Best lubrication for ball nuts

[Robin Hewitt]

Cheap screws can be notchy. I wonder if customers complaining about backlash and demanding refunds cause the manufacturers to use tricks to tighten them up beyond reason.
I bought some cheap 20mm profile rail that is notchy. It glides tightly when you go quick but sticks when you go slow. It's wringing with oil, could be grit. The notch will support a 2.5kg weight but not 5kg. Luckily the finished block of 4 will be supporting more than 20kg so I should be okay.
Yesterday I bought a 500mm screw with nut and end machining for £16. Amazing bargains to be had if you are prepared to fix a few minor issues

[Kitwn]

Cheap screws can be notchy. I wonder if customers complaining about backlash and demanding refunds cause the manufacturers to use tricks to tighten them up beyond reason.
I bought some cheap 20mm profile rail that is notchy. It glides tightly when you go quick but sticks when you go slow. It's wringing with oil, could be grit. The notch will support a 2.5kg weight but not 5kg. Luckily the finished block of 4 will be supporting more than 20kg so I should be okay.
Yesterday I bought a 500mm screw with nut and end machining for £16. Amazing bargains to be had if you are prepared to fix a few minor issues

The only ballscrews I have any experience with are these three that I bought from Fred Lee at BST Automation about 3 years ago so cannot comment on the variable quality of other manufacturer's products. Until now I have never been able to detect any backlash and have been entirely satisfied with them. Fred has quoted what I see as a very reasonable price for replacement ballnuts and has asked me to send him details of the reference numbers stamped on the existing nuts to make sure I get the correct tolerance replacements. As far as I can tell the problem I'm having with this one screw is entirely due to poor maintenance on my part.

Fred's own recommendation is oil rather than grease.