I've had my 1720 XMTC since new - 1998 - and always intended to CNC it but lacked the funds. I have the original CNC hardware kit with the pulley driven Z axis via the fine feed handle. Looking into upgrading it now the kids/leeches are leaving the nest and things are a lot cheaper these days. The machine also has the original single acme nuts on XY, so backlash is going to need addressed.

I have ordered a 3 axis DRO and glass scales (on sale from China) thinking that would be a Good Thing, and digging around on the current state of the technology I'm seeing that stepper motors have come a long way in recent years in terms of strength (rare earth magnets?) and price. Specifically it is really hard to find Nema34 steppers in the size recommended for this machine any more - they seem to be all 1000oz/in and up, which is overkill and with the drivers and power supplies still pretty pricey. On the other hand I have seen 425oz/in(3Nm) Nema23 motors now at a much more affordable price point (set of 3 with drivers, PSU and optoisolated DB25 breakout for $180 on eBay right now). Obviously I'd need to adapt the mounts and sleeve/replace the cogs for the (rather skinny) 8mm shaft on these.

Anybody gone the Nema23 route? Good/bad experience? Pitfalls?

I'm thinking I'll drive this with LinuxCNC and experiment with position feedback from the DRO scales before saving up for ball screws.

Alastair