OK so why would I do this? For a simple and cheap CNC of course. Its not too hard to figure out how to do this, but…what I like is the link on suppliers to find different size collets for different sized motor shafts. Or you could just buy a kit. Me…I have way to many motors to bother with the kit bit.
http://www.instructables.com/id/Make-This-Cheap-and-Easy-Mini-Power-Tool/?ALLSTEPS
Different size collets here
Bigget collets here (need bigger shaft motor of course).
http://www.aliexpress.com/item/2015-NEW-0-5-3mm-Small-Electric-Drill-Bit-Collet-Micro-Twist-Drill-Chuck-Set/32355264408.html?spm=2114.031010208.3.146.3c7Gnw&ws_ab_test=201556_5,201527_3_71_72_73_74_75,0_0