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Taper Attachment Question for John Foster.

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  • Taper Attachment Question for John Foster.

    I am building the Taper Attachment HSM Jan/Feb 2004. The Question involves cutting the cross feed arbor gear which is shown as 12 teeth 20 DP. You say that for 12 teeth the correct cutter is #1. This is in error, the correct cutter is #8 for 12 teeth. (1 cuts a rack.) You do not specify the pressure angle, nor depth of cut. I assume it is 14 1/2 deg gear. I calculate:

    The max diam is 0.690 = Pitch diam + 2 x addendum. Now 12/20 =.6 = pitch diam. Hence the addendum, then equals 0.45. The addendum is usually 1/Pitch diam
    =.05, so this is close. The min clearance =.157/Pitch diam = .007 The milling depth = .097. I would like to know how well your gear meshes with the SB gear, and what parameters you used.

  • #2
    I'm not him, but I recall the article....

    You might re-read it, because IIRC the comment was made in the text that it appeared to be a non-standard gear.

    That said, he may just have inadvertantly reversed the order of numbers.

    The articles are generally NOT edited for errors, as we have seen. Not complaining, just noting it.

    [This message has been edited by J Tiers (edited 02-05-2005).]

    Keep eye on ball.
    Hashim Khan


    • #3
      Ditto that, if you have the original gear on hand, duplicate that. It may be non standard due to space. It is probably 14-1/2* PA.

      To test gears, it is not too difficult to set up a gage with stub shafts on the appropriate center distance and trial fit them. Watch & clock makers use a depthing tool to do this.
      Jim H.


      • #4
        The other replies are correct. I goofed on the cutter number as anyone with any sense would make #1 equal the lowest number of teeth and number 8 the highest. In other words, I didn't check and I know better.
        Yes the gear appears to be non standard but works fine. I would suspect that if you were generating a gear on a hob you could cheat a little to make it fit the space. I ASSUMED that as S.B. uses 14 1/2آ° on the other gears that this one was also. Besides I had the cutter, tried it and it worked!
        For those that do not want to telescoping feature, it is much easier to make a non-telescoping attachment as you have the critical demension on the rear bracket. You just need the new ways and a way to attach your crosss slide eliminating a lot of work. I just wanted to see if I could make a telescoping one since S.B. didn't for that model.
        Good luck and let us know how it turns out. John

        [This message has been edited by John Foster (edited 02-06-2005).]


        • #5
          Thanks all, especially to John Foster for his fine article. I am just getting my shop back in order after a retirement move, and this will be my first serious shop project in a while. I don't want to take the lathe apart to make measurments, and a cross slide screw of uncertain chastity just sold on Ebay for $75.00. I found a 20 DP cutter on the wholesale tool site for $13.00 and just about ordered it until the 20 deg pressure angle hit me. I have a milling machine with indexing head etc, so cutting the gear should not be a problem if I find a cutter. I will keep everyone posted as to progress.