Making Acetal leadscrew nuts the easy way

[iMisspell]

Knurl a short section in the middle of a piece of acme rod.

Cleaver addition to a great 'Evanut' process. Thanks for posting.

[Alistair Hosie]

Strangely enough I was going to ask about doing this with heat on delrin.I didn't envisage cutting it in half first though.That should make life easier so thanks bud.I bought a very nice large six inch milling vice which has a long through screw, all in fact is complete apart from the internal nut, into which the long acme type screw travels.This operates in both directions to left and right, or forward and reverse .Exactly what is needed, to push the front jaw forward, or return it backwards, to hold the workpiece you require to hold.I will try this method and hopefully it will work ok.It seems an awful sin to throw out the entire unit for the sake of such a small piece, thanks Evan youre a good'un.Alistair

[lg1382]

So I'm a complete noob here and am looking to perform this process as the lathe/mill combo unit I bought has a horrible half nut. I have the ShopFox M1018 and the stock half nuts on the x lead screw are two pieces, made of brass I assume. They both engage the screw from the same side. The half nuts are only about 1/8" wide and are spaced approximately an inch apart. So yes, when engaged, there is approximately 1/4" (or 2 threads worth) of half nut engaged on one side of the screw. This seems incredibly weak to me but I don't have the experience to support that opinion officially.

Anyway for my application, the acme screw measures slightly over 3/4" diameter (could be metric I suppose?) and is 6tpi. Originally I was going to buy a tap and just recreate what it ships with as the replacement nuts sell for $58 each and are about the size of a quarter... no thanks. But then I saw this post... seems like I could form the full nut at a length of 1-1/4", and then machine it down to the appropriate diameter so it will fit the half nut base, and then cut it in half again. The result would be a new half nut that is 1-1/4" wide (a gain of 1" in engagement of the screw) and much cheaper than the brass? oem replacements.

The sucky part is that I am likely going to have to do this on the screw that came with the machine as I can't seem to find 3/4"-6 left hand acme screws anywhere. Plus I'm a little concerned that it's measuring .784 (if memory serves). If I use the actual screw to form this I know it will fit... but will heating it damage the screw at all? I skimmed most of the pages in this thread but didn't see much on people doing this on the actual screw.

All thoughts, tips, and critiques welcome on my approach.

[MTNGUN]

will heating it damage the screw at all? I skimmed most of the pages in this thread but didn't see much on people doing this on the actual screw.

All thoughts, tips, and critiques welcome on my approach.

I used the actual screw on my lathe Z axis, and yes most Asian tools use weird metric screws. I formed the nut at the far end of the screw where the nut rarely runs, and also cut the little flute to chase the threads on that far end. The heat did not damage the screw. It might warp a bit but working on the far end of the screw minimizes that.

My lathe screw was not threaded all the way to the end. To unscrew the nut, I turned down the unthreaded portion of the screw, then later fitted it with a delrin sleeve which also functions as a bearing.

[Alistair Hosie]

Good to hear FROM YOU MY FRIEND.
Anyway yes a thermally corrected or shaped plastic. I am very pleased to see this post, as I bought a beautiful big six inch machinists vice minus the nut, and of course also the handle LOL , minus these it had been thrown in a companies scrap pile. I got it for a fiver. I forgot about the heat method, and I simply cut a piece of Delran type Plastic tube to internal diameter ,same as the min diameter of the screw .Then I locked it all down oiled it up (all the while) and nearly killed my poor aging old self by force turning it by hand using the supplied acme or similar type lead-screw to cut the internal threads to correct max diameter. It did quite well but not great. The end result left me with a vice I can comfortably use for about just over half of it's normal travelling length. Now (when I have a rest as I am just back from Hospital, In fact if I go there more often I think they might invite me to the staff dance ) I fully intend to alter it your way. But it is not at the top of my list. Keep well Brother you are a good kindly soul. Alistair

[jkilroy]

Hey, dredging this topic up from 5 years past. Finally had an occasion to try this technique out. First try, not so good as Evan's, second try worked great, check video if interested. Had a lot of trouble getting enough heat into screw using a paint stripping gun no less. Let it run for ten minutes heating the screw before I even got started and it still took 15 minutes after that.

https://www.youtube.com/watch?v=7i3NdmtsQYs

[GillMcLane]

Good job Jay, enjoyed the video.
Gill

[cuemaker]

Watched the video...well done videos.

I made some Evanuts a few years ago for a cross slide on a small Sheldon lathe.

Using a heat gun, especially on that big of a screw, is asking a lot of the heat gun. I used a blow torch. It was much quicker and very effective obviously.

I also had a problem with super tight fit even after trying to cutting grooves into the screw to try to "tap" out the threads.

I pondered the issue of how to fix the close tolerance, or make the whole nut anew, all the while using the lathe. I couldnt come up with anything solid. My best through was to somehow build up the threads that would withstand the heating process, but removable after the threads are formed. But thats all I got...

[elf]

Plumbers tape (PTFE) stretched thin works really well as a release agent and also for slightly looser fit.

[cuemaker]

Plumbers tape (PTFE) stretched thin works really well as a release agent and also for slightly looser fit.

That is a good thought...very pliable..will fill all the little gaps etc...****.. I will give a test run over the weekend..

[Mcgyver]

I was surprised at the comments to the video suggesting lapping compound as a way to create a better fit.

[gzig5]

I was surprised at the comments to the video suggesting lapping compound as a way to create a better fit.

Why? It will reduce the size of the screw in no time and then will turn really easy.

[Mcgyver]

Why? It will reduce the size of the screw in no time and then will turn really easy.

and reducing and reducing and reducing....

except for certain situations, like maybe valve lapping where the unique nature of the geometry makes it ok, lapping is done with a charged lap which is a cutting tool, not by putting abrasives in working parts. Basically if you trying to make something precise, or if you are working on sliding surfaces (such as the flanks of a thread or machine tool bearing) you're probably being given hack advice if instructed to throw abrasives into working parts to make them looser. I say probably as there are exceptions, but I'm trying not to write a book.

There's several reasons, but the one most germane to this application is that lapping compound will embed into the softer of the two materials. That's what charging a lap is. So you will end up with abrasive embedded in the nut and the nut will continue to abrade the screw.

[gzig5]

I was joking. Forgot the smiley. I agree that lapping would be bad idea. The only exception I could think of is if you made two nuts, used one to lap and the other in service. Not that it would make sense to do it that way with much better options available

[Mcgyver]

I was joking. Forgot the smiley. I agree that lapping would be bad idea. The only exception I could think of is if you made two nuts, used one to lap and the other in service. Not that it would make sense to do it that way with much better options available

you know I half wondered when responding if I was unwittingly playing the staight man lol

If it was bonze nut say, I'd buy that a bit of timesaver compound (stuff that's supposed to breakdown) might be a good solution, but figured in plastic it would be a mess. I've also never been 100% convinced that timesaver wouldn't at least partially imbed. I mean how would you know until years latter when its too late. I have done what you suggested, make a nut out of brass, split it, and used it as a lap on a screw. Its still a bit hack-ish though as who's the say the thread profile I made was perfect, but my logic was that I wanted a very smooth finish on the thread; that it would be the microscopic burrs, tearouts,ridges and aretes that would be increasing the rate of wear