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Lathe spindle bushings?!

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  • Lathe spindle bushings?!

    Hi All,
    A few months back I posted some photos of this old 1916 Southbend. Most notably some of you might remember this machine as the one with the nice ground-down-to-expose-the-compound-innards job. Since then I've re-painted it and got it partially assembled, and have managed to make a new compound leadscrew and nut at the local college's machine shop. (BTW, threading on the Hardinge with the auto-stop was SOO COOL!)
    What really blows my mind is that the spindle has bushings instead of bearings. It seems like this was added later in the lathe's lifetime, as was a few other fixes, and modifications (including cutting the 6' bed down to 4' because of the event I refer to as "the accident".) Runout measured from the spindle nose (flat part right before threads start) seems like 2-3 thousands, but runout measure from the dead center seems to be about 4-5 thousands, so it almost seems like the inside of the spindle doesn't exactly match up (if that's possible.)
    The bushings seem like they're aluminum, presumably so the steel spindle wears on the bushing rather than itself, but it seems the spindle diameter at the bushings are about .020" short of: 1.75" on the business end, and 1.25" on the change gear side. So in thinking about retrofitting this with some off the shelf tapered roller bearings, it seems like it might be impossible because the parts of the spindle that run on the bushing have been worn down a little bit. And since it's worn there, even if I did get bearings with the matching bore ID, would I be able to get them on there past the non-worn part of the spindle?
    Any ideas (aside from scrapping this unit) out there? Maybe I just need to live with the bushings, maybe I could learn something from replacing them.
    BTW, how does one go about removing the spindle pulley cone/bull gear arrangement? I'm totally afraid to undo the set screws on the pulley flats to find out if that's what needs to be done.




  • #2
    South Bend lathes used bronze bushings -- sometimes cast iron. I'd stay with bushings, not try to do roller bearings, but use bronze, not aluminum!

    As far as taking it apart: see if you can get an exploded view of how it all goes together. I know a while ago somebody gave a URL of a site that had a copy of a US Army manual for a Soth Bend lathe online -- maybe they can re-post that link.

    Disassembly is not terribly complicated though. Basically, unscrew the take-up nut on the left-hand end of the spindle, and with a soft-faced hammer knock the spindle out. The bull gear is a press fit and takes some tapping, but everything else just slides off...if my memory is not failing me, and if that lathe is the same setup as my 10K, which is by no means certain.
    Keep track of the pieces, of course. You'll also have to deal with the spring-loaded oiler wicks that will pop up when the spindle slides out, so don't be surprised when they do.


    [This message has been edited by SGW (edited 05-31-2004).]
    ----------
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    • #3
      The bushings do not look like a retrofit. Are you sure they are aluminum and not white brass or babbit? Have you had them out to compare weight?
      Plain bushings have some advantages over ball or roller bearings if high speed is not needed. They can be tightened up by removal of shims on bearing halfs or carefully filing the bearing half if shims are gone.
      Plain bearings would probably be more than adequate for most HSM applications. Unless you want the challenge of converting the headstock, I would recommend not changing them.
      Jim H.

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      • #4
        SGW has it right,the spindle stop on the left has to be unscrewed first.The setcrews in the pulley flats are oil holes for the pulley run bushings.

        If it is possible to do so ,you might consider making two shrink fit bushings to fit the bearing surfaces on the spindle and then make up and line bore some new bushings in the headstock.
        I just need one more tool,just one!

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