I started the CNC conversion of my new Milling Machine in a rather random place, with a pneumatic drawbar. This was rather prompted by this thread:
http://www.cnczone.com/forums/showpo...37&postcount=1
In fact I started off posting in that thread (http://www.cnczone.com/forums/showpo...&postcount=124), but have now decided that I should start a new one, as I am not actually making a spindle, just the drawbar. The intention is a full CNC conversion running EMC2. (I have already done one machine, which is working as well as can be expected for the starting machine).

The drawbar fits in place of the standard drawbar with no modifications to the spindle. It uses a finger-style gripper:
From Gibbs

which is released by a specially-made pneumatic cylinder:
From Gibbs

and is held clamped tight by a stack of Belleville washers in the conventional way.

[nomedia="http://www.youtube.com/watch?v=pxrzJ_KfcQ0"]YouTube- Drawbar[/nomedia] shows the drawbar in action.