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Southbend 9a problem with back gear I rebuilt this, and am not sure what's happening

woodchuckNJ

Cast Iron
Joined
Jun 7, 2014
Location
NJ
I rebuilt this lathe, and it's been running fine until tonight. While working on cutting threads and using the back gear things got heated up and I broke my leather belt.

While using the back gear and also supporting the shaft using a tail stock the bull gear on the head stock is now providing friction to the pulley cone. Only when I use a tail stock with pressure.

Looking for ideas.. I can't take it apart until I finish my project. It got pretty hard to turn while the back gear was in. If I take the back gear out it's free to turn.

The bullgear pin is not even engaged, but it acts like it is. Take the tail stock pressure off and it's fine. and free wheels w/o the pulley turning.

Thanks for any help

Jeff
 
Taking a stab in the dark at it. There are two ways of driving the spindle, open belt or back gear (stating the obvious, I know). Open belt uses the pin I think, and you remove the pin for back gear. That gear that you pin has to move freely when the spindle is in back gear. (Try leaving it pinned with the back gear engaged- not actually recommended - the spindle won't move very far before it locks up).

Can't speak for South Bend but I know on the Sheldon there is a set screw in the spindle pulley. You take out that set screw and add oil, there is sort of an oil reservoir there. It is meant to lubricate between that pinning gear and the rest of the spindle. If that gets to the point where it won't turn freely, you will have trouble running in back gear. Found that out the hard way on the Sheldon, took some research to find out about the oil point there (thought the set screw was just to help hold the pulley to the shaft). Its a PITA to add oil, because you have to make sure to keep it clean of oil when finished, otherwise your belts could slip.

Hope this helps, it is a bit of concern that you would have a problem when pressure is applied from the tailstock, like maybe a bearing getting bad. Hopefully the oil will solve it.
 
I rebuilt this lathe, and it's been running fine until tonight. While working on cutting threads and using the back gear things got heated up and I broke my leather belt.

While using the back gear and also supporting the shaft using a tail stock the bull gear on the head stock is now providing friction to the pulley cone. Only when I use a tail stock with pressure.

Looking for ideas.. I can't take it apart until I finish my project. It got pretty hard to turn while the back gear was in. If I take the back gear out it's free to turn.

The bullgear pin is not even engaged, but it acts like it is. Take the tail stock pressure off and it's fine. and free wheels w/o the pulley turning.

Thanks for any help

Jeff

I'd say the issue is most likely galling between your pulley cone and spindle.
 
Ok, I thought about it all night, I think I know where the problem is. If I remember correctly the casting for the head stock had the collar for the main shaft worn down. So the shaft is not held far enough out, which is probably not giving the bull gear enough free play. I need to build a shim to hold the shaft out. The landing on the shaft wore the cast iron down, and probably has continued to. So the question is what to use as a shim, I don't think brass will last long enough, is there something with a good lube property and easy machine ability. It will need to be a ring about 2" id land 2.5 od I'm guessing. I only have the lathe, drill press, and some wood working tools.
 
Memory didn't serve me right. The casting was worn on the gear side , not the chuck side.
No galling. The bull gear was up against the landing of the shaft.
Still perplexed.
SDC11467.jpgSDC11466.jpg
SDC11465.jpgSDC11464.jpg
 
Note: There should not be any pressure between the bull gear and the pulley. The lateral pressure is against the spindle to the rear thrust bearing directly. If the bull gear is contacting the pulley, Use a spacer between the bull gear and the pulley when pressing the shaft back onto the bull gear . Once the bull gear is completely seated to the shaft the cone pulley should rotate freely regardless of tailstock pressure.

Stay safe and have fun.

Joe.
 
Thanks, are you saying a permanent spacer or a temporary spacer?
If perm won't that just create more pressure from the cone to the bull gear?
I know I had good spacing when I originally assembled it as you could hear it rattling the cone I believe.
Now I'm not hearing that rattling.
 
Thanks, are you saying a permanent spacer or a temporary spacer?
If perm won't that just create more pressure from the cone to the bull gear?
I know I had good spacing when I originally assembled it as you could hear it rattling the cone I believe.
Now I'm not hearing that rattling.

A temporary spacer.
 
I reassembled it tonight, used a brass spacer on two sides of the shaft between the bull and cone.
Seems like I got the space back and then I finished putting things back and things seemed tight again.

I am grasping at straws here, but is it possible that my grease is packed too tight, or that I am using too heavy a grease?
I am using lubriplate 930-AA ... for the cone to spindle lube. Originally I didn't use much lube, as I assembled using a dry teflon lube. Could I be packing this too much and causing a problem? I didn't think I was pushing too much in,but I am out of options.
 
Only used the type of Oil/grease specified for your machine by South Bend, you can also use Super lube. Do not use anything else.

You need to take it apart again And clean out all of that Greece. Re-Lubricate with the proper lubricant and reinstall it.

Stay safe and have fun.

Joe.
 
I rebuilt this lathe, and it's been running fine until tonight. While working on cutting threads and using the back gear things got heated up and I broke my leather belt.

While using the back gear and also supporting the shaft using a tail stock the bull gear on the head stock is now providing friction to the pulley cone. Only when I use a tail stock with pressure.

Looking for ideas.. I can't take it apart until I finish my project. It got pretty hard to turn while the back gear was in. If I take the back gear out it's free to turn.

The bullgear pin is not even engaged, but it acts like it is. Take the tail stock pressure off and it's fine. and free wheels w/o the pulley turning.

Thanks for any help

Jeff

During your rebuild, did you change the spindle or cone pulley?
The trust bearing should not touch the cone pulley(gear on the end). There should be clearance there of about .002". I would assemble the spindle on the bench(bull gear and cone pulley) to make sure the shoulder of the spindle sticks out ~.002".
Ted
 
Interesting - I've noticed on my 1938 9" Workshop, the same phenomenon; trouble turning when applying pressure from a tailstock center.

But the spindle on mine is different - it doesn't have the oil slinger/swarf collar (Ted - what's the correct term?). Without that collar, the spindle is not constrained from moving towards the thrust bearing and either applying tailstock pressure or snugging up the takeup nut will force the cone pulley up against the bull gear, as the cone pulley, of course, floats axially along the spindle. But with the spindle collar present, applying tailstock pressure or snugging up the takeup nut only forces the collar against the right-most surface of the headstock. The length of the cone pulley, the thickness of the thrust washer assembly, and the thickness of the bull gear are designed to allow the cone pulley to float axially on the spindle - I think that's what Ted is getting at.

So, if the problem is still being exacerbated by tailstock pressure, I would start by looking at the interface between the spindle collar and the headstock, making sure that the spindle collar isn't somehow displaced/bent. As far as lube, I'd get rid of the grease and just oil it. And do make sure that you've got the bull gear up tight against the shoulder on the spindle. I think you can push the spindle towards the headstock to open up a small gap and using a feeler gauge and a flashlight, check for correct seating of the gear.

Paul
 
If the washer that you are referring to is just behind the threaded portion of the spindle that the Chuck screws to , that washer should never touch the headstock casting. 100% of the load should be transferred directly from the spindle to the thrust bearing on the left side of the cone pulley. You may have a problem with your thrust bearing. Check the parts manual for your lathe. There should be a shoulder on the spindle that pushes against the thrust bearing. The thrust bearing consist of a inner race, a ball bearing cage and a outer race. Make sure you have the proper bearing installed.

Stay safe and have fun.

Joe.
 
- it doesn't have the oil slinger/swarf collar (Ted - what's the correct term?).
Paul

Protecting ring. Like Joe said, it should not touch the headstock. It should be close, the closer the better, but not touch. :nono:
It is movable (light press fit on the spindle). This goes for all size South Bend lathes with the threaded spindle.
Ted
 
Pardon me while I wipe the egg off of my face. I had to look on ebay, to find a picture of a 9" spindle, since it's been a long time since I've seen one. I forgot that there's a shoulder that the thrust bearing race butts up against. Listen to the collective wisdom of the others - the only way that tailstock pressure could be causing binding is if the bull gear is not seated, your thrust bearing is bad, or some of the headstock components are not original. If I say anything else that's ludicrous, please call me out on it guys.

Paul
 
If using a chuck to hold your work, and a dead center in the tail stock, you will get a binding action in the spindle/headstock, if the tail is even slightly out of alignment, side to side or up and down. This usually goes away when the tail stock is released. If done often enough it will cause the chuck to "bellmouth". If turning between centers you won't have this type of binding happen.
 
Check in front of the bull gear between the flat face of the bull gear and the back of the front headstock bearing. If you have a large gap there your bull gear can move foreward. Stick a feeler gauge between the bull gear and cone pulley and the thrust bearing and cone pulley. If you can't get a 2 or so thou gauge in there you're bull gear is on too far/tight. You can fix it with the headstock in if you're gentle. Get a block of wood and put it against the bull gear from the cone pulley side. Give it a few taps. Move 180 degrees and a few taps. Recheck the gap. If you go too far stick in some shims and press it in again. I had to do this with mine when I had taken the spindle out to move the lathe to my new house. Then try putting moderate pressure with the tail stock. Everything should turn free. Also be sure not to over tighten the take up nut.
 
Check in front of the bull gear between the flat face of the bull gear and the back of the front headstock bearing. If you have a large gap there your bull gear can move foreward. Stick a feeler gauge between the bull gear and cone pulley and the thrust bearing and cone pulley. If you can't get a 2 or so thou gauge in there you're bull gear is on too far/tight. You can fix it with the headstock in if you're gentle. Get a block of wood and put it against the bull gear from the cone pulley side. Give it a few taps. Move 180 degrees and a few taps. Recheck the gap. If you go too far stick in some shims and press it in again. I had to do this with mine when I had taken the spindle out to move the lathe to my new house. Then try putting moderate pressure with the tail stock. Everything should turn free. Also be sure not to over tighten the take up nut.

I cannot recommend using this method. Tapping on the side of the gear could potentially crack your gear. A better method is two loosen the take-up nut, Place a block of wood against the end of the spindle, Then tap on the block of wood at the spindle. It produces a even pressure and less chance of damaging something.

Stay safe and have fun.

Joe.
 








 
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