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Making Adaoter Backplate for Bison Set Tru Chuck?

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  • #16
    Originally posted by danlb View Post
    The adjusters in your picture look like they are spaced every 1 and a half jaws. 4 adjusters work well, since it's just like doing a 4 jaw independent.

    RE; the darker color; On my DTC true set chuck the darker material denoted where the chuck splits to get to the scroll and pinions. I don't see a pinion in the picture, so it was not clear which part was which.

    Dan
    4 would be logical but I swear it's not. I'll have to double check. They may not be evenly spaced.

    There is only one pinion unfortunately.
    21" Royersford Excelsior CamelBack Drillpress Restoration
    1943 Sidney 16x54 Lathe Restoration

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    • #17
      Guys,

      I have bitten the bullet and decided to turn my OEM Eldorado spindle and modify it to fit the Bison Set Tru backplate. Also, due to size, I decided to go with the 5" Bison chuck instead of the 6" version as I would have lost too much bed length and the overhang weight on the front bearing would have been a lot. The 5" chuck weights 11 pounds while the 6" comes in around 22 pounds and extends out too far.

      Here is a picture of what the OEM spindle currently looks like after literally hours of turning it at .004" per facing cut. The spindle does not have a lot of meat but there is more than enough to correctly mount the Set Tru backplate. I still have more work to do but am now at the critical part of turning an A5 taper on the spigot, which is 7 degrees 7' 30". After that, I will turn down the outer diameter to match the backplate at 4.92" and then drill/tap it for four 7/16-14" mounting bolts. Having never done this before I am sure that somewhere I have made a mistake but so far by taking a lot of time and carefully thinking through each cut, it seems to be coming out OK.

      I have also never turned a taper before, either. Is there a recommendation on a good piece of equipment I could buy which is of solid quality and will last me for years that allows me to set this taper? Whenever I buy tools my object is for the long term so if I ever get new equipment I already have a number of good tools which can be immediately used with it. Plus, I just happen to like superb quality tools!!!

      The Tom
      Attached Files

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      • #18
        Whoa slow down, before you do something you regret.

        So you're turning this into an American short nose taper, A style? That is a novel approach, I assumed if you did anything to the spindle, you would just turn it into the backplate itself. Are you sure A5 is the right size for that machine? A1 or A2-5 is typically sized for much larger and heavier machines. Does your set-tru backplate really have an A5 sized register? I would think that an A3 would be more appropriate for that machine.

        Go here https://www.smalltools.com/lathe-spi...ication-chart/ or https://prattburnerd.com/pdf%20files...ose%20Data.pdf and double check your numbers with us maybe?

        Turning the register is a very precise operation. It's sort of a "press fit" situation, where the bolts actually draw the chuck up tight on the spindle. That's why you have to bop them with a hammer to get them off. Luckily with a taper, you get 2nd chances by chasing one side or another, but still, it needs to be very well done. Maybe even with a TPG if you've got one.

        Will you have to take your chuck off the backplate to get to the mount bolts? If so it's gonna really suck to change chucks.

        Lastly, all you need to get a precise taper is a dial indicator and a straight bar. With a straight bar chucked up (use your tailstock quill I guess since you've got no chuck). Your dial on the compound will read the hypotenuse of the triangle, and the dial indicator will be placed at a right angle to the bar. The dial indicator will then read one of the legs of the triangle. With a bit of pre-calculated math you can bump the compound to the angle you need. You can set the hypotenuse length pretty long, say 2 inches, so that if you error on the dti is 1 thou, the actual error on a 1/2" part would be 0.00025. I (and I'm sure others) can help with the math if needed. You may wish to indicate the side of the tailstock barrel before by moving the carriage or the tailstock to see if it is parallel to the spindle axis. If it's not, you can add an offset into your measurement. I hope this all makes sense.
        21" Royersford Excelsior CamelBack Drillpress Restoration
        1943 Sidney 16x54 Lathe Restoration

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        • #19
          Butcher,

          Yes, I am turning the spindle into an American short-nose taper. I have the Bison Set Tru backplate and have carefully measured it many, many times to make sure, and it is in fact an A2-5 taper. The picture shows the spindle side of this backplate and the rule laid across the plate shows the register opening has a diameter of 3.25" and then slightly tapers down from there. The spec sheet for this Bison backplate (part number 7-874-055) also shows this specific part has an A2-5 taper.

          The backplate mounts to the modified spindle via four 7/16-14 cap screws and these go in from the front...so, no having to reach behind the spindle and remove the backplate bolts to separate it from the spindle. The Bison chuck also is a front-mount and this is with three M8x1.25 cap screws. My goal once all this is done is for the backplate not have to be removed from the spindle and if chucks need to be swapped out it will be to simply remove the three metric screws from the front.

          Whew!
          Attached Files

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          • #20
            Alright.

            Carry on then!

            Taking the 6 jaw off will require dialing it back in any time you re-mount it. So it will be quite slow and tedious to change. That's one of the major disadvantages of A nose spindles. I don't think you'll find many (any?) other chucks that mount on your backplate, so you'll have to remove both piece every time. Personally, I'd be more tempted to tap the backplate so that you could remove the backplate and the chuck as a unit and not have to dial it in each time. That would also save you from having to remove and re-drill your spindle.

            Do you have a 4 jaw in mind as well on the A2-5 pattern?
            21" Royersford Excelsior CamelBack Drillpress Restoration
            1943 Sidney 16x54 Lathe Restoration

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            • #21
              Originally posted by danlb View Post
              The adjusters in your picture look like they are spaced every 1 and a half jaws. 4 adjusters work well, since it's just like doing a 4 jaw independent.

              RE; the darker color; On my DTC true set chuck the darker material denoted where the chuck splits to get to the scroll and pinions. I don't see a pinion in the picture, so it was not clear which part was which.

              Dan
              Dan it is 4. I think the reason I had so much trouble adjusting it in the past is that it adjusts opposite of a 4 jaw. Not sure why I remember there being more than 4.
              21" Royersford Excelsior CamelBack Drillpress Restoration
              1943 Sidney 16x54 Lathe Restoration

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              • #22
                Any progress SqueakyTom?
                21" Royersford Excelsior CamelBack Drillpress Restoration
                1943 Sidney 16x54 Lathe Restoration

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