Lateral Spindle play causing Chatter SB9 Junior?

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ShagDog

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When turning with my SB9 Junior, I get some chatter and rough with what appears to be an oscillating vibration on the lathe. Thought it was the way the self contained motor unit is mounted; but that has been redone and is not the issue. For more info on this lathe, see this thread https://www.hobby-machinist.com/threads/sb-9-junior.107014/ .

Yesterday, I finally figured out that there is about .005 to .006 movement side to side on the spindle. By side to side, I mean toward and away from the operator. Up and down movement is less than .001, which might be where it should be set (not sure on a 1928 Junior with bronze bearings). Will check the end play today; but , I don't know if the side to side play has much to do with end play adjustment. Will also remove part of gear train to check tightness of the headstock mounting bolt, although I doubt it is loose.

This junior has aftermade bearings. I still have the old bearings which I may try . Here are photos of the spindle. I would really appreciate input on possible issues to check before I tear it down.
 

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I neglected to mention that the chatter is pretty much eliminated when I take heavier cuts of say over .025". which further leads me to think that it is the lateral play in the spindle causing the problem.
 
benmychree said:
Yes, that would likely cause a problem The lateral clearance should be the same as the up/down clearance.
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I was hoping to see you respond to this thread. I would agree that the clearance should be the same. Real question is how to adjust it, if possible. I am trying to avoid tearing down to see the issue. However, it becomes more likely that I will have to do so. It is a different set up from my 9a that I tore down about 2 years ago.
 
Here is another photo.
 

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I had a similar SB many years ago, but with QC and automatic apron, but the bearings were the same type and badly worn, as was the spindle, I had the spindle hard chromed and reground and made new bearings out of 660 bronze, I also relieved the center of the bearing seat to allow oil to flow around and under the bearings and cut a slot in the bottom of the bearing and inserted a piece of hard felt to strain and feed oil to the bearings, which were scraped to fit the spindle and shimmed for clearance. The bronze stock was split in half and the halves soft soldered together before finishing. I see no way to adjust your bearings for lateral clearance.
 
I have had a similar problem with my heavy 9, similar headstock to yours. I think mine are aftermarket/ DIY bronze bushings as they're two piece vs. the original one piece bushings. Also the chuck end bushings are a sloppy fit in the headstock, as there was a brass shim all the way round when I first took it apart. Good fit on the spindle though, best as I can tell. In my case I took a little bit of material off the underside of the top cap and shimmed the sides of the bushing, which allowed me to tighten things up a bit. That plus increasing the end preload using the threaded ring at the other end of the spindle reduced the play considerably, down to around 2 thou side to side and 1/2 thou up and down. Harder to turn the spindle now but it doesn't heat up and the finishes are much better.
 
Well, I went out and tightened spindle end headstock mounting bolt, and it tightened slightly. I then went to tighten the gear end of the headstock mounting bolt, and damn it was tight and I broke the mounting bracket when I tried to tighten more :rolleyes:.

Nevertheless, I measured the side to side play after running the lathe a little to warm up the bearings. Some progress. Before the spindle would move toward me and away from me for a total of about .005 - .006. Now, it only moves about .0005" away from me and about .0035" toward me. I then set the bearing clearance to almost .001", and the end play was okay; but, no improvement over the .0035 side play.

I took some test cuts, very light material removal due to the headstock only being bolted down on the spindle end. Chatter is gone. Now I need to make a bracket to replace the original cast iron one I broke.

I would still like to get the side play out down to .001". At least now it is only side play as opposed to side to side play. Ideas and suggestions welcome.

EDIT: Made a rookie mistake when measuring the movement of the spindle. Left the belt on and tight. Loosened the belt and now there is back and forth movement again. About .0025" pushing and about .0015 pulling. Actually, as I think about it, this might be better since I am getting closer to the .001" clearance I am trying to achieve. Maybe that is why the chatter appears to be gone.
 
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Matt, I was also hoping you would respond to this thread. I was typing my response when you sent yours. Thanks for the input.
 
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