MACHINE TOOLS
Dept. of Mech & Mfg. Engg.
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Functions of Machine Tools
To hold and support job/work to be machined
To hold and support the cutting tool in position
To move the cutting tool, work or both in a desired direction
To regulate cutting speed and provide feeding movement.
Dept. of Mech & Mfg. Engg.
A Machine Tool
A machine tool may be defined as a power driven machine
which accomplishes the cutting or machining operations in it.
Examples: Lathe,
Drilling machine,
Milling machine,
Grinding machine.
Shaping machine
Dept. of Mech & Mfg. Engg.
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ENGINE LATHE
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Working principle of lathe
Chuck
Direction of rotation
of work piece
Work piece
Cutting tool
Direction of cutting tool
Dept. of Mech & Mfg. Engg.
Working principle of a lathe
• Cutting tool can remove material in Chuck
Direction of
the form of chips from rotating work rotation of
pieces to produce circular objects work piece
• Work piece held rigidly by one of
the work holding devices known as
Cutting
chuck Direction of tool
cutting tool
• Uses V – shaped cutting tool
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Lathe classification
Bench Lathe :- Small & Precision work
Speed Lathe :- Wood working, Polishing
Engine Lathe:- Regular lathe used in machine shop
Capstan &Turret Lathe:- Different operations without resetting
Tool Room Lathe :- Small tools, Gauges, Dies & High precise parts etc.,
Automatic Lathe:- For identical parts & heavy duty mass production
CNC Lathe:- Programmed machining high precision
Dept. of Mech & Mfg. Engg.
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BLOCK DIAGRAM OF LATHE
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Dept. of Mech & Mfg. Engg.
MAJOR PARTS
1] Bed
2] Head stock
3] Tail stock
4] Main drive
5] Carriage assembly consisting of
a) Saddle
b) Cross-slide
c) Compound rest
d) Tool post
e) Apron
6] Lead screw
7] Feed rod
Dept. of Mech & Mfg. Engg.
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BED
Foundation part of the machine.
Supports all other parts.
The top of the bed is formed by
two Precession guide ways.
i) Outer guide way--- Carriage assembly mounted and
align it with centre line of lathe.
ii) Inner guide way--- Head stock and Tailstock are mounted
Dept. of Mech & Mfg. Engg.
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Headstock:
• Housing comprising of
– feed gear box
– stepped cone pulley
• Rigidly mounted on the
inner guide ways of lathe
bed at its left end.
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MAIN DRIVE
Cone pulley
• Cone pulley which drives the
main spindle is
driven by the motor.
• Various spindle speeds can be
obtained by shifting the belt on
different steps of the cone pulley.
Dept. of Mech & Mfg. Engg.
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Tailstock:
• Movable part of the
lathe that carries the
dead centre in it.
• Used to clamp tools like:
Twist drills
Reamers
For making holes.
• Mounted loosely on the
inner guide ways of a
lathe bed
• Moved and locked in
any position.
Dept. of Mech & Mfg. Engg.
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Carriage assembly:
• To support the tool
• Moves over the outer guide
ways longitudinally between
headstock
and tailstock.
It is composed of 5 main parts:
1. Saddle
2. Cross slide
3. Compound Rest
4. Apron
5. Tool post
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Saddle
• H shaped casting that slides
over set of guide ways
• Serves as the base for the
cross slide.
Cross slide
• Mounted on the saddle
• Enables the movement
of the cutting tool laterally
across the lathe bed by
means of cross feed hand
wheel.
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Cross Feed Knob
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Compound Rest
•Mounted on the top of the
cross slide
•Supports the tool post.
•Swiveled to any angle in the
horizontal plane
•To facilitate following
operations:
•Taper turning
•Threading operations
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Apron Hand Wheel
Used to move tool along the work - for Turning (Longitudinal Feed)
Apron
Hand
Wheel
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Apron Tool Post
•Mounted on the front of the Compound
Rest
saddle
• Consists of,
- Carriage
- Cross slide mechanisms
Tool post
• Clamps the tool holder in
the proper position for
machining
operations.
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Chuck
Three Jaw Chuck
- For holding cylindrical
stock centered.
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Lead Screw:
• A screw rod which moves longitudinally in front of the lathe
bed.
• Rotation of the lead screw moves the carriage to and fro
longitudinally during thread cutting operation.
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Feed rod:
• A stationary rod mounted in front of the lathe bed
• Facilitates longitudinal movement of carriage during turning
and facing operations.
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Operations that can be performed on a lathe:
The various operations that can be performed on a lathe
are:
1. Turning.
2. Step turning.
3. Taper turning.
4. Thread cutting.
5. Facing.
6. Knurling
7. Chamfering.
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Specification of a lathe.
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Specification of a lathe
1. Distance between centers:
– Maximum distance that can be obtained between the lathe
centers
– Represents the maximum length of the work piece that
can be held between centers.
2. Overall length of the bed:
– Maximum length of the bed starting from the head stock
end to tailstock end.
3. Swing diameter over the bed:
– Largest diameter of the work piece that can be rotated
without touching the bed.
4. Swing diameter over a gap in the bed:
– Maximum diameter and the width of a work piece that
can be mounted between the centers.
Dept. of Mech & Mfg. Engg.
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DRILLING MACHINE
Dept. of Mech & Mfg. Engg. 30
DRILLING
Drilling is a metal cutting process carried out by a rotating
cutting tool (twist drill) to make circular holes in solid
materials.
Drilling Machine
A power operated machine tool, which holds the drill in its
rotating spindle and produces a hole when moved linearly
against the work piece.
Dept. of Mech & Mfg. Engg. 31
Twist Drill
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Types of Drilling Machines
Drilling machines may be classified as
1. Portable drilling machine.
2. Bench or Sensitive drilling machine.
3. Radial drilling machine.
4. Pillar drilling machine.
5. Gang drilling machine.
6. Multiple spindle drilling machine.
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Radial Drilling Machine
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Radial Drilling Machine
• Radial drilling machine is used for medium and heavy duty
applications
• Consists of a heavy, circular column mounted on a very strong base
• Radial arm that can swing around is mounted on the column and the
radial arm can be raised and lowered
• Drill head with drive and feed mechanism is fitted on to the radial
arm
• Drill head can move horizontally along the guides of the arm and
can be locked at any desired position
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List the operation performed on a drilling machine.
The different machining operations that can be performed
on a drilling machine are as follows.
1. Drilling
2. Reaming
3. Boring.
4. Counter Boring
5. Counter sinking
6. Spot facing
7. Tapping.
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Drilling Operations
Dept. of Mech & Mfg. Engg. 39
