Luthier CNC

[Lee Roberts]

Lee, you are a legend, thanks for all the detailed and helpful responses. I will be sure to post a vid showing some of the machine motion once its rebuilt.

Machine is currently in pieces because today I have disassembled all 3 of my ball screws. Cleaned every part with naphtha and relubed with lithium grease (thanks AndyUK - I just smeared about 3cm^3 on the screw and ran the nut over it, repeating until none was left collecting on the rubber seals at the ends of the nut).

Counted the ball bearings - exactly 51 in each ball screw and I managed to get exactly 17 back into each track when reassembling. I reassembled them dry, using the ballscrew itself to guide the balls into their channels. Found this easy and I think its less messy than using grease to stick everything in place. I used the method in this vid to repack the balls https://www.youtube.com/watch?v=GXdt5M8ZeoE

All I have to show for my work is the following vid. Shows all the nasty stuff left floating in the naphtha after cleaning each ballscrew:
https://streamable.com/up3n4

End result certainly feels subjectively smoother - will only know for sure once the machine is rebuilt. One thing I've noticed is that after cleaning the nuts do not spin as easily - though they do spin much more smoothly. I put this down to increased viscosity of the lithium grease compared to what was in there from the factory.

No problem, great that's good to know about the ball count if you ever lose any let me know I can send you some the right size.

Yea that's how I started doing them years ago (dry+screw) I've rebuilt quite a few for people now and found it a little obstructive using the screw (length/weight) so I just use a tube of ali to the right OD with a hose spring clip attached to one side, I slide this in just after I've got the first track filled, it depends on the job though as some people ask for the nut to be on the screw when i send it back because they don't want to risk it again. Both ways though I still use a little grease as a "retainer", they used to ship the nuts with the tube and a clip on both ends but they seem to be a plastic tube with cable tie now.

13mm (1/2") Aluminium Alloy Tube

Best served with some of these: Double Wire Spring Clip