|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|
External threads are made with the help of a threading die or die-stock.
Figure 6 - Threading die
1 - Threading die
2 - Die holder
It consists of a cutting body (similar to a nut with milled-in chip grooves) with a chamfer on either side so that it can be applied both-way.
The threading die is put into a die holder which is equipped with two handles.
Figure 7 - Die-stock
1 - Fixed die
2 - Movable die
3 - Pressure piece
4 - Locking screw
It consists of a handle-equipped holder in which two threading dies are placed. One of them is fixed, the other one can be moved by means of a pressure piece via a locking screw. Three to five pairs of exchangeable threading dies for various sizes of threads belong to a die-stock.
4.1. Application of the tools
- Threading dies cut the thread in one operation; they are used with bolt diameters up to 12 mm. Bolt diameters between 12 mm and 30 mm can be cut by threading die or die-stock as well.
- Die-stocks are mainly used with bolt diameters over 30 mm; they are drawn over the bolt in several operations. Readjustment before every new operation is necessary. In the course of the last operation, the thread is accurately cut to size by a threading die,
Hints for starting the cutting operation
- The threading die is set in exactly horizontal position on the bevel of the bolt and turned clockwise slowly and with slight pressure from above (with right-hand thread). Only when the starting end of the thread is cut and the threading die guides itself, the breaking of chips can begin.
- The die-stock is opened as much as is necessary to shove it over the bolt - a small piece of the bolt must project above. The die-stock is adjusted to horizontal position and the movable threading die is tightened. Then, the die-stock is turned up to the bevel so that it is still guided. The movable threading die is further tightened. Then, the thread can be cut by turning the die-stock up and down adjusting the threading die simultaneously.
Figure 8 - Application of the die-stock
1 - Putting-on and turning-up
2 - Turning-down
What are the distinguishing features in the use of threading