Quote Originally Posted by Jonathan View Post
Springs is the standard way to do it. Just make sure that the force the spring applies is greater than the cutting force on your machine, otherwise the backlash will come back to get you...
This is a common misconception. Having a spring force above cutting force is not enough to minimise backslash.
You should use a spring that have a spring constant high enough to give a displacement which is less than backslash.
displacement = Force / spring constant
Let say you have a fixed nut coupled with a spring loaded nut. The spring is preloaded 10mm to give 100N force (k = 10N/mm). If the cutting force is 10N, the spring will retract 1mm, above typical backslash, so in fact you end up like having fixed nuts with clearance between them. It's not backslash defined as having dead gap displacement when changing direction, but circle cuts will gives you ovals in these conditions as spring is compressed during direction change.

Belleville washer are the one to be used, and strong enough to minimise backslash. The best is to use the nut body itself to be the spring, this way you can achieve very high rigidity. Same thing with oversized balls.