Types of lathes

A lathe is a machine tool in which the work is either rotated between two rigid supports called centers, or is held in chuck or on a face plate attached to the rotating spindle of the machine. On this machine the material is removed from the rotating work by the action of the cutting tool, which may be advanced either parallel or perpendicular to the axis of the work. The lathe is probably the most versatile and important tool in the machine shop.

The lathe is thought to be one of the first machines invented by man.

Modern lathes are highly efficient, accurate and complex devices, capable of doing a great quantity and variety of work. A well constructed engine lathe will, when properly operated, produce work accurate within 0.001 of an inch or even less.

Motion is transmitted to modern lathes by means of individual motors. Sometimes the motor is direct mounted, while on other machines it is connected by means of a short belt, usually of the V-type.

The size and capacity of a lathe is given in terms of swing and length of bed. The swing refers to the diameter of work that can be rotated in the lathe. Thus a 16-inch lathe will swing work as large as 16 inches in diameter. The length of a lathe should not be confused with the maximum distance between centers when the tailstock is moved to the rear end of the lathe bed. The maximum distance between centers however, determines the length of stock that can be machined.

Lathes are made in a wide variety of types and sizes, from the small precision lathe found in watch repair shops to the immense machine used in manufacturing big guns.

There also exist various attachments which can be employed on a lathe to perform functions or operations formerly done on a special machine: a milling attachment, a boring attachment and a gear-cutting attachment. Such devices greatly extend the variety of work that can be performed on a lathe.

As lathes in general are used for a great variety of operations, naturally there are many different designs and sizes. The most common type of lathes is.usually known by manufacturers as an engine lathe. The term " engine" in this connection simply means a machine, and designates that particular class of lathe which is hand-manipulated and used by machinists for general work. Lathe having gears which are changed for cutting threads of different pitch are sometimes known as plain or standard engine lathes. The tool-room lathe is classified according to the general class of work for which the lathe is designed. It is similar in appearance to an ordinary lathe, but has extra attachments and is generally considered a very accurate machine.

Other types of lathes which have some distinguishing characteristics are: the turret lathe, which is so named because tools for performing successive operations are held in a revolving turret; the bench lathe, which in so small that it is mounted on a bench, and intended for delicate work usually requiring considerable accuracy; the precision lathe, which is usually a bench-type that is capable of very accurate work and is more expensive than an ordinary bench lathe; the gap lathe, which has a gap formed in the bed in front of the face plate in order to increase the “swing” or maximum diameter that may be revolved.

The lathe consists essentially of a bed, headstock, tailstock and saddle.

The main casting of the lathe is called the bed, and usually consists of a good quality grey iron casting of rigid design.

The Headstock is bolted rigidly to the bed at the left-hand end. It carries the lathe spindle and gear-box.

The Tailstock consists of a casting fitted to the bed and capable of being firmly clamped to it at any position along its length. The casting is bored for a sliding sleeve which is moved axially by a handwheel at the right-hand end.

The saddle consists of a casting designed to carry the tool post slides, and is fitted to the ways of the bed so that it may slide along it without lateral movement. The front of this casting is called the apron.

EXERCISES

1. Give the main points of the text, answering the following questions:

1. What do we call the lathe?

2. Can it be considered the most important machine tool in a shop?

3. How is motion transmitted to modern lathes?

4. Can you give the definition of the swing of a lathe?

5. Is there only one standard size of lathes?

6. What types of lathes do you know from the point of view of their design?

7. What units does the lathe consist of?

2. Choose synonyms out of the following list:

Costly, various, to operate, delicate, commonly, different, capacity, to manipulate, immense, formerly, accurate, to designate, usually, performance, to determine, expensive, huge, previously.

3. Fill in the blanks with the suitable words from the text. The words are given below:

1. The lathe is probably the most... tool in the machine shop.

2.... is transmitted to modern lathes by means of individual motors.

3. The swing refers to the... of work that can be rotated on the lathe.

4. The most common type of lathe is known as an.......

5. The bench lathe is usually... for delicate work.

6. The main casting of the lathe is called the....

7. The headstock carries the lathe... and....

8. There exist various... on the lathe to perform functions formerly done on a.......

9. The... lathe is similar in... to an ordinary lathe.

10. In a lathe the material is... from the rotating work by the action of the.......

Intended, motion, attachments, removed, special machine, cutting tool, engine lathe, versatile, spindle, gearbox, diameter, tool-room, bed, appearance.

4. Perform the following tasks, basing of the text:

5. Characterize lathes according to the following plan:

- definition of a lathe

- its efficiency

- the main parameters of a lathe

- types of lathes

- main units of a lathe and their functions.

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