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Setting Lathe Compound to Half a Degree

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  • Setting Lathe Compound to Half a Degree

    I want to make a sizing die for 9mm Largo brass using a 38 seating die.
    I plan to anneal the die and make a “D” reamer.
    the taper on the case is .497 degrees per side, one half will be close enough.
    Any suggestions on how to set that angle?

  • #2
    That specification is far within the realm of fantasy.
    I bet that an angle about 0.5° will be more than close enough.
    SE MI, USA

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    • #3
      digital clinometer which has the desired tolerance.

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      • #4
        Got a sine bar and some gauge blocks?

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        • #5
          Originally posted by elf View Post
          digital clinometer which has the desired tolerance.
          I priced them on Amazon and they are reasonably priced but do they work in the horizontal plane or just vertical?

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          • #6
            Trigonometry is your friend.

            Put a straight bar in the chuck, put a dial travel indicator where the lathe tool would go. business end in contact with the straight bar (Get the center height right!)

            Crank the compound an inch and get the travel dial to display .008" (tan of .5 degrees)

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            • #7
              https://www.youtube.com/watch?v=qwMX63_bPAA

              One mans, Joe Pieczynski, method is in the link above.

              lg
              no neat sig line
              near Salem OR

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              • #8
                Usually for precise angles I mount an indicator and calculate the rise over run (using a triangle calculator ap on my phone) for the length of travel of the compound. Then I adjust the compound until my numbers come out spot on. If you don't have glass scales (DRO) always remember to to approach zero from the same direction.
                *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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                • #9
                  Originally posted by CalM View Post
                  Trigonometry is your friend.

                  Put a straight bar in the chuck, put a dial travel indicator where the lathe tool would go. business end in contact with the straight bar (Get the center height right!)

                  Crank the compound an inch and get the travel dial to display .008" (tan of .5 degrees)
                  Thanks for the suggestion, that is how I did it!


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                  • #10
                    The digital crap of 100$ or less is about 0.5 degrees accurate.
                    Useless.
                    100x - 500x less than the looked for accuracy.

                    Very accurate digital ones can be bought for very many thousands, or made for about a 1000$ in parts.
                    --
                    So You did it with an indicator -- well done !
                    Pics ?
                    Size, in use, accuracy ?

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