Quote Originally Posted by Sodster68 View Post
Drive is through M12 threaded rods with anti-backlash nuts. In an attempt to unload motor axles I intend to use thrust bearings and lock nuts to support the rods in the frame.
If this is just plain M12 1.75mm threaded rod then you'll struggle badly in several areas.?
First 1.75mm pitch is far to small and slow for cutting materials like MDF or plastics etc. This will severely restrict feed rates which will cause burning and quickly wear tools out in MDF and composites with melting in plastics.

Second the pitch of threaded rod is not consistent across it's length so accuracy will be all over the place.

Third the quality of thread on Normal threaded rod is rubbish and the roughness wears nuts out very quickly.

By the time you have messed around buying threaded rod and Delrin etc for Lead nuts it's just not worth taking that route and the little difference to buy decent Screws, whether that be Lead or Ballscrew is most certainly worth it from the beginning.

If you want a very accurate alternative slightly more expensive then use timing belt. It will give far greater feed rates and be very very accurate.

Also drop the unsupported linear rails they are rubbish. Go with supported has they don't cost much more and you can transfer to a better machine when you realise just how RUBBISH MDF for a CNC machine frame and build another with steel or aluminium.!!

That last bit should tell you everything about what I think to MDF for the Frame.!!