This Dremel Holder is a milling toolhead based on the Dremel flex-shaft for the RepMan develped by Marcus Wolschon.
There are other milling toolheads for different mills and cartesian bots. e.g. Flex Shaft milling-toolhead.
Developed for the RepMan, Marcus posted a design challenge to convert this reliably working toolhead to the RepRap Mendel.
He discontinued that challenge when Bogdan Kecman posted his FlexShaftHolder on Thingiverse after a discussion in the BitsFromBytes forum.
It is still to be converted to the limited space of the RepRap Mendel or the different toolhead-mount of the Darwin.