If you really want to have a very slow running tool, just connect those machines (Dremel or equivalent) to a 12-48 V transformer. (does not matter DC or AC)
(This method unfortunatelly does not work with semiconductor speed controlled devices (SCR)
:cry:
The older Dremel models with a switch on the side (or the single speed machines) work perfect and the speed is very slow.
This method is good for any mains powered machine (drill, saw etc.) from 110-240V and they will work very well on 24 V an similar with very slow speed (not much power, but the speed is important).
I use my 240V drill machine for winding coils etc. with excellent results (and are very quite at this speed). The power supply is a variable one from 2-36V DC/3A max.