# South Bend 9a new gap between chuck plate and spindle



## dansawyer (Apr 7, 2020)

The machine is a 1945 South Bend 9a. I recently removed the chuck for some 4 jaw work. When I replace the 3 jaw I noticed a gap between the chuck and the spindle ridge. It was an real drill to remove the 3 jaw so I spend a lot of time looking at it, I do not recall the gap. 
Now there is a 1/8 inch gap between the 3 jaw plate and the spindle ridge. The chuck 'clicks' upon seating so I am reasonably confident it is on. But I do not remember the gap.


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## DavidR8 (Apr 7, 2020)

Can you shoot us a photo?


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## dansawyer (Apr 7, 2020)

Pictures attached. Thank you in advance. Dan


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## DavidR8 (Apr 7, 2020)

Has there been any increased run-out in chucked up stock?


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## benmychree (Apr 7, 2020)

Look for chips stuck in the threads inside the chuck backplate.


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## Low tech (Apr 7, 2020)

benmychree said:


> Look for chips stuck in the threads inside the chuck backplate.


Exactly 
 Two chucks for my Logan lathe had that problem . I cleaned out the chips from the chucks and they both ran right up to the spindle register .


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## ericc (Apr 7, 2020)

Get a strong light and take a really good look.  Are you sure that that gap was never there?  I have that problem with a lot of my faceplates and backplates...from an old Atlas lathe.  None of them fit my South Bend 9.  When I get tired, I will sell one on Ebay or skim one so it fits.  I am very aware of any gap.  The tiniest of a gap can lead to a stuck chuck in the future.  It must seat tight against the shoulder without getting too tight on the threads.


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## dansawyer (Apr 7, 2020)

Thank you all 
First, I measured the runout at the chuck, it was about .001 at the chuck. I then measured the runout at 4 inches from the chuck, it was about .004. My take away is the chuck is not perpendicular with the spindle. That would map with the back plate not seating squarely. 
Second, I have a face plate. It appears to sit squarely on the spindle. As a note I can thread the face plate in reverse, I cannot thread the chuck back plate in reverse. 
I will check for chips.


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## dansawyer (Apr 7, 2020)

It was chips in the threads. The chuck back plate now sits squarely on the spindle. The runout is about 2 thousands at the chuck.  (It must have been a lucky fluke for the one thou reading). 
(The chuck jaws do not square with the spindle, there is now about 6 thou runout at 4 inches. )


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## graham-xrf (Apr 7, 2020)

Yes yes. Thanks much for this. I lurked, because I will be critically checking out my 9A soon.

From what I gather so far, chips in the threads stopped the chuck from seating home, but the alignment was better when it was stuck on the chips compared to when cleaned up so that the back face mated.

When we say "runout". Several kinds I read about.

1. There is runout, axial and radial, from when you put a dial indicator to the face and the radius of the chuck itself.

2. There is runout on a drill rod, or some other rod known to be accurately ground, put in the chuck, and you try the dial indicator close to the chuck, and also some inches away.

3. There is runout from a MT3 test bar put into the taper of the spindle. Checked first if you want to diagnose the chuck.

I have to check what might be a typical norm for a SB9A in reasonable condition, but I am pretty sure numbers like 6 thou means it is not yet right. I think the threads are supposed to be regular symmetrical. If you can't put the chuck back plate on in reverse, look hard at the threads of both spindle and chuck. Something is biased to one side.

Short of taking a damaging whack, it might be that using the chuck under load, when it was not fully home, locked up onto chips in the threads, may have had it doing a little high force axial banging wobble, impacting on the chips, and  "modifying" the chuck somewhat. A pure speculation on my part - but you got me thinking!


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## Manual Mac (Apr 7, 2020)

Maybe take the chuck off the back plate, check runout of the backplate.
Re fit the chuck if you have to?
EDIT I have a SB 9 also, have fitted a couple chucks to back plates and they run very true.


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## SLK001 (Apr 7, 2020)

This is a lesson on ensuring that your chuck threads are clean _before_ you put it on.  The fact that the 3-jaw was "a real drill" to remove leads me to believe that it, too, had chips in the threads.  

The OP is lucky.  Chips in the chuck threads can make removal of the chuck nearly impossible, especially if the chuck had difficulty going on.  Stuck chucks have had to be TURNED off to recover usage of the lathe.  

A chuck should easily spin on it's intended lathe.  If there seems to be resistance, remove the chuck and clean the threads again.  A 3-jaw can hold chips hidden from view and fall out while it is spinning on.  A really dirty chuck should be disassembled and thoroughly cleaned before use.  Run the spindle in reverse and put a toothbrush on its threads to clean it up, too.


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## graham-xrf (Apr 8, 2020)

Even after you have done your best, I think you only finally drive it home if you regrind the jaws to eliminate "bell mouth wear". There is a ton of videos on YT on how to do it, using every kind of router, Dremmel, apparently anything with a motor, and at least one strapped to a plywood jig with cable ties. Also, various trick ways to hold the jaws open, disc in the back, wide rings, etc.

Stopping the grinding dust getting where it shouldn't would be a problem, and I have not yet attempted such, although I must admit, I have thought about it. So far, for me, I am happy to carefully and completely clean, lubricate, and re-assemble the chuck(s), and the threads they go on.

I am going to invest some time and quality marine ply into making up chuck carrier holders with handles that can sit on the ways, and allow the chuck to be offered up for threading onto the spindle. The dings I can see probably came from dropping a chuck.


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## dansawyer (Apr 11, 2020)

Update on this: The chuck is mounted on the back plate with 3 screws and therefore only 3 combinations. The best was 3 thou runout as measured with a dial indicator and a section of drill rod. 
I then remove the chuck and mounted the drill rod to the spindle via a collet. This measured less than but close to a thou. It would seam that there is some runout in the spindle. 
I do not see a way to improve the chuck.


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## SLK001 (Apr 11, 2020)

dansawyer said:


> The best was 3 thou runout as measured with a dial indicator and a section of drill rod.  I do not see a way to improve the chuck.



Did you face the back plate before you put on the chuck?  Also, just because there are holes in the BP doesn't mean you have to use those.  Just put in three new holes.


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## graham-xrf (Apr 11, 2020)

Check the spindle without the chuck. Discover if the face the chuck will mate with has run-out. Even if it has, it need not be a problem if you face the back-plate while on the spindle.

Check also for radial run-out on the spindle - just in case it is something to do with the spindle bearing. A bit far-fetched, but you should be able to get to the point where you know exactly the state of all measures and alignments, and then choose a fix.


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## dansawyer (Apr 12, 2020)

Thank you all for your input, it is helpful I have done extra testing. 
First, after removing the chuck the spindle itself is good. The inside edge where an MT3 collet would sit is on the order of half a thou. 
Second, the outer lip of the spindle where the chuck would mate is also on the order of half a thou. 
Third, placing a drill rod in a collet in the spindle shows just over one thou on the drill rod. This could be either the from the collet or the rod itself.
Finally, after cleaning the chuck and spindle threads and carefully seating the chuck the drill rod measures about 2 thou. 
Based on the above I am assuming the run-out is the sum of the spindle, the chuck, and the drill rod itself. My next step is to take a piece of rod and carefully remove a small amount and check for equal radius round and end to end. The proof of the pudding ...


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## SLK001 (Apr 12, 2020)

dansawyer said:


> My next step is to take a piece of rod and carefully remove a small amount and check for equal radius round and end to end. The proof of the pudding ...



All this will do is hide the runout.  Repeat the runout test with the drill rod in the chuck.  Mark the "highest" point with a Sharpie on both the chuck and the rod.  Now rotate the drill rod in the chuck 90º and repeat.  If the mark is in the same place on the chuck, the problem is with the chuck.  If it moves with the rod, the problem is with the rod.


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## MrWhoopee (May 15, 2020)

dansawyer said:


> Finally, after cleaning the chuck and spindle threads and carefully seating the chuck the drill rod measures about 2 thou.



This is as good as you can reasonably expect from a 3-jaw unless it's an Adjust-Tru. Trying to get it closer is doomed to failure.


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