Session 3  Classification of lathes  Kinematics system of centre lathe  Working principle of lathe machine

Classification of lathes Lathes are very versatile of wide use and are classified according to several aspects: (a) According to configuration Horizontal -Most common for ergonomic conveniences Vertical - Occupies less floor space, only some large lathes are of this type.

Classification of lathes (b) According to purpose of use General purpose -Very versatile where almost all possible types of operations are carried out on wide ranges of size, shape and materials of jobs; example : centre lathes Single purpose Only one (occasionally two) type of operation is done on limited ranges of size and material of jobs; example – f acing lathe, roll turning lathe etc. Special purpose - Where a definite number and type of operations are done repeatedly over long time on a specific type of blank; example: gear blank machining lathe etc.

Classification of lathes (C)According to size or capacity Small (low duty) - In such light duty lathes (upto 1.1 kW), only small and medium size jobs of generally soft and easily machinable materials are machined Medium (medium duty) - These lathes of power nearly upto 11 kW are most versatile and commonly used Large (heavy duty) Mini or micro lathe - These are tiny table-top lathes used for extremely small size jobs and precision work; example : swiss type automatic lathe

Classification of lathes (D)According to degree of automation Non-automatic - Almost all the handling operations are done manually; example: centre lathes Semi-automatic - Nearly half of the handling operations, irrespective of the processing operations, are done automatically and rest manually; example : capstan lathe, turret lathe, copying lathe relieving lathe etc. Automatic - Almost all the handling operations (and obviously all the processing operations) are done automatically; example – single spindle automat (automatic lathe), swiss type automatic lathe, etc.

Classification of lathes (E)According to type of automation Fixed automation - Conventional; example – single spindle automat, swiss type automatic lathe etc. Flexible automation - Modern; example CNC lathe, turning centre etc. (f) According to configuration of the jobs being handled Bar type - Slender rod like jobs being held in collets Chucking type - Disc type jobs being held in chucks Housing type Odd shape jobs, being held in face plate

Classification of lathes (g)According to precision Ordinary Precision (lathes) - These sophisticated lathes meant for high accuracy and finish and are relatively more expensive. (h) According to number of spindles Single spindle - Common Multispindle (2, 4, 6 or 8 spindles) - Such uncommon lathes are suitably used for fast and mass production of small size and simple shaped jobs.

Classification of Lathes Bench Lathe

Engine Lathe

Tool room Lathe

Special purpose lathe (Gap bed)

Kinematic System Of Lathes

Kinematic System and working principle Of Lathes

Lathe Components 1.Bed: It supports all major components of lathe as it is the base of machine. These have large mass, rigidly built as single piece casting from gray/ toughened C.I to resist deflection & absorb vibrations generated during cutting process. Three main parts head, tail stocks, carriage are mounted on bed

2. Head stock: It is a part which secured permanently at left hand end of bed which supports spindle & equipped with power driving mechanisms (motors, pulleys, V-belts ) for spindle at various rotational speeds. It have a hollow spindle to which Work holding devices such as chucks, collets are attached.

3. Tail stock/ Loose head stock/ Puppet head: It is mounted on inner ways at right hand end of bed which can slide along the ways & can be clamped at any position, supports the other end of w/p. It is equipped with a centre that may be fixed(dead centre) or may be free to rotate with w/p called (live centre) Drills & reamers can be mounted on tailstock quill (a hollow cylindrical part with tapered hole) to drill axial holes in w/p. Quill can move in & out with hand wheel.

4.Carriage: It slides along the guide ways between head stock, tailstock & consist of assembly of saddle, cross slide, tool post, compound rest, apron. Main function of carriage is to hold cutting tool & move it to give longitudinal & / cross feed to it. Operator moves carriage manually by hand wheel/ automatically by engaging feed shaft with carriage feed mechanism.

Carriage consists of: a)Saddle:  Part of carriage which slides along bed ways & support the cross slide, compound rest, tool post. b)Cross slide:  Mounted on top of saddle & always moves in direction normal to axis of main spindle.  It can be either operated by hand by means of cross feed screw or may be given power feed through apron mechanism.

c) Compound rest: It is mounted on cross slide & carries a graduated circular base called as swivel plate. Upper part is called compound slide can be moved by means of compound rest feed screw. d)Tool post: Top most part of carriage, used for holding tool/ tool holder in position.

e) Apron: It is hanging part in front of carriage. It serves as housing for number of gear trains through which power feeds can be given to the carriage & cross slide.

5. Feed rod & Lead screw: Feed rod is powered by set of gears from head stock. It rotates during operation of lathe & provides movement to carriage & cross-slide by means of gears, friction clutch, key way along the length of rod. Lead screw it transmits power to carriage through a gear & clutch arrangement in carriage apron.

Working Principle of lathe The lathe is a machine tool which holds the work piece between two rigid and strong supports called centers or in a chuck or face plate which revolves as shown in Fig. The cutting tool is rigidly held and supported in a tool post which is fed against the revolving work. The normal cutting operations are performed with the cutting tool fed either parallel or at right angles to the axis of the work. The cutting tool may also be fed at an angle relative to the axis of work for machining tapers and angles.

Working Principle of lathe

Working principle of turning