Collet, portable 12mm

My initial attempt at a 12mm collet . Works very well but printed surprisingly 0,57mm undersized in PLA+ when the bore was modeled precisely at 12,0mm, which is the case for the rev 2 files enclosed. Easy to print, no supports required. 

Added second pair of STEP files (rev 03) & photos, with a 0,55mm larger bore to accommodate rods or tubes being 12,0mm +0,00-0,56mm. I have yet to do a full tolerance study of the design - i.e., how much the rod/tube can vary in diameter and the collet remaining functional in its grip and the elastic recovery of its fingers. I have confirmed that the rev 03 model will satisfactorily grip the butt ends of either 29/64 (.453) inch or 15/32 (.4688) inch drill bits. From that I infer the grip is right for a 12mm rod or tube. Finally, in the stationary end of the rev 03 collet I added counterbored holes to accept #8 SHCS if one desires to affix it to something (perhaps a workbench).

Incidentally, the angle of attack on the sloped fingers is 5 degrees.