Turning

is the most prevalent lathe operation. In its most common form, a single-point cutting tool is moved on
a precise path with respect to a rotating work piece.

Form turning

occurs when a single point cutting tool moves longitudinally in a path other than a straight line, or when
a cutting tool ground to a particular curved or otherwise irregular edge is fed radially into the rotating
workpiece.

Form turning – The tool is ground to The shape desired and is fed into the workpiece As it rotates,
cutting a surface whose shape is the Inverse of that of the form tool

Tracer turning

is a process for form Turning.

The inward and outward motions of the cutter as it moves longitudinally along the length of the Part are
controlled by the motion of a stylus as it Bears against a template or master part. Several Passes may be
used, after which the part duplicates The shape of the template.

(The movement may also be controlled electronically without tracing, by using numerical or computer
numerical control, CNC). Some tracer lathes have

An additional tracer-controlled cross slide at the rear Of the work to facilitate the machining of grooves,
undercuts, and chamfers
Facing -In facing, the tool moves perpendicularly to the axis of rotation of the spindle And a flat surface
is produced.

Produces Flat surface in casting.

Straight Turning - In straight turning, the tool moves parallel to the axis of rotation and a cylindrical
surface is generated.

Taper Training - In tapered turning, the tool moves at an angle to the axis of rotation and a tapered
surface is produced.

Grooving - The cutting tool, usually ground to the width and bottom shape required, is fed into the work,
cutting a groove of the desired dimensions. Groves can be cut into any external or internal surface that
such a cutting tool can reach.(Internal grooves are usually called recesses.)

Knurling – is not really a machining (cutting) operation because the knurl is formed, not Cut, in the
workpiece. Knurling is a common lathe Or screw machine operation. The hardened knurling Tool rolls
against the cylindrical surface of the rotating Workpiece with high pressure, causing the surface Material
of the workpiece to flow into peaks and Valleys according to the pattern of the knurling Tool. The result
is a surface in the finished part that Is roughened to a particular pattern, useful to Improve the grip if the
part must be held or rotated By hand when it is used. Several different patterns Are possible. Other uses
for the operation are for decoration and to increase the diameter of the part Slightly to facilitate a press
fit.

Tracer Turning - In tracer turning, The single point cutting tool moves inward and Outward as it moves
longitudinally, creating a Contoured or other shaped surface on the rotating Workpiece. The tool’s path
can be controlled by a Template or by computer numerical control (CNC) template or by computer
numerical control (CNC)

Cutting off (parting) – When parts are Made in lathes and screw machines from bar stock, The final
operation is to sever the part from the Remaining bar material. This is accomplished by Advancing the
cutoff tool, a narrow grooving tool, Radially into the work. When the cutting edge Advances to the axis
of rotation of the part, the part Is severed and falls to the bed of the machine. Some Machines, which
make blanks for further machining Or other operations, are designed to perform only Cut off operations
and other simple ones on bar and Tubular stock.

Drilling -

Reaming -

Boring –

Lathes and Other Turning Machine

 Engine Lathes - are general purpose machines that provide the most basic means of performing
turning, facing, grooving, knurling, and threading operations. These machines can also drill,
ream, and bore holes at the center of rotation
 The major function of the engine lathe is to change the size, shape or finish of a revolving work
piece with various cutting tools. The lathes in most shop consist of a headstock, tailstock,
carriage and bed. Pulleys used to change the spindle speed and feed rate.
 Turret Lathes - A turret lathe is one that is equipped to change cutting tools quickly. A standard
lathe has a single tool post mounted on the cross slide. Turret lathes generally have a four-sided
Turret on the cross slide of the machine.
When the turret lathe’s tooling arrangement Permits more rapid production than is feasible with
 Screw machines - are automated lathes which can machine turned parts. The machine
components spin very quickly on a rotating lathe, which shaves down metal to the size desired.
Developed for the mass production of Screws from bar stock but long since used for a Wide
variety of parts from bar stock over a broad size Range Engine lathes.
1. Single-spindle screw machine
Two common Varieties
 Sharpe(Swiss type)
 Brown( Turret type)
2. Multi spindle screw machine
Have 4, 6, or 8 spindles instead of the single spindle Of the Brown and Sharpe and Swiss-
type machines. Turning machines that use a number of tools mounted on a central
spindle to simultaneously operate on material pieces.

3. Swiss type screw machine - Swiss screw machine is a type of automatic lathe with
multiple tool holders arranged radially about the spindle, and a tailstock coaxial to it. It
is designed for rapid production of small, high precision parts.

Tools are mounted on two Cross slides and three upper slides arranged radially Around
the spindle.
 Chucking machine – are automatic Lathes designed for operations on castings, forgings, and
other parts, rather than on bar-stock. Mechanisms and other features are similar toThose of
screw machines except for the bar feeding.

Round Hole Making Method

 Drilling
 Creates a round hole in a workpart
 Contrasts with boring which can only enlarge an existing hole
 Cutting tool called a drill or drill bit
 Customarily performed on a drill press
 Counter Boring
Provides a stepped hole, in which a larger diameter follows a smaller diameter partially into the
hole. The operation is most often performed to provide clearance for a bolt head or Multi-
diameter part.
 Counter Sinking is an operation that adds a chamfer at the entry end of a hole. A rotating
cutting tool, with the edge set to the angle of chamfer desired, is fed into the hole and removes
material at the edge.
 Reaming - is a finishing operation of high-precision holes performed with a multi-edge tool. High
surface finish, superb hole quality and close dimensional tolerance are achieved at high
penetration rates and small depths of cut.
The primary purpose of reaming is simply to create smooth walls in an existing hole
 Boring - is a cutting process that involves the use of a single-point cutting tool or boring head to
enlarge an existing hole in a workpiece. This is in stark contrast to drilling, which is performed to
create an initial hole in a workpiece.
 Jig boring - is used for the production of jigs, fixtures, tools, and other parts. That
requires a high degree of accuracy. They are defined by terms of highest accuracy
through rigidity, low thermal expansion, and precise means of measuring distance for
locating and spacing holes.
 Jig may be defined as a device which holds and located a workpiece and
guides and controls one or more cutting tools. The holding of the work and
guiding of the tool is such that they are located in true positions relative to
each other.
 Is a device which holds and locates a workpiece during an inspection or for a
manufacturing operation. The fixture does not guide the tool.
 Horizontal boring mills - (Some machines have a table that also swivels.) The headstock
that holds the spindle can be raised or lowered. The tool-holding spindle can move
inward or outward. These machines are used in the machining of large components that
have horizontal holes requiring the precision that boring provides.
 Vertical boring mills - using a vertical boring mill, the workpiece is rotated around a Y-
axis while the boring head moves in a linear pattern. When machining using a vertical
boring mill, the workpiece is secured on a horizontal table that rotates along a vertical
axis.
 Gun drilling - is a deep hole drilling process that uses a long, thin cutting tool to produce holes in
metal at high depth-to-diameter ratios. Gun drilling is effective in diameters from 1 – 50 mm
[0.04 – 2.00 in].
A standard gundrill has a single effective cutting edge that removes chips as it advances into a
metal workpiece. The gundrilling process is able to drill deep holes beyond what is possible with
 conventional machinery and tooling such as twist drills, by using high pressure coolant for clean
chip exhaust, even at extreme depths.
Originally developed For manufacture of gun barrels.
 Trepanning - a drilling process that leaves a core. Trepanning is a deep hole drilling process
a technique used for drilling larger hole diameters where machine power is limited as it is not as
power consuming as conventional drilling where the entire hole is converted into chips. The
trepanning tool does not machine the whole diameter, only a ring at the periphery.

 Multiple Spindle Drilling - are generally used for drilling number of holes simultaneous together.
They are used in mechanical industry in order to increase the productivity of machining system
and to reduce the operation time.

Grinding and Abrasive Machining

He workpiece is cut by the Sharp edges of small pieces of abrasive material, Rather than the edge of a
hardened steel or carbide Cutting tool.
The particles commonly consist Of aluminum oxide, silicon carbide, cubic boron Nitride, diamond, or
other hard materials.
(Some grains, depending on their shape, do not cut But instead rub or slightly deform the surface of the
Workpiece.)
 Cylindrical Grinding Center type -Is used to produce External cylindrical surfaces by removing
material, Creating smoother surfaces, and providing more Precise dimensions
The headstock wheel head, and tailstock (both of which may be swivelling or non-swivelling type)
are mounted on a swivel table which itself is mounted on a sliding table that can move to and fro in
the bed guideways. A special feature of these is to grind multi-diameter shafts and control their
concentricity.

a) cylindrical Grinding center less Grinding

A centerless incorporates the use of two wheels, the regulating wheel, and the grinding wheel.
The workpiece is passed between these two wheels, or you can plunge grind the part between
the wheels where the part remains between the wheels until the desired diameter is achieved.
You can grind above or below the center of the wheels, hence the name Centerless.
In centreless grinding, the workpiece is rotated by the friction between the regulating wheel and
the workpiece.
b) Through-feed centerless grinding
In this method, the regulating wheel is canted Slightly, causing the work piece to move axially
across the grinding wheel as
the grinding takes place.
The process is Used for grinding pins, shafts, and similar parts of Constant diameter.
c) infeed centerless grinding
differs from the through-feed process in that the part does not move axially
The method Is used when a portion of the workpiece is larger Than the ground surface. The
workpiece is placed In position; the grinding wheel is fed into the Work; the wheel retracts after
grinding and the Workpiece is removed or ejected.
d) end-feed centerless grinding – is used for tapered parts. Either the regulating wheel or the
grinding wheel, or both, are dressed to provide the desired taper angle. The two wheels and the
work rest blade are set in fixed relationship to each other. There is a stop to control the position
of the workpiece, which is fed and removed axially.
 internal grinding - is a process for finish machining existing round holes.
Internal grinding is most commonly used to finish Machine precision holes in hardened
workpieces.
 Internal centerless grinding - The workpiece is Held between three rolls, which locate it
and provide rotation. The grinding wheel is inserted into The center hole and fed radially
to contact the inner Surface of the hole as in regular internal grinding.
Can be Used to finish machine sleeves, rings, and similar Parts.
 Surface Grinding - moves the workpiece in a horizontal plane so that it passes under a revolving
grinding wheel which contacts it and removes surface material.
a) horizontal spindle surface grinding - is surface grinding with a horizontal grinding wheel
spindle.
 b) vertical spindle surface grinding – uses a grinding wheel mounted on a vertical spindle
with either a rotary or reciprocating table
c) creep feed grinding – is characterized by lower workpiece speeds and higher depths of
cut resulting in a larger arc length of contact between the grinding wheel and workpiece
when compared with reciprocating or pendulum grinding.
tool post grinding - involves the mounting of a power-driven grinding wheel for either
external or internal grinding on the tool post of a lathe. The wheel then performs
conventional grinding operations on parts held in the lathe. This method is a useful means
to provide cylindrical grinding in shops not equipped with the conventional cylindrical
grinding machines.
 Low stress Grinding - is a variation of conventional grinding in which the objective is to minimize
stresses developed in the workpiece by the grinding operation.
The process is applicable when the part to be ground is subject to high stresses in use or is
susceptible to damage from heat.
 Plunge grinding - is simply a center-type
grinding operation where there is no transverse feed of the grinding wheel.
 Disc Grinding - is a means for producing flat surfaces. The workpiece is held against the flat side
(face) of a large rotating abrasive disc. Double Disc sometimes employed. The workpiece is fed
between
Two abrasive discs which grind the opposite surfaces of the workpiece at the same time, thus
controlling flatness, thickness, and parallelism in the Same operation same operation
 Abrasive belt Grinding - uses an abrasivecoated cloth belt to remove metal.
The process can provide lower heat levels than grinding with an abrasive wheel because the belt
carries away heat effectively. Lubricants may be used to facilitate the operation. The approach is
used for rough metal removal from castings, forgings, and other shapes, especially when the work
piece is large.
 Abrasive Jet machining - Abrasive jet machining is the process of impinging the high-speed
stream of abrasive particles by high-pressure gas or air on the work surface through a nozzle and
metal removal occurs due to erosion caused by high-speed abrasive particles.The stream is
directed at the desired place on the workpiece.
To control the size and shape of the cut, either workpiece or nozzle is moved by cams,
pantographs, or any other suitable mechanism
Abrasive generally used are Aluminium oxide, Silicon carbide or glass powder.
 Abrasive Flow Machining (AFM) - an interior surface finishing process characterized by flowing
an abrasive-laden fluid through a workpiece .This fluid is typically very viscous, having the
consistency of putty or dough. AFM smooths and finishes rough surfaces, and is specifically used
to remove burrs, polish surfaces, form radii, and even remove material. The nature of AFM
makes it ideal for interior surfaces, slots, holes, cavities, and other areas that may be difficult to
reach with other polishing or grinding processes. Due to its low material removal rate, AFM is
not typically used for large stock-removal operations, although it can be.
 Ultrasonic Machining - utilizes an abrasive in a water slurry and a shaped tool. With them
abrasive between the tool and the workpiece, the tool is vibrated at ultrasonic frequency. The
vibration of the tool drives the abrasive particles against the workpiece, cutting a cavity that has
 the same shape as the tool. It is most advantageous for shallow cuts in hard, brittle, non-
conductive materials that are difficult or unfeasible to cut by other methods.
 Rotary Ultrasonic machining - uses a rotating tool, coated with diamond abrasive and
ultrasonically vibrated, to machine hard and brittle materials. There is no abrasive slurry but a
liquid coolant, usually water, is used. Milling, drilling, and threading operations can be
performed, but drilling is the primary application. Non-metals: glass, alumina, ceramic, quartz,
sapphire, and composite materials are normally processed.
Milling - means of creating a desired surface with a rotating multi-toothed cutter. Each tooth of
the cutter removes material as the workpiece advances against it. The axis of rotation of the cutter may
be either horizontal or vertical. The cutter can provide cutting action on its side or at its end
(face), or both. The cutter rotates rather rapidly and its position is normally stationary.
Milling is the most common machining operation for producing flat surfaces, but slots, and contoured or
stepped surfaces and screw threads can also be produced.
 Face milling - produces a flat surface at a right angle to the axis of rotation of the cutter.
For flat surfaces, face milling is generally preferable to peripheral milling from the stand-
points of tool economy, simplicity of set-up, and cutter rigidity. However, the operation is limited
to flat surfaces.
 Peripheral Milling - The operation is usually performed on horizontal-spindle machines.
The surface maybe flat or contoured, depending on the profile of
the cutter. Flat and contoured surfaces, slots, and key-ways, are machined by this method.
(Fig. 3D,
in views a), b), f), and g), shows peripheral
milling. Views c), d), and e) show both peripheral
and face milling.)
 End Milling - uses a cutter, commonly of smaller diameter, with teeth on both the end (face) and
periphery.
less rigid than cutters for other milling methods. Lighter feeds may be required to reduce cutter
deflection. Material removal rates are less than with other milling methods and accuracy may
not be as great.
 Slab Milling - is peripheral milling with cutters that produce a flat surface over a wide area. The
axis of rotation of the cutter is parallel to the machined surface. The cutter often removes large
amounts of material. Sometimes, two or more cutters are used per arbor with opposing helixes
to balance cutting forces.
 Form Milling - When the peripheral cutting edges of the milling cutter are ground with a form
rather than in a straight line, that form is transferred to the workpiece as the milling operation
proceeds.
 Gang Milling - is simply milling with more than one cutter on the arbor of the milling machine.
This produces multiple surfaces on the workpiece with one pass of the cutters.
 Straddle Milling - involves the use of two cutters on one arbor with a space between them. Two
surfaces are cut in one pass, but the area between them is not machined,
 Fly Cutter Milling - involves the use of a single point cutter rather than a multiple-tooth cutter to
per form a milling operation. It is face milling with only one cutting tooth. The method is useful
for producing flat surfaces in a tool room situation where the optimum multiple-toothed cutter
may not be available.
 Pin routing - involves the use of a template to guide the movement of a high speed routing
cutter (small diameter end mill). Typically, the process is used to blank flat stock of sheet metal
or other materials. Stacks of thin material can be cut by this method, to produce multiple parts.
 Spot Facing -  is normally used to provide a small flat bearing surface, perpendicular to the
axis of a hole, for a bolt head or nut.
Spot facing is the operation of smoothing and squaring the surface around and at the end of a
hole so as to provide a smooth seat for a nut or for the head of a cap screw. Spot facing is
generally done on castings and forgings.