not sure if this goes into new tools or tool hack... anyways, i owned a dremel moto tool 380 for 30 years until some bastard took it away from my truck, bought another one and already burned 4 rotors, mind you i know the limits of the machine and owned one for many many years zero issues
so fed up with this, and having a broken angle grinder (conic gear exploded breaking everything - ok not the best quality tool to begin with...) decided i wanted a replacement for the moto tool.
original idea is to use this with the flex shaft of the dremel but have to make the adaptor and used as is for certain job will update as soon as is ready (but may... take a while)
fill the woodruf key slot with er70s6 (tig) and turned to 6mm (ish) did file a flat for a 7mm wrench to hold the collet
cheers tool makers!