that the collars vary in thickness and the critical reference is from
>the TOP of the collar to drill tip.
>
>AWEM
>
>
Don't see much need for this manually, so I'm guessing you're using a
CNC of some type. Just move your contact's reference point to the back
side of the collar. You still need the front to push against, but
instead of connecting your contact plate to that mechanically, have a
seperate plate that just rests against the other side of the collar and
attach the contact to it..
Easier to not worry about the collars, and have the CNC move the bit
down until it touches a contact plate, and figure the offset for the
bit. Use a piece of scrap flat leaf spring (often a guide for the
printhead conductor cable for older dot matrix printers or similar), so
it won't break bits if it doesn't sense contact the moment it touches.
Not as good for just 'pause' and replace bit though.
Alan