[Jon.N.CNC]

Thought id post this image for anyone considering using a 20mm sfu ballscrew and nut with an nema 34 8.1nm. This is the second nut the balls have worn their own grooves in. Think these are really only rated to 4nm.

[ger21]

Did you grease it regularly?

[Jon.N.CNC]

Did you grease it regularly?

No grease. Found Grease clogs these up, even the lightest of lithium grease. Clogging destroyed the nylon ball return jumpers on the first one I had, on nut 4 now. They are now oiled automatically at the beginning of each day. I had run dti's up and down screw on various occasions to check for ballscrew alignment and it's very good. With new nut it's runs great, very quiet and friction free. The only cause I can see is the cheap Chinese steel it's made from and having a semi powerful motor on it.

[ger21]

If the steel is too soft, then motor size is somewhat irrelevant. They'll fail with any size motor eventually, if the steel isn't the correct hardness.

[Jon.N.CNC]

If the steel is too soft, then motor size is somewhat irrelevant. They'll fail with any size motor eventually, if the steel isn't the correct hardness.

Maybe thats what it boils down to, SFU nuts are rubbish plain and simple. 4 months contunous use 5 days a week seems to be the average life of one of these.

When I complained to the shop they were purchased from they sent out 2 replacements which suggests its a known issue.

Had a hard time replacing it to another more professional screw, had one turn up with two bends in, and another incorrectly machined, now out of stock indefinitely. Will need to source another screw and nut before the current one does the same. Hopefully I have more luck third time around.