Dept. of Mech & Mfg. Engg. 1 MACHINE TOOLS. Dept. of Mech & Mfg. Engg. 2 A Machine tool A machine...

Dept. of Mech & Mfg. Engg. 1

MACHINE TOOLS


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

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.

Functions of Machine Tools


Working principle of lathe

Direction of cutting toolCutting tool

Work piece

Direction of rotation of work piece

Chuck


• Cutting tool can remove material

in the form of chips from rotating

work pieces to produce circular

objects

• Work piece is held rigidly by one

of the work holding devices

known as chuck

• Uses V – shaped cutting tool

Working principle of a latheChuck

Direction of cutting tool

Cutting tool

Direction of rotation of work piece


Lathe BasicsLathe Basics

Cross Cross SlideSlide

APRONAPRON

Half Nut Half Nut LeverLever

Friction-Friction-clutch clutch ControlControl

Lead Lead ScrewScrew

BedBed

TAILSTOCKTAILSTOCK

Carriage Carriage Hand Hand

WheelWheel

Tailstock Tailstock Spindle Spindle ClampClamp

Feed Feed Change Change LeverLever

Tool PostTool PostCompound Compound

RestRest

SaddleSaddle

BED BED WAYSWAYS

Motor Motor DriveDrive

Gear Gear BoxBox

Feed Feed Reverse Reverse LeverLever

HEADSTOCKHEADSTOCK

Spindle Spindle NoseNose


Explain with neat diagram the principal parts of an engine lathe.


LATHE


MAJOR PARTS1] Bed2] Head stock3] Tail stock4] Main drive5] Carriage assembly consisting of

a) Saddleb) Cross-slidec) Compound restd) Tool poste) Apron

6] Lead screw7] Feed rod

BED


Foundation part of the machine Supports all other partsThe top of the bed is formed by

two Precession guide waysi) Outer guide way--- Carriage assembly mounted

and align it with centre line of latheii) Inner guide way--- Head stock and Tailstock

are mounted


Headstock:

• Housing comprising of

– feed gear box

– stepped cone pulley

• Rigidly mounted on the

inner guide ways of

lathe bed at its left end.


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.


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.


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


Lathe Carriage and ApronLathe Carriage and Apron

Compound Rest Knob

Half Nut Lever

Carriage Lock Screw

Apron Hand

Wheel

Compound Compound RestRest

Cross Cross SlideSlide

Cross Feed Knob

Tool PostTool Post


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.


Cross Feed KnobCross Feed KnobUsed to move cutting tool across the Used to move cutting tool across the end of the stock - Facing (Cross Feed)end of the stock - Facing (Cross Feed)


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


Apron Hand WheelApron Hand Wheel

Apron Hand

Wheel

Used to move tool along the work - for Used to move tool along the work - for Turning (Longitudinal Feed)Turning (Longitudinal Feed)


Apron •Mounted on the front of the saddle • Consists of, - Carriage - Cross slide mechanisms

Tool post

• Clamps the tool holder in the proper position for machining operations.

Compound Compound RestRest

Tool PostTool Post


ChuckChuck

Three Jaw ChuckThree Jaw Chuck

- For holding cylindrical - For holding cylindrical stock centered.stock centered.


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.


Feed rod:

• A stationary rod mounted in front of the lathe bed

• Facilitates longitudinal movement of carriage during

turning and facing operations.


Center DrillingCenter Drilling


Turning Between CentersTurning Between Centers

Dept. of Mech & Mfg. Engg. 1 MACHINE TOOLS. Dept. of Mech & Mfg. Engg. 2 A Machine tool A machine...

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