WTB: Colchester/Clausing Mk 1.5 Master lead screw half-nut

Looking for a leadscrew half nut for my '68 Clausing Colchester mk1.5 Master. Doing a rebuild and the previous owner had the engagement lever adjusted to only engage halfway on the leadscrew which wore down all the threads. Looking for a replacement.

Did you check with Frank at FDK 3. ?

If the you cannot source a useable half nut and yours still works well enough, turn a bushing with the thread internally, and cut a section to replace the threads in yours.

If the threads are damaged beyond trusting them, casting a set of threads directly in to the half nut using a lower temp alloy, or a machine epoxy like is used to build up the sliding way surfaces of machine tools during rebuilds. Moglice? Then use them to make the parts you need.

All is not lost!

trevj said:

If the you cannot source a useable half nut and yours still works well enough, turn a bushing with the thread internally, and cut a section to replace the threads in yours.

If the threads are damaged beyond trusting them, casting a set of threads directly in to the half nut using a lower temp alloy, or a machine epoxy like is used to build up the sliding way surfaces of machine tools during rebuilds. Moglice? Then use them to make the parts you need.

All is not lost!

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I assume you mean in the leadscrew? That's an interesting approach I hadn't considered. I guess I could also 3d print one and use lost pla to cast one out of bronze, then cut a proper one out of cast iron.

I did speak with Frank, told me he sells used half nuts for $500. I heard a supersonic crack come from my spinchter on that one. May still be my only option. Not sure if I'll be able to clamp down on that half nut reliably enough to cut some internal threads. Might be my best option. I'll make sure to take some dimensions from it so I can make a new one. Just my luck I need the part that needs replacement to make the replacement part.

Couldn't you use Moglice to cast new threads into the existing half-nuts
by moving the saddle to where the leadscrew is least warn? Generally as
far to the right as possible. Use a release agent on the leadscrew.
This could be a semi-permanent fix. Or it might last long enough to
where you could make your own set of half-nuts out of iron or bronze.

Pyrex said:

I assume you mean in the leadscrew? That's an interesting approach I hadn't considered. I guess I could also 3d print one and use lost pla to cast one out of bronze, then cut a proper one out of cast iron.

I did speak with Frank, told me he sells used half nuts for $500. I heard a supersonic crack come from my spinchter on that one. May still be my only option. Not sure if I'll be able to clamp down on that half nut reliably enough to cut some internal threads. Might be my best option. I'll make sure to take some dimensions from it so I can make a new one. Just my luck I need the part that needs replacement to make the replacement part.

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Yeah, use the leadscrew to form your replacement threads on the half nuts, if casting them.

By your picture, the threads look like if care was used, you should be able to hook them on to the correct section of the threads, as you use it to single point a bushing of either bronze or cast iron to match.
It may take some dancing of the fingers, to keep a hand on the half nut lever during ops, so it does not skip out and 'half thread'.

I think if those were mine, my first act would be to clean and degrease, then smear a decent size goober of whatever "Liquid Steel" or similar epoxy with metal particles in it I could lay hands upon, and clamp the half nut to a section of well oiled lead screw somewhere there is no appreciable wear. Just add enough epoxy to fill the wear grooves. Then use that to make the replacement threads as a spool shaped bushing. Think, hat section bushings, end to end. Space the ends so they overhang the ends of the original half nut, and the inserted thread section has some mechanical retention as well as whatever you use to secure it (epoxy, solder)in the half nut body.

Far easier to fly cut or bore out he original halfnut for a replacement thread section than to make the whole unit from scratch.

Fixing the half nut is a few hours of dicking around, but even at that, it amounts to a pretty good hourly wage at those prices!

Did a quick search for 'half nut repair' and found this picture https://www.hwymachinery.com/images/kurakihalfnut.jpg . There are lots of websites and videos that show the process.

Pyrex: Do you have an inch leadscrew or is it metric? I have a 13" x 36" Clausing/Colchester that needed a half-nut years ago. My lathe came from a shop class in a school that had been wrecked. the half-nut had been cobbled in its repair. I needed a new half-nut. Like you, the company in Michigan wanted $500.00 for a new one, this was about 20 years ago. I purchased a piece of cast and fabbed a new one on a friends lathe. I made it big enough for two and split it to make one half-nut for myself. My leadscrew is 1.125 dia. x 6 T.P.I. If yours is metric, this probably wont do you any good. I would take $100.00 shipping included, if someone can use it.

JH

James H Clark said:

Pyrex: Do you have an inch leadscrew or is it metric? I have a 13" x 36" Clausing/Colchester that needed a half-nut years ago. My lathe came from a shop class in a school that had been wrecked. the half-nut had been cobbled in its repair. I needed a new half-nut. Like you, the company in Michigan wanted $500.00 for a new one, this was about 20 years ago. I purchased a piece of cast and fabbed a new one on a friends lathe. I made it big enough for two and split it to make one half-nut for myself. My leadscrew is 1.125 dia. x 6 T.P.I. If yours is metric, this probably wont do you any good. I would take $100.00 shipping included, if someone can use it.

JH

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Wow, yes I'm imperial, that's my lead screw size. That would be great

These lathes are notorious for the poor design of nut and screw.....I suggest you have a real good look at the leadscrew,and if damaged in the critical area,consider turning it around to get an unworn thread for the new nut.Or the problem will be back sooner rather than later.

Leadscrew is in remarkably good condition. The reason my nut is damaged is because someone pulled the engagement handle off and reattached it incorrectly so it was only half engaged on the threads.

Pyrex said:

Leadscrew is in remarkably good condition. The reason my nut is damaged is because someone pulled the engagement handle off and reattached it incorrectly so it was only half engaged on the threads.

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Pyrex: I have replied to your Private message, but not sure if it went thru. Let me know if you didn't get it.

JH

James H Clark said:

Pyrex: I have replied to your Private message, but not sure if it went thru. Let me know if you didn't get it.

JH

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Yes sir, I sent you a response. Thank you.

Pyrex, I sent you some pics via Email. Let me know if they don't come thru.

JH

Hey Pyrex , as long as you are working on the lathe how are you sight glasses ? Dirty and unclear ? I am getting some for my 13" Colchester that look like originals , my sight glasses are 1.5" OD , the ones I am getting are new old stock for a decent price. If interested send me a PM. mike

romie24 said:

Hey Pyrex , as long as you are working on the lathe how are you sight glasses ? Dirty and unclear ? I am getting some for my 13" Colchester that look like originals , my sight glasses are 1.5" OD , the ones I am getting are new old stock for a decent price. If interested send me a PM. mike

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Thanks for the heads up. I found a retailer that sells all sizes for around $12-17 each. It took me a while to lock down one of the manufacturers of the original glasses. They're all pretty poor and I'll be replacing all of them.

Not a problem, just thought I'd throw it out there. Good luck with the lathe and have a Happy New Year.