# Chuck Not Running True?



## PAturner (Oct 1, 2016)

So the lathe I bought is now powered, running, and so far the tools I've ground cut well. Yay for that. 
However, I've run into a problem that I'm very worried about. First of all, the chuck (really the backing plate I guess) does not spin all the way onto the spindle, and worse, the chuck does not run true. I am very wary of forcing the chuck on, because I can see that going all kinds of wrong. When I chuck up a round piece, it runs very very close to true- close enough that you have to look closely to see what's wrong, but noticeable.
 I took the chuck off and looked at the spindle and that seems to be running quite true. I put the chuck back on and noticed the backing plate wobbling a little.

Based on this info, I have a few questions (numbered so they're easier to answer I hope)
1.) Based on the above, would I be correct in assuming the backing plate would be the first thing to check?

2.) could the problem possibly be solved by finding a way to spin the chuck all the way onto the spindle? 

3.) If yes to number two, any suggestions on how to safely go about getting the chuck on properly? What kind of tools, cleaning procedures, etc should I know? 

4.) If all else fails, will I be able to make a new backing plate with only a lathe and a drill press? 


And before anyone mentions it, yes, I absolutely need a dial indicator- I'm working on that currently. 

Thanks for any help!


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## Ulma Doctor (Oct 1, 2016)

1) YES
2)YES
3) see below

if you can remove the chuck, do so





just place a piece of wood (or thick cardboard doubled up) to prevent the chuck getting dropped on the ways
inspect the spindle threads for damage and bits of metal, clean with a brass wire brush
inspect the chuck threads for damage or bits of metal, clean with a brass wire brush
if there is no damage seen, apply a drop or 2 of light oil to the spindle threads and try to reinstall the chuck

4) YES! you sure can


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## PAturner (Oct 1, 2016)

That's the only imperfection in the threads, it's quite a small little chip and its early in the threads so I doubt it's the issue.


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## Ulma Doctor (Oct 1, 2016)

the dreaded red X


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## Ulma Doctor (Oct 1, 2016)

i can't see the chip,
but if it scores the threads as it goes on, it may cause some interference


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## PAturner (Oct 1, 2016)

I'm not sure what you mean by score the threads. It spins on well past the chip if that's what you mean 


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## Ulma Doctor (Oct 1, 2016)

that's a good sign then
is there any damage to the internal threads of the chuck?


scoring refers to worn or damaged thread contact interface
it may be very slight or very pronounced.


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## PAturner (Oct 1, 2016)

From what I can clearly see, no- however I cannot see all the way in as I can't get the backing plate off. I'm soaking the bolts in wd-40 overnight and will get back tomorrow. From what I can see though, there is a very clear line of clean metal and then a bit of surface rust. Very light, could scrub off with 0000 steel wool if the part were flat, but it's there. The clean metal is towards the headstock end of the threads that screw on first, so I have a creeping suspicion that this could be part of the issue. Perhaps a vinegar soak when I get the backing plate off and see if it helps?


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## Ulma Doctor (Oct 1, 2016)

vinegar will work and take off some rust too
it may leave the metal a little gray looking


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## PAturner (Oct 1, 2016)

Also, the chuck is a three jaw- 
Could I possibly get around any runout issues if I got my hands on a 4 jaw independent chuck? 


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## Ulma Doctor (Oct 1, 2016)

out of curiosity,
what kinda lathe are we working on?


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## Ulma Doctor (Oct 1, 2016)

PAturner said:


> Also, the chuck is a three jaw-
> Could I possibly get around any runout issues if I got my hands on a 4 jaw independent chuck?
> Sent from my iPhone using Tapatalk



Yes, you can dial a 4 jaw in to any desired runout

a 3 jaw will always have some run out,
the best i have seen was on my (New) old Hercus- it had .001" runout when i got it
i have not checked it's accuracy since but it has very little runout by eye


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## RJSakowski (Oct 1, 2016)

The questions that come to mind for me are:
1. What is the make and model of the lathe?
2. How far on are you able to thread the chuck?
3. Do the thread pitches match on the backing plate and the spindle?
4. Does the spindle diameter match the recess cut into the backing plate?

I would confirm that the backing plate was properly made before I tried to force thread it on


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## 4GSR (Oct 2, 2016)

Ulma Doctor said:


> 1) YES
> 2)YES
> 3) see below
> 
> ...


Mike, I hope that's not your video.  
The first no-no shown in the video is the spindle is locked in using the back gear.
Yeah, I know, we are all guilty of doing that and in most chuck removals works fine.  It's the situations where the simple bump to break loose the chuck where you are having to use a big hammer of six foot cheater pipe and brute force to get it broke loose.  This is where you could loose a tooth off of one of the back gears in the head stock.  
Just a word of caution here to those that have never experienced the sound of a tooth breaking off on a gear during chuck removal..... Ken


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## PAturner (Oct 2, 2016)

Update on everything- removed the backing plate this morning and checked everything out. First issue I saw was that the bur thrown up from threading was never knocked off. This was on the side that mates with the chuck. I got that taken care of. 

Also checked how far the chuck is threading on, and it's definitely getting stuck right at the rust line. So I'll soak it in vinegar today and see if I can get it to thread on properly, check the runout and update again.


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## Ulma Doctor (Oct 2, 2016)

4gsr said:


> Mike, I hope that's not your video.
> The first no-no shown in the video is the spindle is locked in using the back gear.
> Yeah, I know, we are all guilty of doing that and in most chuck removals works fine.  It's the situations where the simple bump to break loose the chuck where you are having to use a big hammer of six foot cheater pipe and brute force to get it broke loose.  This is where you could loose a tooth off of one of the back gears in the head stock.
> Just a word of caution here to those that have never experienced the sound of a tooth breaking off on a gear during chuck removal..... Ken



Yes it is my video,
i know the video and sound quality are poor.
i agree to not put too much pressure on the gear teeth.
i did warn against putting too much pressure on the geartrain and only used a slight bump from a 2x4 to back the chuck off.
thanks for the clarification!


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## Wreck™Wreck (Oct 2, 2016)

I am not particularly experienced with threaded spindle lathes although have owned 2 in the past, I suspect that the flat shoulder past the thread relief controls the axial position of a chuck or faceplate, the thread controls the radial position. This is exactly why tapered spindles were developed. Also changing threaded spindle attachments is a chore.

One may easily skim cut the shoulder in place. In an effort to find exactly where the thread interference is color the threads with a sharpie marker or blue lay out fluid, screw the chuck on tight, remove and inspect, there will be witness marks where the problem lies.

Good Luck


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## jpfabricator (Oct 2, 2016)

Can y'all see the picture?
I think I figured out a way to fix the detestable red "X".

Sent from somwhere in east Texas by Jake!


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## jpfabricator (Oct 2, 2016)

If you have thread pitch gauges, check the threads on both pieces. You may be trying to thread metric onto sae.

Sent from somwhere in east Texas by Jake!


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## JR49 (Oct 2, 2016)

I can see the pic you posted jpfabricator, so whatever you did worked, cause I always get the red X's.
   PAturner, you are probably experiencing the same problem I had.  Although the back plate and spindle have the same threads, the narrow "register" on the spindle is sometimes a different size.  My Logan Lathe came with a 3 jaw chuck mounted, it too had runout. The PO never noticed that the back plate was made for a Southbend and the register was about .015" too small to fully seat on my Logan's spindle register. Once I turned approx. .016" off the back plate register, it screwed on all the way and has been much better ever since.  It still has some runout, as all scroll chucks do, but it is much improved.  If you want no runout, you need a 4 jaw independent chuck that you dial in every time you mount a part in it.  Hope this helps,  happy machining,  JR49


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## Ulma Doctor (Oct 2, 2016)

the boogers on the thread may be causing the issue.
a thread file or a small 60* triangle file may be lightly employed to improve any high spots
you could add some ink from a sharpie pen to the spindle and try to see where the interference lies


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## PAturner (Oct 2, 2016)

JR49 said:


> I can see the pic you posted jpfabricator, so whatever you did worked, cause I always get the red X's.
> PAturner, you are probably experiencing the same problem I had.  Although the back plate and spindle have the same threads, the narrow "register" on the spindle is sometimes a different size.  My Logan Lathe came with a 3 jaw chuck mounted, it too had runout. The PO never noticed that the back plate was made for a Southbend and the register was about .015" too small to fully seat on my Logan's spindle register. Once I turned approx. .016" off the back plate register, it screwed on all the way and has been much better ever since.  It still has some runout, as all scroll chucks do, but it is much improved.  If you want no runout, you need a 4 jaw independent chuck that you dial in every time you mount a part in it.  Hope this helps,  happy machining,  JR49



What do you mean by the register? The unthreaded portion of the spindle threads?


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## 4GSR (Oct 2, 2016)

PAturner said:


> What do you mean by the register? The unthreaded portion of the spindle threads?
> 
> 
> Sent from my iPhone using Tapatalk


Yes, the area behind the thread.


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## Wreck™Wreck (Oct 2, 2016)

PAturner said:


> What do you mean by the register? The unthreaded portion of the spindle threads?


Yes, he means the axial control surface is defined by this surface, the radial control is dependent on many variables. A threaded lathe spindle is not the beat approach.


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## JR49 (Oct 2, 2016)

PAturner said:


> What do you mean by the register? The unthreaded portion of the spindle threads?





             Yes, its the area at the end of the threads. In the pic that jpfafricator posted, follow the thread to the left, and right where it ends there is approx. a 3/8 to 1/2 inch of smooth surface. That is the spindle register, HOWEVER, on every spindle I've seen that register is higher than the top of the threads (max thread dia.), and on the back plate internal threads, the register is lower than the minimum dia of those threads, so that when the two parts are screwed together the two registers are a tight sliding fit. In your pic, the register looks to be level with the top of threads, which can't be right because then the backplate register would have to scrape over the top of the spindle threads in order to fit tightly on the spindle register. But I'm basing everything on that pic, which may look different than the actual spindle, but regardless, I'm hoping my explanation will give you some insight as to how they are supposed to fit together. As a novice myself, I'm basing my info on what I did to the southbend back plate to fit it on my Logan lathe. If this is no help to you, then don't worry, you can be assured that someone on this great forum will have the answer you need. Good luck, and keep us informed, JR49


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## PAturner (Oct 3, 2016)

After many hours of scrubbing, vinegar, and lubricating, there has been no improvement. 

The backing plate still refuses to screw on. I don't think that the backing plate threads are metric since it screws more than halfway on with no problems and the part seems to be homemade anyway. I'm really blanking on what to do here, and I doubt my abilities to make an accurate backing plate as a first project. 
Any advice on what to do next? I saw on practical machinist someone used a fine lapping compound on the threads and screwed the plate back and forth a few times and got it to fit all the way on. Would this destroy the threads or is it worth a shot?


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## mksj (Oct 3, 2016)

Backing plates come semi-finished in that the thread and machining mating surfaces are already done, they are inexpensive ($60-70). The only thing that is necessary is to cut a step in the front of the plate so it matches the lip on your chuck. This is actually a good thing to do, as it gives a specific alignment of the plate to your machine. Once you have done that, all you need to do is make/use a transfer punch to mark the holes for the bolts that hold on the chuck, it is very easy to drill these on a drill press. These might be threaded into the backings plate, so you would need to get a tap for the chuck mounting screws.  This is one of the most basic steps in using a lathe, and is really the only practical way to fix your problem. If you let people know what lathe you have, the chuck and the size, people can provide you with more specific details.


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## PAturner (Oct 3, 2016)

I'm not sure where one might find these plates for that cheap. I'm coming up with prices in the 200 ish dollar range. The spindle size is 1-3/8", I'm not sure of the teeth per inch.


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## JR49 (Oct 3, 2016)

PA, as I said in my previous post, there are many members here willing and able to help you BUT, you need to provide them with more information.  I was about to say you need a pitch gauge, but actually all you need is a ruler to count the # of threads in one inch, both on the spindle, and on the backplate. Then you will know if the 2 threads are a match.  If they are, then you need to screw it on until it stops, and figure out what is causing it to stop.  No one can figure this  out for you without being there at your lathe.  I don't think that tiny gouge the needle is pointing to would stop the backplate from screwing on.  As far as the plate being homemade, I've made 2 backplates at home and they work fine.  You shouldn't be buying anything (except of course for some measuring, and indicating tools), until you figure these things out.  I apologize if I offended you with my tone, but I'm sincerely trying to help.  Good luck,  JR49


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## RJSakowski (Oct 3, 2016)

PAturner said:


> After many hours of scrubbing, vinegar, and lubricating, there has been no improvement.
> 
> The backing plate still refuses to screw on. I don't think that the backing plate threads are metric since it screws more than halfway on with no problems and the part seems to be homemade anyway. I'm really blanking on what to do here, and I doubt my abilities to make an accurate backing plate as a first project.
> Any advice on what to do next? I saw on practical machinist someone used a fine lapping compound on the threads and screwed the plate back and forth a few times and got it to fit all the way on. Would this destroy the threads or is it worth a shot?
> ...


I don't believe that you have told us the make and model of your lathe.  That will go a long way in enabling us to help you.  

Check spindle thread diameter and thread pitch carefully.  Grizzly, for example has been known to mix English and metric units for spindle diameters and pitches.  1-3/8" is very close to 35mm.  You could get a reasonable facsimile of the internal pitch by pressing some modeling clay into the threads and carefully removing it.  Compare to the spindle threads.  

I don't recall your mentioning trying the bluing.  This will definitely tell you where the interference is.


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## PAturner (Oct 3, 2016)

Here's where I'm at now. I'm sure the threads are a match as I've FINALLY gotten it to thread on- it's now running much truer but still slightly out- maybe as good as I can get with a 3 jaw. I did discover two things:
The previous owner made the backplate very poorly. He didn't cut away the threads to fit onto the register, and didn't cut the diameter properly to fit the recess of the chuck. So, seems like I'll need to acquire a new plate.

As far as the lathe itself goes, I have no idea what it is. People here seem to think it was built in the early 1900's but I've been unable to find a manufacturer. I believe the spindle to be 1 3/8" in diameter and 8 TPI so I'll begin looking for a new plate.
Thank you for all the help!


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## John Hasler (Oct 3, 2016)

PAturner said:


> As far as the lathe itself goes, I have no idea what it is


Post some pictures.


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## PAturner (Oct 3, 2016)

I posted pictures in another of my threads a while back. 


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## francist (Oct 3, 2016)

Some photos of the lathe show up here in an earlier post. Maker unknown, only the dealer tag is evident. An accurate measuring of the spindle diameter and threads per inch might be a way to help ID the machine though. I've heard from other sources that some old Flather lathes used 1-3/8" spindle diameters and in around the 8 to 10 tpi range. 

Here's the earlier post:

http://www.hobby-machinist.com/thre...ning-and-other-tips-needed.49830/#post-419364

-frank


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