A very simple yet effective way to make anti backlash nuts.

[rgsparber]

These are also called EvaNuts and there is more to the story.

First of all, they will deform under pressure. So on the one hand you don't get backlash, but you do get an error that is a function of depth of cut.

The second issue has to do with leadscrew alignment with the ways. If a perfect leadscrew is perfectly aligned with the ways which are perfectly straight, you can achieve zero backlash. But as this alignment error increases, one of two things must happen. Either the leadscrew must bend so it always aligns with the zero backlash nut or the mechanism binds and you can't move the full length of the axis. This is most often seen at the ends of table travel because the leadscrew can bend in the middle but not at the bearings.

If the leadscrew binds, the side force will wear on the plastic nut and cause backlash over time.

Another problem has to do with the uniformity of the leadscrew diameter. The EvaNut is cast on the leadscrew and can be a tight fit if no packing is used. I found that a variation of a tenth was enough to bind the nut on the leadscrew. Add packing or cast the EvaNut at the point of maximum leadscrew diameter. Either way, you introduce backlash.

For more information on making these nuts, see https://rick.sparber.org/EN.pdf
For more information on how leadscrew alignment and backlash are related see https://rick.sparber.org/XAA.pdf

My goal here is to encourage others to prove me wrong and advance the "art". Just because I could not make this work does not mean others can't solve the problem.