are
normally used for small to medi-
um sized production runs where
the engine lathe is too slow but
the additional production rate Forward and
desired does not warrant a spe- reverse
cial machine. Stop rod
A schematic illustration of the
components of a turret lathe is Feed
shown in Figure 5.5. shaft
Square and Hex Turrets: A
square turret is mounted on the
top of the cross slide and is capa- Longitudinal Cross- Turnstile
ble of holding four tools. If sev- feed lever Carriage feed Feed selectors
eral different tools are required, handwheel lever
they are set up in sequence and Cross-slide
can be quickly indexed and handwheel
locked in correct working posi-
tion. So that cuts can be dupli- FIGURE 5.5: Schematic illustration of the components of a turret lathe.
cated, the slide is provided with

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 Chap. 5: Turning Methods & Machines
A vertical turret lathe, shown in
Figure 5.7, is provided with two cutter
heads: the swiveling main turret head
and the side head. The turret and side
heads function in the same manner as
the hexagonal and square turrets on a
horizontal lathe. To provide for angle
cuts both the ram and turret heads may
be swiveled 30 degrees right or left of
center.
The machine can be provided with a
control that permits automatic operation
of each head including rate and direc-
tion of feed, change in spindle feed,
indexing of turret, starting, and stop-
ping. Once a cycle of operations is pre-
set and tools are properly adjusted, the
operator need only load, unload, and
start the machine. Production rate is
increased over those manually operated
machines, because they operate almost
FIGURE 5.6a: Ram-type horizontal turret lathe has the turret mounted on a slide or continuously and make changes from
ram. (Courtesy: National Acme Co., Div. DeVlieg-Bullard Inc.) one operation to another without hesita-
tion or fatigue. By reducing the han-
dling time, and making the cycle auto-
matic, an operator can attend more than
one machine.
The turret lathe normally has a jawed
chuck to hold the workpiece; however, a
collet may be more suitable when pro-
ducing parts from bar stock. A turning
machine equipped with a collet and a
turret is called a screw machine, but it is
actually a special turret lathe. The spe-
cial features of screw machines are
aimed primarily at reducing idle time on
the parts being machined, thereby
increasing productivity.
In Figure 5.8 a vertical turning center
is shown machining a heavy part.
5.3.3 Advantages of Turret Lathes:
FIGURE 5.6b: Saddle-type turret lathe has the turret mounted directly on the saddle. The difference between the engine and
(Courtesy National Acme Co., Div. DeVlieg-Bullard Inc.) turret lathes is that the turret lathe is
adapted to quantity production work,
side head have their respective whereas the engine lathe is used primar-
stops set so that the length of cuts ily for miscellaneous jobbing, toolroom,
can be the same in successive or single-operation work. The features
machining cycles. It is, in effect, of a turret lathe that make it a quantity
Ram the same as a turret lathe standing production machine are:
Cross rail
on the headstock end, and it has all • Tools may be set up in the turret in the
Turret Column the features necessary for the pro- proper sequence for the operation.
duction of duplicate parts. This • Each station is provided with a feed
Workpiece machine was developed to facilitate stop or feed trip so that each cut of a
mounting, holding, and machining tool is the same as its previous cut.
Cross slide of large diameter heavy parts. Only • Multiple cuts can be taken from the
chucking work is done on this kind same station at the same time, such as
Base of machine. two or more turning and/or boring cuts.
• Combined cuts can be made; tools on
FIGURE 5.7: Vertical turning lathes the cross slide can be used at the same
are used for machining large-diame- time that tools on the turret are cutting.
ter and heavy parts. • Rigidity in holding work and tools is

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 Chap. 5: Turning Methods & Machines
built into the machine to permit multiple A single-spindle
and combined cuts. automatic lathe is
• Turret lathes can also have attach- shown in Figure 5.9.
ments for taper turning, thread chasing Tooling: Any of the
and duplicating, and can be tape con- several available work-
trolled. piece holders that are
suitable for the particu-
5.4 Automated Equipment lar application may be
There are turning machines which allow used, including chucks,
automatic chucking, indexing, feeding, faceplate drives, collets,
spindle speed changes, and other work and specially designed
that has to be done by the operator on fixtures. Chucks,
the engine lathe. These automatic lath- where used, should be
es represent a refinement of the turret power operated to avoid
lathe, and they are particularly suitable the time lost to manual-
for long run, mass production applica- ly actuate chucks.
tions. Toolholders are nor-
Automatic lathes may be made up as mally designed with
single-spindle or multiple-spindle slots to locate, and FIGURE 5.8: A vertical turning center
machines. Generally, single-spindle clamps to hold individ- machining a heavy part. (Courtesy Giddings & Lewis, LLC)
machines provide for turning the work- ual cutting tools in their
piece, which is held in a collet or required locations. The
chucked on the headstock. Multiple- assembled toolholders are, in turn, Applications: Axle and transmission
spindle automatic lathes usually provide keyed and clamped in a specific loca- shafts, gear blanks, pump drives, and pin-
means for indexing the workpiece to tion on the front and rear tool slides. ions are all particularly well suited for
tools mounted on the various spindles. It is good practice to provide spare machining on single-spindle automatic
These tools might include drills, coun- toolholders wherein a set of sharpened lathes. In fact, almost any machinable
tersinks, boring bars, and other rotating tools can be preset and clamped, ready metal part falling within its size capacity
cutters. Both single- and multiple-spin- to exchange for a set of dull tools. that can be chucked, fixtured, or run
dle automatics may be made up with Setup time can also be saved by having between centers is a potential candidate
vertical as well as horizontal spindle spare toolholders preset with the tools for this machine. Single-spindle auto-
alignment. required for the next part to be run. matic lathes perform turning, facing,
As far as the machining processes on DeVlieg tooling for a single- or mul- chamfering, grooving, and forming oper-
an automatic lathe are concerned, the tiple-spindle automatic lathe is shown ations, and are usually used for parts with
fundamental considerations are the high in Figure 5.10. moderate production rates.
speeds desired for good productivity,
the economics of the cutting process,
and the balancing of speeds on various
phases of the operation to obtain the
desired rate of wear on each cutting
tool.

5.4.1 Single-Spindle Automatic

Lathes
The majority of single-spindle automat-
ic lathes are designed to machine work-
pieces that are located between two cen-
ters. Some, however, hold the work-
piece in a chuck, collet, or specially
designed fixture. Most have horizontal
spindles. A conventional single-spindle
automatic lathe has six major compo-
nents: base, bed, and ways; headstock;
work spindle; front tool slide; rear tool
slide.
The feed rates of the tool slides are
controlled by cams, hydraulics, or lead
screws. Spindle speeds are changed to
suit workpiece diameter/material FIGURE 5.9: Single-spindle automatic lathe (Courtesy: National Acme Co., Div.
requirements by means of change gears DeVlieg-Bullard Inc.)
in the headstock.

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 Chap. 5: Turning Methods & Machines
5.4.2 Single-Spindle Automatic
Screw Machines
Automatic screw machines are the pre-
sent-day developments of earlier
machines whose only function was the
production of screws. Modern machines
not only retain thread-cutting capabili-
ties but are also capable of performing
all turning operations. These machines
produce a wide range of parts from bar
stock fed through a hollow work spin-
dle. Some machines are arranged to
produce parts from coil stock.
Single-spindle automatic screw
machines have horizontal hollow spin-
dles aligned with stock feeding tubes.
Most are cam controlled but camless
versions, sometimes NC or CNC con-
trolled, are more flexible and quickly
set up, making them more suitable for FIGURE 5.10: DeVlieg tooling for single- or multi-spindle automatic lathe (Courtesy:
shorter production runs. Machines are National Acme Co., Div. DeVlieg-Bullard Inc.)
available in several sizes and have six
major components: base, headstock, 5.4.3 Multiple-Spindle Automatic broken up into increments. For exam-
hollow work spindle, front tool slide, Bar and Chucking Machines ple, a drilled hole that is the longest cut
rear tool slide, and turret, as shown in Conventional multiple-spindle automat- of a certain part may be completed in
Figure 5.11. A conventional single spin- ic bar and chucking machines have two three or more positions.
dle automatic screw machine is shown major advantages over single-spindle Part sizes and complexity of design
in Figure 5.11 automatics - both of which reduce the can be accommodated equally well on
The feed rates an motion of tool time required to produce a part: multi-spindle or single-spindle
slides are controlled by cams or • The multiple-spindle machine per- machines. Shorter changeover time
hydraulics. Spindle speeds are changed forms work on each of its working sta- favors single-spindle machines for short
to suit workpiece diameter/material by tions concurrently; it is also possible to production runs, but the shorter machin-
means of change gears in the machine complete a different operation on a part ing time per piece of the multi-spindle
base. Bar stock is fed automatically to at each position within the same time. machine makes it more economical for
a swing stop, or a turret stop, after each • The maximum time required to com- long runs.
part is completed and cut off. The col- plete one piece is the time required for A schematic diagram of s six-spindle
let is automatically released during the longest cut, plus index time, and in automatic bar machine is shown in
stock advances. certain instances the longest cut can be Figure 5.12
Tooling: Round, square, hex, and
other standard-shape collets are avail-
able in sizes to suit commercial bar
stock sizes. Specials are also made to
suit.
Many special tools and toolholders
are designed and made for certain appli-
cations, but a significant savings of time
and money can be realized by the use of
the standard tools and holders available.
A large selection of standard tools are
available from stock.
Applications: Single-spindle auto-
matic screw machines are used to pro-
duce an extremely wide range of small
parts including shafts, pins, knobs,
screws, bolts, and so on, from any
machinable metal. Flats and slots can be
milled and cross holes drilled, It is nor-
mal for one operator to operate several
machines, the number depending on the
frequency required for reloading bar FIGURE 5.11: Conventional single-spindle automatic screw machine. (Courtesy
stock and adjusting or changing tools. Courtesy National Acme Co., Div. DeVlieg-Bullard Inc.)

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 Chap. 5: Turning Methods & Machines
are more flexible in applica-
tion. They do not, however,
accept bar stock. Some other
advantages are that they are
convenient to load, operate,
and adjust or change tooling.
The machine illustrated in
Figure 5.13 has three major
components: base and center
column, carrier and work
spindles, and machining
heads. The machine is
designed to permit each spin-
dle to operate independently,
having independent speeds
and feeds. In effect, the
machine illustrated can oper-
ate as seven individual
machines all loaded and
unloaded at a common sta-
tion.
Machines with dual spin-
dles and multiple-tool
FIGURE 5.12: Schematic diagram of a six-spindle automatic bar machine (Courtesy National Acme
Co., Div. DeVlieg-Bullard Inc.)
machining heads are avail-
able, permitting duplicate
setups, or first and second
5.4.4 Multiple-Spindle Vertical chucking machines are manufactured chucking work to be performed (both
Automatic Chucking Machines by several machine tool builders in sev- ends). Double indexing is available and
Multiple-spindle vertical automatic eral sizes and models ranging from 4 to is used with dual-spindle setups. A mul-
8 spindles. One maker sup- tiple-spindle vertical automatic chuck-
plies a 16-spindle machine ing machine is shown in Figure 5.13.
that is, in reality double
spindles for each position 5.5 Computer Controlled Lathes
of an 8-spindle machine. In the most advanced lathes, movement
These machines use less and control of the machine and its com-
floor space than an equiva- ponents are actuated by computer
lent horizontal model and numerical controls (CNC). These lath-

FIGURE 5.13: Multiple-spindle vertical automatic FIGURE 5.14: Multi-station tool holder with four-plus-four tools
chucking machine. (Courtesy National Acme Co., Div. (Courtesy: Dorian Tool)
DeVlieg-Bullard Inc.)

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 Chap. 5: Turning Methods & Machines
es are usually equipped with one or
more turrets. Each turret is equipped
with a variety of tools and performs sev-
eral operations on different surfaces of
the workpiece. A multi-station tool
holder is shown in Figure 5.14.
These machines are highly automat-
ed, the operations are repetitive and
maintain the desired accuracy. They are
suitable for low to medium volumes of
production. A high precision CNC lathe
is shown in Figures 5.15.
More sophisticated machining sys-
tems, including boring and milling
operations, will be discussed in a later
chapter.

FIGURE 5.15: A high production computer controlled Swiss type lathe (Courtesy:
Hardinge, Inc.)

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