Howdy Folks,

I've got an RF-25 clone working as a funcitonal CNC, and at some point I have dreams of having a 4th axis. Now.... I have a number of 5c spin index fixtures, including the Master-Grind from Suburban Tool as well as the HV-4 from Hardinge. I use neither of these, and I recently restored them both and they are in great shape. What are the chances that I can turn one of these into a 4th axis? It's easy enough to get a 5c 3/4-jaw chuck of decent quality, and adding a direct-drive stepper on the back end doesn't seem all that unreasonable. Direct driving would mean that I would lose linearity in torque, but WHO CARES with a 4th axis? And with microstepping, I find it hard to believe that I would not have the resolution that would satisfy my (hobby) requirements. I could always add a harmonic-drive gearbox etc, but for my applications I think this would be overkill, as direct driving a stepper would minimize this anyway (with the appropriate coupler etc).

I don't usually ask these types of questions because usually I've found that someone has already asked them, but I can't find much on the subject, which leads me to believe this isn't such a great idea in and of itself. Maybe this will help someone in the future.

Thoughts?