Thanks, Dean. That's thrown a few good ideas into the melting pot, and because my mind tends to think "steppers" I had forgotten the pulse rate issue with encoders. There's a few broad decisions to make, like what do we keep/replace, and whether he wants a self-contained control system or PC-driven motion controller. I've only had a quick look at the machine so I need to do a bit more investigation before making too many decisions. I've no idea at the moment how easy it will be to swap motors (mounting arrangements) or change to modern encoders, for instance. We'll see!