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  • replacement lathe spindle & more

    Hi everyone, haven't posted in a while.
    A few months ago, my nephew was given an old turn of the century
    Goodell-Pratt lathe as can be seen on Tony's uk site.

    The lathe had been sitting for decades in the loft of a barn with
    a leaking roof apparently.

    When he brought the lathe to me to see what I could do to help,
    he had already gone over much of it with a wire wheel.

    The headstock spindle was broken in two pieces, followed
    by the two of us breaking off the spindle nose end in an attempt
    to remove what we thought was a taper fitting of some kind.

    No matter, as the plan was to replace the spindle with one that
    would accept readily available wood lathe spindle chucks, face plates
    and such.

    Fiddling around with the machine over the past few months, this
    is the level of progress to this point.


    First pic shows a temporary assembly of lathe and drive system.
    Next shown is a better view of the drive assembly.

    The following shows the old broken spindle and the new replacement
    spindle that I turned for the lathe.

    As you can see, the new spindle is comprised of two main parts,
    including the main spindle shaft and a seperate spindle nose end
    that is threaded into the shaft end with the taper.

    More on next post........
    Mike
    Mike Green

  • #2
    This pic shows the two spindle parts assembled.


    Here is a close up of the details of the spindle nose.
    I designed it so that I could include the addition of
    a thrust bearing.


    The thrust bearing will contact the existing surface original on the
    inboard end of the headstock.
    The shoulder just past the small threaded end on the nose piece
    wil bottom out against the counter bore in the end of the main shaft,
    and lock up.

    This allows just enough clearance for the thrust bearing to spin freely
    and not lock the bearing.

    A shot of the end of the main shaft slipped in the headstock
    showing the internal threads and the counter bore.


    More coming soon......Mike
    Mike Green

    Comment


    • #3
      The original spindle had a nut that threaded onto the outboard end
      to keep the spindle in place and adjust end play I'm guessing.

      The nut has a sloped surface aprox, 45 degrees that appeared
      to contact a mating surface machined in the outboard end of
      headstock casting.

      As seen here,

      I turned a bushing of sorts with a straight bore ( no threads) to take
      the place of the nut, so that I could add a thrust bearing at the
      outboard end and use the original nut flipped 180 degrees using the
      non sloped side to bear against the thrust assembly, giving a way
      to adjust end play and hopefully smooth operation.
      Mike Green

      Comment


      • #4
        In the first two pics you can see the original 3 jaw chuck for
        which I had to make a new back plate to fit the new spindle
        nose threads which are 1"x8tpi.

        The weight of this chuck and the load it will put on the new spindle
        or anything that will apply forces to the spindle for that matter,
        have me concerned about the weakness of the small threaded
        end of the spindle nose piece.....

        I am considering taking extra steps to add strength to the
        connection of the nose to shaft.
        Perhaps cross drilling a through hole and using a split pin,
        being sure that the pin does not protrude above the surface
        of the tapered area of the shaft.

        I can't get my head around whether or not centrifugal
        forces will tend to want to spit the pin outward??????

        Anyone want to take a guess?
        Or have suggestions to strengthen the nose to shaft ?

        Mike
        Mike Green

        Comment


        • #5
          It looks like (maybe it's just the photo) your thrust bearings will be pinched against the shoulder of the "Inner Spindle" when you screw the spindle adapter into place.
          Is there a particular reason that you made a two piece rather than one piece spindle?
          edit: the closer I look it looks like like one of those "looks good in theory", real world - not so much things, sorry.
          I really like the little lathe though, cool project!
          Last edited by Scottike; 10-05-2011, 09:57 PM.
          I cut it twice, and it's still too short!
          Scott

          Comment


          • #6
            I see no reason for the spindle nosepiece to unscrew under normal rotation direction. And the chuck is a hand-scroll chuck is it not ? And therefore not very heavy ?

            However, by having a smaller thread and spigot you will have reduced the strength compared to the original one-piece spindle.

            So it won't unscrew, but it might break !

            There is discussion about what parts of a threaded chuck (backplate) do the work. My opinion is that it is the rear face and the thread. Some say a good fit on the register is needed. If the fit of your register is not tight, you may find out, but if you really are turning wood, and between centres, you shouldn't have a problem.
            Richard - SW London, UK, EU.

            Comment


            • #7
              Scrap the thrust bearing behind the chuck. The whole point of the tapered front bearing is to pull it in with a take-up nut to adjust the running clearance both radially and axially. The thrust bearing prohibits that.

              Put some locktite on the sub spindle.

              allan

              Comment


              • #8
                Originally posted by kitno455
                Scrap the thrust bearing behind the chuck. The whole point of the tapered front bearing is to pull it in with a take-up nut to adjust the running clearance both radially and axially. The thrust bearing prohibits that.

                Put some locktite on the sub spindle.

                allan
                Well.......

                the taper will lock up, maybe. That one there is a maybe, since the taper is neither really shallow nor rather steep...... the usual is a 2 degree or so taper for radial alinement, and a 45 deg on the front for thrust.... musta worked originally

                But SEVERAL makers installed ball thrust bearings so as to to set the radial alinement taper just right.... thus getting a setup that would NEVER lock up, but had all the alinement of the original 45 deg type.

                if he has the thrust bearing correctly set, it will be perfectly fine, or better.
                CNC machines only go through the motions.

                Ideas expressed may be mine, or from anyone else in the universe.
                Not responsible for clerical errors. Or those made by lay people either.
                Number formats and units may be chosen at random depending on what day it is.
                I reserve the right to use a number system with any integer base without prior notice.
                Generalizations are understood to be "often" true, but not true in every case.

                Comment


                • #9
                  Originally posted by J Tiers
                  Well.......

                  the taper will lock up, maybe. That one there is a maybe, since the taper is neither really shallow nor rather steep...... the usual is a 2 degree or so taper for radial alinement, and a 45 deg on the front for thrust.... musta worked originally
                  The 45 is on the takeup nut.

                  But SEVERAL makers installed ball thrust bearings so as to to set the radial alinement taper just right.... thus getting a setup that would NEVER lock up, but had all the alinement of the original 45 deg type.
                  Which makers use a thrust bearing on the big end of a cone bearing?

                  allan
                  Last edited by kitno455; 10-06-2011, 09:43 AM.

                  Comment


                  • #10
                    I swear this must be a sign of some sort as I posted just a few days ago on PM's Antique board for the first time in quite awhile over an almost identical GP lathe that I saw Sunday in one of our local thrift stores for $14.95! The only difference between that one and yours (other than condition) is the "saddle" on it.

                    I think I am going to have to go back and see if its still there when I get off work in a few...

                    Nice resto btw. Sorry, but I will let the lifelong machinist "Silver-hairs" here give you advice about the spindle.
                    "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."

                    Comment


                    • #11
                      Oops, I should have mentioned at the begining that the tapered
                      bore in the headstock is very worn and off center.

                      As can be seen here, there is a lip at the large end of the
                      entrance of the tapered bore.
                      Just behind that lip you can see the off center wear maybe
                      0.020"....0.030" just by eye.

                      The lip area looks to be practicaly unworn due to the original
                      design of the spindle, which had a relief machined in that location.

                      So the worn bore cannot be used to run the new spindle.

                      My thinking was that I could use lip area for radial location
                      albeit a small area, and so that as the take up nut was tightened,
                      and the taper drawn in, the thrust bearing would take the
                      axial load rather than the taper just wedging itself tight.

                      That is why I did things the way shown above.

                      Also, I have no way to rebore the headstock casting back
                      to concentricity.

                      justanengineer,
                      We also have the "saddle", but no tool post.

                      Behind the saddle can be seen the original 1/2" tailstock quill,
                      which is in really bad shape.
                      The end of the quill has a #0 Morse taper socket which is
                      in bad shape as well.

                      Salvaged from part of an old table saw, I had a 1/2" O.D.
                      shaft with right hand V-threads on one end, and at the
                      time decided to use it as a replacement quill.

                      I milled a key slot in the location of the original, and
                      used a threaded stub arbor from one of those
                      cheap electric hand drill chucks and attached it to
                      the inboard end of the quill.

                      The above idea was something to get started with,
                      and I pressed on.

                      The cheap threaded back keyless drill chuck
                      wobbled badly and so I abandoned that drill chuck.

                      On hand I had 1/2" keyed drill chuck and gave that a go.
                      I cut off the taper arbor, mounted & indicated the chuck
                      in my South Bend 10L and faced, bored and threaded that
                      to a better fit of the tailstock quill threads O.D. 0.508"

                      There is no register or shoulder for the back end of the
                      drill chuck to mate with on the quill.

                      A steel disc fastened to the quill will at least provide
                      a stop for the back end of the drill chuck with shimming
                      where needed to put the axis not perfect, but closer
                      and more than likely usable for this lathe.

                      I may revisit the quill at a later date.
                      Mike
                      Mike Green

                      Comment


                      • #12
                        As the tailstock quill no longer has a taper socket, I
                        made up this little live center.
                        It will mount in the drill chuck.

                        To the left of the live center is a wood turning spur drive
                        center that i was given some time ago.
                        The back end of it was gone, some part of it had been
                        snapped off and disposed of.

                        So in the lathe it went and was cleaned up and a section
                        was turned down concentric.
                        Also, there was no center point, so I turned up a new one.

                        The spur drive for now at least will be held in the 3 jaw.
                        Mike
                        Mike Green

                        Comment


                        • #13
                          So if the front bore is too worn to use, then what is providing radial support for your spindle nose?

                          allan

                          Comment


                          • #14
                            Very nice work but I'm curious why you didn't make the spindle one piece and why you didn't put a MT2 in it. Typical spindle nose dimensions for that size wood lathe is 1" x 8TPI with a MT2 hollow spindle. The larger lathes commonly use 1-1/4" x 8TPI with MT2 internal taper. At one time large wood lathes came with a 1-1/2" x 8TPI and MT2 internal taper. These days it's very hard to find fixings for them though. Not a big deal for a machinist though.

                            Still... very nice work on a very pretty old machine!!

                            Chris

                            Comment


                            • #15
                              Several makers put ball bearings in,. refer to the Goodrich book on jeweler's lathes where it is discussed.

                              A 45 on the NUT won't take thrust, but it does tend to prove that there was some sort of thrust bearing at the nose, to make it worth while to have an aligning bearing at the rear... otehrwise the adjustment would be tricky... that shallow nose taper likely will lock up.

                              This isn't quite that nice a machine, even before the hacks got to it earlier in its career, apparently the G-P were low cost, almost the "109" of their day, but had some nicer features.

                              No doubt there was a flat shoulder thrust bearing in the recess, now of course gone.... but the cone would have been the radial alignment, and unless that is restored somehow, the lathe won't be much use. the roller thrust bearing provides ZERO radial alignment except where teh spindle rides on teh edge of the fixed side washer..., not a good bearing.
                              CNC machines only go through the motions.

                              Ideas expressed may be mine, or from anyone else in the universe.
                              Not responsible for clerical errors. Or those made by lay people either.
                              Number formats and units may be chosen at random depending on what day it is.
                              I reserve the right to use a number system with any integer base without prior notice.
                              Generalizations are understood to be "often" true, but not true in every case.

                              Comment

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