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  • What Angle?

    Hi All, I am trying to make a cone that has an overall length of 4 inches. It needs to be 2.5 inches diameter on one end, and 1.5 inches on the other. what angle do I need to set my compound to on my lathe to make this shape?
    Thanks in advance, Mike


    (Yep, I know, shoulda paid better attention in Geometry class)

  • #2
    7.125 degrees

    Do you have enough travel in your compound for the 4 inch length?

    Mark
    Last edited by 67chevelle; 05-16-2012, 06:10 PM.

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    • #3
      Cyclotron Guy

      I agree with mark

      You need 7.125 Degrees per side

      The large dia. minis the small dia divided 2 divided by the length equals the ATAN, of the angle per side.


      Jim Connell, DeLand FL.
      Daytona Beach is near us.

      You haven’t begun learn until to learn until you learn how little you know.

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      • #4
        Thanks for the help. If I don't have the 4 inches in the compound I'll have to break out the taper attachment and read the instructions. (hopefully the compound goes 4 inches......)

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        • #5
          What size lathe do you have? My 16 x 40 has just about 4 inches of travel, though probably 100mm, as it's Taiwan made.

          Many taper attachments (wish I had one!) top out at 3 degrees or less. If you can't get the 7.125؛ with the taper attachment and the compound doesn't have the length, you can still get it done.

          Using the compound to start it, machine as much of the length as you can. Retract the compound to start position, back up your cross slide, advance the carriage a bit. Bring the tool to touch (or very near it) and continue making the taper with the compound feed.

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          • #6
            Originally posted by PixMan
            Using the compound to start it, machine as much of the length as you can. Retract the compound to start position, back up your cross slide, advance the carriage a bit. Bring the tool to touch (or very near it) and continue making the taper with the compound feed.
            That is what I'd do if the compound won't reach it. It's going to be
            a bit over 4" along the diagonal for a 4" long piece. figure it out.
            ...Lew...

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            • #7
              Is 4" the distance between flats at the center axis of the cone, or the length of the sloping side between flats?

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              • #8
                Originally posted by Lew Hartswick
                That is what I'd do if the compound won't reach it. It's going to be
                a bit over 4" along the diagonal for a 4" long piece. figure it out.
                ...Lew...
                Length = 4"
                Small D = 1.5"
                Large D = 2.5"

                Change in diameter = 1"
                Change in radius = 0.5"

                Angle for compound or taper attachment = arctan(0.5/4) = 7.125 deg.

                Length of cut along diagonal = 4 / cos(7.125) = 4.031" or about 4 1/32".

                So you only pick up about 1/32" for the length of the cut over the length of the truncated cone.
                Paul A.

                Make it fit.
                You can't win and there is a penalty for trying!

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                • #9
                  There was a thread a while back that showed a boring bar set up between centers with the tailstock offset using a small boring head. The part was mounted on the cross slide. That might work to get a cone longer than the compound method.
                  Byron Boucher
                  Burnet, TX

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                  • #10
                    If you can offset your tailstock, then 7.125 degrees shouldn't be too terrible. 0.124" offset per 1" between centers.

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                    • #11
                      I think he wants an external taper.

                      Do you have a link to the thread? How does an offset boring bar between centres produce a conical bore in a part mounted on the cross-slide? Does the boring head rotate in the tailstock?

                      Phil

                      Originally posted by Boucher
                      There was a thread a while back that showed a boring bar set up between centers with the tailstock offset using a small boring head. The part was mounted on the cross slide. That might work to get a cone longer than the compound method.

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                      • #12
                        Sorry, I misread the original post. The senior moments are getting worse all the time.
                        Byron Boucher
                        Burnet, TX

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                        • #13
                          No worries, I just poured the milk in my cognac instead of my coffee.

                          Phil

                          Originally posted by Boucher
                          Sorry, I misread the original post. The senior moments are getting worse all the time.

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                          • #14
                            Offset Boring Head

                            Yes, I remember seeing that post in the last few weeks as well. It looked like a very interesting set up. Used a boring head with a ball bearing substituted for the tail stock. It was used for turning external tapers.

                            Ken

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                            • #15
                              Who would have thought it, Why do I need to learn this stuff, I'll never need it. Paying attention in geometry class would not have helped, for this stuff you needed to stick it out through triginometry, AND payed attention!. Bob.

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