Machine tools

1. According to the direction of major axis :
• Horizontal center lathe, horizontal boring machine etc.
• Vertical – vertical lathe, vertical axis milling machine etc.
• Inclined – special ( e.g. for transfer machines).
2. According to the purpose of use :
• General purpose – e.g. center lathes, milling machines, drilling machines etc.
• Production purpose – e.g. facing lathe, roll turning lathe etc.
• Special purpose – for mass production.

3. According to the degree of automation
• non-automatic – e.g., center lathes, drilling machines etc.
• semi-automatic – e.g., capstan lathe, turret lathe, hobbing machine etc.
• automatic – e.g., single spindle automatic lathe, swiss type automatic lathe,
CNC milling machine etc.
4. According to size :
• Heavy duty – e.g., heavy-duty lathes (e.g. ≥ 55 kW), boring mills, planning
machine, horizontal boring machine etc.
• Medium duty – e.g., lathes – 3.7 ~ 11 kW, column drilling machines, milling
machines etc.
• Small duty – e.g., table top lathes, drilling machines, milling machines.
• Micro duty – e.g., micro-drilling machine etc.

5. According to precision :
• Ordinary – e.g., automatic lathes
• High precision – e.g., Swiss-type automatic lathes
6. According to a number of spindles :
• Single spindle – centre lathes, capstan lathes, milling machines etc.
• Multi-spindle – multi-spindle (2 to 8) lathes, gang drilling machines etc.
7. According to the type of automation :
Fixed automation – e.g., single spindle and multi-spindle lathes
Flexible automation – e.g., CNC milling machine

• Cutting speed is defined as the speed at which the work moves with respect to
the tool (usually measured in meters per minute (mpm)).
It is thus the amount of length that will pass the cutting tool per unit of time.
Cutting speed (V) = π DN (mm/min)
D = diameter of the work piece (mm)
N = rpm of the work or spindle

• Feed rate is defined as the distance the tool travels during one
revolution of the part.
It is expressed in millimeters per revolutions.(mm/rev)
• Depth of Cut (t):It is the total amount of metal removed per pass of
the cutting tool.
It is expressed in mm. It can vary and depending upon the type of tool
and work material. Mathematically, it is half of difference of diameters.
Depth of cut (t) = D-d/2 mm
where, D = outer diameter, (mm)
d = Inner diameter (mm)

Milling
Machines
Horizontal Knee
and Column Milling
Machine

Vertical Knee
and Column
Milling Machine

Basic principle of a lathe machine :
• Lathe machines are normally used to produce cylindrical
surfaces. The job is held in the chuck attached to the head stock
or between the centers provided at the head stock or tail stock. The tool
is held on the compound rest. Job is rotated at the predetermined
speed by the head stock. The tool is moved relative to the workpiece
with the help of carriage, cross slide or compound rest. Desired quantity
of metal is removed in the form of chip from the workpiece.

Specification of a lathe machine
A lathe machine is specified by the following
 Height of the centers measured from the lathebed.
 Swing diameterover bed. This the largestdiameterof work
piece which will revolve without touching the bed. It is
equal twice the heightof centers from the bed.
 Swing diameterovercarriage. It is the largestdiameter that
can revolve over the cross-slide. This always less than the
swing diameter over thebed.
 Maximum bardiameter. This is the maximumdiameter
thatwill pass through the head stock spindle.
 Length of the bed.

Fig.- Specifications of lathe machine

Classification of Lathe machines
Lathes can beclassified into following three types
 Engine Lathes
 Light weight bench enginelathe
 Precision Tool Room lathes
 Gap lathes
 Turret Lathes
 Special Purpose lathes

Basic Operations Performed on a Lathe Machine :
1. Turning –Plain turning , Stepturning
2. Facing
3. TaperTurning
4. Drilling :
5. Boring :
6. Reaming :
7. Knurling :
8. Forming :
9. Chamfering :
10. Parting Off:
11. Threading or threadcutting

Plain turning on lathe machine

Fig.- step turning on lathe machine

Eccentric turning on lathe machine

Knurling on lathe using knurling
tool

Reaming on lathe using reamer
tool

FIGURE – GROOVING AND PARTING

Shaping Machines
 A shaper is used for producing relatively
small flat surfaces. A single point tool is
mounted on a tool box fitted to a
reciprocating ram. The job is clamped in a
vice. There is a cutting action in the forward
motion of the tool while the return stroke is
idle. Job is given indexed feed.

Shaper operations
Horizontal cutting
Vertical cutting
Inclined cutting
Irregularcutting

HORIZONTAL AND VERTICAL CUTTING ON
SHAPER

PLANNING MACHINE OR PLANNER
 Planning machines are used for generating large flat
surfaces. These flat surfaces may be horizontal,
vertical or inclined. Planing machines also perform all
the functions that a shaping machine does. The
planning machines handle larger and heavyjobs.
 In planning machines the job is mounted on a table
which moves forward and backward. The tool is held
firmlyon thecross rails in the middleof the machine.

Diff. between shaper and planer
Planing Machine Shaping Machine
reciprocating the workpiece
3. Heavier cuts can begiven
employed at atime
5. Several jobs requiring
operations can be machined
time
6. Indexed feed is given to the tool
during idle stroke of the worktable.
1. Machine is heavy and is used for 1. Machine is light and only small job
producing largesurfaces can beproduced.
2. Cutting takes place by 2. Cutting takes place by
reciprocating thetool.
3. Only lightcutscan begiven.
4. Several tools can be mounted and 4. Onlyone tool is used ata time.
5. Only one job can be taken up at a
similar time.
at a 6. Indexed feed is given to the job
during idle stroke of theram.

Drilling Machine
Drilling is an operation through
which a drilled hole is produced
in a job. The machine tool used
in this case is called drilling
machine and the cutting tool
used is called a drill bitordrill.

Operation performed on a drill
machine
 Drilling : Operation of producing acylindrical hole in a solid body by
means of adrill.
 Reaming : Operation of finishing the drilled hole (that is achieving
theclosertolerancesand desired surface finish) by means of a reamer.
 Boring : A drilled holecan beenlarged also by meansof boring tool on
the drill machine.
 CounterBoring : Enlarging thediameterof thedrilled holeonly upto
certaindepth. Forthiscounter boring tool is used.
 CounterSinking : It is enlarging the topend of a drilled holeand
giving itaconical shape by the help of acountersinking tool.
 Spot Facing : Squaring the surfaceat the topend of a hole toprovidea
trueseat forthe bolt head orcollar.
 Tapping : A tapcan be rotated insidean already drilled hole to
produce internal threads.

Grinding:
Grinding is a process of removing material by abrasive action of
a revolving wheel on the surface of a work-piece in order to
bring it to required shape and size
The wheel used for performing the grinding operation is known
as grinding wheel
It consists of sharp crystal called abrasive held together by a
binding material or bond
The wheel may be a single piece or solid type or may be
composed of several segments of abrasive blocks joined
together.

Wheel Materials
1. Abrasive: it is that material of grinding wheel which does the
cutting action
(a) Natural Abrasive:
The common natural abrasives are sand stone, emery (50-
60%crystalline AL2O3+iron oxide) corundum (75-90%
crystalline aluminium oxide+iron oxide), and diamond
The sand stone is used only for sharpening some wood-working
tool
Diamond is used for dressing the grinding wheel and acts as an
abrasive material for hard material

Artificial abrasive:
These are manufactured under controlled conditions in closed
electric furnaces in order to avoid the introduction of
impurities and to achieve the necessary temperature for
chemical reactions to take place
Example: Silicon carbide(Sic), Aluminum oxide(Al2O3)
Artificial diamond:
artificial means are quiteThe diamond produced
comparable to the
through
natural diamond in their grinding
characteristics and give better result than the latter.

Advantages and use of artificialAbrasive
The artificial abrasives have lately superseded the natural
abrasive for following reason
1. The controlled conditions in the electric furnace enable
uniformly in the product
2. The quality of production and supply can easily be varied
according to the demands
3. They have largely abolished the dependence on natural means
to meet the growing demand of more abrasive material in the
modern manufacturing process
Bond is the substance that acts as a binder to hold the abrasive
grains together

Material to be ground Recommended abrasive
Cast Iron Silicon carbide
Soft brass and bronze
Glass and stone
Aluminium
Copper
Rubber
Leather
Plastics
Heat treated carbon and alloy
steel
Aluminium Oxide
Malleable Iron
Hard brass and bronze
Mild steel and Wrought Iron

A bond is a substance that is employed to hold abrasive grains
together in the form of sharpening stones or grinding wheels.
Several types of bonding materials used for making grinding
wheels,
1-Vitrified bond
2-Silicate bond
3-Shellac bond
4-Resinoid bond
5-Rubber bond
6-Oxychloride bond
These bonds may be used with either silicon carbide or aluminum
oxide.

GRIT SIZE
Small grit sizes produce better finishes
Larger grit sizes permit larger material removal rates
Harder work materials require smaller grain sizes to
cut effectively
Softer materials require larger grit sizes
Grit size is measured using a screen mesh procedure
Smaller grit sizes indicated by larger numbers in the
screen mesh procedure and vice versa Grain sizes in
grinding wheels typically range between 10 (very
coarse) and 250 (very fine)

GRADE
The grade of a bonded abrasive is a measure
of its bond strength
The grade is also referred to as the hardness
of a bonded abrasive
A hard wheel has a stronger bond and/or a
larger amount of bonding material between
the grains than a soft wheel

Structure of a bonded abrasive is a measure of its porosity

Specifying of grinding wheel
To maintain uniformity throughout the country in the system of
making grinding wheel, the Bureau of Indian Standard has
devised a standard system to be followed by all manufacturer
According to the system, the various elements and characteristics
of grinding wheels are represented on all the wheels in a
definite sequence as follows:
1. Abrasive 2. Grain size 3. Grade 4. Structure 5. Bond

Example:
A grinding wheel carrying the marking
125 x 25 x32 WA46 L4 V 17
125(mm)---wheel diameter
25(mm)--- Thickness of wheel
32 (mm)---Bore diameter
W---Manufacturer’s prefix to abrasive. It is optional.
A---Abrasive(Al2O3)
46 ----Grain size(medium)
L ---grade (medium)
4 --- Dense structure
V --- Vitrified bond
17----it is the suffix denoting the bond type of the manufacturer

• Major and inevitable defects in grinding are glazing of
grinding wheels. Its remedy will be discussed later. After the
continuous usegrinding wheel becomes dull orglazed.
• Glazing of the wheel is a condition in which the face or
cutting edge acquires a glass like appearance. That is, the
cutting points of the abrasives have become dull and worn
down to bond. Glazing makes the grinding face of the wheel
smoother and that stops the processofgrinding.
• Sometimes grinding wheel is left ‘loaded’.
• In this situation its cutting face is found being adhering with
chips of metal.
• Theopenings and pores of the wheel face are found filled
with workpiece material particals, preventing the grinding
action.
• Loading takes place while grinding workpiece of softer
material.

Dressing
The remedies of glazing and loading is dressing of grinding
wheels.
Dressing removes the loading and breaks away the glazed
surface so that sharp abrasive particles can be formed again
ready for grinding.
Different type of dressing operations are done on a
grinding wheel.
One of them is the dressing with the help of star dresser.
It consists of a number of hardened steel wheels with sharp
points on their periphery. The total is held against the face
of revolving wheel and moved across the face to dress the
whole surface.
Another type of wheel dresser consists of a steel tube filled
with a bonded abrasive. The end of the tube is held against
the wheel and moved acrosstheface.

Truing
• Truing is the process of restoring the shape of
grinding wheel when it becomes worn and break
away at different points. Truing makes the wheel
true and concentric with thebore.

Selection of Grinding Wheel
1.Properties of the material to be machined i.e hardness,
toughness, strength
2. Quality of surface finish required
3. Grinding allowance provided on the work-piece i.e the amount
of stock to be removed
4. Dimensional accuracy
5. Method of grinding i.e wet or dry
6. Rigidity, size and type of machine
7. Relative sizes of wheel and job
8. Type of grinding to be done
9. Speed and feed of wheel

Types of grinding Machine
Grinding machines according to quality of surface finish, may be
classified as
1.Rough /Non-precision grinding
2.Precision grinding
Rough/Non-precision grinding
To remove more stock than other grinding
a)Floor stand and bench grinders
(b)Portable and flexible shaft grinders
(c)Swing frame grinders
(d)Abrasive belt grinders

Floor stand and bench grinders
Used for snagging and off-hand grinding of various materials and
cutting tools in tool rooms, foundries and general repair shops
It carries a horizontal spindle having grinding wheels mounted on
both ends
It can be suitably bolted on a bench at convenient height
The floor or pedestal grinder is nothing but a bench grinder of the
above type mounted on a steel stand or pedestal of suitable
height
The horizontal spindle carrying the grinding wheel is normally an
extension on both side of the armature shaft of the motor
These grinder are also be used for polishing by replacing the
grinding wheel by polishing wheel

Precision grinders: according to the type surface
generated or work done they may be classified as:
• (a)cylindrical grinding machine
• (b) surface grinding machine
• (c) Internal grinding machine
• (d) Tooland cutter grinding machine

Surfacegrindingmachine
Horizontal spindle and reciprocating table
Vertical spindle and reciprocating table
Horizontal spindle and rotary table
Vertical spindle and rotary table

Horizontal spindle reciprocating table surface grinder

Cylindrical Grinders
The wor-kpiece is hold on centre by a chuck or in a suitable
holding fixture, rotating it about its axis and feeding a fast
revolving grinding wheel
If the work surface to be ground is longer than the face width of
the grinding wheel, the work is traversed past the wheel or the
wheel past the work.
Traversing of wheel or work is done either by hydraulic or
mechanical power or by hand
Feed is given to the work or the wheel at the end of each
traversing movement

In case of width of wheel face is more or equal to the length of
work surface to be ground, the wheel may be fed in with no
traversing movement of it or that of work.
This is known as Plunge Grinding
The simplest and quite commonly used type of cylindrical grinder
is tool post grinder used on lath
When wheels of large diameters are used, they can be mounted
directly on the motor shaft
For mounting small wheels, an auxiliary shaft is provided, which
runs at a relatively much higher speed than the motor
Both external and internal cylindrical grinding can be done on
lathe by this equipment

Types of cylindrical grinding:
1. Plain cylindrical grinding
2. Universal cylindrical grinding
3. Centreless grinders

Centreless Grinders
Here the work is supported by a combination of grinding wheel,
regulating wheel and a work rest blade
The relative movement of work-piece and two wheels shown in
figure
It is used for both external as well as internal grinding
Many hollow cylindrical and tapered workpiece, like bushes,
pistons, valves tube and balls etc either do not or cannot have
centre are best ground on centreless grinder

It carries a heavy base and two wheel heads, one carrying the
grinding wheel(large one) and the other regulating
wheel(smaller)
The workpiece rests on the blade of the work rest between these
two wheel
Each head carries a separate wheel trueing mechanism for the
wheel it carries
A housing is provided on one side of the machine body to house
the main driving motor
There are two control panels on the front
The left hand panel carries controls for speed adjustments of two
trueing mechanism and the infeed grinding mechanism
The right hand panel carries control for hydraulic mechanism,
speed adjustment of regulating wheel, automatic working
cycle switch, start and stop switch etc

In operation, grinding operation is performed by grinding wheel
only while the function of regulating wheel is to provide the
required support to the work piece while it is pushed by
cutting pressure of grinding wheel
It helps the work-piece to remain contact with the grinding wheel
At the same time, required support from bottom is provided by
work-rest as the work-piece while rotating rests on the blade of
worksheet
The regulating the wheel essentially carries rubber bond and
helps in the rotation of work-piece due to friction
The methods used for feeding the work are:
I. Through feed
II. Infeed
III. End feed

Through feed
The work-piece is supported and revolved as described above but
simultaneously given an axial movement also regulating wheel
and guides so as to pass between wheels
The axis of the regulating the wheel is inclined at 2 to 10 degree
with vertical
The amount of stock to be removed determines as to how many
time a workpiece has to pass between the wheels
The actual feed(S) can be calculated by the formula
S=πdn. sinα
S=feed in mm per minute.
n=revolutions per minute.
d=diameter of the regulating wheel in mm.
α=angle of inclination of wheel.

Surface Grinder
The main objective to machine flat surface, irregular, curved and
tapered surfaces
Classification
1. According to the table movement
a) Reciprocating table type b) Rotary type
2. According to the direction of wheel spindles:
a) Vertical spindle type b) Horizontal spindle type
3) Special type and single purpose machine
a) Face grinder b) Way grinders c) Wet belt grinder

Reciprocating table type
A reciprocating type surface grinder may have a horizontal
spindle or a vertical spindle
The former will carry a straight wheel and latter a cup type
wheel
Hydraulic drivers are commonly used
Cutting is done on the periphery of straight wheel.
In case of horizontal spindle type and on revolving edge of the
cup wheel on vertical machine
The work-piece held on the magnetic chuck. These are used for
grinding flat surface
The longitudinal feed is given to the work by reciprocating the
table

In case of vertical spindle reciprocating table grinders the table,
along with the work-piece, reciprocates under the wheel
The wheels covers all or major portion of the width of the job
Cross feed to the work can be given as usual by moving saddle
A manual or power feed can be employed to feed the wheel-head
vertically
An individual motor drive is usually provided to rotate the wheel

Rotary type
It is two type
i) Having a horizontal wheel ii) vertical spindle wheel
A circular shaped magnetic chuck is mounted on a circular table to hold
job
The work-piece is normally arranged in a circle, concentric with the
round chuck
If it is a single piece, it can be mounted centrally on the chuck
The table is made to rotate under the revolving wheel, both rotating in
opposite direction
The vertical feed to the wheel is given by moving wheel head along
a column and cross-feed by the horizontal movement
of the wheel spindle

A straight wheel is used on these machines, which cuts on its
periphery

The relative movements of the wheel and the table of a Rotary
table vertical spindle surface grinder is shown in the fig
A cup wheel has to be used on these machine
Vertical feed to the wheel is given by moving the wheel head
The work-piece are on the round chuck in same way as in
horizontal spindle type
The table rotates in a direction opposite to that of wheel and
bring the work-piece one after the other under rotating
wheel
The table is mounted on a slide so as to give cross feed

Internal grinders
Used for grinding internal surface of different holes, cylindrical,
tapered etc
Types:
1. Plain internal grinders
2. Universal internal grinders
3. Chucking internal grinders
4. Planetary internal grinders
5. Centreless internal grinders

Plain internal grinders
It carries an individual driven wheel-head mounted on a cross-
slide
The workhead either carries a chuck or face-plate to hold the
work or latter can be mounted on a fixture attached to the
workhead spindle
The work can be swiveled to the grind tapered holes

Universal internal grinders
Here the work head is mounted on a cross-slide which enables a
cross feed to the workhead
The work head can be swiveled though 90 degree
It is used to grind cylindrical and tapered holes, flat surfaces,
outside the cylindrical surfaces, convex and concave
surface

Centreless internal grinders
The work-piece is supported between three rolls known as
pressure roll, supporting roll and a regulating roll
These rolls while supporting the work-piece also rotate the same
All rolls rotate in same direction while the work-piece and
grinding rotate in opposite direction
The grinding wheel remains contact with the internal surface of
the work-piece at the horizontal centerline of regulating wheel
It ensures that a uniform wall of thickness of the work-piece and
therefore concentricity of the ground internal hole with the
external surface
The pressure roll is so mounted that it can be swung to a slide to
allow loading and unloading of the work-piece

The wheel head is mounted on a slide and can be given a
reciprocating motion by hand to feed the grinding wheel in
and draw it out of the operation

Planetary internal grinders
• To grind holes in large, irregular shaped and heavy work-piece
• The work-piece remains stationary, which is
mounted on a
• slide
• The wheel head carries a mechanism due to which the axis of rota
grinding wheel travels along a circular path around the axis of ho
the work piece
• The longitudinal traverse obtained by
1) By reciprocating movement of the grinding wheel spindle
2) By moving the slide forward and backward on which work-

The spindle of the grinding wheel is given a radial infeed after
completion of each planetary circle to increase the depth of cut

Super-finishing: it is mostly done for obtaining high quality
surface finish along with an almost complete absence of
defects layers.
Honing: it is an abrading process mostly used for polishing bored
and reamed holes and also cylindrical surfaces using bonded
stones(called hones)
Lapping: It is finishing process and is done after grinding

WHY SUPER FINISHING REQUIRED
Parts Worn Out Fast Due To Defects Of Grinding Operation. The Defects Are
Chatter Marks, Helical Type Scratches, Surface Cracks, Smear Metal Etc. Are
Responsible For Wearing Out The Parts. In Certain Circumstances High
Surface Quality Is Required. Hence For Removing Grinding Defects, To Obtain
Desired Surface Finish And To Improve The Geometrical Shape Finishing
Processes Are Used. It Includes Honing, Lapping, And Super Finishing.

FINISHING METHODS
• With material removal – generative methods
-fine machining, honing, super finishing, lapping
• Without material removal – forming method
-glazing, blasting, tumbling, polishing

TYPES OF SUPER FINISHING
PROCESS
• Honing
• Lapping
- Hand Lapping
- Machine Lapping
• Super Finishing

HONING
• Hole made by boring is obtained to required dimension and
finishing by honing. In this process abrasive stone is used.
The dimension to an accuracy of 0.005 mm can be obtained
by honing process

• Honing is wet cutting
process. 6 to 8 honing sticks
are held together and metal
is removed by rotating or
reciprocating the holder.
• Honing tool is rotated at a
speed of 0.5 - 2.5 m/s and
reciprocates at a speed of
0.2 – 0.5 m/s.

• Objectives are achieved by honing
1. Metal is removed
2. Roundness & straightness is obtained
3. Accurate dimension is obtained
4. Required surface finish is obtained.
•Application :
-Honing Of Automobile
Cylinder
-Honing Is Also Used For
Repair Work

LAPPING
• This process mainly done on the meting surfaces. Abrasive
compound or solid bonded abrasive is used in it. More
accuracy is obtained as heat & pressure are less in lapping.
Lapping compound is made by mixing diamond, silicon
carbide, aluminum oxide in oil or water. There are many types
of lapping process.

HAND LAPPING
• In this method lapping
compound is spread on cast
iron plate and work piece is
moved manually on it on a
path like English figure - 8

Machine lapping
• In this method a rotating table
is used in place of the plate.
Again the work piece to be
lapped is given rotary by a
cage and rotated on the
surface of the table. Rotating
lap is used above & below the
work piece to produce parallel
surfaces.

- Machine lapping process is carried out for gauge
blocks, piston pin, ball bearings and engine valves.
Application of lapping:-

Machine tools

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Machine tools

Similar to Machine tools (20)

More from Ubaid Shah

More from Ubaid Shah (13)

Recently uploaded

Recently uploaded (20)

Machine tools