Quote Originally Posted by Robin Hewitt View Post
The concern with grease is that if you don't have enough load then the balls stop circulating and start rubbing.

Ballscrews bed in and develop backlash. The cure might be springs rather than lube.
Thanks Robin. I spent most of yesterday evening searching for info online but as ever YT and Google are full of conflicting ides from 'use light machine oil' to videos of grease oozing out of the ends of the bearings after injection with a grease gun to comments about too much grease preventing the balls circulating. It seems to depend a lot on the individual circumstances, including load as you say.

I think it's fair to say my machine is quite slow running (5m/sec is my normal max cutting speed) and lightly loaded (I cut wood with 6mm tools) so an oil rather than grease look like the best option. I did find a Mobil product that is made for machine ways and was recommended for ballscrews but the minimum package size is 16Kg and would have to be delivered so I think that would be a little over the top.

Replacement ballnuts are cheap enough so I've ordered those. Only one is showing backlash but I plan to replace both and then be more diligent with the oil. I can always use 2 nuts per screw and springs as you suggest if need be in the future.

Kit