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9" SM Utilathe Restoration

Success.... I got the chuck mounted.

TPUNCHES.JPG


Here are my transfer punches ready to rock.

PUNCHMARKS.JPG


And the resultant punch marks.

BHOLES.JPG


Nailed the bolt holes.

MOUNTED.JPG


And the chuck mounted on the lathe.

The runout on the mounting plate and chuck body are about the same as my PRAT. 0.004" (high-low) so didn't really gain anything there. The runout on mounted stock is significantly worse. 0.015" v.s. 0.005":(

I'm now wondering if the jaws are mounted in the wrong scroll slot. The jaws and slots aren't numbered or keyed to each other.

Craig
 
Could be. Worth a try to change jaws around. You'll typically see a step discrepancy if they are out of phase. Also try gripping different (larger/smaller) diameter to see if you see the same runout & direction. Also snug each key hole the same torque. Doesn't have to be gronked but equal. Don't register off any kind of stock unless its accurate, just chasing your tail. Use like a ground dowel pin or maybe edge finder or EM shank...
 
Good job. That will be usable as is.

As far as the run-out -> do as @PeterT says. Try all key and jaw combos. Label all key holes and jaws. Write down everything. When you find the best combo, stick with that.

If you want even better (i.e. zero run-out), go back to my post #451 above. The chuck only needs to be able to move 1/2 of your largest TIR on its backing plate. Stefan Gotteswinter talks about this in one of his earlier videos.
 
With a scroll chuck there should only be 3 combinations. The jaws have to be installed in the same order no matter which slot you start with or they won't come to a point at the centre. Once you figure out the best starting slot, you really only need to mark that one.
 
Brian Ross said:
With a scroll chuck there should only be 3 combinations. The jaws have to be installed in the same order no matter which slot you start with or they won't come to a point at the centre. Once you figure out the best starting slot, you really only need to mark that one.
Click to expand...

:confused:
 
Confused? If you have the jaws out of the chuck, turn them over and take a look at the grooves that engage the scroll of the chuck. If you compare them, you will find that the "teeth" are somewhat offset from jaw to jaw. That is because the scroll is a spiral so the "teeth" need to be offset a third of a tooth gap so they form a circle at the jaw face. They need to be installed in the right order for this to happen.
 
Brian Ross said:
Confused? If you have the jaws out of the chuck, turn them over and take a look at the grooves that engage the scroll of the chuck. If you compare them, you will find that the "teeth" are somewhat offset from jaw to jaw. That is because the scroll is a spiral so the "teeth" need to be offset a third of a tooth gap so they form a circle at the jaw face. They need to be installed in the right order for this to happen.
Click to expand...

OK...…As @RobinHood suggested, I need to back up and give this thing a good cleaning LOL. The jaws and slots are numbered, they were just covered with gunk. And they weren't installed per the numbering?
 
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Is this a pretty snug fit to you chuck now?

Another thing you can check is mount & remount your back plate only & get a reading on the lip boss. Possibly your issue is with mating the spindle & not the plate-chuck?
 

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PeterT said:
Is this a pretty snug fit to you chuck now?
Click to expand...

Yes, it's a closer fit than on my PRAT actually, and the chuck body runout is close to the plate run out at about 0.004" (high-low). But this reminded me that I could try mounting the chuck on the plate in all three orientations as well thanks.

UPDATE: I'm down to 0.006" (high-low) on chucked stock by changing the chuck orientation on the plate:)
 
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YYCHobbyMachinist said:
Really? 0.015" is acceptable???
Click to expand...

I believe I said “usable”. Which it is, since any stock held in that chuck will run true after you turn it.

“Acceptable“, well that depends on your “standards”. If it was my only chuck and I needed it right away for a job - you bet that it would be acceptable and I’d use it. I’d then go back and improve on it later - just like you are doing.

When you are trying to make an old 3J chuck hold a thou or so at any jaw opening, it takes baby steps to get there, as everything matters. Heck, it is very difficult to have a brand new 3J hold a thou. And these are the very expensive ones like Rohm and https://www.swisschuck.com/xml_1/internet/en/intro.cfm
etc...
 
Yes, it would. Indicate the original flange face onto your mill table - shim the rim if required to make it dead nuts zero run-out before you mill off the excess. If you don’t, you will have to face the plate again once it is back on the lathe to make it run true to the spindle. Then remount the chuck.

How are you planning on chamfering the new face? On the milling machine? Or by hand after? Reason for the question: if you plan on milling the chamfer, you’ll also need to center the bore under the spindle and not just get the face parallel to the mill table ==> more complexity.
 
@YYCHobbyMachinist

Hey Craig, Well working on my backing plate on my chuck we noticed that the center register internal diameter (Red arrow) was larger than on my original Atlas 3 jaw chuck and on my 4 jaw chuck.

2020-11-22_9-22-58.webp
(Picture borrowed fror the other thread.)

This larger internal register had me concerned about how the chuck would line up properly on the lathe. I haven't had a lot of time to play with this, but from the short time I put into this I can tell you this.

The original 3 jaw Atlas chuck has tight fit register with the lathe. Run out on the outer diameter of the chuck. 0.003" Surface is rough as it is an older chuck.

4 jaw new Bison chuck has a tight fit with the lathe register. Run out on the outer diameter of the chuck. 0.003"

The new Bison 3 jaw chuck with a loose fit with the lathe register has 0.003" runout.


I did a lot of research reading on the internet and found different opinions on this. Lots of people post stating that the internal register diameter is used for alignment of the chuck.

A couple of sites mention that this is incorrect. It should be a loose fit. The threads will self center the chuck as it is pulled back onto the register face. (Green arrow.) One user with issues was suggested to clean the register faces and check the register internal diameter for being a tight fit. Apparently if the register diameter is tight it can prevent the chuck from being centered as it is tightened on.


I'm not sure which of these theories is correct, but something to think about.


Something else I've been thinking about.......
Can I drill and tap 4 radial holes equally spaced on the outer diameter of the backing plate nipple? I could install set screws and use them to fine adjust the register internal size.
I got this idea from YotaBota who posted this link in his thread to a youtube video by tublacain.
In the video he shows an Adjust-chuck and how it works.

 
YYCHobbyMachinist said:
OK...…As @RobinHood suggested, I need to back up and give this thing a good cleaning LOL. The jaws and slots are numbered, they were just covered with gunk. And they weren't installed per the numbering?
Click to expand...

Craig the numbering on your 3 jaw wont make any difference on the run-out of the chuck....they are only relevant when re-introducing a work piece back into a chuck to try to match the original run out of the piece.

The scroll is the defining item for run out...if it has any imperfections in casting and final machining or over stressed during a tightening of a workpiece, they will show up as run-out.
Edited to add; I will also add that due to scroll imperfections that arise for previously mentioned reasons...you can actually have chuck with a run-out # at a small dia (say 3/4") workpiece and have no run out at a much larger workpiece (say 4"). the scroll may have an imperfection for only a short distance at any position and it will be always repeatable at that position.

Brian Ross's posts are very correct, the jaws can be assembled in any of the slots and work the same as every other combination as long as they are inserted in the proper order...any improper order will have an immediate recognizable error run-out measurable in fractions of an inch not thousands.

If the register rim on your plate & chuck are meshing exactly, then bolt adjustment will be unavailable to you and your left with what you have short of having the jaws re-ground I'm thinking.
 
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RobinHood said:
Yes, it would. Indicate the original flange face onto your mill table - shim the rim if required to make it dead nuts zero run-out before you mill off the excess. If you don’t, you will have to face the plate again once it is back on the lathe to make it run true to the spindle. Then remount the chuck.

How are you planning on chamfering the new face? On the milling machine? Or by hand after? Reason for the question: if you plan on milling the chamfer, you’ll also need to center the bore under the spindle and not just get the face parallel to the mill table ==> more complexity.
Click to expand...

Hmmm.... sounds like I should just do it on the lathe. I have no means of chamfering on the mill.

Need to find a way to get the spindle registration to meet the plate before the threads bottom out...…

An 1-1/2" ID bushing of sorts.
 
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Hey @YYCHobbyMachinist : can you post a few pictures of the threaded spindle on your lathe and any measurements if there is a collar or gap after the threads? This is purely for making a spindle nose adaptor thing a ma bob :)
 
historicalarms said:
... the jaws can be assembled in any of the slots and work the same as every other combination as long as they are inserted in the proper order...any improper order will have an immediate recognizable error run-out measurable in fractions of an inch not thousands.
Click to expand...

This is a much better way of wording what I was trying to say. If you have no jaw number reference or get the jaws out of order like 1,3,2 there should be a noticeable discrepancy as they converge. They will be out quite obviously to the naked eye ~one tooth width of the scroll. But if you first flip them over & line them up & examine the starting thread position relative to one another you will see a progressive thread sequence. Number them 1,2,3 on this basis and also enter them into the slots in this same order. Engage jaw #1 to the beginning of the scroll, turn the scroll 1/3 of circumference to engage #2 in next slot, then #3.

Now what I was trying to say is if you are already this far, then it could be that you get some improvement by shifting the (1,2,3) bank of jaws one or two slots over. The reason being (as I understand it) once the jaws are positioned & slots uniquely stamped the same as jaw#, then they do the ID grind. That's the factory position you are trying to get back to if possible. When you don't have numbers, that makes life more interesting & trial & error is the only option I know of.

With this established, it could well be you have a chuck with wear and/or distortion. Could be the scroll, could be jaws.... any number of things. If its worth saving the normal remedial action is a re-grind in-situ. But before you do that, you need the backplate sorted out because it controls the chuck.
 
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