On many modern CNC machining centres the rotation of the spindle can be synchronized with the feed axis. This makes it possible to produce threads with tool holders without length compensation. However, practical experience shows that even with this kind of "rigid tapping", synchronization errors can come up.
Possible causes are:
When rigid tool holders are used, these errors can lead to problems. High axial forces come into play, and can have serious negative consequences on the production process, such as:
heimatec collet holder softtap for driven tools
- easy to disassemble
- allowing trouble-free maintenance
- hardly any inﬂuence of torque on axial force compensation
- no inﬂuence on the cutting edge of the tool through axial vibration during work
- allowing axial movement only after the pre-tensioning force is exceeded
- reduced friction (rolling friction), and consequently extra short reaction times
- no effect on axial force from coolant-lubricant pressure, consequently no axial movement
Many tests regarding this topic have been made with taps and cold-forming taps. Depending on the individual case, our customers were able to increase their tool life by up to 150%. In the following diagram, you will ﬁnd the axial forces which come into play in the cold-forming of an M10 thread in St37.
We have traced the axial forces at a speed of 2000 rpm.
The following collet holders were tested:
All tested collet holders were used with a collet type ER16-GB, i.e. with integrated square.
Axial force [N] Speed 2000 rpm
The following results were veriﬁed in these tests:
The collet holder softtap makes the optimum use of driven tool holders in the production of threads possible, with the best imaginable tool life and thread surface quality.