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Excessive runout on Sheldon Lathe

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B1akeM

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#1
Hello!

I have a Sheldon model 3-R lathe. It has about 3 thousands of runout when measured using a dial indicator on the outside of the spindle taper which is certainly not great. I knew it always had some amount of runout but I always blamed it on the beat up jaws in the 3-jaw chuck. I never thought of checking the spindle. I'm not sure if it is common or even possible, but could the spindle be bent? Are there other things that would cause that amount of runout? I don't know the history of the machine, but I can tell that it has seen plenty of use. I'm wondering what to do now, and if I might be stuck with a giant paperweight.

Here are links to clips (vid1, vid2) that might help explain the problem.

Thanks
 

mikey

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#2
Have you checked the concentricity inside the spindle taper when not under power? It will be a far more reliable index of your issue. See the third to the last post here: http://www.hobby-machinist.com/threads/new-pm-1228vf-lb.62688/

There can be all sorts of artifacts when running under power so check concentricity correctly first. If it is unacceptable then you're likely looking at a spindle and/or a spindle bearing change.
 

4GSR

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#3
If the spindle was bent any at all, you would hear a "rumping" noise that would be in sync with the spindle rotation in the higher RPM's. You might try to tighten the spindle bearings, but doing so on the 3R will require pulling the cover on the headstock. Just behind the main bearings will be a takeup nut, bend the ear back on the bearing nut washer and tighten the nut by one notch. And be sure to bend over the ear on the washer into a notch on the take up nut. You should be able to check runout by hand before putting the cover back on the headstock.
What kind of finish do you get on your work? Is it rough? or is it a nice finish? This is not an easy headstock to change out bearings on if there is an bearing issue. There's a good chance someone has changed out the bearings with standard off the shelf bearings without buying precision class bearings for replacement. Let's hope not. Watching the two videos I suspect the spindle is slightly out of adjustment. It could have left the factory this way and never re-adjusted.
Let us know how you make out. Ken
 

B1akeM

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#4
If the spindle was bent any at all, you would hear a "rumping" noise that would be in sync with the spindle rotation in the higher RPM's. You might try to tighten the spindle bearings, but doing so on the 3R will require pulling the cover on the headstock. Just behind the main bearings will be a takeup nut, bend the ear back on the bearing nut washer and tighten the nut by one notch. And be sure to bend over the ear on the washer into a notch on the take up nut. You should be able to check runout by hand before putting the cover back on the headstock.
What kind of finish do you get on your work? Is it rough? or is it a nice finish? This is not an easy headstock to change out bearings on if there is an bearing issue. There's a good chance someone has changed out the bearings with standard off the shelf bearings without buying precision class bearings for replacement. Let's hope not. Watching the two videos I suspect the spindle is slightly out of adjustment. It could have left the factory this way and never re-adjusted.
Let us know how you make out. Ken
Thanks for both of your replies.

The surface finish is fine actually, it's the entire part that is oblong. I will try to get a good look at the bearings tonight and see if they need tightening. I will also check the concentricity inside the spindle and see if I get a different numbers. Hope to report good news.

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4GSR

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#5
If you have a parts breakdown of the headstock, it will be items 26 and 27.

Ken
 

B1akeM

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#6
Update:

I checked runout from the inside of the spindle, still getting ~0.0015". I also checked the runout from the other end the spindle and got identical results when measuring both the inside and outside. This leads me to believe that it has something to do with the bearings, although I am not 100% certain. Also, I think that I need to make a special spanner if I want to tighten the take up nut. I could have done it with a screwdriver and a hammer, but I figured I should probably do it the right way so that I don't cause any problems. I included pics of my method for measuring the inside of the spindle, I am sure it is not ideal but I only have 1 dial indicator. Also have pics of headstock and the unlucky dog gear that most likely experienced the wrath of an impatient operator. Hopefully this gives some idea of the condition of the gearbox (and possibly the bearings).

Headstock:



Measuring inside spindle (hopefully correctly)



Dog Gear:




Thanks again,
B1ake
 

mikey

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#7
0.0015" of run out seems excessive to me. I will defer to Ken but I do wonder if you can adjust the preload on the spindle bearings to minimize that number. Also, at some point you might consider buying a dial test indicator. I am not sure how reliable a dial indicator is when used as you're doing; something tells me there will be an error.
 

4GSR

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#8
Mikey is right, you need a test indicator that needs to read in tenths for checking this with. At least one that reads in 0.0005" increments. I did check the runout of my 15" Sheldon lathe a while back, which has the same head stock, and I was getting close to .0005" T.I.R.. I see this being normal for most older lathes.
Making a spanner is ideal but not necessary for adjusting the takeup nut with. A big screwdriver may work, get a piece of 1/2 OD mild steel rod and a 12 oz ball peen hammer and give it a couple of sharp blows and see if it moves. Be sure to tighten toward you. And also be sure to adjust the nut to the right of the shifter in your picture not the one next to the bull gear.
 

Doubleeboy

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#9
The dial indicator in message above is at an angle to the spindle bore, not a good situation for accurate readings. Like the guys said, get a test indicator.
 

B1akeM

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#10
Thank you for the advice, friend is willing to let me borrow a test indicator on Monday and will check the spindle again. Hopefully I can get that takeup nut tightened tomorrow.

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mikey

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#11
Thank you for the advice, friend is willing to let me borrow a test indicator on Monday and will check the spindle again. Hopefully I can get that takeup nut tightened tomorrow.

Sent from my Pixel using Tapatalk
May I suggest you take your concentricity readings before and after adjusting your spindle bearing preload?

I don't know how to adjust preload on a Sheldon lathe but I'm sure Ken does. I did want to relate how Emco does it on their Austrian gear head lathes in hopes that it will give you another option.

They put the lathe in neutral - out of gear and with the leadscrew and feed screw gears disengaged. With a 3 or 4 jaw chuck mounted, grab one of the jaws and give it a strong spin. Adjust the preload until it gives you one revolution with that spin, not more and not less. This comes from an Emco engineer at the factory so as simple as it sounds, it works for them. My lathe runs cool at the bearings and has zero run out so it also seems to work for me.
 

B1akeM

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#12
May I suggest you take your concentricity readings before and after adjusting your spindle bearing preload?

I don't know how to adjust preload on a Sheldon lathe but I'm sure Ken does. I did want to relate how Emco does it on their Austrian gear head lathes in hopes that it will give you another option.

They put the lathe in neutral - out of gear and with the leadscrew and feed screw gears disengaged. With a 3 or 4 jaw chuck mounted, grab one of the jaws and give it a strong spin. Adjust the preload until it gives you one revolution with that spin, not more and not less. This comes from an Emco engineer at the factory so as simple as it sounds, it works for them. My lathe runs cool at the bearings and has zero run out so it also seems to work for me.
Good point, I don't mind waiting until Monday. I imagine using the chuck to gauge tightness can get you pretty close but on the Sheldon there are 2 nuts that can be adjusted. I am not sure how to tell how tight each bearing is, and if I'd run the risk of overtighting one. The bearings run cool right now too.

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wa5cab

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#13
I strongly suggest that you not just arbitrarily tighten up the spindle bearings until you have read the procedure for checking whether it needs to be done and how to properly do it in the manual on your lathe. If the bearings are too loose, tightening them will probably fix it. But if they aren't, the only thing that tightening them is going to accomplish is to make them run hot.

With your dial indicator set as in one of your photos, push and pull on the spindle nose without touching the indicator. If the needle moves, they are too loose and should be tightened. If it doesn't, they probably aren't.
 

4GSR

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#14
Good point, I don't mind waiting until Monday. I imagine using the chuck to gauge tightness can get you pretty close but on the Sheldon there are 2 nuts that can be adjusted. I am not sure how to tell how tight each bearing is, and if I'd run the risk of overtighting one. The bearings run cool right now too.

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There is only ONE nut to adjust. Read my post above and follow! The adjusting nut only needs to move about a 1/16 of a turn. Anymore than this could make your bearings too tight!!! And run hot and damage the bearings!!! These Timken bearings are UNTAINABLE at any price, unless you want to put wheel bearing grade bearings in your headstock!
 

B1akeM

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#15
Ok, thanks for letting me know. I understand that spindle bearings are very finicky, and would not try something without confirming it here first. I was just making sure that the nut closest to the right was the correct one to adjust. I have a fraction of the service manual that I got when I purchased the machine, but most of it is completely illegible. It looks like it sat somewhere wet. Where can I find another one?

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4GSR

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#16
Here's a link to the manual for the 15" Sheldon lathe. The only thing it will not cover is the turret and carriage assembly for the turret lathe. Everything else is exactly the same. I haven't yet found a service manual for the turret lathe. You can contact B & K and see if they have a manual or any maintenance information for the turret and carriage for the 3R lathe. Probably cost you upward around $150 for a 12 page manual!

http://www.hobby-machinist.com/reso...s-manual-for-15-precision-sheldon-lathe.3184/

Ken
 
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