Per Lathe City specs: Lead screw M8-1.0 left hand.
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But it might be easier and cheaper to just buy a new lead screw.

https://www.ebay.com/itm/Unimat-DB-SL-Mini-Lathe-Lead-Screw-Ref-DB201-5/133336735349?hash=item1f0b7d1e75:g:8kIAAOSwfzJeSnQb

http://www.tomstoolstore.com/unimat-leadscrew-key-no-4/

THat is indeed the slitting saw/table saw arbor.? Match the bore of your blades to your arbor.? If you need to make an arbor patterned after the one pictured adjusting to fit gear cutters , slitting saws etc.

Hi:
To straighten a shaft, roll it on a flat surface. You will know if it bumps. Then if you have an arbor press, put the shaft between two V blocks with hump high in the center. Press it gently down. At work we would put an indicator on the press. We would press just a bit more each time until the shaft was straight.
Carl.
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"Peter ashby via Groups.Io" <aescinga.pgen@...> wrote:

Hi:
You could try a thread file. They don't care if the thread is left or right handed. You just need one with a 1mm pitch, the files I have, have 8 different pitches on them. 25 TPI might work OK.
Carl.


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The thread size doesn’t spring to mind, but there may be a suitable thread file available. Just an example here:?

On Sat, Feb 29, 2020 at 05:05 AM, Gerald Feldman wrote:

You do know this is a left-hand thread, so tap and die need to be left handed.? Also, the cross slide may not move freely if the locking screw is still engaged.? ?Before even thinking about trying to rethread, take the cross slide apart and clean all the parts and threads with solvent to remove any dirt and dried grease.? Check that the threaded shaft runs true and does not have a slight bend in it (which will make it bind up as it is turned.? Rethreading will likely lead to introducing more backlash between the screw and nut, so avoid this if you can.

?

Check all the things mentioned above before re-cutting the thread. If you do need to re-cut it I had no difficulty finding a left handed tap, and I assume a die would be available. If you get a split die you can adjust it to take off the minimum to clean up the thread.

I made a cross slide to my own design (drawing in Photos) and it worked well. I didn't notice any problems with backlash.


Keith

Thanks Jerry,

Good point on the reversed thread didn't even cross my mind. I've given it a clean and re-grease. It's running much smoother but it does appear to have a bit of a bend in it when I wind the screw. I did hold it up against a straight edge to look for any bends but didn't notice anything so it's a little hard to pin down where the bend in the screw is

Thanks!?
--
Heather Carpet Daemon

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On the unimat SL I just purchased it looks like the thread has been crushed a bit. This? makes it difficult to use the . I'm thinking of running a tap through the cross slide support and a die over the lead screw to recut it. Looks to be 8mm x 1mm thread any one have an experience with thread size on the lead screw?

So I traded a guy a motor that would trip the breaker for one that wouldn’t. Since I am an electronics tech and I have overhauled a half dozen U90 motors I was confident in the swap. Noise suppression caps were good, brushes good, but what I found was one of the field wires had worn through right where it comes through the plates, that was the short. A piece of shrink tubing, cleaned and dressed the commutator, lubed it, and put it back together. Runs like a new motor.

So look where the wires pass through the field plates and make sure there is nothing rubbing there or on the commutator itself, I have seen both modes of failure.
You can check the caps (3) by using a multimeter each end to center and end to end, they should show open or a cap charge curve (slow rise in resistance to open).
The caps are only there to shunt the arc noise generated by the brushes to ground, (emi).

Pat

Did you use the same type of bearing that're already in the headstock or a different type?

I've stripped the whole thing down and reassembled. Bushes are fine and very little carbon build up. I will go through at some point and try rebuild it and rewire but for now I have ordered a replacement 24V DC motor and peripherals for a reasonable price.?

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Check that the brushes are still good & check how much carbon build up is in the motor.

Capacitors may be shot too.

Both can trip circuit protection.

When you pull the motor apart place indexing marks or take some pics to ensure that you put everything together correctly.

Flipping a field coil or other parts upside down or around 180 degrees is possible with many motors & may cause problems or make it run the wrong direction.

It helps to draw a diagram or take pics to make sure wires go back where they don't rub or get pinched.

Regards,
Brian.

I had to repair the capacitor in mine wasn’t a hard job just split the motor casing and swap out the capacitor while your there clean you can clean out the carbon dust and replace the brushes....

original brushes are still available, while I was in there I also replaced the original cable. These jobs I must point out I didn’t do until i did a full restoration of my machine, which also included new headstock bearings, paint job etc...

it’s a cheaper option if u want to keep the original motor.