METAL FORMING PROCESS

ME8351 MANUFACTURING TECHNOLOGY 1
UNIT 3 METAL FORMING PROCESSES
S.BALAMURUGAN
ASSISTANT PROFESSOR
MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEEERING & TECHNOLOGY

• FORMING – Change the shape of an existing solid body
• Ex – Metal body of a car(Sheet metal forming)
• SHAPING – It involves Molding & Casting
• Ex – White ceramic insulator for a spark plug of a car
FORMING & SHAPING
ME 8351 MANUFACTURING TECHNOLOGY -1 S.BALAMURUGAN, AP/MECHANICAL, AAACET

• The size & shape of a part is obtained by plastic deformation under the
action of large external forces.
• The size & shape of a part is obtained by deforming & displacing the material
under the action of large external forces.
• Due to the application forces, the stress induced in the part. This stress must
be greater than the Yield Strength & less than the Fracture strength of the
material.
• Chip less Manufacturing Process
• Mechanical Working Process
• Metal Forming Process
• Rolling – Uniform cross section - Simple
• Forging – Complicated shape
• Extrusion – Uniform cross section
• Drawing – Wire/Bar
• Press Working – Sheet Metal
METAL FORMING

METAL FORMING
PROPERTIES FOR METAL FORMING
• Low yield Strength + High Ductility - Preferable
• High Yield strength + Low ductility leads to High Power Consumption, High
Load required
MICROSCOPIC – PLASTIC DEFORMATION
• Slip & Twinning – Atomic Movement
MACROSCOPICALLY – PLASTIC DEFORMATION
• Flow of metal in the direction of applied force
ADVANTAGES OF METAL FORMING
• Inclusion & Impurities are broken – Well distributed
• Pores can be collapsed – More Density
• Strength Increases
• Hot Forming – A new fine grains – High Mechanical property
• Cold Forming – Strain Hardening

ADVANTAGES OF METAL FORMING
• HIGHER PRODUCTIVITY – Rolling & Forging
units fabricate hundreds of tonnes of end
product.
• High-Standard Quality Products – Required
physical, Mechanical & structure can be
achieved
• High strength, Corrosion & Wear resistance
• High dimensional accuracy & Surface finish
• Extra thin Foil, Wire, Sheet steel can be made.
Other processes can’t able to produce
• Minimum waste of metal – No chip formation
• By controlling the end forming temperature &
the degree of deformation, it is possible to
impart the strength within the permissible
range
• During metal working, the grains of the
material get elongated in the metal flow. The
part able to offer more resistance to stress
them.

FORM OF MATERIALS FOR METAL FROMING PROCESS
BLOOM – Square or Rectangle - 150 mm × 150 mm to 250 mm × 250 mm
BILLET – Square - Rods & Wires - 50 mm × 50 mm to 150 mm × 150 mm
SLABS – Rectangular – 50-150 mm Thickness & width 300-1500mm

CLASSIFICATION METAL FORMING PROCESS
Based on Working Temperature
• When material is heated, Yield Strength decrease, Ductility increases
• Low yield Strength + High Ductility – Preferable
• COLD FORMING - The working temperature for cold working is below
recrystallization of metal or alloy.
• (Temp. Less than 0.3 × Melting point of the metal)
• HOT FORMING - The working temperature for hot working is above
recrystallization of metal or alloy. ( 0.7 – 0.9 × Melting point of the metal)
RECRYSTALLIZATION TEMPERATURE
• It is the minimum temperature at which the plastic deformation of metal forms a
new grains with in the specified time.
• The new grains in reduced size. - Iron - 400°C, Steel - 1000°C
GRAPH – RECRYSTALLIZATION TEMPERATURE VS GRAIN SIZE
IMPORTANCE OF FORGING
https://www.forging.org/about/forgings-where-why-how

COLD FORMING, HOT FORMING, WARM FORMING
COLD FORMING
• The working temperature for cold working is below recrystallization of metal or
alloy. (Temp. Less than 0.3 × Melting point of the metal)
• The Plastic deformation of metals & alloys under conditions of temperature &
strain rate.
• Work Hardening or Strain Hardening not relieved
• Work hardening – Strengthening of metal by Plastic deformation. It occurs
because of dislocation movements & dislocation generation in the crystal
structure
• When a metal is heated & deformed under mechanical force, an
energy level will be reached. when the old grain structure starts
disintegrating, an entirely new grain structure with reduced size
starts forming.
• This phenomenon called Recrystallization. The temperature at which
this phenomenon starts is called Recrystallization temperature.
Some case, it takes sometime to get completed.

• For pure metals, Tcr = 0.3 Tm
• For alloys, Tcr = 0.5 Tm
• For lead & Tin, Below Room temperature
• Cadmium & Zinc, Room temperature
HOT FORMING
• The working temperature for hot working is above recrystallization of metal
or alloy. ( 0.7 – 0.9 × Melting point of the metal)
• The Plastic deformation of metals & alloys under conditions of temperature
& strain rate.
• At the end, a fine grained recrystallized structure is obtained.
GRAPH
• In cold working, the forces increases with increased deformation
• In hot working, once the force equals the yield point load, the deformation
proceeds at almost constant value of force.

HOT FORMING COLD FORMING
ADVANTAGES ADVANTAGES
Plastic deformation above Recrystallization temp. Plastic deformation below Recrystallization temp.
By heating, Yield strength reduced, ductility
increases, So less force required
Metal gets Strain hardened, strength increases,
Hardness increases, Toughness & Ductility
reduces.
No strain hardening effect – allow deformation up to
any extent
No scale formation, No oxidation – Low
temperature – Good surface finish
Controlled deformation at the high temperature
leads to fine grain structure – High mechanical
property
No additional heat supply – So no thermal
expansion – Good control over the dimension
At high temperature, even brittle materials can be
deformed
DISADVANTAGES DISADVANTAGES
Heating the metal to high temperature leads to
Oxidation & Scale formation – Reduce the finish of
the component.
Decarburization – Loss of carbon in the surface of
the steel – reduction in strength, hardness
Deformation due to strain hardening, Limited
deformation is possible in one go.
We need to apply Annealing(Softening), then only
we can do further deformation
Poor control over the dimension due to thermal
expansion & contraction
Limited deformation due to high yield strength –
deformation limited due to press capacity – High
capacity hammer required
Handling of the part is difficult – High temp No working of the Low Ductility metal
Easy to carry out - Poor finish, Dimension control Difficult to carry out – Require More force

TYPE OF STRESS APPLIED
Direct Compression process
Squeezing Processes
• Rolling, Extrusion, Forging
Pure Tensile Stress
• Stretch Forming, Vaccum
forming
Combined Stress Process
Tensile + Indirect Compressive
• Drawing, Deep Drawing
Shear Stress
• Piercing, Blanking, Notching
Bending Moment
• Straight Bending, V-Bending

ROLLING
• To reduce the cross sectional area of the metal.
• To reduce the thickness of the metal.
• Width remains same, Wo = Wf, Lo < Lf, To > Tf,
• Wo – Initial Width, Wf – Final Width, To– Initial Thickness, Tf – Final
Thickness, Lo – Initial Length, Lf – Final Length
• Uniform cross section along the length alone can be obtained
• Square, Plates, T Section, I section, C Section, L Section, Oval
Shape, Hexagonal shape.
• Draft d = To – Tf, Draft Δt = µ2 × R
• µ - Coefficient of friction between Roller &
metal (Cold forming µ = 0.1,
Hot Forming µ = 0.4 – 1, Warm µ = 0.20
• R – Radius of Roller
• If Surface roughness more then More
Draft is possible
• At high temperature, Coefficient of friction
increases, increase the draft.

• Angle of Bite – It determines the extent of thickness reduction which will be
taking place.
Angle of Bite depends on
Condition of the process – Hot rolling (24°– 32°) or Cold Rolling (3° – 4°)
Diameter of the Roller
• Large dia roller – Low angle of bite
• Small Dia roller – High angle of bite
Surface roughness of Roller
• Smooth – Low angle of Bite,
• Rough – High angle of Bite
• At entry, Metal speed < Roller Surface speed
• At Exit, Metal speed > Roller Surface speed
• At neutral plane, Metal speed = Roller Surface speed
True Strain = e = ln (
𝑻𝒐
𝑻𝒇
), Average Flow Stress of Metal = σf =
𝑲 𝒆𝒏
(𝟏+𝒏)
K – Strength Coefficient, n –Strain Exponent, e - Strain, W –Width of the plate
Length of Contact = L = √(𝑹 𝑻𝒐 − 𝑻𝒇 ), Roller Force = F = σf × L × W
Torque = T = 0.5 × F × L, Power for Rolling = 2πN × F × L
ROLLING

TYPES OF ROLLING MILL
TWO – HIGH ROLLING MILL
• Two Horizontal rolls - Lowe roll is fixed, Upper Roll movable
• The Direction of rotation is fixed
THREE – HIGH ROLLING MILL
• Three horizontal rolls – Direction of Rotation, Upper & Lower roll same
• Workpiece is fed in one direction between the Upper & Middle rolls, Reverse direction between
middle & Lower roll
FOUR HIGH ROLLING MILL – Hot & Cold rolled sheets & Plates
• Four Horizontal Rolls – Two small dia rolls & Two large dia rolls
• Larger dia rolls – Backup rolls – To prevent the deflection of smaller rolls
• Smaller dia rolls – Working rolls – Concentrate the total working pressure over the metal

TANDEM ROLLING MILL
• It is a set of two or three stands of roll sets in parallel alignment
• Without changing the direction of metal, metal continuously passed through the rolls
CLUSTER ROLLING MILL
• Special type of Four High rolling Mill
• For rolling hard thin materials, very small diameter work rolls used
• This working rolls supported by two or more large rolls

PLANETARY ROLLING MILL
• For larger reduction in thickness, this type
of mill used. Free rotating wheels instead
of single small roll
• Heavy backing roll surrounded by large
number of planetary rolls
• Hot Slab is converted into a coiled strip in
single pass
• Stage by Stage reduction in each pair of
mills
• Planishing Mill – to improve the surface
finish
UNIVERSAL ROLLING MILL
• Metal is reduced by both horizontal &
vertical rolls
• The vertical rolls makes the edges of the
bar even & smooth

ROLLING PROBLEM
Roll 300 mm wide strip, that is 25 mm thick, to 22 mm thickness in one
pass with roll speed of 150 rpm and radius = 250 mm. Material has K =
275 N/mm2, n – 0.15 and µ = 0.12. Determine if feasible and calculate F, T
& Power.
• Draft Δt = µ2 × R = (0.12)2 (250) = 3.6 mm > d = 25 – 22 = 3 mm
This process is feasible to produce the required dimension.
Contact Length = L = √(𝑹 𝑻𝒐 − 𝑻𝒇 ) = √(𝟐𝟓𝟎 𝟐𝟓 − 𝟐𝟐 ) = 27.38 mm
True Strain = ϵ = ln (
𝑻𝒐
𝑻𝒇
) = ln (
𝟐𝟓
𝟐𝟐
) = 0.1278
Average Flow Stress of Metal = σf =
𝑲 𝝐 𝒏
(𝟏+𝒏)
=
𝟐𝟕𝟓 𝟎.𝟏𝟐𝟕𝟖 𝟎
.
𝟏𝟓
𝟏+𝟎.𝟏𝟓
= 175.636 N/mm2
Roller Force = F = σf × L × W = 175.636 × 27.38 × 300 = 1.44 × 106 N
Torque = T = 0.5 × F × L = 0.5 × 1.44 × 106 × 27.38 = 19.76 × 106 N mm
Power for Rolling = 2πN × F × L = 2π(150) × 1.44 × 106 × 27.38
= 3.78 × 1010 N mm/min = (3.78 × 1010 ) / (1000 × 60)
= 629.5 × 103 Nm/s = 629.5 W
N m / S = W

FORGING
• It is defined as a metal working process by which
metals & alloys are plastically deformed to the desired
shapes by the application of a compressive force.
• Pressure is applied intermittently
• Dies used to apply pressure
• Dies have a linear working motion
• It is extensively used for producing Crank, Crank
shaft, Connecting Rod for automobiles, Wrenches,
Crane hooks
• Improved mechanical properties – Dense Products -
Pores & Inclusions are removed by forging.
• Hot forging & Cold Forging
Based on the method of applying the Blows
• Impact forging & Gradual Pressure forging
Based on the flow of metal constrained in the Dies
• Open Die & Closed die or Impression-die Forging

FORGING
• Drawing out – Cross Sectional Area Reduced – Length Increased
Application of force is perpendicular to the elongation / Flow of Metal
• Upsetting – The Flow of metal or plastic deformation, increases the cross
sectional area at the cost of Length(Reduced)
Force is applied along the length of the job.
FORGING

BOLT MANUFACTURING - FORGING
1.Wire - Uncoiled, straightened and cut to length.
2.Cold forging - Molding the steel into the right shape at room temperature.
3.Bolt head - Progressively formed by forcing the steel into various dies at high
pressure.
4.Threading - Threads are formed by rolling or cutting.
5.Heat treatment - The bolt is exposed to extreme heat to harden steel.
6.Surface treatment - It depends on the application. Zinc-plating is common to
increase corrosion resistance.
7.Packing/stocking - After quality control to ensure uniformity and consistency,
the bolts are packaged.

• FULLERING – Reducing the stock to the desired size
• EDGING – Ensure defect free flow of material, complete die fill & minimum
flash loss
• BENDING – For the parts having a bent shape
• BLOCKING – The material flows to deep pockets, sharp corners etc. Before
finishing process
• FINISHING – It is the final impression for actual shape. At this stage, a little
extra material is added to the stock forms the flash & surrounds the forging
In the parting plane.
• TRIMMING – Removal of flash.

OPEN DIE FORGING
• Shapes – Shafts, Disks, Rings
• A solid workpiece placed between
the two flat dies, By compression
load – Height reduced
• The workpiece is deformed uniformly,
but the workpiece develops a barrel
shape. It is called as Pancaking or
Barreling
• This Barreling effect due to frictional
forces at the die-workpiece interface,
friction can be minimized by effective
lubricant COGGING – Blooms & Slabs from cast ingots

CLOSED DIE or IMPRESSION DIE FORGING
• It is performed with dies which contain the
inverse of the required shape of the
component
• Initial step – Used to redistribute the metal
in the work part to achieve a uniform
deformation
• Final step – the final geometry of the
component can be achieved
• Complex parts leads to Flash formation.
This flash can be removed by Trimming
operation

OPEN DIE FORGING CLOSED DIE FORGING (IMPRESSED DIE)
• The workpiece is compressed
between the two flat dies.
• The workpiece is compressed between
the two impressed dies.
• The process is simple. The cost of
die is low.
• The process is complex. The cost of die is
high.
• During the process, there is poor
utilization of material
• During the process, there is better
utilization of material
• After the process, machining of
component is required.
• After the process, machining of
component is not required.
• The dimensional accuracy of
obtained products is not good.
• The dimensional accuracy of obtained
products is good.
• Used for low quantity production. • Used for high quantity production.
• Used for simple components. • Used for simple & complex components.

PRECISION FORGING or NEAR NET SHAPE FORGING
• Forging operation become very precise – reduce the additional operation
• The process which produces a component to the final dimensions of the
desired product is called Near Net Shape or Net Shape Forging.
• Little Flash formed – By Trimming it will be removed.
• Special dies used to produce the parts with high accuracy than impression
die forging
• High force required to obtain the fine dimensions – High capacity equipment
needed.
• Materials – Aluminium, magnesium Alloy, Steel & Titanium
• Application – Gear, Connecting rod, Gear box housing, Turbine Blades
ADVANTAGE
• Less material waste, requires less machining
• Very thin webs & flanges can be produced
DISADVANTAGE
• Large force required, High Investment
• Precise control of the billet volume & shape
• Accurate positioning of billet in the die cavity

HAMMERS
HAND OR SMITH HAMMER SLEDGE HAMMER
• Small in Size
• Flat head – Face, Half Ball shape – Peen
• Ball peen Hammer – Riveting
• Cross Peen Hammer – Peen at right angle
to the axis of the handle – Stretching
purpose
• Straight Peen Hammer – Peen is parallel
to the axis of the hammer – Stretching the
metal.
• Larger in size compared to Hand
hammer
• Used for heavy blow
• Heavy in weight
• Striking surface is slightly convex –
To avoid the damage in workpiece
• No peen –Double ended or Double
faced hammer

POWER HAMMER - SPRING HAMMER
SPRING HAMMER
• Simple design to regulate the speed & force - Suitable for small forging
• Heavy rigid frame carrying vertical projection. At its tip which act as a housing for
Bearings in which leaf or laminated spring oscillates.
• One end is connected with connecting rod
• Other end connected with vertical tup which reciprocates between fixed guides
• Connecting rod is attached to eccentric sheave.
• Eccentric sheave is attached to crank wheel.
• To operate the hammer, treadle is pressed downwards that makes the sheave to
rotate through the crank wheel & then leaf spring oscillates.
• This oscillation cause reciprocating motion of the tip & blows provided
• Hand lever is used to adjust the intensity of the Blow
• Heavy component require a
great degree of deformation
• Repeated Blows – Power
Hammer
• Application of gradual
pressure – Forging Press

PNEUMATIC HAMMER – STEAM HAMMER
• The compressor cylinder compresses
the air & delivers it to the ram cylinder.
• By using this compressed air
pressure, the ram cylinder is piston is
actuated.
• The piston carries tup at its bottom,
which can slide inside the fixed dies.
• A hand lever operates an air valve to
sent the air from compression cylinder
to Ram cylinder. 70 – 200 Blows/min
• Steam or Air is admitted on both sides of
cylinder
• Both strokes performed by the pushing
action of compressed air or steam.
• In single acting type, steam is admitted from
bottom which push the piston upwards.
• Then steam supply is cutoff when the piston
attains the required height & the tup falls
under the gravity on the anvil.
• Atmospheric air – Cushioning effect – Air
ports

POWER HAMMER – DROP HAMMER
Used in mass production - 300 Blows/min
• It consists of two die halves
• One half of die is attached to the Tup or
hammer
• Other half of die is attached to Anvil Block
• The tup carrying upper die half is raised to a
suitable height with the help of friction rolls or
Belt or Rope.
• The heated metal is placed on the lower die
• The hammer along the upper die is allowed
to fall under gravity & its own weight, called
as Drop Hammer.
DROP FORGING
• Use closed impression die forging.
• During operation, there is a drastic flow of metal on the die caused by repeated
blows of hammers on the metal
• To ensure proper flow, the operation is divided into a number of steps.
• Each step changes the metal gradually & control the flow of metal.
• The force of blow can be varied by changing the distance of fall.
APPLICATION – Connecting rod, Leaf spring, Crane Hooks
DISADVANTAGE – More noise & Vibration, Less dimensional accuracy.

PRESS FORGING
• The action is relatively slow squeezing instead of delivering heavy blow.
• It penetrates deeply because it gives the metal time to flow
• Press forgings are shaped at each impression with a single smooth stroke.
• Less vibrations – Less noise compared to hammering
• The process controlled automatically, does not require high skilled labour
• APPLICATION – Toothed wheels, Propellers, Crank shaft

PRESS FORGING HAMMER / DROP FORGING
• The metal is shaped by means of a
single, continuous stroke.
• The metal is shaped by means of a
series of blows.
• The pressure applied is slow, steady
and continuous in a single squeezing
action in press forging.
• The pressure applied is impact, and in
multi-stroke in drop forging.
• The deformation obtained is uniform,
simultaneous and deep penetrating at
the centre of the metal part.
• The deformation of metal is more at
the surface layers than that of centre
of the metal part.
• In press forging, the draft angles used
are less.
• The draft angles used are more than
that of press forging.
• The initial cost is higher than the drop
forging.
• The initial cost is less comparatively.
• The process forging is a faster
process and has higher production
rates.
• The drop forging is relatively slow
process and has moderate production
rates.
• There is no restriction in the size of
the component.
• The drop forging is suitable for almost
all types of medium size forgings.

HYDRAULIC PRESS MECHANICAL PRESS
Used for Heavy work Used for light work
Operating speed is slow Operating speed is faster
Life of die is short Life of die is more
Initial cost of the machine is high Initial cost of the machine is low
Pressure can be changed at any point in
the stroke by adjusting the pressure control
valve
Pressure cannot be changed during the
process
Designed to provide greater squeezing
force
Less squeezing force is applied by the
mechanical presses.
PUNCHING & DRIFTING
• The workpiece is first heated & then placed on the anvil
face
• The punch is then forced into it up to about half its
thickness
• The workpiece is then turned upside down & placed over a
tool called as Bolster.
• The punch is again forced into the workpiece & made to
pass through by Hammering. (PUNCHING)
• In drifting, a tool(drift) is made to pass through the
punched hole to produce a finished hole of the required size.

MACHINE OR UPSET FORGING
• The pressure is applied on the longitudinal hot bar, which is gripped firmly
between grooved dies, to upset a required portion of its length.
• This machine is called as Upsetter or Forging Machine.
• This operation is performed by using Die & Punch which is called as
Heading Tool.
• It provides pressure in a horizontal direction.
• The complete operation is performed in several stages, & the final shape is
attained gradually.
APPLICATION – Bolt, Nut & Washers
ADVANTAGES
• No flash formation, Better dimensional accuracy,
• It can be automated
DISADVANTAGES
• Tooling cost is high, Unsymmetrical parts are difficult to be forged

FORGING DEFECTS
INCOMPLETE COMPONENTS
• This is due to poor design of die or poor forging technic. This is also due to
less raw material or poor heating.
COLD SHUTS
• Cold shut includes small cracks at corners. These defects occur due to
improper design of forging die.
• It is also due to sharp corner, and excessive chilling in forge product.
• The fillet radius of the die should be increase to remove these defects.
MISMATCHED FORGING
• Misalignment of upper die and lower die.
• When both these dies are not properly aligned the forged product does not
get proper dimensions.
SCALE PITS
• Scale pits are due to improper cleaning of forged surface. This defect
generally associated with forging in open environment.

ROLL PIERCING OR SEAMLESS TUBING
• It consists of two tapered rolls, called as piercing rolls.
• A round heated billet is passed between these rolls over a mandrel.
• One end of the billet is drilled with small hole.
• Billet is heated to 1100°C.
• Then this billet is pushed into the two piercing rolls which impart axial &
rolling movement to the billet & forces it over the mandrel.
• This will produce the rough shaped tube.
• To obtain better surface finish, further machining like rolling, sizing is done on
the part.
APPLICATION - Copper, Steel alloy, Aluminium & Brass Tubes

EXTRUSION
• First billet or ingot (metal work piece of standard
size) is produced.
• This billet is heated in hot extrusion or remains at
room temperature and placed into a extrusion
press.
• Extrusion press is like a piston cylinder device in
which metal is placed in cylinder and pushed by a
piston. The upper portion of cylinder is fitted with
die.
• Now a compressive force is applied to this part by
a plunger fitted into the press which pushes the
billet towards die.
• The die is small opening of required cross section.
This high compressive force allow the work metal
to flow through die and convert into desired shape.
• Now the extruded part remove from press and is
heat treated for better mechanical properties.
• As the ram approaches the die, a small portion of
billet remains which cannot be forced through the
die opening. This extra portion is known as Butt.
At the end, it is separated from the part.

DIRECT EXTRUSION INDIRECT EXTRUSION
Forward Extrusion Backward or Reverse Extrusion
Solid ram is used Hollow ram is used
There is a friction between the workpiece &
chamber walls. This friction is overcome by
providing additional ram force.
There is no friction between the
workpiece & chamber walls, because
the billet does not move inside the
chamber.
Large amount of force is required to move
the billet in the cylinder.
The billet is stationary, does not require
large force.
Handling of extruded metal is very easy Handling of extruded metal is difficult.
Die is mounted on the cylinder Die is mounted over the bore of the ram.

HYDROSTATIC EXTRUSION
• This process uses fluid to apply pressure on billet.
• In this process, the friction is eliminated because the billet does not contact
the cylinder wall or plunger.
• There is a fluid between the billet and plunger.
• The plunger applies force on fluid which further applied on billet.
• Normally vegetable oils are used as fluid.
• This process accomplished by leakage problem and uncontrolled speed of
extrusion.

COLD EXTRUSION (IMPACT EXTRUSION)
• 60 components / minute
• The raw material is in slug form which have been turned from a bar or
punched from a strip.
• The slug is placed in the die & struck from top by punch operating at high
pressure & speed.
• The metal flows along the surfaces of the punch, forming a cup shaped
component
• Then the punch moves up, to separate the part from punch, compressed air
is used.
APPLICATION
• Tubes for shaving cream, Tooth
paste & paints.
• Condenser cans & other thin walled
products are impact extruded.
• Lead, Tin, aluminium & Zinc.
• High speed process, No wastage

SHAPE ROLLING OPERATION
RING ROLLING
APPLICATION – Steel tyres of
railway car wheels, Rotating ring of
jet engine
• Initial material for ring rolling is a
pierced billet.
• Driving roll is fixed, but it can rotate
freely about its axis
• Pressure rolls applies pressure on
the rings towards driving roll.
• To ensure circular shape, guide
rolls used
THREAD ROLLING
APPLICATION – External Thread in
Screws, Bolts
• Cold working process
• 2000 pieces / minute
• Chip less manufacturing (16-27%
material saving)
• Two dies. One die – Stationary,
Another die – Reciprocating
• Reciprocating die stroke depends on
thread diameter.
• In one complete revolution, thread is
completely formed.

WIRE DRAWING
• It is an operation in which the cross section of a bar, rod or wire is reduced
by pulling it through a die opening.
• Bar Drawing – Used for large diameter stock
• Wire Drawing - Used for small diameter stock
• Total drawing can be done by single die or in a series of die. It depends on
the amount of reduction required & material used.
• One end of rod to be drawn into wires is made pointed, entered through the
die & gripped at the end using tongs.
• After pulling to certain length, the wire will be wounded to a reel or draw
pulley.
• Die – high wear resistant material – Tungsten Carbide

TUBE DRAWING
• By using extrusion, drawing process,
initial shape in the tube is prepared. The
diameter or wall thickness of seamless
pipe reduced.
• If the tube drawing is carried out without
mandrel means, it is called as Tube
Sinking.
• In tube sinking, there is no control over
the inner diameter & wall thickness of the
tube.
• To overcome this drawback, mandrels are
used in the process.
• In this method, mandrel is fixed &
attached to a long support bar to produce
inside diameter & wall thickness during
the process.

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