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    Greetings group.
    Newbie question here...
    I would like to buy a new Bison chuck 6-1/4, 3 jaw, with backplate D1-4.
    How will I true this unit up? Does the backplate have extra material left for truing. In photos it looks like there is a shoulder on the plate that mates with the rear of the chuck.

  • #2
    I highly recommend that you buy the chuck with the built in D1-4 mounting - this will give least overhang and greatest space between the chuck and tailstock. It should work fine right out of the box. Read the instructions that came with it. Make sure you tighten each cam on each pin - also insure the face of the spindle is spotless as is the chuck mounting plate before attaching it to the spindle. You may get better runout in one of the different possible pin/hole combinations. Make note which gives best runout and always remount the chuck to that spindle position.

    If you decide to get a D1-4 backplate and mount a universal chuck to it you need to do the following. Insure spindle and blate are spotless befor mounting. Mount the backplate and tighten all pin cams. Follow Bison's recommendations included with the chuck for proper fit of the chuck to the backplate. Normally you ensure all corners are broken and inside corners should be slightly under cut. The register is machined so that the backplate can be pressed onto the chuck with hand pressure. Bolts should be loctited and torqued to spec in a star pattern - start at 40% and increase 20% per pass.

    I replaced Bison's supplied bolts with high quality fasteners - SS on the top jaws and black in the back. I also machined a UHMW PE wheel to fill the void between the backplate and the chuck because I hate having chips collect in there.

    Have fun, I love my forged steel 6 1/4" Bison - they rock!

    [This message has been edited by Thrud (edited 05-21-2002).]


    • #3
      Thank you for the info.
      Do the jaws unbolt and reverse for OD grabbing. In the picture there are bolts on the jaws?

      Thanks Again,



      • #4
        Yes they do unbolt, they are called "top jaws". When you get your chuck do yourself a favor and go buy a really good Allen wrench for it. The first time I tried to loosen my bolts the wrench twisted. Bison makes beautiful stuff, but the bolts and L-wrench are not upto the rest of the gear. I replaced my bolts with Stainless Steel - cuz its "shiney"! I tighten mine with a tommy bar made from a Cummins pushrod <g>. It is easier for me to grip the pushrod as the allen wrench bothers the CTS in my hands.

        They come with a set of hardened steel jaws but you can purchase soft steel jaws to machine to fit workpieces. As well large Aluminum Jaws are often used in production - machined with a cavity to hold oddly shaped difficult to hold parts for machining.

        I have seen many people make their own jaws for these chucks to fit their own particular needs. They are far more versatile than the old fixed jaw chucks. Just remember to always put the same jaw on the same master jaw (they are numbered on the edge) to maintain accuracy.

        Have fun, don't drop it on your foot! One more thing - it is always a good idea to have a piece of plywood under the chuck when intalling or removing it from the spindle. John Stevenson <member> made wood cradles for his to protect the lathe bed - the older you get the heavier they get!

        [This message has been edited by Thrud (edited 05-22-2002).]