Lathe Machine-Introduction, Working Principle, Types, Various Parts, Accessories of lathe, Operation

INTRODUCTION:

  • Lathe machine refers to a machine tool which is used to remove unwanted metals from the work-piece to give desire shape and size.

 

  • In the metal working industry,Lathe is one of the most important machine tools. It operates on the principle of a rotating work piece and a fixed cutting tool.

 

  • The cutting tool is feed into the work piece which rotates about its own axis causing the work piece to be formed to the desired shape.

 

  • Lathe machine is also known as ” the mother/father of the entire tool family”.

 

  • It was invented by  DAVID WILKINSON (05 Jan. 1771 – 03 Feb. 1852) .

                                               

MAIN  PARTS:

  •  Lathe machine is also known as “ Center Lathe ” because of two centers between which the job can be held and rotated.  The main parts of  lathe machine are :-

 A. Bed 

  • Bed is the main body  of a lathe which provides supports to all parts of the machine .
  • The bed is a heavy, rugged casting in which are mounted the working parts of the lathe.

 B.  Head Stock

  • It has the spindle shaft and support bearings,speed shift levers and gear trains .
  • The head stock spindle is a hollow cylindrical shaft that provides a drive from the motor to work holding devices.
  • Head stock is hidden in a box and  spindle is hidden in a gear cover

  C. Tail Stock 

  • The main function of tail stock to support the job when required.
  • Tail stock is  situated on bed.
  • It can be offset for taper turning operations.

 D. Lead Screw

  • It is  used to transmit power  to carriage through gear  and clutch arrangement in the carriage apron.

  E. Carriage and Saddle

  • Carriage supports cross-slide , compound rest and tool post and it moves along the ways under manual or power feed.
  • It comprises the saddle a casting , which rides across the top of the ways and the apron .
  • Compound slide permits angular tool movement for taper turning .

 F.  Cross Slide and Compound slide

  • Cross slide is a dove tail slide which is assembled on the top of the saddle and moves at right angle to the ways.
  • Compound slide supports the tool post and cutting tool in its various positions and it is above the cross slide and it can be rotated to set the tool to advance cutting of work piece .

G. Feed Mechanism

  • Feed mechanism is used to transmitted power to carriage .
  • For this purpose a system of gear trains is provided.
  • The quick change gear is arranged between spindle and lead screw and rotational speed of lead screw with respect to spindle speed can be adjusted manually by means of gear trains.

H. Tool Post 

  • It is used to hold the tool at correct position.
  • It is bolted on the carriage.
  • It can be set at any desired angle.

I. Apron

  • It is situated on the carriage
  • It consist all controlling and moving mechanism of carriage.

J. Spindle

  • It is the main part of lathe which holds and rotates the chuck.

K. Live Center

  • It allows higher turning speeds without the need for separate lubrication and also greater clamping pressures.

L. Dead  Center

  • A dead center may be used to support the work piece at either the fixed or rotating end of the machine.
  • Dead centers are typically fully hardened to prevent damage to the important mating surfaces of the taper and to preserve the 60° angle of the nose

FUNCTION 

  • For producing cylindrical jobs.
  • Flats surface and holes.
  • It can be used for producing different types of surfaces ,cutting threads ,cutting grooves.

WORKING PRINCIPLE

PRINCIPLE 

  • The lathe is a machine tool which is used to removes unwanted materials  from a work piece in the form of chips with the help of a tool which travels across the work piece and can be fed deep in work.

 

  • If the tool is moved parallel to the work piece then cylindrical surface is formed.

  • If the tool is moved inclined to the axis then it produce a taper surface and is called taper turning.

WORKING
  • It is held the work between two supports called centers.
  • Face plate or Chuck are used for holding the work.
  • Face plate or Chuck are mounted on machine spindle.
  • The cutting tool is held with the help of Tool post.
  • The movement of the job is rotated about the spindle axis.
  • Against the revolving work, the tool is feed.
  • The movement of the tool is either parallel to or at any inclination to the work axis.

LATHE OPERATION & MACHINE TOOLS

OPERATIONS DIAGRAM MACHINE TOOL
  Tapper Turning   Turning Tool
Facing Facing Tool
Drilling Drilling Tool
Boring Boring  Tool
Internal & External Threading Threading Tool
Knurling   Knurling Tool
Grinding Tool Post Grinding
Parting Parting  Tool
                                                                                                           

 OPERATIONS

1. Turning

  • Turning is an operation in which diameter of the work piece is removed as shown in above table.

2. Facing

  • Facing is an operation in which length of the work piece is reduce as shown in table.
  • Turning tool is used

a.  Feed

  •  The rate at which the cutting tool crosses the work piece in the direction perpendicular to work piece axis.

b.  Depth of cut

  • It is the perpendicular distance measured from the machine surface to the UN-cut surface of the work piece.

3. Drilling

  • Drilling is an operation to produce a hole on the work piece.

4.  Boring

  • Boring is done to enlarge a hole or cylindrical cavity to produce circular internal grooves.

5.  Knurling

  • Knurling is done to produce regular pattern type roughness on the work piece.

TYPES

          According to their construction and design we are generally classifying the lathes as follows :

  1. Bench lathe
  2. Speed lathe
  3. Engine lathe or center lathe
  4. Tool room lathe
  5. Capstan and turret lathe
  6. Special purpose lathe
  7. Automatic lathe

BENCH LATHE

  • Bench lathe is a small lathe usually mounted on a bench.
  • This is used for small and precision work.

SPEED LATHE

  • Speed lathe is the simplest of all types of lathe in construction and operation.
  • It consists of a bed , a head stock, a tail stock and a tool – post mounted on an adjustable slide.
  • This types of machine is used where cutting force is Minimum such as in wood working ,sniping,centering,polishing ,etc.
  • They are named so because of very High Speed of head stock  spindle.

ENGINE  LATHE (CENTER LATHE)

  • This lathe is the most important member of the lathe family and is the most widely used.
  • The engine lathe can feed the cutting tool both in cross and longitudinal direction with reference to the lathe axis with the help of a carriage , feed rod and lead screw .
  • With these additional features an Engine lathe has proved to be a versatile machine adopted for every type of lathe work.

Advantages

  • It is used for mass production of products.
  • It is used for manufacturing cylindrical shapes like steels and plastics.

Disadvantages 

  •  It is very difficult to program in machine language
  • corruption, poor service, and racial issues.

 

TOOL ROOM LATHE 

  • A tool room lathe having similar features to an engine lathe but some extra attachments to make it suitable for a relative more accurate angle of speed and feeds.
  • This lathe is mainly used for precision work on tools ,Dies,Gauges and in macing work where accuracy is need.
  • The machine is costlier than an engine lathe.

CAPSTAN AND TURRET LATHE 

CAPSTAN  LATHE

  • Capstan lathe having features of the basic lathe and have short slide tail stock.
  • The main body is fixed to the bed in the required position and its longitudinal movement is along with short  slide.

Advantages

  • Capstan lathe machining is done on short and light wok pieces.

Disadvantages

  • The heavier work piece cannot machine by  capstan lathe.

TURRET LATHE 

  • The turret lathe is a form of metal working lathe that is used for repetitive production of duplicate parts or mass production.
  • In a turret lathe , a longitudinally feed able, hexagon turret replaces the tail stock.

Advantages

  • Turret lathe is used to machine the long and heavy work pieces and it have hexagonal tool post or head , so there is no need of changing  the tool.

Disadvantages

  • The have manual indexes.

SPECIAL PURPOSE LATHE 

  • Special Purpose lathe are used for special purposes and for jobs which cannot  be accommodated or conveniently machined on a standard lathe.

AUTOMATIC LATHE 

  • In the automatic lathe ,the various operations are automated like change of the work piece.
  • After the job is completed ,the machine will continue to repeat the cycles producing identical parts even without the attention of an operator.

Advantages 

  • Various operations are automatic though no need of extra hard work like work changing.

Disadvantages

  • Lots of consideration are being taken on fixing the setup. 

LATHE ACCESSORIES 

  •  Generally lathe accessories are divided into Two categories :-
  1. Work Holding device and 
  2.  Cutting Tool Holding device

   1. Work Holding device 

  • The work holding devices are  device which is  used to hold and rotate the work pieces along with the spindle.
  •  The different work holding devices which are used according to the shape, length, diameter and weight of the work piece and the location of turning on the work. They are as follows :-

A. CHUCKS

  • A Chuck is one of the most important device which is used for holding and rotating the piece of the work on lathe.

  Types of chucks :

  1.  Three Jaw Chuck
  2.   Four  Jaw chuck
  3.   Collect Chuck
  4.    Spindle Chuck
  5.    Magnetic Chuck
  6.    Combination Chuck
  7.    Air Operated Chuck

B. FACE PLATE

  • Face plate is a circular disc bored out and threaded to fit to the nose of the lathe spindle.
  •  They having  radial plain and ‘T’ – slots for holding the work by bolts and clamps.

C.  MANDRELS 

  • Mandrel is a device which is used for holding a hollow work piece that has been previously drilled or bored.
  • Mandrel is mounted between centers and work revolves with it .

D.  CENTERS

  • In Lathe centers are used for supporting the work piece during turning operations .
  • There are two centers :-
  1. Live center
  • A live center is a center which fits into the head stock spindle and revolves with the work.
  • A live center is constructed so that the 60 degree  center which runs in its own bearing .

b. Dead center

  • Dead  center is the center which is used in a tail stock spindle and doesn’t revolve .

c.  Half center

  •  Half center is the center which is often used in the tail stock  for facing up to or for Turning close to the end of the work .
  •  It cuts away almost to its point .

 E.   DRIVING PLATE OR CATCH PLATE

  • Catch plate is plane disc which is made up of cast iron or steel .
  • They having a central

f. CARRIERS

  •   Carrier is a device that Clamps around the work piece .
  •   They allows the rotary motion of the machines spindle to be transmitted to the work piece .
  •   There are two types of carrier :-

a. Straight Tail Carrier

  • This is used to drive the work by means of the pin provided in the driving plate .

b. Bent Tail Carrier

  • It fits into the slot of the catch plate to drive the work .

c .   ANGLE VISE

  •   Angle vise is an angular adjustment on base to allow operator to drill holes at an angle without tilting table .

2.  Cutting Tool Holding device

  • The cutting tool holding device is a device which is used to hold the cutting tools .
  • The different cutting tool holding devices are as follows:-

A. Tool Post

  • Tool Post is a device which holds the cutting tool on a lathe and some other machine.

B. Collect

  • Collect is a device which is used to hold a cutting tool in the spindle of a milling machine.

C.  Drill Chucks

  • It is the most common devices used for holding straight-shank cutting tools.
  • There are two common types:-

a.  Key Type

  • It  has loosened or tightened by key.

b.  Keys Less Types

  • It has loosened or tightened by hand without key.

D. Drill Sleeves

  • It is used to adapt drill shank to machine spindle because of taper on tool is smaller than taper in spindle.

E.  Drill Socket

 

  • Drill socket is used when hole in spindle of drill press too small for tapper shank of drill.
  • They have used often an extension sockets.

F. Straight Tool Holders

 

  • Straight is used for taken cuts in either direction and for general machining operations.

Specifications of Lathe

 1. a.  Center distance

b.    Height of center

c.     Type of bed

2. a.  Swing in gap

b.   Gap in front of face place

c.    Swing over cross slide

d.   Swing over bed

3.  a.  Spindle bore

b. Spindle speed range

c.  spindle nose

d.  Taper nose

4.  a.  Longitudinal feeds

b.  Cross  feed

c.  Lead screw pitch

d. Metric thread pitches

5. a.  Top slide travel

b. Cross slide travel

c. Tool section

6. a.  Taper in sleeve bore

b.  Tail stock  sleeve travel

7.  Motor horsepower in RPM(Revolution per minute).

8.  Shipping dimension

Thanks for reading.