Manufacturing Processes

Mr. ANSAR A. MULLA
AUTOMOBILE ENGG DEPARTMENT
R.I.T. ISLAMPUR
- R.I.T. ISLAMPUR
1
AE 2091 – Manufacturing Processes
Chapter 05- Milling Machine and Grinding Machine

Contents
1. Milling Machine - Types, various operations,
Accessories and attachments,
2. Grinding Machine - Types, various operations,
Accessories and attachments,
3. Grinding wheels Abrasives, bonds and bonding
processes grit, grade and structure of wheel, wheel
shapes, wheel specifications
2

01 Milling Machine - Types, various operations, Accessories and
attachments,
3
A milling machine is a machine tool that removes metal as the work is fed against a
rotating multipoint cutter. The milling cutter rotates at high speed and it removes metal at
a very fast rate with the help of multiple cutting edges.

attachments,
4
PRINCIPLE OF MILLING
In milling machine, the metal is cut by means of a rotating cutter having multiple
cutting edges.
For cutting operation, the workpiece is fed against the rotary cutter.
As the workpiece moves against the cutting edges of milling cutter, metal is removed in
form chips of trochaic shape.
Machined surface is formed in one or more passes of the work.
The work to be machined is held in a vice, a rotary table, a three jaw chuck, an index
head, between centers, in a special fixture or bolted to machine table.
The rotatory speed of the cutting tool and the feed rate of the workpiece depend upon the
type of material being machined.

attachments,
5
MILLING METHODS
There are two distinct methods of milling classified as follows:
1. Up-milling or conventional milling
The metal is removed in form of small chips by a cutter rotating against the direction of travel of
the workpiece.
The chip thickness is minimum at the start of the cut and maximum at the end of cut.
So the cutting force also varies from zero
to the maximum value per tooth movement
of the milling cutter.
The major disadvantages of up-milling
process are the tendency of cutting force to
lift the work from the fixtures and poor
surface finish obtained.

attachments,
6
MILLING METHODS
There are two distinct methods of milling classified as follows:
2. Down milling or climb milling.
Metal is removed by a cutter rotating in the same direction of feed of the workpiece.
Teeth cut downward instead of upwards.
Chip thickness is maximum at the start of the cut and minimum in the end.
less friction involved and consequently less heat is
generated on the contact surface of the cutter
and workpiece.
Advantage
•saws cut long thin slots more satisfactorily.
•slightly lower power consumption is obtainable,
since there is no need to drive the table against the cutter.

attachments,
7
MILLING CUTTERS
Milling cutters are made in various forms to perform certain classes of work, and they may be
classified as:
(1) Plain milling cutters,
(2) Side milling cutters,
(3) Face milling cutter,
(4) Angle milling cutters,
(5) End milling cutter,
(6) Fly cutter,
(7) T-slot milling cutter,
(8) Formed cutters,
(9) Metal slitting saw,
Milling cutters may have teeth on the periphery or ends only, or on both the periphery and
ends. Peripheral teeth may be straight or parallel to the cutter axis, or they may be helical,
sometimes referred as spiral teeth.

attachments,
9
TYPES
Choice of any particular machine is determined primarily by the size of the workpiece to
be undertaken and operations to be performed.
4. Machining center machines
5. Special types of milling machines
(a) Rotary table milling machine.
(b) Planetary milling machine.
(c) Profiling machine.
(d) Duplicating machine.
(e) Pantograph milling machine.
(f) Continuous milling machine.
(g) Drum milling machine
(h) Profiling and tracer controlled milling machine
1. Column and knee type milling machines
(a) Hand milling machine
(b) Horizontal milling machine
(c) Universal milling machine
(d) Vertical milling machine
2. Planer milling machine
3. Fixed-bed type milling machine
(a) Simplex milling machine.
(b) Duplex milling machine.
(c) Triplex milling machine.

11
Column and Knee Type Milling Machine
Most commonly used milling machine used
for general shop work.
Column and knee type milling machine
comprises of the following principal parts-
1. Base 2. Column
3. Saddle 4. Table
5. Elevating screw 6. Knee
7. Knee elevating handle 8. Cross feed handle
9. Front brace 10. Arbor support
11. Arbor 12. Overhanging arm
13. Cutter 14. Cone pulley
15. Telescopic feed shaft.

12
Milling Operations
Various Milling Operations

13
Milling Operations

14
Milling Operations

15
02 Grinding Machine - Types, various operations, Accessories
and attachments,
Grinding is generally called as fine machining or finishing operations of
removing materials from surface usually 0.25-0.50 mm in most operations
through the use of grinding wheel.
In grinding, the work is held pressed against the high speed rotating grinding
wheel and the metal gets reduced by abrasion.
Abrasives form the cutting points in a wheel and are termed as grains.
Grinding machines known as grinders

16
and attachments,
Grinder may be various types such as
•cylindrical grinder,
•surface grinder,
•pedestal grinder,
•tool and cutter grinder,
•centre-less grinder,
•internal grinder and jig grinder and profile grinder.

17
and attachments,
Fig. a) illustrates the surface grinding
machine and principle of surface grinding.
Fig. b) illustrates the principle of
cylindrical grinding.

18
and attachments,
Grinding Machines are also regarded as machine tools. A distinguishing feature
of grinding machines is the rotating abrasive tool. Grinding machine is employed
to obtain high accuracy along with very high class of surface finish on the
workpiece.
Grinding machines can be broadly classified as:
(a) Surface grinding machine
(b) Cylindrical grinding machine
(c) Internal grinding machine
(d) Tool and cutter grinding machine

19
and attachments,
Grinding Machines (a) Surface grinding machine
This machine may be similar to a milling machine used mainly to grind flat
surface.
However, some types of surface grinders are also capable of producing contour
surface with formed grinding wheel.
Basically there are four different types of surface grinding machines
characterised by the movement of their tables and the orientation of grinding
wheel spindles as follows:
1. Horizontal spindle and reciprocating table
2. Vertical spindle and reciprocating table
3. Horizontal spindle and rotary table
4. Vertical spindle and rotary table

20
and attachments,
Grinding Machines (a) Surface grinding machine 1. Horizontal spindle and
reciprocating table

21
and attachments,
Grinding Machines (a) Surface grinding machine 2. Vertical spindle and
reciprocating table

22
and attachments,
Grinding Machines (a) Surface grinding machine 2. Horizontal spindle and rotary
table

23
and attachments,
Grinding Machines (a) Surface grinding machine 2. Vertical spindle and rotary table

24
and attachments,
Grinding Machines (a) Cylindrical grinding machine
This machine is used to produce external cylindrical surface. The surfaces may
be straight, tapered, steps or profiled. Broadly there are three different types of
cylindrical grinding machine as follows:
1. Plain centre type cylindrical grinder
2. Universal cylindrical surface grinder
3. Centre less cylindrical surface grinder

25
and attachments,
Grinding Machines (a) Cylindrical grinding machine 1. Plain centre type
cylindrical grinder

26
and attachments,
Grinding Machines (a) Cylindrical grinding machine 2. Universal cylindrical surface
grinder
Universal cylindrical grinder is similar to a plain cylindrical one except that it is more
versatile. In addition to small worktable swivel, this machine provides large swivel of
head stock, wheel head slide and wheel head mount on the wheel head slide.

27
and attachments,
Grinding Machines (a) Cylindrical grinding machine 2. Centre less cylindrical surface grinder
Principle of cylindrical grinding is being used for thread grinding with specially formed wheel
that matches the thread profile. A single ribbed wheel or a multi ribbed wheel can be used as
shown in

28
and attachments,
Grinding Machines (a) Cylindrical grinding machine 2. External centre less grinder
This grinding machine is a production machine in which out side diameter of the workpiece is
ground. The workpiece is not held between centres but by a work support blade. It is rotated by
means of a regulating wheel and ground by the grinding wheel.

29
and attachments,
Grinding Machines (a) Cylindrical grinding machine 2. External centre less grinder
Parts with variable diameter can be ground by Centreless infeed grinding as shown in Fig.(a). The
operation is similar to plunge grinding with cylindrical grinder. End feed grinding shown in Fig. (b)
is used for workpiece with tapered surface.

30
and attachments,
Grinding Machines (c) Internal grinding machine
This machine is used to produce internal cylindrical surface. The surface may be
straight, tapered, grooved or profiled.
Broadly there are three different types of internal grinding machine as follows:
1. Chucking type internal grinder
2. Planetary internal grinder
3. Centre less internal grinder

31
and attachments,
Grinding Machines (c) Internal grinding machine 1. Chucking type internal grinder
The workpiece is usually
mounted in a chuck. A
magnetic face plate can also be
used.
A small grinding wheel
performs the necessary
grinding with its peripheral
surface.
Both transverse and plunge
grinding can be carried out in
this machine.

32
and attachments,
Grinding Machines (c) Internal grinding machine 2 Planetary internal grinder
Planetary internal grinder is used where the workpiece is of irregular shape and can
not be rotated conveniently as shown in Fig. below. In this machine the workpiece
does not rotate. Instead, the grinding wheel orbits the axis of the hole in the workpiece.

33
and attachments,
Grinding Machines (c) Internal grinding machine 3 Centre less internal grinder
This machine is used for grinding
cylindrical and tapered holes in
cylindrical parts (e.g. cylindrical
liners, various bushings etc).
The workpiece is rotated between
supporting roll, pressure roll and
regulating wheel and is ground by the
grinding wheel.

34
and attachments,
Grinding Machines (d) Tool and cutter grinder machine
Simple single point tools are occasionally sharpened by hand
on bench or pedestal grinder. However, tools and cutters with
complex geometry like milling cutter, drills, reamers and hobs
require sophisticated grinding machine commonly known as
universal tool and cutter grinder.

36
03 Grinding wheels Abrasives, bonds and bonding processes grit,
grade and structure of wheel, wheel shapes, wheel specifications
Grinding wheel is generally made from silicon carbide or aluminium oxide.
It is generally made up of particles of hard substance called the abrasive and is
embedded in a matrix called the bond
Abrasives form the cutting points in a wheel and are termed as grains.
The abrasives are of generally two types namely natural and artificial.
Emery and corundum are two natural abrasives,
while carborundum and aloxite are artificial abrasives.
Hard wheels of aloxite are used for grinding soft materials and
soft wheels of carborundum for grinding hard materials using various types of
grinding machines known as grinders.

37
Grinding wheel DEFINITION:-
•A grinding wheel is a multitooth cutter made up of many hard particles known as
abrasives which have been crushed to leave sharped edges for machining.
•Every grinding wheel has two constituents:
i. abrasive used for cutting.
ii. bond that holds abrasive grains.
BASIC FUNCTIONS OF A
GRINDING WHEEL:-
1. Removal of stock
2. Generation of cylindrical, flat
and curved surfaces
3. Production of highly finished surfaces
4. Cutting off operations
5. Production of sharp edges and points.

38
CONSTRUCTION OF GRINDING WHEEL:-
Grinding wheel consists of
1. Abrasives
2. Bond
3. Grit/grain size
4. Grade
5. Structure of wheels

39
1. Abrasives
An abrasive is a hard and tough substance, having sharp edges. It cuts or wears
away materials softer than itself.
Important properties of abrasives are penetration hardness, fracture resistance and
wear resistance.
TYPES OF ABRASIVES:-
Natural abrasives- they are obtained from nature.
Natural abrasives are sand stone, emery/corrundum, diamond and garnet.
Artificial/synthetic abrasives- they are manufactured to have well defined and
controlled properties of hardness, roughness and type of structure. Artificial o
synthetic abrasives are silicon carbide(SiC), aluminium oxide(Al2O3)

40
2. Bond
•The bond is an adhesive substance which cements or holds the abrasive grains
together to form a grinding wheel.
•Depending upon the application, bond imparts the qualities of hardness or softness
to the grinding wheel.
•The choice or selection of the bond depends upon the accuracy, the required
surface finish and the nature of grinding operation.

41
2. Bond

42
3. GRIT/Grain Size
•Size of grain grit is determined by sorting or grading the material by passing
through screens with the no. of meshes per linear inch.
•The grain size influences stock removal rate and the generated surface finish.
•The selection of grain size is determined by
1. Nature of grinding operation
2. Material to be grinded
3. Material removal rate
4. Surface finish required

43
3. GRIT/Grain Size

44
4. GRADE OF THE WHEEL:-
Structure of the grinding wheel represents to the grain spacing or the manner in
which the abrasive grains are distributed throughout the wheel.
•The entire volume is occupied by abrasive grains, bonding material and pores.
•The primary purpose of structure is to provide chip clearance and it may be open
medium or dense.

45
5. Wheel Shapes and Sizes :-
The shape of grinding wheel should be such that it permits proper contact between
the wheel and all of the surface must be ground.
They are classified in the following groups:
1. Straight side grinding wheel
2. Cylindrical wheels
3. Cup wheels
4. Dish wheels

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5. Wheel Shapes and Sizes :-

47
6. Wheel Designations :-
It consists of 6 symbols representing following properties of grinding wheel:
1. Manufacturer’s symbol
2. Type of abrasive
3. Grain size
4. Grade
5. Structure
6. Type of bond
7. Manufacture symbol (optional) for reference

48
Example of a wheel specification:
51 A 36 L 5 V 40
51 Manufacturer’s symbol indicating type of abrasive
A Abrasive (aluminium oxide)
36 Grain size(medium)
L Grade(medium)
5 Structure(dense)
V Bond(vitrified)
40 Manufacture symbol (suffix) optional

49

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Ansar Allauddin Mulla
ansarmulla212@gmail.com

Manufacturing Processes

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