Low cost 0 backlash transmission - Ball bearing + trapezoidal screw

[Jonathan]

Have any of you tested this technique? What are the feedbacks?
I am wondering what is this "nut" in which the ball bearing is maintained?

I have done it on my Y axis as 'Chip' said it's in my thread and videos on youtube. There's a good shot of it in the long video about wind turbine blade mould if I recall correctly.

http://www.mycncuk.com/forums/showth...ding.../page11

(I've measured the backlash and recorded it somewhere in the thread - pun not intended!)

I used 16mm threaded rod with a bearing that happened to fit - can't remember the dimensions offhand but I'll check if you want. I didn't put any sort of insert on the bearing - it's just running directly on the screw. At the moment it's working perfectly well, however the screw is visibly worn. Not much, but noticeable. Initially the backlash was very very low (practically zero - clearly you're never going to actually get zero), now it's a little more but still good. Better backlash than a cheap ballscrew at least.

The situation you describe is a bearing is used to run down the thread. Now for the problem, the bearing "The Cheap Part" is hardened and it is gonna wear the expensive leadscrew in no time at all as its harder than the leadscrew.

Easily solved - press a brass/bronze insert into the bearing. I did this for an M12 threaded rod (was going to use it on Z) and machined the insert to fit the thread profile better. I think if you want it to work for a long time then that's the way to go. I'll do it at some point on my Y axis, but for now it's adequate - better than the X-axis nuns.