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Sheldon Sebastian 13" Gear Head Headstock Issue

Discussion in 'QUESTIONS & ANSWERS (Get Help Fast Here!)' started by Jahue, Jan 31, 2017.

  1. Jahue

    Jahue United States Iron Registered Member

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    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.
     
  2. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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

    Jahue United States Iron Registered Member

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    No, not yet. So far I just have your numbers. But the back numbers are identical.
     
  4. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    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
     
    Last edited: Feb 8, 2017
  5. Jahue

    Jahue United States Iron Registered Member

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    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?
    IMG_6582.JPG IMG_7153.JPG IMG_7166.JPG
     
  6. wa5cab

    wa5cab Downloads Moderator Staff Member H-M Supporter-Premium

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

    Jahue United States Iron Registered Member

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    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.
     
  8. wa5cab

    wa5cab Downloads Moderator Staff Member H-M Supporter-Premium

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    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.
     
  9. Jahue

    Jahue United States Iron Registered Member

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    I See, this is the picture of the back/ left of the machine.
    IMG_7143.JPG IMG_7144.JPG
     
  10. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    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.
     
  11. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    I thought about this a little more. The front bearing issue is not from an improperly fitted cup. This is from a bearing running loose over time. When I say loose, it may have only been a half thousandth to a couple of thousandths loose, hard to say. There is a fine line on adjusting this bearing arrangement. Always start off with the adjustment tight. Not so tight the spindle does not turn easily. Run the spindle as a medium RPM say 350-375 for this lathe. When the bearing housings get warm to touch, back off the adjustment about a 1/8 of a turn. Run again and see if the temperature goes down a little. This is where a digital thermometer can be helpful. If it goes down a little, and it should, Takes some cuts and see how it does.
    You want the bearings adjusted to where is -0- zero running clearance in the bearings. Trying to adjust using a .0001" dial indicator is not going to work. May help in determining of the bearings are loose, but that's about it. Ken
     
    Last edited: Aug 6, 2017
  12. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    Running the spindle in the 600 or 900 RPM range is not going to help you any, in adjusting the bearings, since it runs hot (100-160 deg. F) in these ranges anyways in normal use on this lathe. Another inherited issue with this lathe. After about 40 hours of running, if still hot when running in the 350-375 RPM range, back off the spindle nut another 1/8 of an turn. And run another 40 hours. If no change in temperature, it should be good. Next is watching the cutting pattern in your work. Of course, the lines you are getting are not going to go away until you rework the saddle to the bed ways. Okay? What you want to look for is linear lines in the work piece. This will either relate to gear teeth or the rollers in the bearings. Hopefully, neither of these will show up. Ken
     
  13. Jahue

    Jahue United States Iron Registered Member

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    I assumed the same thing, however the patten is perfectly uniform no matter where on the bed the tool is cutting. If I move the saddle out and use my big boring bar the lines show on the inside. If I cut near the end on a very long bar they show. And the pattern is exactly the same the entire length of cut. Wear in the saddle would change the pattern, given that the machine would not have worn consistently. So the pattern showing absolutely uniform over the entire length means it can't be wear in the ways. The pattern also shows up if I hand feed the saddle and put the feed in neutral taking out the apron worm gear entirely. I have also adjusted all the gibs. I know the ways are worn, because the machine is noticeably tighter near the far end. But I still get the pattern there.
     
  14. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    It's in your saddle. It starting to have enough wear that it is riding high on top of the ways instead on the vee as it should. If you have a mill, go in and mill the relief at the bottom of the vee a little deeper and maybe a few thousandths wider, too. Next look for the ridges that are starting to show up on the edges of the vee's and flat. Take a flat file and carefully file them flush with the adjacent surfaces. Then lightly hone the surfaces to get rid of any high spots missed. Go back together and try some cuts and see if you get better results. Ultimately, this needs to be rescraped and fitted. Since you said the bed has some wear, this would be a waste of time to try to rescrape and fit without regrinding the bed.

    As I've said many time over, your spindle bearings are fine for now. Spindle bearing like the tapered roller type when worn or damage from excessive use create a whole different set of issues that show up on your work piece. And I don't see that in the posted pictures.

    Ken
     
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  15. Jahue

    Jahue United States Iron Registered Member

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    I will check it, however the other machine I have which is identical has a crap ton more wear and abuse on in, and it doesn't show the same thing. It cuts beautifully. I still wouldn't think that wear in the saddle would produce a perfectly uniform pattern in the work down the entirety of the bed.
     
  16. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    Check it out and let us know what you find. Also check the leadscrew and see if it is bent. It could be lifting the carriage a tenth or two causing the lines in the work. The worm in the apron that rotates off of the lead screw could be causing some funny things that show up on the work piece rather its feeding or not. It could be moving the carriage around. Just have to go down a list and mark off things that you check.

    Is your other lathe a Sheldon Sebastian Lathe, too?
     
  17. Jahue

    Jahue United States Iron Registered Member

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    I went back and checked the saddle, I haven't fully pulled the saddle but looking from both ends there appears to be about .002" of v in the saddle before relief groove. I also checked against the tailstock flat to see how much drop there is in the ways between the tight section and the section near the headstock. over the 24-28" near the head stock the ways drop maybe .0005 once you get to the tight section near the far end the drop.. or rise from the front is about .003" So near the headstock it is lower but its consistently lower. I checked this by putting a mag bas on the saddle and indicating off the tailstock flat.
     
  18. Jahue

    Jahue United States Iron Registered Member

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    Yes the other lathe is exactly the same, oddly enough the serial numbers are only about 75 apart.
     
  19. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    Okay. Pull the lead screw and put up in your other lathe and see how bad of runout you get.

    I know you posted over on PM, I watch over on that forum, too. You received some good responses from over there, too. Keep at it. You'll get to the root of the problem some day. If not, sell it, buy something else and move on. Ken
     
  20. Jahue

    Jahue United States Iron Registered Member

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    A partial update, the other machine I have access to is A-6 the one i'm working on is an A-5 identical except for the length. So I can't pull the leadscrew and swap them. But I have attempted to run some other diagnostics. The pattern shows up in all chucks new Bison 3 Jaw, Buck 6 Jaw, and 4 jaw. I haven't checked the 4 jaw this go around but I have in my previous tests. Yesterday I put a long bar in on the machine and maxed out the distance I used a high precision live center. On the end closest (last 1inch) to the live center the pattern appears to go away, as the tool cuts the pattern appears about 1.5-2" from the far end and is present the remaining distance. I checked a few things late last night but they seem inconclusive thus far. I pulled the support block for the leadscrew and with my hand at the lower speed held the leadscrew to keep it from whipping and made a cut near the headstock mostly to see if the leadscrew was in a bind. The pattern was still visible. I also tried the threading lever... still there. I then pulled the leadscrew completely and hand feed the best I could at a constant speed... and it seems to go away, I won't say yet that its gone, its hard to be consistent when hand feeding the apron. I'm going to try and rig up a small motor to see if I can drive it without the leadscrew more constantly.

    It's worth noting that I also quickly indicated the leadscrew near the gearbox and it runs out about .003, without the support on the other end, the other end runs out enough to see by eye. I did check the leadscrew with a very high end level (the straightest surface I could find) and it appears to be straight, even by eye it doesnt seem to be bent... I also did the roll test and it has no discernible wobble.

    My bigger question is, can I detect with a .0001 indicator the wobble in the saddle if I measure off the ways? Or is there a way to isolate and narrow it down to either the spindle or the saddle?
     
  21. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    Yes, you can set up and check for wobble in the saddle. It takes two dial indicators, I would think .001" increment is sufficient. They need to be mounted so they touch off, one at at the vee way touching the saddle at the vee, and the other at the flat touching the saddle at the flat. Rock the carriage handwheel back and forth enough to get readings on the indicators. Perfect alignment, they should read the same at all movements. If worn, both will jump around and not be consistent with each other. Check this at the chuck, midways on the bed, and at the tailend of the bed. Report back with your findings.
     
  22. Jahue

    Jahue United States Iron Registered Member

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    If the wobble is leadscrew related is it possible to measure the wobble while the carriage is engaged? So theoretically you could see the moment that is patterned into the work.

    Did you put class three spindle bearings in your machine?
     
  23. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    No, it's not leadscrew specific. You want to check this without the carriage engaged, feed or half nuts.

    As for class 3 bearings, I've never had to replace any spindle bearings in the lathes I've had over the years. My dad replaced a double row tapered roller bearing on the head stock of his Axelson lathe that was a class 3 bearing. The original bearing had water damaged from when the lathe was on a navy ship that was sunken in WWII and salvaged years later. You will never notice the difference between a class 3 or 0, 00 Timken bearing on a lathe. And we used to do some tool post grinding on that lathe that left very nice finishes, too!

    One other thing you can try related to the lead screw. Remove the leadscrew support on the tail end of the leadscrew. Engage the half nuts on the lead screw. Do this out on the tail end of the leadscrew. Slip the bracket back on the shaft and see how close the bolt holes line up. Should be pretty close if not right on. Also attempt this at the QCGB end of the leadscrew too. Since the lead screw will be hanging and flexing, this may be a little harder to detect alignment. If it's out any at all, it should magnify as a bunch of movement in the leadscrew when the half nut are engaged. Also, the leadscrew bracket may or may not line up very good, maybe even to the extent, that you can't get the bolts back into the holes.

    Is this the Quick Change gear box you replaced the gear in? If so, this could be your culprit.
     
  24. Jahue

    Jahue United States Iron Registered Member

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    Ken,

    I will check the alignment this afternoon. Yes it is the box I replaced the gear in, but the gearbox is tight on guide pins, I wondered if it had moved so I checked it and it can't go anywhere but straight off, no movement up or down or side to side. I also indicated the shaft at the gearbox without the lead screw and there isn't any play, maybe .001 -.0005 if I'm forcing it. I'm going to double check this again to be sure.
     
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  25. Jahue

    Jahue United States Iron Registered Member

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    Ok so I checked the alignment, with the half nut engaged it aligns perfect on either end, when you disengage the leadscrew drops maybe .03 or less, you can easily still put the bolts in but you have to put slight upward pressure. I replaced the bronze bushings in the apron but I kept the old ones so tonight I put the old ones back in which are 1.04+ vs the new ones 1.00... no change. The bronze bushings also let the worm gear slop around more so if I had it too tight its now loose... but it still patterns. The gearbox is next, but the new gear I made was turned on the spindle thats in the gearbox so I know that gear isn't wobbling. Not saying thats not it but. Im going to check the gears in the head stock and I may go through and replace all the non spindle bearings. I assume these don't need to be class 3.

    I sent timken the pictures and they are not sure if the bearing wear pictured would produce that particular pattern. I did check the preload on the other machine... when I take it out of gear and give the chuck a flick it rotates maybe 2/3 of the way around, the one I'm working on goes around maybe 1.5 - 1.75. The other machine is noticeably stiff. Not saying its not worn out but. As a note the bed on that lathe drops .08 over about 20 inches. and the ways are beat. But it cuts like a dream.
     
  26. Jahue

    Jahue United States Iron Registered Member

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    One other thing, I was contemplating the gears and bearings in the headstock, I also have a vibration issue, so I was wondering if that could be it... but then I remembered that I tested this with no motor, and no gears engaged, so just a drill and the carriage. Needless to say when you run it on a drill a lot of vibration goes away. But I still get the patterns.
     
  27. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    I wouldn't worry about the gearing in the gear box or headstock. If the gears in the headstock was causing problems, it would show up as straight horizontal lines on the part. They would be superficial, too.

    I had the same problem show up on my 9" SBL a few years ago when I was trying to turn the OD on a piece of steel about 3" in diameter. The exact pattern. Didn't do it any smaller diameters, which I cut most of the time on this lathe. What I did to fix it was take the saddle and blued the bed and did a few impressions to check for bearing on the vee's. I found the top of the vee ways was riding in the relief of the vee on the saddle. Milled it out a bit. Then rescraped and fitted the saddle to the bed again. Went back together and tried it again. Problem went away.
     
  28. Jahue

    Jahue United States Iron Registered Member

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    I'm planning on pulling the saddle tomorrow night and checking it. When I blue it anything in particular to look for. I don't have scraping experience, so my repair will have to be just to the groove if I find a problem.

    But that brings up another test, I need to see if the pattern is the same on large and small diameter work.
     
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  29. 4gsr

    4gsr Global Moderator Staff Member H-M Supporter-Premium

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    Give it a try and see what happens. At this point, anything is worth trying. On the saddle, mainly see where it is rubbing along with what kind of wear pattern your seeing. Once done, before going back together, as I said earlier, file down any ridges that may have started. You never know, that little bit may solve the problem. Remember, the wear ratio between harden ways and soft ways bearing against each other is like 10-20 to 1. So for every .001" lost on the bed ways is equal to .010" or more off of the ways on the saddle. Good lubrication and cleaning can reduce this to near zero.
     
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  30. Jahue

    Jahue United States Iron Registered Member

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    Ok so tonights tests. Took the apron apart, took the saddle off, stoned and filed carefully all surfaces to make sure no burrs were standing. Blued the ways and put the saddle back on. Of course its not bearing 100% but its bearing all the way along the back side of the front way and periodically on the back, mostly near the rear. I reassembled the whole thing cleaned every surface, new way oil, even surface lubricated, and readjusted all the gibs. I also filed the relief on the v grove to make sure it wasn't riding on anything it wasn't suppose to. Ran a test... same pattern, and this time I over tightened and under tightened (loose, very loose) the gibs front and back to see if the pattern changes. No changes. I moved on to the chucks, 3, 4, and 6 jaw all have identical patterns. I was even using the same rod to verify. The pattern also shows with the gearbox in neutral and hand feeding the carriage.
     

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