Sheldon Sebastian 13" Gear Head Headstock Issue

[Jahue]

I have spent most of my time over on the yahoo forum... so I hate to duplicate questions but I am in need of assistance...

At this point in my restoration I have the QCGB off and getting ready to replace a broken gear, I replaced the pulley on the motor and changed out the belts. The only thing currently attached and running on the machine is the headstock. I am now chasing a vibration / thump issue in the headstock that has me scratching my head. So the runout on the spindle is about .0003 give or take a hair. But when running the machine between 600 and 900 rpm I get vibration that shakes the machine (leveled and double checked on solid concrete foundation). I also get a thump that I can feel but the thump only happens at an interval of about 1 -1.5 seconds. The gears are in good shape, no dings, no trash, no rough spots. I can't feel it below 600. I know I can just run it below 600, but I have come this far!



I would assume if it was the headstock spindle bearing I would see that in the runout test, so for now I am holding my breath that those bearings are fine. Could one of the other bearings in the headstock cause this?



If so, I would assume the drive set to be the most susceptible. If I am correct the other issue is can that bearing be replaced without removing the spindle. How does it come out? If I do have to remove the spindle, is there any danger in making anything worse?



Thanks.



I am also in the process of making the input gear for the QCGB its a phenolic presses onto a steel hub. If anyone in interested I can get you the specifics. BTW the gears are 20degree with a 12 diametrical pitch.

 

[4GSR]

Say, did you have any responses from anyone else on the bearing numbers I provided you the other day by email?

 

[Jahue]

No, not yet. So far I just have your numbers. But the back numbers are identical.

 

[4GSR]

One thing I forgot to mention. If your bearing guy has good connections with Timken, they should have record of whose machine tools use this bearing series on hand. At least they used to. Be worth a call to see. This would verify if the bearing numbers are correct. B & K may share bearing numbers with you too. May send John Knox a personal email or call him and see if he can shed some light on the bearing numbers. Ken

 

[Jahue]

So I am still tracing down the front bearing... I am also trying to make sure my issue is bearing related. In the pictures you can see the pattern that is made when any part is turned at any speed. And to eliminate the possibility that it might be the carriage, headstock gears, or the motor I ran the lathe with a drill and slowly hand feed the carriage to make sure the pattern shows up under and condition. From there I took the spindle out which was way easier than I expected. I wanted to see if the Cup and Cone were damaged, at first glance they look fantastic for 60+ years. But when you look really close you can see an almost wavy pattern in the cup only detectable if you get in the right light, you can't feel it. I have a back bearing coming 650$ but I still can't find the front. Anyone have any ideas? If I can't get the front is it ok to change out the back only, or will this damage an expensive bearing? Anyone seen this in a spindle before?

 

[wa5cab]

If by back bearing you mean both cup and cone of the left bearing, no, that will not hurt the right bearing.

 

[Jahue]

If by back bearing you mean both cup and cone of the left bearing, no, that will not hurt the right bearing.

I mean the back spindle bearing in the rear of the machine, The one at the chuck is larger bearing and is almost impossible to find. Both have similar issues, but the back bearing the one in the rear of the machine I can get in a Class 0 or Class 3. Thanks!

Edit: I think I read your reply wrong, that would be the left bearing, if the right bearing is the one near the chuck.

 

[wa5cab]

OK. I just wanted to be sure, (as there were only photos of the right cup and cone (nearest the chuck)) that you weren't referring to the right cone and cup as being the front and rear bearings. The answer to "that" question is different. Because of the way that a lathe is operated, I have always thought of "front" as being the side nearest to the operator and "back" or "rear" as being the other long side, away from the operator.

 

[Jahue]

I See, this is the picture of the back/ left of the machine.

 

[4GSR]

The lines that you are getting in the work piece is not spindle bearing related.

You have a wear issue with the saddle to the bed of your lathe causing this.

The rear bearing of your lathe is fine, it doesn't need replacing. The front bearing, well looks good except for the funny places as shown in your picture, is a different issue and again is not causing the lines you are getting in your work piece. I think what you are seeing is a bearing cup that was not fitted properly in the headstock housing as it came from the factory. Unless, someone has been into the headstock over the years and replaced the bearings and did not get the cup seated properly. It could also be from a improperly adjusted bearing from years of running. I never saw this issue from my 13" Sheldon Sebastian lathe that I had when I tore it down for repairs when I receive it. The bearings showed a good wear pattern as your rear bearing shows. This is normal and common with any tapered roller bearing of any size or precision. If you were to replace a bearing, it would be the front bearing. How does all of the gears look in the headstock? I see in your last picture a glimpse of the herringbone gear that causes most of the noise that comes from this headstock.