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Used Lathe Runout?

Discussion in 'Newbie' started by Dan Bevilacqua, Nov 15, 2017.

  1. Dan Bevilacqua

    Dan Bevilacqua

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    I'm always on the lookout for used lathes. Not really interested in old lathes but in a good deal on something more modern. When inspecting a used lathe, is "spindle runout" something that you inspect to make certain it is within a certain tolerance?

    When I say "spindle runout", I am talking about measuring with a dial indicator the smooth portion of the spindle just behind the threads and also the inside of the morse taper of the spindle. I turn the spindle by hand and check for any deviation of the dial indicator in the rotation of the spindle.

    Although I like to see zero runout, I understand that we are discussing wood turning lathes, and runout is not as critical as on a metal turning lathe. What would be acceptable maximum runout to you? Is anyone aware of an industry standard for spindle runout on a new lathe?

    Thanks.
     
  2. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Any runout that can be seen or felt is too much. My first lathe had a bent spindle which caused the chuck to vibrate. When I figured out what was going on, I called Delta and they expedited a replacement spindle plus bearings and retaining clips. That made all the difference in the world.

    My opinion is that runout is critical ... maybe not as critical for turning between centers with some caveats, but if you have an eight pound scroll chuck that isn't running true, that is a really big problem because that is vibration that can't be mitigated any way other than replacing the spindle.

    This shouldn't be confused with bearing radial free play.
     
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  3. Dan Bevilacqua

    Dan Bevilacqua

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    Thank you, Bill. Is there anyway to quantify the amount of spindle runout that would be the cause of the vibration to which you referred?

    Also, I am not familiar with the concept of "bearing radial free play". Is that play in the spindle from pressing laterally on the spindle?
     
  4. Bill Boehme

    Bill Boehme Administrator Staff Member

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    It would depend the sturdiness of the lathe, the lathe speed, the mass of the chuck, and the degree of precision needed. For example, if I put my Oneway Stronghold chuck on the lathe (jaws closed and no wood mounted) and ran the lathe with a finger lightly resting against the back edge of the chuck, I would consider it unacceptable if I felt any vibration at any speed.

    Standard tolerance bearings aren't preloaded and have a little radial play. That is the type of bearing most commonly used in wood lathes. That's not a problem and won't lead to vibration.

    Most vibration begins with the wood. Low frequency vibration is caused by the wood being out of balance and it peaks when it happens to be at a structural resonant frequency. High frequency acoustic vibration occurs as the wood gets thinner and begins to flex resulting in the tool skipping across the surface. This is the type of vibration that leads up to getting a catch if you don't recognize what is about to happen.
     
  5. Gerald Lawrence

    Gerald Lawrence

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    Ok Bill you won me over and I will remove the plastic washer. I had a chuck stuck on my Delta Midi when I started turning (more than once) and upon reflection I think I probably powered up before seating the chuck and then lots of catches then.
     
  6. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Gerald, it seems like you may have read Leo's recent post in the thread about using setscrews to hold the chuck since he talked about using plastic washers. My post in this thread on runout was about a bent spindle. However, I don't use a plastic washer and have never had a stuck chuck except on my first lathe that did have a bent spindle. :D
     
  7. odie

    odie

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    It's been many years since I checked the runout on my Woodfast spindle, but it was .002" to .003" when it was new. Now you make me wonder, since I replaced the bearings last year. I'm writing myself a note to check the runout tomorrow, and will report back later.

    -----odie-----
     
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  8. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I don't think that would have changed unless there was some scuffing going on when you replaced the bearings. With your machinist background, I would discount that possibility.
     
  9. odie

    odie

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    Are any of the wood lathe manufacturers using tapered roller bearings for the spindle?
     
  10. Bill Boehme

    Bill Boehme Administrator Staff Member

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    I think that there might be one or two that use angled ball bearings, but I don't recall reading about tapered roller bearings which are normally used for things like car and truck axles where there are extreme loads. I don't think that they would be a good choice for a wood lathe.
     
  11. odie

    odie

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    There was a centerless grinder where I used to work, that had tapered roller bearings. The runout on that machine was very critical.
     
  12. Bill Boehme

    Bill Boehme Administrator Staff Member

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    That sounds like an application where where tapered roller bearings would be justified since they can be adjusted to eliminate any slack. The downside is the power loss in roller bearings which explains why they run much warmer than the normally used ABEC 3 ball bearings.
     
  13. odie

    odie

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    You don't suppose the heat generated by the roller bearings is the result of more contact surface between the rollers and the races than would be with a ball bearing? Of course, the amount of torque applied would be a factor, too. Anyway, a ball would be a single point of contact, while a roller would be a line, which would be a much greater contact surface.

    As I recall, there was a set of bearings for this machine that were greater precision than standard bearings. The difference was that each individual roller was mic'd and subject to a higher tolerance requirement. Of course, these bearings came at a much greater cost, but would produce higher consistency in the product.

    -----odie-----
     
  14. Bill Boehme

    Bill Boehme Administrator Staff Member

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    There's not much difference at all in contact area since a sphere or cylinder or a truncated cone rolling on another surface has a theoretical contact area of zero. In reality I'm sure that there would be more rolling friction. The big difference in friction is due to the hydraulic pressure as the grease being forced between the roller bearings and the additional back pressure created by the cage that holds the rollers in position.
     
  15. Hy Tran

    Hy Tran

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    Runout: No such thing as zero runout. With better instruments, you will detect both synchronous and asynchronous error motion. And to really geek out, I much prefer the term spindle error motion to runout; it's more precise (see ASME B89.3.4:2010).

    Anyway, I put a clone steb-center into the Morse taper in the spindle of my Nova Comet ii (about 5 months old, lightly used), and set up a dial indicator against the side of the steb-center. Hand rotation shows a total of 0.003" of TIR (all right, all right--that's the wrong term). But this number combines both the spindle error motion, non-roundness on the side of a turned surface (the side of the steb center), and misalignment of the axes of the steb center and the Morse tapers. I was too lazy to use the Donaldson reversal method (look it up, virtual applause if you know what his first name is and where he worked) to actually separate out the non-roundness of the steb-center from the spindle error motion.
     
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  16. Dan Bevilacqua

    Dan Bevilacqua

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    Thanks, Hy Tran. I looked up the Donaldson Method and didn't get very far. Too complicated for my brain. :D

    By the way, did you happen to measure what I called "runout" and what you prefer call "spindle error motion" of just the spindle, inside the morse taper and just behind the threads of your Comet.
     
  17. Hy Tran

    Hy Tran

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    Hello, Dan,

    Unfortunately, I don't have a "last word" indicator at home, so I really can't measure the spindle error motion that you want to see. I have a magnetic stand (wouldn't work on a Robust lathe...) and a couple of straight dial indicators from a home project several years ago. Based on size of the indicators, the lathe, and the stand, I can't get the indicators inside the taper to measure, and there's not enough space outside the taper to get the indicator to read without bumping into something. I suppose I could chuck up something and turn a nice clean cylinder (using a skew, of course...;)) and then measure the error motion on the turned surface. That would actually be a pretty close representation to what you want. I'd need a really good hard wood with fine grain so the dial indicator doesn't dimple the wood; all the spindles in my garage are soft maple or cherry or elm (or Home Depot pine).

    Hy
     
  18. Dan Bevilacqua

    Dan Bevilacqua

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    Thanks again, Hy. No need to go to any trouble. I was just curious if you had measured it when you measured the side of the steb center.

    In any event, I do have a Nova Comet II, and like it alot. I also just looked at your intro post, and noticed you started on a Shopsmith as I did. I still turn on my Shopsmith 10er.
     
  19. Bill Boehme

    Bill Boehme Administrator Staff Member

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    Hy, if you chocked up something and turned it round then it will be aligned with the true axis of rotation and not the axis of the nose of a bent spindle. This is easy to visualize if you have an Escoulen chuck or something equivalent that would simulate a bent spindle. To answer Dan's question, unless the runout is significant enough to cause noticeable vibration when a large chuck or faceplate is mounted on the spindle then it's not a problem.
     
  20. Hy Tran

    Hy Tran

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    You'd still pick up the asynchronous error motion. (Or in my case, the spectacular catches!)

    That said, we're turning wood--not optics!
     

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