Originally Posted by
Daedalus308
Hi Everyone, I'm with a student group and we are building our own cnc milling machine to gain experience in engineering and we are having some troubles converting our spindle. We have received a 15k rpm 40 taper belt driven spindle that we believe to be out of a haas mini mill and we are trying to convert it to direct drive so we can use our machine for rigid tapping. The tricky bit is that since the drawbar is in the center (shown in first pic), and the drive is on the outside of that, that means that we have to have some interesting intermediary system between the motor (intended to be a high speed servo) and the spindle to allow for automatic tool changes and minimal backlash to allow for rigid tapping. My question is, does anyone know how industry direct drive spindles in machines capable of rigid tapping accomplish this? In a different haas machine I see a pin and slot method (shown in pictures) that would work but I am worried about the clearance between the pin and slot being too large too accommodate rigid tapping. I have thought of using a tapered slot and a trapezoidal cross section to reduce backlash, but that's fully custom and hard to manufacture. Do y'all have any suggestions or industry knowledge that might help?