Lathe

Lathe

Introduction

Turning

Lathe is one of the most important machine tools. It is used for producing cylindrical parts of revolution and the operation of producing such parts is called “Turning”

Types of Lathe

1.Bench Lathe

Bench Lathe 

Bench Lathe

This is a small precision Lathe, Usually mounted on a bench. This is very useful for turning small, precision components and used mostly in tool making. Normally these are not provided with automatic feed mechanism.

2. Center Lathe

Center Lathe

Center Lathe

This is most important and commonly used type of lathe. In older days, it was called as engine lathe. This is called as Centre Lathe because; work can be mounted and turned between centers which is a development from olden days Speed Lathe. This is a versatile machine adapted to every type of Lathe work. The centers of lathe are made in a large no. of sizes and designs.

3.Tool Room Lathe

Tool Room Lathe

Tool Room Lathe

This is a high precision Centre Lathe used in tool rooms. This is provided with a no. of accessories and attachments and has a wide no. of speeds and feeds. The machine is costlier than an ordinary Center Lathe of same size.

4.Turret Lathe

Turret Lathe

This is a general name for a variety of Lathes used for production work. It differs from a Centre Lathe, in that the tail stock is replaced by a hexagonal or octagonal turret on the face of which, multiple tools may be fitted and fed into the work in a proper sequence. Therefore, a no. of identical parts can be produced at a time without the need for resetting the work on tool every time.

5. Capstan Lathe

Capstan Lathe

Capstan Lathe

This is a type of Turret Lathe. The difference is, in a Capstan Lathe, the turret is mounted on the ram, which moves in a saddle. The Saddle can be fixed to the bed of the Lathe at any desired place, but in a Turret Lathe, the turret is mounted directly on Saddle, which can be moved over entire length of the bed. Thus in a Capstan Lathe, the length of movement of the turret carrying slide is less compared to a turret lathe. The Capstan Lathe is used for batch production of small and medium size components. Usually in a Capstan Lathe turret movements are controlled by hand.

6. Single Spindle Automate

Single Spindle Automate

This is an automatic Turret Lathe, used for mass production of precision components. All operations are done automatically including feeding of the bar stock. The operations are controlled by cams.

7. Swiss Type Automate

Swiss Type Automate

The special feature of this automatic lathe is that there is no turret. The tool slides are mounted radially to the spindle. The feed movement is given to the work piece i.e. to the spindle. This Lathe is used for mass production of very small high precision watch and instrument parts.

8.Multi Spindle Automate

Multi Spindle Automate

This is an automatic turret lathe having six or eight spindles. Through each spindle one bar stock is fed, and rotated of speeds, independent of others. The spindles are mounted around a circular turret when the turret makes one full rotation one cycle is completed and one component comes out. At each stage, one operation is done on the work piece. The tool turret will not rotate. The feed movement is given by the tool turret. This is a heavy duty Turret Lathe, Used for mass production of short, medium size components.

9. Chucking Lathe

Chucking Lathe

This is a heavy duty Lathe, specially used in railway workshops for facing and turning of large diameter locomotive wheels. In these jobs facing length is more and longitudinal turning is less. Therefore, this Lathe is made with short bed length and log cross slide and a heavy duty tool post.

10. Vertical Lathe

Vertical Lathe

Vertical Lathe

This Lathe is having its spindle in vertical direction and provided with circular bed, similar to a face plate. The job is clamped on this bed and rotated. Other features of this lathe are similar to a planer. Tool holders are provided in the vertical and horizontal direction also. This Lathe is used for facing, turning and boring of large work pieces mostly casting which are difficult to hold and rotate on other types of Lathe. The main advantage of this type of lathe is that the weight of the work piece is supported vertically downwards and is equally distributed on the bearings the clamping is rigid.

11. Vertical Turret Lathe

Vertical Turret Lathe

This is a vertical lathe, having a turret type tool holder. This is used for production work. CNC Vertical turret lathes are used in machining of large turbine housings.

12. Copying Lathe

Copy Lathe

Copying Lathes are used for profile turning. In this Lathes, the required profile is duplicated on the work piece by a hydraulic or electrical copying device, by means of a sensitive stylus, which traces an accurate master. The master may be a finished turned work piece or template. These Lathes are used for turning of parts such as shafts, axels, piston rods, handle grips etc. in batch production.

Specification of Centre Lathe

The size of a centre lathe is specified by

         i.            The length of bed
       ii.            The Swing Diameter over the bed
      iii.            The height of centers measured from the bed
     iv.            The maximum distance between the centers
       v.            The Swing Diameter over the carriage
     vi.            Diameter of the spindle bore
    vii.            Taper of Spindle nose
  viii.            Power of motor
     ix.            Range of spindle speeds and feeds etc.

Major Parts and Functions

1.     Bed

The lathe bed forms the base of the machined. The head stock and the tail stock are located at either end of the bed and the carriage rests over the bed in between the head stock and the tail stock and slides over the bed.

2.     Head Stock

The Head Stock is located at the left side of the Lathe Bed. It is a hollow box which contains the spindle and its drive mechanism.

3.     Tail Stock

The tail stock is located at the right hand end of the bed. The tail stock carries the dead center. The supports the other end of the work. When it is being turned between centers, it also holds a number of tools for operations like drilling, reaming etc.

4.     Carriage

The Carriage of a Lathe has several parts that serve to support, move and control the feed. The parts are

a)      Saddle

b)      Cross Slide

c)       Compound Slide

d)      Tool Post

e)      Apron

5.     Feed Mechanism

The feed mechanism consists of the feed gears in the head stock that moves the feed bar or Lead Screw and the gears in the Apron which get the motion through the Feed bar and move in the Carriage.

6.     Screw Cutting Mechanism

The thread cutting mechanism in the lathe consists of the lead screw, the change gears in the head stock and the half nut in the apron. The rotation of lead screw is not used to move the tool to cut the thread.

Accessories and Attachments of Lathe

Accessories:

Accessories are certain clearances which may not be supplied along with machine. They are not integral parts of the machine but they are essential for performing the basic functions of the lathe.

For Example: 3 Jaw Chuck, 4 Jaw Chuck, Tools, Centers etc.

Attachments

Attachments are Certain Special Assemblies with suiting provision to the machine. They are not essential to perform basic functions but they help to extend the utility of the lathe. Some Lathe attachments are

·         Milling Attachment

·         Taper Turning Attachment

·         Tool Post Grinder

·         Copy Turning attachment

·         Relieving  Attachment

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