[Barefooter]

Hi all,

I ordered and just received some acme thread rod 1/2 10tpi the other day. The Delrin nut that came with it is very tight. So tight that it causes my stepper (205oz) to stop. Is this how tight a Delrin nut should be or did I get a bad one? Here's an example of how tight it is... with the acme rod free from the machine and held in one hand, and the Delrin nut in the other, you can't spin it on with your index finger and thumb.

Thanks,
Gregg

[Rob K]

I got the delrin A-B nuts from Dumpstercnc and they were rather tight. I used some pneumatic tool oil and ran them up and down by hand until they were reasonably easy to rotate.

[Barefooter]

Thanks Rob. I ran mine while it was on the machine back and forth several times, and it just does not seem to be changing on the tightness. Not sure what to do at this point.

[Rob K]

I probably ran the nuts up and down a dozen or more times. My hands were hurting for a while after that. I also removed the nuts and cleaned some gunk that collected in the threads.

I bought the black coated precision acme screws from McMaster. I cleaned them up a little, then struggled to get the nuts on and run them up-and-down a dozen or so times, then removed the nuts to clean out any remaining gunk that collected in the threads, and then ran the nuts back on. I also applied a light coating of pneumatic tool oil (recommended by someone on this forum).

[arizonavideo]

The leadscrews look smooth when new but they will polish to a fairly high gloss as the nut runs up and down a bunch.

I would run the nut full length of the screw at low speed for half a day and see how things look then. I would stop the setup every half an hour or so to clean off the oxide and re lube them.

After the lead screws break in, it is amazing how smooth they run and how long they last.

Don't run them at high speed when new or they will over heat and lap themselves out.

[louieatienza]

You can chuck a drop-off piece in a drill, and keep spinning it back and forth that way. I would do this without oil.

If it's still too tight, take the drop-off piece, and cut a slot with an angle grinder. It will work as a makeshift "tap" and help fit the nut to the screw....

[ger21]

There's some info on the Dumpster site on loosening nuts that are too tight.
dumpsterCNC

[Barefooter]

Thanks, everyone. I'll give these suggestions a try.

[Barefooter]

Well, the Delrin nut is not a problem anymore. The binding was partly caused by the nut, but the other was the acme rod. It came in via postal service warped about 1/4" in the center. It was packed with a wooden stick to help protect it. The stick was broken in two places. Thanks USPS!!! I spent a couple of hours today trying to straighten the rod. Now it's useless. Back to square one. Does anyone have a good source for precision acme rod? I want to try a different source.

Thanks,
Gregg

[nova24]

McMaster-Carr has served me well.

[arizonavideo]

Roton is lower priced and good quality.

I have some extra 1/2 -8 two start I would let go almost free if you need less than 20" length.

I straightened out a few rods on the milling machine with two V blocks and a indicator using the quill to press them. This works quite well. I see no reason two wooden V blocks and a drill press would not work just fine. Place the indicator on the head and use the quill to bend the shaft to get a low reading.

[Barefooter]

Thanks guys. I'll take a look at those sources.