|Manual Thread Cutting - Course: Technique for manual working of materials. Trainees' handbook of lessons (Institut für Berufliche Entwicklung, 22 p.)|
|1. Purpose of thread cutting|
|2. Kinds of threads|
|3. Tools for internal threading (tapping)|
|4. Tools for external threading|
|5. Operation of thread cutting|
|6. Special hints on the designation of threads by the example of the metric threads|
|7. Technological process of cutting internal threads (tapping)|
|8. Technological process of cutting external threads|
Thread taps take off material from the periphery of the bore hole. This is done by permanently turning them forwards and backwards alternately with the help of a tap wrench.
In doing so, lubricating and cooling agents must be fed in.
Figure 9 - Thread cutting
The forward turn should amount to half a rotation approximately, the backward turn to a quarter-turn. The material is squeezed and removed within the thread groove the total quantity of chips sticking in the thread grooves.
The backward rotation causes the crushing of the chips, so that they can fall out of the chip grooves of the thread tap.
The backward turn up to the crushing of the chips, with medium hard and hard materials, is marked by a clearly noticeable jerk. Only then one can be sure that the chip is really broken.
If one fails to crush the chips continuously, the thread grooves and chip grooves become stuffed up. The thread tap becomes jammed and breaks. It can no more be screwed out of the bore hole. The same applies to the cutting of external threads.
Describe the movements with the cutting of
Why is it necessary to move the thread tap or threading die or
die-stock, respectively, backwards at regular
Why must lubricating and cooling agents be