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LeBlond Regal - Chuck Plate to Spinde Runout

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oldmachinegary

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I'm getting to know my first lathe - a 1945 LeBlond Regal - 15". When I bought it I didn't realize it was this old but preliminary checks seemed to be OK - speeds, feeds and general operation.

I'm trying to do a few projects and I see the 3 jaw 8" chuck I have has about .009" runout at the OD of the chuck. Concerned this is way too much, I checked the chuck plate that the chuck bolts to and found it had the same amount. So at that point, I didn't see the chuck being the problem since the chuck plate also had the same amount. The chuck has a shallow counterbore which pilots on the chuck plate OD. It's a slip fit and three fasteners pull the chuck home onto the chuck plate. I can't feel any clearance between the two so I don't see an issue here.

I pulled the chuck off and checked the spindle runout with a .0005" dial indicator (at ID of spindle shaft). The indicator says the spindle has about .0005" runout so I think the bearings and shaft are running true.
The problem seems to be the chuck plate interface with the spindle.
This vintage lathe has a threaded spindle that the chuck plate attaches to. From LeBlond literature I have, they made a change to a tapered seat chuck attachment I'm guessing sometime in the 50's which should eliminate my problem but that's not an option right now.

Does anybody know if my runout issue is common with the threaded LeBlond spindle and is there a way to adjust or compensate for all this runout?
I haven't pulled the chuck plate off the spindle yet but that's my next move. I'm wondering if a shim over the spindle nose would re-position the chuck plate radially when tightened and reduce the runout. The other thought I had would be to just turn down the chuck plate to remove the runout but then I might get a slight clearance between the chuck plate and chuck.

Any comments or experience with this would be greatly appreciated.

Thanks very much.
Gary :thinking:
 

benmychree

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I have a 19" Regal, 1944 vintage with threaded spindle and have no trouble with chuck runout, within a small amount. You would do best by making a new backplate and remounting your chuck so that the body does not run out, then regrind the jaws, but all this depends on the condition of the chuck; if it is the same age as the lathe itself, all that time may be wasted. That was the case with mine, I bought it in the 1980s, it came with a old chuck that was missing one set of jaws, so I bought a "Buck Adjustru" chuck and made a new backplate for it, and can adjust it's centering for close work as needed, and occasionally regrind the jaws when they get bellmouthed from wear.
In making a new backplate, do not be tempted to use anything but cast iron, as steel will gall and mess up the spindle. I made a thread gage to the thread size of the spindle, made with a knurled handle like commercial plug gages, used an accurately ground and set threading tool, and sized it with the three wire method. When cutting the recess in the end of the new adaptor, give a few thousanths clearence on the spindle to avoid binding; from what I have seen in my 50 years of machine work is that clearence between the backplate and spindle does not seem to effect centering to any great degree; the threads seem to do the centering as they pull up tight; I had one lathe with a driving dog plate that the clearence and the threads were both quite sloppy, and it centered up true. I also had a Regal with tapered spindle nose, and I like them better, as there is no chance of the chuck unscrewing when stopping or reversing the lathe and the lathe may be operated in reverse for jobs that require it; the taper spindle machines had an belt drive the same as the threaded on spindle, but used an electric brake, which would not have been possible with the threaded spindle due to unscrewing; having said that, I stop my Regal by "plugging" the motor, that is reversing it to slow the spindle down to a stop, and have had only a few instances of it coming loose; if one sees this happening, just go back to forward rotation, and it will thread back on. When changing chucks, I start them on by hand, then, under moderate speed start the spindle and run it on by power for the last thread or so, so that it tightens securley against the shoulder of the spindle. I remove them by inserting a wooden block against one of the chuck jaws placed on the rear way and starting the spindle at low RPM until it loostens, then insert a wood cradle under the chuck body and thread it off under moderate speed.
 

Chuck K

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Gary, The problem isn't the threaded spindle. Lot's of old lathes have them and they can run just as true as tapered and camlock spindles. There are a couple of different thoughts on truing 3 jaw chucks. The method I always used was to cut the plate so the chuck fit tight on the shoulder in the center of the plate. If it's cut on the machine it's being mounted on and you have a good chuck, it should run true. The other method is to cut the center shoulder a little undersize so you can snug the mounting bolts and then tap the chuck around a little until it is running dead true and then torque the mounting bolts. I did this with my last chuck (it was a cheap chuck) and got it running fairly true. If I was in your situation and I found the plate to have runout, I would start by taking a skim cut on the plate and remounting the chuck to see if that fixes the problem. Make sure to have the spindle threads and register clean and mount and dismount the plate a few times before cutting it just to make sure it's firmly mounted. If you have the back plate running true at least you have a starting point.

Chuck
 

THE OLD MILLER

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Hi Gary,strange l,v got a 10ins LeBlond that l,m in process of doing up,l,v got a list to do as long as my arm,one of the things on list is the chuck its running out .010ins,havn,t looked into it further as yet,but l did put clock on chuck as l said its a .010 run out,put clock on backplate runs true,so my backplate is true to spindle,chucks out so the holes arn.t true to spindle the chuck is locked solid on,so thats main reason l havn,t done anything about it yet,l,m waiting till its bolted down.I will be redrilling holes in correct posistion,and putting a helicoil in.-brian

- - - Updated - - -

Hi Gary,strange l,v got a 10ins LeBlond that l,m in process of doing up,l,v got a list to do as long as my arm,one of the things on list is the chuck its running out .010ins,havn,t looked into it further as yet,but l did put clock on chuck as l said its a .010 run out,put clock on backplate runs true,so my backplate is true to spindle,chucks out so the holes arn.t true to spindle the chuck is locked solid on,so thats main reason l havn,t done anything about it yet,l,m waiting till its bolted down.I will be redrilling holes in correct posistion,and putting a helicoil in.-brian
 

oldmachinegary

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Thank you Gents for your replies and suggestions.

I did some more work on my lathe to see if I find the cause and/or reduce the runout of the chuck and chuck plate. It seems what I found had a little bit of everyone's comments. I also reviewed a book I got, "Running a Regal" and found a little bit more information.

From the book, it appears my chuck plate and chuck were "full-fitted" from LeBlond. This is a tap-fit meaning a slight interference is present and probably the reason the chuck plate and chuck OD had the same run-out.

I had trouble unscrewing the chuck plate off the spindle, finally giving a hard rap with a brass hammer to a pry bar placed across the plate/chuck through bolts. I only say that because the spanner wrench hole in the plate was well worn as was the wrench indicating the plate had been on and off many times. My inspection of the spindle nose and plate showed no real wear issues with the threads, nose, or plate bore. I did see some nicks on the plate face where it bottoms on the spindle. Probably careless handling of the plate. I double checked my spindle runout on the nose OD and it was about .0002".

My next steps were to try the spacers at the spindle nose (where plate bottoms when tightened) to try to shift the runout and reduce it. I fabricated a couple of "washer shims" and tightened the plate on the spindle. No runout change but I thought there may be a distortion issue as the plate is tightened. This is based on some engine design experience with threads and fasteners in critical joint locations.

I removed the spacers and reinstalled the plate hand tight. The runout dropped to about .0025" - not bad and probably useable but too loose to stay on the spindle reliably. My guess at this time is that the previous owner may have had the chuck plate on and off many times and possibly over tightened the plate wearing the threads (even though I don't see any obvious signs). I put it back together and gave it a quick couple of raps with the brass hammer and re-checked the runout. Right back to the .009" runout.

It was getting late so I put it back together and tried changing the chuck position on the chuck plate (3 hole attachment) and the best I could get was .0075". So after all that, I picked up .0015".

I haven't quite surrendered yet but I'm close. I wanted to turn the OD of the chuck plate to allow me to shift the chuck on the plate but I was afraid the chuck would shift with machining loads and I wouldn't know about it until it was too late. I would be taking off at least .009", probably a bit more to clear the tap-fit of the chuck counter bore. Chuck K, you've suggested this. How much did you remove on your plate if I may ask and did you have any loosening issues? With no tap-fit at the counter bore, you're relying on just the clamp load of the fasteners to hold the chuck.

benmychree, you sound like a very experienced and skilled machinist. I don't think I could ever cut the threads accurately enough to keep the pitch diameter concentric with the plate OD. I may look into it but I would have someone else do it - these are huge threads.

Thanks again to everyone - I really appreciate your responses.
oldmachinegary
 

Chuck K

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" Chuck K, you've suggested this. How much did you remove on your plate if I may ask and did you have any loosening issues? With no tap-fit at the counter bore, you're relying on just the clamp load of the fasteners to hold the chuck."

I have only used the method once and I haven't used the chuck enough to give you any decent feedback. Maybe Ray will chime in here. I decided to the try the method after reading one of his posts about mounting a 3 jaw chuck. I think he has been doing it that way for years. On the small 6" chuck I was mounting I didn't consider it an issue. On a large chuck that I intended to use for heavy cuts....I don't know. How are you taking your measurements for runout on the plate? I don't really see how thread wear would affect the setup as long as your register is right.

Chuck
 

oldmachinegary

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Chuck K
How are you taking your measurements for runout on the plate? I don't really see how thread wear would affect the setup as long as your register is right.
I'm taking measurements on the OD of the plate using a magnetic base on the bed with a dial indicator perpendicular to the point of tangency. I think that would be the standard method of checking radial runout.
Interesting comment about the register being right. I assume by register, you mean the shank portion of the spindle nose just inboard of the threads that also serves to pilot the bore in the chuck plate. On this LeBlond, the register is fairly narrow on the spindle and the fit with the chuck plate bore is what I'm guessing would be called a slip fit - meaning there is always some clearance. I also have a face plate for this lathe and I tried a fit-up to on the spindle to compare how tight the register fits with the face plate. Very similar although I wish I would have mic'd both. I had thought about sleeving the chuck plate bore but seeing it was so narrow, I wasn't sure how effective it would be.
So point well taken. If the register doesn't firmly guide the chuck plate, as the slip fit would suggest, then maybe there is some translation of the plate as it tightens on the threads. Perhaps the sleeve would help.
I think I'll look into the skim cut as it seems the most doable option.

Thanks very much!
oldmachinegary
 

Chuck K

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I would want to measure the outer perimeter of the shoulder on the front of the plate where the chuck is centered for run out. It's possible to have zero run out on the the cut shoulder while showing runout on the outer perimeter of the mounting plate. It's also possible that the chuck was not original to the machine and the mounting plate needs to be cut in place to true it up. You would also want to check the face of the plate to make sure it's straight. This is where you get into having a plate that is a very snug fit on the chuck versus some clearance allowing you to tweak it. I'm guessing if yours needs to be cut to true it you'll end up with some clearance to work with. Worst case, if you find that the chuck moves on the fasteners under heavy interupted cuts (I doubt that will be a problem if you have them torqued), you can always buy a new plate and cut it to fit your chuck. The other thing to keep in mind is, if your scroll is worn in your chuck, it's never going to be real precise anyway. That's what I would check but I'm by no means an authority on truing chucks.

Chuck
 

oldmachinegary

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Thanks for the additional tips, Chuck. I'll keep those in mind. By the way, I did make the runout checks at the front edge of the chuck plate - right where the chuck mounts. If you go towards the center, you get interrupted by the hole used to remove the plate from the spindle.

Thanks again.

oldmachinegary
 
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