If I properly understand your question, it sounds like you probably want to loosen [unscrew] the collet nut in order to remove and exchange tool bits.
If THAT is the issue, then the answer is that it is not necessary to "hold" the shaft with any kind of hand-tool!
Dremel, and most of its imitators, install a "pin" type shaft lock right near the collet nut.
When gently pressed inward, the pin engages with a SINGLE hole in the shaft. This means you must gently hold the pin down against the shaft while very slowly turning the shaft with your fingers only.
When the hole in the shaft comes into alignment with the pin, your finger pressure will cause the pin to fully insert into the shaft hole, effectively "locking" the shaft.
As the pin is spring loaded to keep it away from the shaft, you must continue to hold the pin down until you have finished installing a tool bit, or finished whatever operation you intended. Or, if you release it, just go through the locking process again when needed!
Answers & Comments
If I properly understand your question, it sounds like you probably want to loosen [unscrew] the collet nut in order to remove and exchange tool bits.
If THAT is the issue, then the answer is that it is not necessary to "hold" the shaft with any kind of hand-tool!
Dremel, and most of its imitators, install a "pin" type shaft lock right near the collet nut.
When gently pressed inward, the pin engages with a SINGLE hole in the shaft. This means you must gently hold the pin down against the shaft while very slowly turning the shaft with your fingers only.
When the hole in the shaft comes into alignment with the pin, your finger pressure will cause the pin to fully insert into the shaft hole, effectively "locking" the shaft.
As the pin is spring loaded to keep it away from the shaft, you must continue to hold the pin down until you have finished installing a tool bit, or finished whatever operation you intended. Or, if you release it, just go through the locking process again when needed!
I persisted , and hav got it doing , thnx !