[Newbie] Unimat Sl, Not True.

[Topsy]

Did you take apart the chuck? On a 3 jaw chuck, the jaws NEED to be in proper order. Or it will not hold parts on center.

Yep I did, however I had no clue that they need to be in the right order! I only remember myself wondering how they all end up in the right position in the end... I'm quite happy I didn't quite manage to describe my issue properly, I'm learning way more like this!

If the test rod starts true, then progressively becomes more eccentric as it furthers the headstock (cone shaped pattern), the chuck or spindle is wonked. If the test rod orbits in a cylindrical pattern, the jaws are not installed in the correct order, as Chips and More explains above.

It sadly does get more eccentric as it furthers the headstock, both with the 3jaw-chuck and with the collet chuck.

Your last description was pretty good.
Does the collet fit into the bore, or does it fit into a collet chuck that threads on the spindle.

I am thinking the spindle face has a ding in it or something causing the chuck to mount cock-eyed.

It's a collet chuck, screws on the same thread as the 3jaw. So I kinda guess the only thing that's left is, as you say the spindle face or the thread. I can't quite see the thread causing it though!?

Post a picture of the lathe and chuck. that might help .

I thought I'd best do that anyways when I'm with it tomorrow (it's by my grandmother). You might all just spot many more things that aren't quite right.


Thanks a lot everyone, it's very seldom that you get this much help!

 

[David VanNorman]

If your chuck is like others you should have numbers on the jaws and on the chuck body. find the number one jaw and the number one on the body turn the scroll so that the first jaw gets picked up then pick up the second jaw and the third jaw.
once you have them in order it will come together.

 

[David S]

Topsy I have the same lathe. When you screw the chuck onto the spindle, check to make sure the back of the chuck is tight against the spindle locating shoulder. Perhaps there is a ding in the thread that is not allowing the chucks to seat tightly against the shoulder.

David

 

[uncle harry]

If your chuck is like others you should have numbers on the jaws and on the chuck body. find the number one jaw and the number one on the body turn the scroll so that the first jaw gets picked up then pick up the second jaw and the third jaw.
once you have them in order it will come together.

I have used a simple method to synchronize the sequential starts on my 3 jaw in my SB 9A. This assumes that all 3 jaws are starting in their correct slots. What I do is insert all 3 jaws and snap a stretched O ring or strong rubber band around the jaws to place a light force inward on them. After that I rotate the scroll backwards until I recognize 3 or more clicks. Then I rotate the scroll inward and the jaws will find their way into the correct position. If 1 jaw is out 1 notch I reverse the procedure until all 3 synchronize.

 

[David S]

I have quite a few accessories with my Unimat. Both the 3 jaw and the collet chuck screw on to the spindle and register to the shoulder of the spindle. If both chucks are not running true, it sounds like for some reason they aren't screwing completely onto the spindle.

David

 

[David S]

Here are the instructions for the Unimat 3 jaw.



David

 

[Wreck™Wreck]

What is a Unimat?

 

[David S]

W W a Unimat SL or DB200 is a small engine lathe that was popular around the 1970's or so. It is a light duty lathe, but with care is capable of some nice work.

David

 

[Topsy]

So, the 3Jaw chuck was assembled properly by pure luck I guess (though I do remember seeing that page in the manual..) but it didn't help much..

I noticed that, as far as I can tell, the collet chuck is off by less than the 3jaw chuck, and they both get better if I screw them on harder, however I don't think trying to strip the threads is the way to go.

I've made a few short videos with various combinations, maybe you can spot something I've failed to see.

1. ensuring that the headstock is aligned. Sadly on centre is pretty mauled, no clue what happened to it, it looks as if someone tried to drill through it on one side..

Looks okay enough to me, though there is a slight wobble there too..

2. 3jaw chuck + 10mm diam steel, steel looks straight on kitchen counter

The chuck itself does also wobble a bit, so it's not all from me (maybe) not clamping the rod straight..

3. Collet Chuck + new M6 bolt, fixed on unthreaded shaft. I don't think I've got anything else that would fit at the moment.
I'd say this runs a bit truer than the 3jaw chuck..

4. Backside of both chucks:
3jaw

collet


..To be continued in the next post, media limit..

 

[Topsy]

5. And here's a video of the spindle alone:

Though yeah, this does weirdly also wobble, but since I had it checked and the chap that it's as fine as it can be it can't be the spindle (was Haag Streit, I doubt they'd employ someone that can't measure. Infact, I was quite surprised they just let me in!)
However, bearings? They seem solid though..


I then dismantled the 3jaw chuck again after reading that page of the instructions again to check the mounting plate. This appears to have some lateral (#6) play.. The face however isn't perfect either, but then, maybe that's the same amount of wobble you see in the video of the spindle?

6.

7.

I could not repeat this with the plate of the collet chuck, that is corroded together a bit at the moment.


I've also got a drill chuck that threads on that does the exact same thing, but I don't think another video would add much anymore.


Not entirely sure what's best to do now. Exchanging all the parts doing trial and error also doesn't tickle my fancy much!