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  • Jocobs #2 taper: how to

    I need to make a taper for a Jacobs #2 chuck on the end of a shaft held between two bearings. This taper is short enough so I plan to cut in using the tool post and not a taper attachment. The question is: how do I arrive at the angle of 2.335 degrees? I'm sure I can get close just by the markings on the SB lathe. But how can I get exactly this degree?

    The original shaft had a thread for the chuck which introduced way too much play. I will get a precision hand chuck for the taper.
    Vitَria, Brazil

  • #2
    Put the tapered piece in the lathe headstock chuck (with the small diameter facing towards the tailstock). Make sure that it runs true at both ends (concentric with the lathe axis). Then put a dial indicator in the tool post to indicate off the side of the taper. Run the compound back and forth so that the indicator slides along the tapered surface. Adjust the compound's angle until the indicator holds a constant reading across the whole length of the taper. Now the compound is set correctly, so you can make the new piece.

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    • #3
      That would work except that the taper I have to work with is a double taper. It is tapered on both ends so I don't see how I could chuck it up.
      Vitَria, Brazil

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      • #4
        If the arbor you have is centerdrilled just put between centers

        And indicate from that. If not you can make a reverse(or cup http://www.rrosand.com/articles/18-2.html) center for chuck and put one end of taper in that and other can be held loosely in a drill chuck (even if tapered), or another reverse center in drill chuck in tailstock.

        You are just indicating, no real pressure or force. Just need to be centered between spindle and Tailstock....
        Last edited by Bguns; 05-01-2008, 03:18 PM.

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        • #5
          Hey, why didn't I think of that. It does have drilled centers on both ends. That should work fine.

          Thanks so much for the help. I'm getting a lot of good advice on this forum.
          Vitَria, Brazil

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          • #6
            Also make sure that the indicator indicates at the height of the centerline of the part. Otherwise, it will run "around" the taper and give an unusable reading.
            If ignorance is bliss, why aren't there more happy people?

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