3 jaw chuck vs. backplate...

I just recently joined this forum after getting some very useful information before joining. I cannot seem to find the exact situation, as I have previously, in already answered threads. I recently purchased about a mid-late 70's Clausing 1300 lathe. Ran the machine up a little higher than previously and noticed a decent vibration. To make a long story short, I've found that the backplate to the 3 jaw is running true while the chuck itself is out by several thousandths. I've read/watched about truing the jaws via. grinding but my question is...is there a way to adjust the chuck to run true with the backplate so I can get the wobble out?

Twsmith said:

I just recently joined this forum after getting some very useful information before joining. I cannot seem to find the exact situation, as I have previously, in already answered threads. I recently purchased about a mid-late 70's Clausing 1300 lathe. Ran the machine up a little higher than previously and noticed a decent vibration. To make a long story short, I've found that the backplate to the 3 jaw is running true while the chuck itself is out by several thousandths. I've read/watched about truing the jaws via. grinding but my question is...is there a way to adjust the chuck to run true with the backplate so I can get the wobble out?

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"Several" I read as three or more? So one surely wants to do that FIRST. After which you should not HAVE to mess with the jaws until it has seen wear and/or abuse.

So.. are you telling us the back of the chuck is not true to the body? Or that it simply wasn't fully set-down correctly when mounted to the "trued" face of the backplate?

Otherwise, a poorly-made chuck "is what it is", might be better used on a DH or as a bench fixture once you acquire a better one.

Set-true/adjust-true feature recommended for any scroll-operated chuck, BTW. Or just learn how to use a 4-J independent and not have a runout problem you can't simply correct for yerself on a per-task basis.

To answer the OP's original question.

I have machined the little "boss" as I call it, or register that the chuck sits on and bolted the the back plate, down about .010" undersize. You may also need to take a facing cut on the face of the back plate just in case it is out. Be careful here, if there is any runout on the face, that may indicate trash on the bore of the back plate where it registers on the spindle nose of the lathe. Re-inspect and deburr as you see necessary. Next mount the chuck and indicate in the OD of the chuck. You do this by snugging the cap screws slightly that hold the chuck on the back plate. Bump the OD of the chuck around until it is running true. Use a brass slug or lead hammer and bump gently. Once done, tighten the cap screws gradually in sequence until they are reasonable tighten.
Now, chuck up on a piece of bar stock the is know to be round and straight. Check the runout at the face of the chuck. If it is not where you want it, which I suspect it will not be, may be time for a new chuck. I personally do not like the idea of grinding the jaws of a chuck. Just my preference. Ken

Just wanted to answer my own question. I did not figure this out but for anyone else that may run into this, perhaps this may help. When I originally posted this, I did not know the chuck was a Buck "Adjust-tru". I knew it was a Buck but not the rest. When this chuck was mounted to the backplate the difference between the I.D. of the chuck and the O.D. of the backplate is 0.020". It was never "shimmed" to center the chuck to the backplate and thus giving me a 0.022" runout. I was able to get it down to 0.017" after learning about how the chuck works. The outside of the chuck and the runout was the same, the 0.022", while the backplate's O.D. was running true. If this was a "normal" chuck, all of the responses would have been correct. If I had known what I had and how it worked, I'm sure I would have received different answers. I appreciate the ones that responded in trying to help me, and you did, had I known enough to ask the proper question.

If that is an actual Buck Adjust-tru chuck, it shouldn't have that much difference in runout between the OD of the chuck and the jaws when chucked up on a shaft or so. Really need to take it apart, clean it real good, and re-assemble using a dab of grease on the scroll and bevel gearing. Check for damage on the scroll, the spiral looking thread. Also check the numbers on the chuck jaws, they all should have a four digit number (maybe) along with 1, 2, 3 for the jaws.numbers. If after all of this, you still have the excessive runout, might be time to buy a new chuck. From the Buck chucks I have run, 8" in size, I haven't seen anything over .002"-.005" thousandths runout. Ken

Twsmith said:

Just wanted to answer my own question. I did not figure this out but for anyone else that may run into this, perhaps this may help. When I originally posted this, I did not know the chuck was a Buck "Adjust-tru". I knew it was a Buck but not the rest. When this chuck was mounted to the backplate the difference between the I.D. of the chuck and the O.D. of the backplate is 0.020". It was never "shimmed" to center the chuck to the backplate and thus giving me a 0.022" runout. I was able to get it down to 0.017" after learning about how the chuck works. The outside of the chuck and the runout was the same, the 0.022", while the backplate's O.D. was running true. If this was a "normal" chuck, all of the responses would have been correct. If I had known what I had and how it worked, I'm sure I would have received different answers. I appreciate the ones that responded in trying to help me, and you did, had I known enough to ask the proper question.

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A "shim" is interposed material. I take it you meant it was not adjusted.

I also HOPE you mean you got it to .0017", rather than .017" runout ?

Page Two:

Unless "round" stock is ground, and even then, to a specified goal, most "round-looking" stock, is not.

Measure it at several points of the clock. Split the out-of-round figure.

Otherwise, using the set-true feature to chase the impossible can be a serious time-waster!

This information is really impressive.

4squarelogicseo1 said:

This information is really impressive.

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According to the funny papers, some folk are carrying $37,000 in student debt to be able to say things that nicely.

Never had a dime in student loans. My generation just said: "Bullshit!"

Even though it is an Adjust-Tru chuck, the body should still run as close to zero as possible. Remove the chuck from the backing plate and check the size and concentricity of the register, along with the TIR of the face (surface that contacts the back of the chuck). Either the register is undersize or not concentric. If it is undersize but concentric and the face runs true, remount the chuck and tap the chuck around as necessary to bring it as close to zero as possible while snugging the mounting bolts. Once you have it running true, tighten the bolts. If the register is not concentric or the face does not run true, re-machine as necessary, even if you have to completely remove the register and create a new one. Ideally there should be less than .001 clearance between chuck and register. If there is not enough material to do this, you need a new backing plate.

Once you have the body running true, there is no reason you should not be able to get runout down to .001 or less (assuming the stock is actually round). Even if the scroll is damaged, you will be able to adjust runout just like a 4-jaw.

If the foundation is not level and square, the house won't be either.

Take it apart and clean it, should do that fairly often. The thread fish in the photo points to the pivot the scroll rides on, if this point wears more then a few thou, the chuck will be off, and not repeat. The photo shows a brass bushing I used to repair the pivot on the Buck 6" 6jaw.


These Buck chucks are expensive, they can be repaired using basic machining methods.

4squarelogicseo1 said:

This information is really impressive.

Click to expand...

thermite said:

According to the funny papers, some folk are carrying $37,000 in student debt to be able to say things that nicely.

Never had a dime in student loans. My generation just said: "Bullshit!"

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Nothing but a simple minded spammer:
"About 4squarelogicseo1
Country:UNITED ARAB EMIRATESState / Province:not United States or CanadaLocationubaiBiography:Those are seeking for best Mobile app development services in their budget they are at fine place. 4 Square Logic IT Solutions is leading brand who work for delivering best featured mobile app. Call or Whsatsapp at diespammerdie Interests:Mobile DevelopmentOccupationeveloperdisplayname:4Square"

digger doug said:

Nothing but a simple minded spammer:
"About 4squarelogicseo1
Country:UNITED ARAB EMIRATESState / Province:not United States or CanadaLocationubaiBiography:Those are seeking for best Mobile app development services in their budget they are at fine place.

Click to expand...

Who cares how it started? The PM community is better than that.

Several folks took what might have been s**t and turned it into fertilizer - useful information for others who need it and can get past confusion and save time by having that information.

The post right above your one is one of the best out of Walla Walla in several years as to conveying a lot of information efficiently.

I ain't too proud to praise him for it. I hope to see more of the same.