Thread Wear Issues

[tanky321]

Im building a small (30x60) table out of MDF. Were using 1/2" acme screws and regular hex nuts. We welded a large washer on to the nut, for a flange. The threads look fine, no weld in them or anything.

When we put in the Z-axis yesterday we put a cordless drill on the screw to turn it, just to see how it worked. At first it was ok, then it seemed to get tighter and tighter. Below the nut there was a whole mess of metal shavings, and the screw looked like it was worn down. The thickness of the actual thread was thinner than it was originally.

Any ideas as to what this is about?

[ger21]

Sounds like the nut was possibly not aligned accurately? Did you oil or grease it? most people use Delrin nuts, as they won't cause the problems you're having, have little to no backlash, and are self lubricating.

[tanky321]

It seems like its on correctly. At first we didnt grease it, but afterwards a squirted a little bit of oil on it and it did get a little better.

We were concerned that delrin nuts would wear, considering what was going on with the steel nuts. But then again it was the screw as far as I can see.



Thanks.

[ger21]

The nut was probably harder than the screw. If you're using cheap acme threaded rod, then plastic nuts may wear, but good quality acme leadscrews are very smooth.

[RICHARD ZASTROW]

Possibly the washer/nut welding distorted the lead of nut causing the nut to "shave" the screw? Just a thought. When you say "regular hex nuts" I ASSume you mean ACME threaded hex nuts. I would suggest making a bronze flanged nut to replace the weldment. Anytime you apply heat to something like that you might "chase" the threads with a tap or die.

Dick Z

[tanky321]

Originally Posted by RICHARD ZASTROW Possibly the washer/nut welding distorted the lead of nut causing the nut to "shave" the screw? Just a thought. When you say "regular hex nuts" I ASSume you mean ACME threaded hex nuts. I would suggest making a bronze flanged nut to replace the weldment. Anytime you apply heat to something like that you might "chase" the threads with a tap or die. Dick Z

Il have to see if I can get a ACME tap, I dont have access to anything I could make a bronze flange nut out of, unfortunately. I guess we will try this out, if it doesnt work il get some delrin nuts.

[bbutcher85710]

McMaster Carr sells Acme taps, but they are not cheap. They also sell Acme nuts in bronze, also not cheap.
Enco Tool
http://www.use-enco.com/
also sells both of these items, maybe cheaper.
Perhaps you could cut threads using a lathe? This should be easy in Delrin if not too long or too small a diameter.