Are my lathe's spindle bearings out of whack?
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  1. #1
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    Default Are my lathe's spindle bearings out of whack?

    Hello all,

    I've recently acquired a Logan 1825 that was an old shop class lathe and has taken some love to get cleaned up and running. I noticed that I was getting some wobble on my workpiece so I've been trying to track down the cause. After putting my dial indicator on the outside of my chuck I found that it wobbles about 4 thou. I pulled it off and put my dial on the spindle just above the treads where it's flat and it's off about 0.6 - 0.8 thou.

    Is this enough of a misalignment that I should be concerned?

    Would this be a bearing issue? Damaged spindle?
    How do I tell?

    I'm still climbing that learning curve so drawing it out in crayon is much appreciated.
    Thank you!

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    Put the chuck back on and set up a dial indicator on top of it. Then using a 2x4, gently pry up on the chuck to see if the indicator reads it moving up and down. You can also check the end-play of the spindle this way. Lateral and/or axial movement of the spindle typically indicates bearing failure.

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    If you making table legs out of wood then it might be acceptable. Otherwise forget it. "oh my poor bearings".

    For a reference, a Hardinge lathe runout is +/-.000025.

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    Personally, I wouldn't give up on the old Logan without first adjusting the spindle bearings. (A Logan can't be a Hardinge even if touched by a fairy wand at midnight, so don't presume that .000025 runout is even remotely possible for your lathe. Quadruple that and you'll be in the ball park.)

    Adjustment procedures differ depending on the type of bearings your machine has but there's a fifty-fifty chance that you can improve that runout with a bit of work, given the lathe's history.

    Do some internet research on adjustment procedures before diving into this, however. It's ALWAYS possible to make a poor situation worse !

    P.S. When measuring spindle runout, the usual practice is to measure the internal morse taper. Make sure that the taper is clean and free of dings.

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    First of all, I'm lefthanded also

    2nd What are you using for an indicator? If you don't have a "tenths" indicator, you're probably just seeing dings in the spindle.

    3rd. 4 thou on the OD of a chuck means very little. It's the OD of the chuck and nothing more. In fact, that's really pretty close.

    4th. You "newbies" tend to think you need to check everything before making any chips. Put a piece of steel in the chuck and turn the diameter down. If you can't take a 0.030" DOC without a bunch of chatter, then start looking for stuff.

    Don't look for problems where there are probably none.
    JR

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    Quote Originally Posted by IAmTheSouthpaw View Post
    ...I noticed that I was getting some wobble on my workpiece...

    I think that he's suggesting that there is a problem (although he wasn't very specific) ?

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    Quote Originally Posted by Spruewell View Post
    Put the chuck back on and set up a dial indicator on top of it. Then using a 2x4, gently pry up on the chuck to see if the indicator reads it moving up and down. You can also check the end-play of the spindle this way. Lateral and/or axial movement of the spindle typically indicates bearing failure.
    I did this and with medium pressure on 3 foot 2x4 it moves about 3-4 thou. but returned to almost the same location. I rotated over to the "low" spot and gave a little more pressure. Now it's only out about 2 thou. There is no obvious lateral movement.
    Should I keep prying with the 2x4 and try to get it close?
    Is this an indication that the spindle is damaged?
    What would you do next?

    Thanks Spruewell

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    Then there's the most likely clapped out old three jaw that's been crashed a few times in shop class holding the work that is "wobbling".

    Edit - the 2x4 test is just to see how much movement there is, not to bend anything! Note the word "gently" before the word "pry".

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    There is a bit of surface rust on the inside of the taper. Would a brass brush be too aggressive? Would a brass brush be too aggressive on the ways?

    I'll clean out the taper and measure again.

    Thanks Randyc

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    Quote Originally Posted by JRIowa View Post
    First of all, I'm lefthanded also
    ...
    JR
    1) Being left handed is hard, we're the only people in our right minds.

    2) Starrett 656, it does have a "tenths" indicator.

    3) I was thinking that it may just be the chuck, but it's nice to be reassured.

    4) I love this lathe. It has also been sitting for a good long while. I had to push through a solid layer of hardened crem in the apron plug.

    I've turned some aluminum which went pretty nicely, but later noticed the wobble and started hunting. If you think that it's pretty close then I may just be hunting snipes.

    Thanks JRIowa

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    Quote Originally Posted by Rudd View Post
    Then there's the most likely clapped out old three jaw that's been crashed a few times in shop class holding the work that is "wobbling".

    Edit - the 2x4 test is just to see how much movement there is, not to bend anything! Note the word "gently" before the word "pry".
    Good call. That's what I thought but just wanted to double check before I did any real damage.

    You are absolutely correct in assuming the chuck has been hit.
    There is obvious damage on the compound rest where it's been run into the chuck by a teacher (students wouldn't dare!). The chuck has been replaced but the strike may have thrown the bearings out of alignment?

    In hindsight I should have included this little detail in the original post, my bad.

    Thanks Rudd

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    Quote Originally Posted by randyc View Post
    Personally, I wouldn't give up on the old Logan without first adjusting the spindle bearings.
    ...
    P.S. When measuring spindle runout, the usual practice is to measure the internal morse taper. Make sure that the taper is clean and free of dings.
    I cleaned out the taper and measured the runout again. Luckily the hand on my dial indicator landed right on a tick mark because I could barely tell when it moved when I turned the spindle. I'm going to assume this is good

    Thanks Randyc

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    Coming from a school, anything is possible, even a bent spindle. Yes a brass brush is fine for cleaning out spindle, and on ways.

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    Iamthe southpaw,
    Your indicator (starrett 656) is graduated in thousandths or .001" increments. Generally when someone here mentions "tenths" they are referring to tenthousandths or .0001" and not .01" which would be 1/10 of an inch. If your lathe has tapered roller bearings in the headstock you should be able to tighten them a little to reduce that deflection with the 2 x 4. Light pressure, with the 2 by is important, remember that. Do not over tighten the bearings. Should you adjust the bearings be sure they are lubricated well and watch for excessive heat. Enjoy your toy. Oh yeah, I'm in my right mind as well...

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    Quote Originally Posted by IAmTheSouthpaw View Post
    1) 2) Starrett 656, it does have a "tenths" indicator.
    The 656 is a travel indicator. Save up some money and get an Interapid 312-B
    http://www.metronprecision.com/Merch...jpgammaadj.jpg
    60 thousands travel, shock resistant, and auto reverse.

    OK, back to the lathe. Mos used 3 jaw chucks are probably junk by the time your get them. New, they usually aren't much better. The one I have and rarely use probably has 0.003" runout with the jaws re-cut. If you want accuracy, get a 4-jaw chuck. So many guys are scared of them because they really don't know how to use them. If you use one enough, you can put a piece of round stock in and have running within 0.001" in less than 10 minutes.
    JR

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    First off, THANK YOU!
    You guys have been extremely helpful to this novice.
    tl;dr Cool story, new chuck, all better.

    I've haven't had a ton of time lately (life gets in the way of play), but I wanted to leave an update to where I'm at.
    After checking and re-checking everything I was still stumped, but I think the 3 jaw was the culprit.

    By coincidence I met a very nice retired machinist and was talking with him about a totally unrelated subject. By some miraculous stroke of luck we were right next to his storage unit and he invited me over to see his stuff. When he opened the overhead door it might as well have been the Pearly Gates. It was packed with old, some ancient, tools and machines. I must admit that I didn't even recognize %90 of what was in there or could even guess at it's purpose, but I was elated.

    During our chat I happened to mentioned my problem and asked if he had any advice. He asked some followup questions about the machine, what I've tried, etc. and came to a similar conclusion. Get a 4 jaw chuck. Then he thought for a second and said "... let me see something". You can imagine my surprise when we walked across the row to a second unit, again, chock full of goodness. He started digging through a crate of discarded things and emerged with a rusty 4 jaw chuck complete with back plate and years of grime. It was exactly what I needed and, seeing my excitement, he offered me a generous deal.

    Got it home, cleaned it up, went to put it on. It didn't fit.

    The first thread would grab but something was wrong so I re-checked the size and threads, re-cleaned the spindle and back plate threads, still wouldn't go. I'm still unsure what brand the back plate is because the logo is worn off, but the chuck is a Pratt Burnerd so I called them up. Those guys are amazing! After a good talk with a very patient technician he said they do free assessments and gave me pricing if a new back plate is needed, but he'd call me first. I packed it up and shipped it off. About a week later I got a call from the PB tech. All done, just need a credit card to ship it back.

    Wait, what?!

    Turns out that the thread depth was just a hair too tight, so he took it out to the shop and chased the threads. No charge.
    He shipped it back to me and when I opened the box I thought he had accidentally sent me the wrong thing!
    This chuck looks brand new!
    Turns out that during their assessment the Pratt Burnerd techs tear it all the way down, clean everything REALLY WELL (did they polish this?), then measure, lube, and put it all back together. They went above and beyond on this one and I could not be more satisfied.

    The new 4 jaw chuck fits and looks wonderful. Made a few cuts and the wobble appears to be gone. I don't have any of the right size of round stock right now to duplicate when I was getting issues, but it already cuts and looks better.

    I know this is a big wall of text but there were just too many people being helpful and awesome that I had to share.
    Thanks again! I'm sure I'll be bugging you about some other rookie mistake soon.

  20. #17
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    The sweet smell of success.

    Regards Tyrone.

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    Sounds like you need to revisit your retired machinist and find out what else he would consider selling...Metrology items for one.
    Good asset to have as a contact for sure.

    Joe

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    Lemme see, the folks at Pratt Burnerd did a clean/tune up & just needed you to do the shipping? Outstanding!

    I figure they get a few thousand “Atta-boys” which automatically cancel at least a few hundred “Aw-shits”.

    Matt


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