Module 1 Note

8/4/2019 Module 1 Note

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Lathe

1.1 Introduction

The lathe is a machine tool used principally for shaping articles of metal (and sometimes

wood or other materials) by causing the workpiece to be held and rotated by the lathe

while a tool bit is advanced into the work causing the cutting action. It is also known asmother of machine tools. The basic lathe that was designed to cut cylindrical metal stock

has been developed further to produce screw threads. tapered work. Drilled holes.

knurled surfaces, and crankshafts etc.

1.2 Function of a Lathe

Lathe is one of the machine tool, which rigidly & securely hold and rotate the work piece

and provide desired movement to tool also, to remove the unwanted material from the

stock to obtain the desired size and shape.

1.3 Turning

Turning is the machining operation that produces round parts. In its basic form, it can bedefined as the machining of an external surface:

(i) With the workpiece rotating,

(ii) With a single-point cutting tool, and

(iii) With the cutting tool feeding parallel to the axis of the workpiece and at a

distance that will remove the outer surface of the work

1.4 Classification of lathes

A lathe can be classified according to various aspects

(i) According to Configuration (Horizontal lathe, Vertical lathe)

(ii) According to the Purpose of Use (General purpose e.g. Centre lathe , Single

purpose e.g. Facing lathe & Special purpose lathes e.g. Wheel lathe, T lathe etc.)

(iii) According to the Size or Capacity(Light, Medium, and Heavy duty lathes)

(iv) According to the Degree of Automation(Non automatic e.g. Centre lathe , Semi

automatic e.g. Capstan and Turret lathe & Automatic lathes e.g. Swiss type automatic lathe )

(v) According to the Type of Automation (Fixed automation e.g. Single & Multi spindle

lathe and Flexible automation e.g. CNC lathe)

(vi) According to the configuration of the Jobs Being Handled (Bar type, Chucking

type and Housing type lathe)

(vii) According to the Precision required (Ordinary lathe e.g. Automatic lathe, High

precision lathe e.g. Swiss type automatic lathe )

(viii) According the Number of Spindles ( Single and Multi spindle lathe )

1.5 Types LatheSpeed lathe

It is the simplest form of the lathes used in manufacturing sector. The spindle of this lathe

rotates with high speed, because of this characteristic it is termed as speed lathe. And it is



used in the area especially where light cut and high speed is needed , like wood working,

spinning, polishing etc. It consists of a bed, a headstock, a tailstock, a tool post mounted

on a adjustable slide and it is fed into the work purely by hand control. There is no feed

box, lead screw or conventional type of carriage.

Engine or Centre lathe

Engine lathe is the one of the most versatile and general type lathe.

Bench lathe

It is a small lathe mounted on a bench or cabinet. It is generally employed for light duty

and precision work

Tool Room lathe

Turret lathe

A turret lathe is used for repetitive or batch production work. It is medium production

semi-automatic machine. The tailstock is replaced with an indexable tool holder called a

turret. The turret is directly mounted on the lathe bed and can be fixed at any desired position. It allows multiple cutting operations to be performed, each with different cutting

tool. The turret can accommodate up to six tools at a time which can be sequentially used

with the help of an indexing mechanism. Turret lathes are generally heavy duty

machines. It is also called saddle type lathe.

Capstan lathe

It is also semi-automatic production lathe. Though similar to the turret lathe, here the

tailstock is replaced by a hexagonal tool holder which can carry six different tools at a

time. The turret head slides with a help of the ram which in turn can be fixed at a desired

position on the bed. Capstan lathe is usually a small-sized light-duty machine. It alsocalled ram type lathe.

Special purpose lathe

Automatic lathe

1.6 Constructional Features of a Lathe



1.5 Power Transmissions in a Lathe

1.6 Driving Mechanisms

1.7 Lathe Operations

1.8 Machining Parameters

1.8.1 Speed

1.8.2 Feed

1.8.3 Depth of Cut

1.8.4 Machining Time

1.9 Lathe Specifications

1.9 Work Holding Devices

1.10 Tool Holding Devices

1.11 Automatic & Semiautomatic Lathes

1.11.1 Capstan Lathe

1.11.2 Turret Lathe

1.11.3 Constructional Features



1.11.4 Tool Layout

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Module 1 Note