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A tale of two spindles

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  • A tale of two spindles

    While chasing a "draggy" quill handle and hand wheel problem on my Bridgeport Series1 J-head, I removed the quill pinion shaft.

    The pinion shaft came out quite hard, requiring some heavy tapping (almost pounding) all the way through the 4" bronze bushing. A couple times I stopped, thinking something was wrong, but it seemed to be coming, just really stiff.

    When I got it out, there was no apparent galling nor scoring, but it came out so much harder than I expected that I wondered if the shaft was bent, possibly explaining the cyclic dragging on my hand wheel. I started to slide it back in to get a sense if was bent, but it was too tight a fit, even to get it started without some force.

    I tried a spare quill pinion shaft I happened to have on hand, and it slid right in to place with just some slight drag.

    The only mic I had on hand was 1" - 2" which was too big. I couldn't see any difference between the diameters of either shaft with my dial calipers. But there is obviously is a difference.

    I'm thinking the spare shaft is a better candidate for smoother quill operation.

    I think I found the source of the "draggy" hand wheel.

    How easy should a quill pinion shaft slide into place? Do these shafts typically require reaming for a good fit.

    Does anyone have any insight as to why two "identical" parts would have such a drastically different fit?
    Last edited by jmarkwolf; 03-25-2013, 11:38 PM.

  • #2
    ones not round the spare is but I would guess the one you persuaded out may not be



    • #3
      After sleeping on it, I've decided that the original shaft can only be described as a firm "interference fit", which is not desirable for shaft that needs to spin in it's bushing.

      It's so tight, that the clock spring could not possibly impose any influence on the shaft.

      Maybe it's bent, or out of round as Blackadder suggests, or just oversize, but either way it's too damn tight.

      I'll try the spare shaft for awhile. They're easy enough to change out if i'ts too loose.
      Last edited by jmarkwolf; 03-26-2013, 09:32 AM.


      • #4
        Things don't happen for no reason. I doubt BP would have let the mill leave their plant in that condition.
        Check the bad pinion shaft for twisting. I think some one used your mill for an arbor press at one time.