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VII. Talk about machine tools according to the plan:

 definition of a machine tool

 the classification of machine tools

 the way the machine tools can be powered

 the function of machine tools

Part II

Text a Lathe

I. Read the text about lathes and find answers to the following questions.

1. What are the oldest machine tools?

2. What operations can be performed on a lathe?

3. What are the main parts of the lathe?

4. How is metal removed from the workpiece in the lathe?

5. What provides cooling and lubrication of the lathe?

6. What type of lathes is used for individual part production?

7. What type of lathes is used for turning workpiece with large diameters?

Lathe is a machine tool that performs turning operations in which unwanted material is removed from a workpiece rotated against a cutting tool. Lathes are among the oldest and most important machine tools, used in France from 1569 and important in the Industrial Revolution in England, when they were adapted for metal cutting. Lathes (usually called engine lathes) today have a power-driven, variable-speed horizontal spindle to which the workholding device is attached. Operations include turning straight or tapered cylindrical shapes, grooves, shoulders, and screw threads and facing flat surfaces on the ends of cylindrical parts. Internal cylindrical operations include most of the common hole-machining operations, such as drilling, boring, reaming, counterboring, countersinking, and threading with a single-point tool or tap. Lathe is a machine tool for holding and turning metal, wood, plastic, or other material against a cutting tool to form a cylindrical product or part. It also drills, bores, polishes, grinds, makes threads, and performs other operations. Its principal parts are the headstock (attached to the bed or base of the machine), which holds one end of the material in a rotating spur; the tailstock, which holds the other end, moves along the bed, and can be clamped in position at any point; the cutting tool; and the power feed, comprising the drive and its motive parts.

There are a lot of varieties of lathes.

Lathes that sit on a bench or table are called “bench lathes”.

Lathes that do not have additional integral features for repetitive production, but rather are used for individual part production or modification as the primary role, are called “engine lathes”.

Lathes with a very large spindle bore and a chuck on both ends of the spindle are called “oil field lathes”.

Fully automatic mechanical lathes, employing cams and gear trains for controlled movement, are called screw machines.

Lathes that are controlled by a computer are CNC lathes.

Lathes with the spindle mounted in a vertical configuration, instead of horizontal configuration, are called vertical lathes or vertical boring machines. They are used where very large diameters must be turned, and the workpiece (comparatively) is not very long.

A lathe with a cylindrical tailstock that can rotate around a vertical axis, so as to present different facets towards the headstock (and the workpiece) are turret lathes.

Metalworking lathes

In a metalworking lathe, metal is removed from the workpiece using a hardened cutting tool, which is usually fixed to a solid moveable mounting called the “toolpost”, which is then moved against the workpiece using hand wheels and/or computer controlled motors.

The toolpost is operated by leadscrews that can accurately position the tool in a variety of planes. The toolpost may be driven manually or automatically to produce the roughing and finishing cuts required to turn the workpiece to the desired shape and dimensions, or for cutting threads, worm gears, etc. Cutting fluid may also be pumped to the cutting site to provide cooling, lubrication and clearing of chip from the workpiece. Some lathes may be operated under control of a computer for mass production of parts.