Half-nut

[SteveF]

Well, here's the nut part:

https://www.roton.com/products/acme-lead-screws-nuts/acme-bronze-plastic-sleeve-nuts-part-numbers-dimensions/

Steve

[BCRider]

Smokedaddy, on the one that is complete the "nut" seems very red. More red than I'd expect if it were brass or bronze. Is that piece actually plastic? If it is then I think the guys suggesting you soften some plastic in a toaster oven have the right idea.

I would not heat the rod and push on directly though. Plastic is often way too good an insulator for heat. So you'd need to get the screw fairly hot so it would hold the heat long enough to form the thread. Hotter for longer than I think would be prudent.

Instead I'd get a lump of heat softening but fairly durable plastic and warm one end with a heat gun slowly until it's soft and pliable and then force THAT against the thread to get a perfect match. Then cut away what you need to match the shape of the existing nut. There's some plastic around that is firm and tough when cool but softens to a formable manner in this just in boiling water. I've no idea what it is but a bit of checking around should turn it up. To avoid "chilling" too fast I'd use a hair dryer or carefully use a heat gun to warm the thread as well to where it's just a bit too hot to comfortably hold. Or if the heat might damage the frame around the screw perhaps use a soldering iron held on the thread for a few seconds to warm the thread to avoid sudden chill freezing of the plastic.

It also appears that you could buy a plastic nut and cut it down to use for this threaded nut plate/bar/block/shoe/whatever it is we'd call such a small segment.

[Smokedaddy]

Well, here's the nut part:

https://www.roton.com/products/acme-lead-screws-nuts/acme-bronze-plastic-sleeve-nuts-part-numbers-dimensions/

Steve

Very cool, thanks for looking that up Steve. Expensive little puppy, even the plastic one. Hopefully I will be able to conjure something up with it.

-JW:

[Smokedaddy]

I think I'm going to go with the link that Steve posted for the nut but I'm still going to wait a few days to see if the manufacture responds to my email. If not then I will call them. Below is a side by side comparison of the two items in question. I haven't a clue what it's supposed to look like since I haven't seen another one of these. They are obviously different. It looks to me that all I need to do is secure the stage to the lead screw via a coupling in some manner. I'm not sure why the threaded rod isn't parallel with the stage either. It was made that way as far as I can tell. Anyway naturally I don't want any drag on the coupling but this seems very doable. Eventually I plan to remove the linear scales and install motors on the knobs.

[BCRider]

The threaded rod on the right is parallel to the edge of the lower part. And since I'm assuming that the threaded rod is supported at the ends by that lower plate/part I'd say that the lever and carriage the lever is attached to is the part which is out of square. The lever assembly being square to THAT part.

I'm also seeing that the lever itself for the right side assembly is missing altogether. It's not hiding around your place somewhere is it?

[danlb]

Looking at the latest picture, you can literally take a plastic fork and carve grooves into it with a nail file to make a usable (but not necessarily durable) nut.

[Smokedaddy]

The threaded rod on the right is parallel to the edge of the lower part. And since I'm assuming that the threaded rod is supported at the ends by that lower plate/part I'd say that the lever and carriage the lever is attached to is the part which is out of square. The lever assembly being square to THAT part.

I'm also seeing that the lever itself for the right side assembly is missing altogether. It's not hiding around your place somewhere is it?

No it was missing when it arrived. It was packaged extremely well, lots of bubble wrap around it and in a separate box. It had to be damaged before hand. I doubt the seller knew that since he was clueless what he was selling.

I'll make a video in a few minutes that will show it in operation. It will explain what I found out after further inspection.

Regards,
-JW:

[Smokedaddy]

Here's a short video ...

https://www.youtube.com/watch?v=pKRI...ature=youtu.be

-JW:

[elf]

Any chance you can disassemble the working axis and the broken axis and photograph the parts?

p.s. DumpsterCNC has anti-backlash nuts that would probably fit.

[Corbettprime]

For ten bucks, you can buy 3' of regular acme 1/4" -16 threaded rod, a couple of ditto hex nuts from mcmaster carr, and fabricate a tap to make your own plastic nuts

[BCRider]

I'd say odds are good that you're right about it being dropped. And that the missing spring lever with threaded fitting was a casualty.

Looking at the two nut assemblies though clearly they are not the same. Unless you remove the one that is all in one piece and find that for whatever reason they are the same but flipped around? But the width seems wrong and for whatever reason it was originally done I don't thing they are the same.

Here's a question.... Is it possible that the platen with the broken travel stop lever nut was attached to some other assembly? Could the spring loaded lever with the "teeth" that fit the thread have gone away with whatever fits on top of the assembly you have? Or do you have the specimen carrier that goes onto this movable platen?

I'm grasping at straws here of course. But as it sits now it would appear that you're looking at needing to make a new lever as well as the little toothed "nut plate".

[nickel-city-fab]

For ten bucks, you can buy 3' of regular acme 1/4" -16 threaded rod, a couple of ditto hex nuts from mcmaster carr, and fabricate a tap to make your own plastic nuts

Thats amazing -- before today, I had no idea you could even get Acme in that size... but if I was the OP I would definitely look into that

[Smokedaddy]

I'd say odds are good that you're right about it being dropped. And that the missing spring lever with threaded fitting was a casualty.

Looking at the two nut assemblies though clearly they are not the same. Unless you remove the one that is all in one piece and find that for whatever reason they are the same but flipped around? But the width seems wrong and for whatever reason it was originally done I don't thing they are the same.

They're not the same but have the same function.

Here's a question.... Is it possible that the platen with the broken travel stop lever nut was attached to some other assembly? Could the spring loaded lever with the "teeth" that fit the thread have gone away with whatever fits on top of the assembly you have? Or do you have the specimen carrier that goes onto this movable platen?

I haven't a clue but I'm pretty sure nothing else was attached to this. It a specialty accessory for this particular microscope, not made by Polyvar. I'm sure it's not as precision as it once was if it was dropped and I had to lightly tap it with a rubber mallet.

https://www.semprex.com/catalog/prod...aq8ttmf2gem1n6

I'm grasping at straws here of course. But as it sits now it would appear that you're looking at needing to make a new lever as well as the little toothed "nut plate".

Yep, that seems to be the case IF the manufacture no longer has parts for this which is highly likely. Maybe I can 3D print something as well. These metallurgical scopes were very expensive back in the day (40k on up) and built like tanks. Parts for the microscope itself are rare and very expensive if you can find them in excellent condition. I'm glad nothing else was wrong with it.

-JW:

[old mart]

You could make a usable nut with a Dremel and patience.
That is an impressive microscope.