Making Acetal leadscrew nuts the easy way

[Astronowanabe]

I don't know anything about plastics but do have a bit of something old called "Nalatron GS" squirreled away. How would you anticipate something like that working? I think it was intended as a low speed low pressure bushing material.

I think this is similar stuff from a different company

http://www.matweb.com/search/DataSheet.aspx?MatGUID=cc9f3ba248e448608ca328203d599132&ckck=1

[Evan]

I have some but the melting point is 500F. That is too high to consider using in part because you would run into the issue of toxic fumes being released from the plastic. Another issue with nylon is that it will change size considerably with changes in humidity. Specifically, Nylatron GS will absorb up to 7% by weight water. It is an excellent self lubricating bearing and bushing material but only when dimensional changes can be tolerated.

[dp]

I pulled the apron from my little Grizzly lathe last night to do some cleanup and check wear. The half nut (#628 in image) is truly half a nut but might be convertible to plastic.

The cross slide is very definitely a candidate.

http://metalworkingathome.com/images/G0516HalfNut.png

[Peter.]

I though of Molyslip but I hate the stuff because it migrates faster than spotting ink. I used to service equipment at a molybdenum mine and the entire place was a uniform shade of dark gray including the surrounding trees and landscape. It was a very monochrome place, very strange to see.

We have a place like that here in the UK.

It's called 'up north'

[willmac]

Peter -

Couldn't let that one go.

The grey areas are the posh regions. The rest you can't tell what the colour is due to the thick smog and blinding rain and snow.

I love these stories. They keep the masses in the deep South all huddled together in endless expensive housing estates commuting to London.

Those who are in on the secret enjoy the wide open countryside, low population density and limited yuppiedom.

Written from the depths of Lancashire - dark Satanic mills NOT (any more).

[Peter.]

*resists temptation to post python sketch of four yorkshiremen*

[small.planes]

Hole in the ground....

You were lucky.


IGMC

Dave

[derekm]

We have a place like that here in the UK.

It's called 'up north'

Nowt like Trough of Bowland, or Windermere, or Rudyardlake
Pickmere or even Thurstaston in Kent then? And how many more Red Squirells are ther in Kent than Ainsdale? (look them up in an atlas)

[snowman]

So for a 1" - 10 screw on a full sized mill, how long would you suggest making the nut for adequate strength?

[mochinist]

Found this place yesterday when I was looking for some acme threaded rod, there is lots of PDFs and formulas for different acme rods and nuts there, including plastic, although they have a trade name for it, not sure if it is acetal

http://www.nookindustries.com/acme/AcmeProcesses.cfm#PlasticNut

[noah katz]

Fantastic!

But I can see spending a whole day making one; does anyone make them for Bridgeports?

I didn't see anything in the first couple of pages of google hits

[Evan]

So for a 1" - 10 screw on a full sized mill, how long would you suggest making the nut for adequate strength?

There is no reason that the same process cannot be used. Acetal is available in sections plenty large enough for the purpose. As for the durability that shouldn't be an issue either. Some time ago I repaired the trunnion pins on my shaper by bushing the worn pins using acetal bushings. It has had a lot of use since then and there has been no indication that the bushings have worn or are failing in any way. It is a pretty severe application and the bushings are not very thick so if they can take this sort of punishment then I see no reason why they won't work well on a larger machine in leadscrew service.

[jkilroy]

This is great stuff, and gives me an idea for a related use. I'll post pictures if it works, and maybe even if it doesn't!

This may have been pointed out but keep the temp of the plastic BELOW 450 Deg. F. At that point, or above, it decomposes directly to a gas, mostly formaldehyde, RAPIDLY.

[kenrinc]

Apologize for such a simple question but to clarify, minus one thread depth means? Half one side of the thread?

Ken

[Evan]

Minus one thread depth mean the crest to root measurement of the thread. Make the ID of the bore equal to the OD of the screw minus that amount. With ACME threads that value is one half the thread pitch, crest to crest. So, for a .5" screw with ten threads per inch the thread depth is .050". The bore should be about .450". This will give just enough plastic to fill the threads plus some extra because of the kerf allowing some extra compression.