Silicone lubricant is excellent with delrin on steel. It even embeds a bit in the delrin.
Just watch out if you use spray lubricant once spray gets on something you won't ever be able to paint it! Fortunately you can get simple liquid silicone lubes. I've used "Armor all" in a pinch, it works very well as a silicone lubricant.
I've come back to this thread as I have run into a problem. I bought a 36" acme rod with delrin nut from a different supplier on ebay and the nut is exceptionally tight and when I run the screw it makes a horrible shuddering sound.
I've tried light oil, no good, motor oil, no joy, white lithium grease, helped some but not enough, next I tried something called tri flow, has teflon in it, and it did make the noise go away but its only a temporary solution as after several runs back and forth the noise comes back and I have to reapply, in fact if I wait overnight its almost like I never put any on. I've been hesitant to use silicon as I'm still in building stage and have several parts I still need to paint.
any more suggestions?
You could hacksaw a fine slot in the nut allowing it to flex and reduce the clamp force. I suggest not cutting too much, as they will settle in over time.
Another suggestion would be to heat the nut and screw in an oven etc to get it up near the Thd (temperature of heat deformation) of the Delrin, this will allow the Delrin to reform slightly around the screw so it is not so tight. That method can risk damaging the nut if you get it too hot.
Probably the first thing I would try is some silicone lube and "running in" the nut (just as it is) with a power drill, you don't have to do that anywhere near your paint. If it starts to run in ok you don't need the other methods. Running in a tight nut with a power drill causes the heat right at the thread surface, so it tends to reform plastic nuts quite well to be a good fit.
I hope somehting there helps.
I always polish my home made taps before I make them....so the nuts
are usually a little tight...(better a bit tight than a bit loose...)
But my secret for making "perfect" fitting nuts is that I also make a secondary
These are all variations and are for different screw makers/batches/whatever
causes the screws to be different from one time to the next...
but you can see the follower tap with the handle for one of them.
What that does is removes the tiniest bit of material each time you pass it
through the nut. A couple times and a nut can be made nearly perfect.
Mine was made with a grinder and has a fairly good sized notch in the end,
but all it really takes is a small notch in the end of a scrap of acme...from
the same screw you want to use...and it'll work perfectly.
Worse case....a notch can be made even on a screw that there's no
extra scrap of with a dremel cut-off wheel. Then if it's polished out
really well after it's done it's job, it won't hurt anything.
Maybe you can get an idea from that....
I'll try running it in with silicone lube, I am going to write a small g-code to run that axis back and forth at speeds varying from 500 rpm to 1k rpm (50ipm, 100ipm) and hopefully that will do it. I've run it an hour or two with the Teflon but that hasn't eliminated it as of yet.
Thanks to both of you for your help, I truly appreciate it.
Last edited by WoodSpinner; 05-17-2012 at 11:04 PM. Reason: spelling
well, I've been running a "break in"/Wear in routine about a hour a day utilizing the silicon, so far so good, still getting noise at high speeds but I think in part thats because my screw is wobbling at those speeds. I'm going to find someone with a lathe around here to extend the bearing areas on the ends of the screws so I can use self locking nuts to secure the screws, as it is they are held by bearing pressure in from the ends placing the screws in compression which I believe is a large part of the screw whip I'm experiencing. So I'm hoping by locking the bearings to the shaft I will be able to put the screws in tension (just a little) in the hopes it will reduce the problems.
Speaking of speeds, I went from using 5/16 18 tpi screws to 1/2 10 single start screws, I thought the difference in speed would be dramatic, like doublt what I was doing before but not the case..I'm curious, what speeds are others getting using acme screws like mine?
75-100ipm is about the max you'll see from 1/2-10 single start.
I get between 150-195ipm with 1/2-8 2 start, and a lot of people get 300-400ipm with 1/2-10 5 start.
Absolutely, plastic nuts settle in very well after enough heat cycles as they re-form around the screw.
well, I've run them quite a bit and here is where I'm at, so far silicon does the best to shut it up but only lasts about 15-20 minutes, each day I have to spray the screw down at the beginning and again every 20 minutes(wife suggested I just spritz it once in a while when its running) personally its driving me nutts, I'm now considering cutting it down one side as a relief and see what happens.
ps, if I dont continue to spray it it gets worse and worse until I cant move it at even 10ipm without it suddering/loosing steps and so on
If you have a Dremel, cut a slot in the threads near the end of the screw and run the nut over it a few times. It will act like a tap and loosen it up. Just don't make it too loose.
See "What if my nuts are too tight?"
If it's really tight, you may gain a little more speed if you can get it looser. Personally, I doubt it will really loosen up much on it's own unless you run it a lot, for quite a long time. Especially since you're lubricating it, as the job of the lubricant is to reduce wear.