VII Oral practice

Ex.20. Speak on the main machining operations using the table:

operation

function

application

Ex.21. Make up the dialogues on the situations.

1. You take the industrial practice at the plant. A foreman asks you about the main machining operations, their applications and advantages.

2. You are taking exam. Your question is “Basic engineering operations”. But you are in difficulties about it. The teacher is asking you some questions on the subject.

3. You could not visit the lecture “Basic machining operations” on account of your disease. But you want to know about the difference and the similarity of these operations. Ask your group – mate about it.

VIII. Reading and comprehension.

Ex. 22. Read the text C without a dictionary for 5 minutes and say what problems are mentioned in the text.

Text c types of lathes

All the machine-tools operate on either a reciprocating or rotary type principle; either the tool or work reciprocates or rotates. Cutting tools must be hard. A tool must also have the correct cutting angle, and the correct speed to cut satisfactorily. Heat dissipation is another factor in considering the correct speed. The engine lathe has a large range of spindle revolutions and of feeds, and in can cut threads. The bench lathe is adapted to small work, having a maximum swing capacity of 9 inches.

The shaper is a flexible machine in many respects complementing the lathe in the work it performs. It has a reciprocating cutting tool, which takes a straight-line cut. It can produce flat surfaces, and by means of special tools, attachments, and devices for holding the work, a shaper can also cut external and internal key-ways, spiral grooves, gear racks, dovetails, T slots and other shapes. The planer, a much larger and heavier machine than the shaper, is designed to remove metal by moving the work in a straight line against a stationary single-edged cutting tool.

The automatic lathe is designed so that all of the tool movements are automatically controlled, although the work must be inserted and removed by an operator. In the automatic lathe two or more heavy duty slides, each with its own drive, rate of feed and direction of feed may be applied. All functions of the machine are completely automatic, including advance of the platen to working position, feeding of all tools, and retraction of slides and platen at completion of cycle, at which time stopping of the spindle is also accomplished automatically. One operator may run two or more lathes. Such lathes are not limited to automative parts but are reducing production time and cost on pump parts, motor and generator parts, pipe flanges, brass and bronze castings, chuck bodies, bevel gears, airplane engine cylinders, etc.

Notes:

Shaper – поперечно – стругальний верстат

Planer – подовж – стругальний верстат

Dovetail – лапа, шип

Platen – станина

Ex. 23. Agree or disagree with the following statements:

1. All the machine – tools on neither a reciprocating nor rotary type principle.

2. A tool must have the correct cutting angle and the correct speed to cut satisfactorily.

3. The bench lathe has a large range of spindle revolutions and of feeds.

4. The shaper is a flexible machine in many respects complementing the lathe in the work.

5. The planer is designed to remove metal by moving the work in a parallel line against a stationary single – edged cutting tool.

6. The automatic lathes is designed so that all of the tool movements are automatically controlled.

Ex.24. Answer the following questions:

1. How do all the machine – tools operate?

2. What kind of work is bench lathe adapted to?

3. How can the shaper produce flat surfaces?

4. What is the structure of the automatic lathe?

5. What functions do the automatic lathe perform?