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  • Need help with a machining job

    I need to cut grooves down the center of this tube, ID is .5" Diam. Now the quick answer is "cut it like it is rifling" The quick answer is:
    1. I don't have the equipment
    2. it is wider then rifling would be so the load on the cutter might be to high to work, at least for anyway I can think of. Maybe OK for professional equipment which I don't have.

    The twist is about 1 in 30, the groove is 0.050" wide and 0.008" deep. 4 grooves spaced equally around the bore.
    I don't have any special equipment like a CNC shaper with a 4th axis rotary table etc. (don't laugh, that might actually work)

    Any ideas?

    Last edited by loose nut; 09-13-2018, 07:27 PM.
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

    Southwestern Ontario. Canada

  • #2
    How must are planning spend or time for the set.
    What size of mill do you have

    Dave

    Originally posted by loose nut View Post
    I need to cut grooves down the center of this tube, ID is .5" Diam. Now the quick answer is "cut it like it is rifling" The quick answer is:
    1. I don't have the equipment
    2. it is wider then rifling would be so the load on the cutter might be to high to work, at least for anyway I can think of. Maybe OK for professional equipment which I don't have.

    The twist is about 1 in 30, the groove is 0.050" wide and 0.008" deep. 4 grooves spaced equally around the bore.
    I don't have any special equipment like a CNC shaper with a 4th axis rotary table etc. (don't laugh, that might actually work)

    Any ideas?

    Comment


    • #3
      My quick answer would be turn it over to someone that DOES have the equipment.

      Or make it. The hardest part will be to make the helix cutter. Think broach with a pull cable or press. You do have a press, right?

      Comment


      • #4
        interesting challenge. What sort of accuracy is required? How Rube Goldberg are you prepared to go? what machines are available?

        you've got to turn the work while moving the work axially relative to the cutter (obviously). if you need accuracy, you'll need to synchronize the feed of tool relative to work and rotation of tool relative to work as well make the four divisions.

        Perhaps work mounted in the lathe, carriage moves back toward tailstock pulling cutting through the work. As it does so, a cable connect the to carriage turns the the spindle....obviously geared or from pulling the cable off a large dia drum. Not super elegant, it gets Rube'ish (rubbish?) quickly. The other direction is in the mill some how with a electronic coupling ala John Stevenson between rotation and feed....still some challenges on what holds what
        in Toronto Ontario - where are you?

        Comment


        • #5
          Do it the old fashioned way by making your own rifling guide by rolling a log over a chalk line and chiseling a groove in the log. Then using the log on a slide to drive a tiny little scraper bit.
          *** 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.

          Comment


          • #6
            I'd do it on the lathe. Workpiece in the spindle, supported on the back side by a spider. Large gear on the headstock, small gear on the leadscrew or gearbox input (potentially with a compound in there too). Now, drive the lathe using a handwheel or motor on the leadscrew. Just have to figure out the gear ratio.

            As for the tool, I'd probably make something like a sliding fit boring bar, but I'd use it pulling rather than pushing. I'd probably point the toolbit out the bottom of the bar, and cut a flat area around the toolbit, so chips drop down and don't get wedged. Infeed would be by a small jacking screw behind the toolbit, perhaps on a shallow angle with a wedge behind it, and a second screw to lock it.

            allan

            Comment


            • #7
              I visited colonial Williamsburg, Virginia many years ago. It is a living museum where they dress in 1700 1800 clothing and do things they way it was done in that time period. One of the things I never forgot was they had a device for rifling a barrel of a gun made out of wood. It was a piece of round wood with grooves in a spiral pattern that matched the rifling they wanted to produce. For the OP, something like that could be done to produce to grooves if no other equipment is available. Here is a video. The rifling starts around the 10 - 11 minute mark.

              As an aside they had sheep there with long tails. Never saw that before lol.

              Comment


              • #8
                Don't know if this would fit your need or not, but this young lady shows one way to do it.

                https://www.youtube.com/channel/UCrT...MHnpWFw/videos
                Jim

                Comment


                • #9
                  [QUOTE=Mcgyver;1194859]interesting challenge. What sort of accuracy is required? How Rube Goldberg are you prepared to go? what machines are available?

                  Accuracy is not critical, some amount of error is OK.

                  Lathe, Bench mill.

                  I have thought about the rifling method but not having done it before I would probably scrap a lot of pieces to get a good one just as someone trying to learn how to rifle a real barrel would.

                  Something I forgot to mention, overall length is 10", grooved length is 8".
                  The shortest distance between two points is a circle of infinite diameter.

                  Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

                  Southwestern Ontario. Canada

                  Comment


                  • #10
                    What material is the tube?
                    When I get Time... I'll...

                    Comment


                    • #11
                      [QUOTE=loose nut;1194912]
                      Originally posted by Mcgyver View Post
                      interesting challenge. What sort of accuracy is required? How Rube Goldberg are you prepared to go? what machines are available?

                      Accuracy is not critical, some amount of error is OK.

                      Lathe, Bench mill.
                      You already have more equipment than smiths 150 years ago
                      Or this guy https://www.youtube.com/watch?v=ihPFjuxBjPo
                      Location: Helsinki, Finland, Europe

                      Comment


                      • #12
                        Sounds the mill will do the job
                        But a BS2 is to big for the mill
                        You build a spin jig gear to mill screw

                        Dave


                        [QUOTE=loose nut;1194912]
                        Originally posted by Mcgyver View Post
                        interesting challenge. What sort of accuracy is required? How Rube Goldberg are you prepared to go? what machines are available?

                        Accuracy is not critical, some amount of error is OK.

                        Lathe, Bench mill.

                        I have thought about the rifling method but not having done it before I would probably scrap a lot of pieces to get a good one just as someone trying to learn how to rifle a real barrel would.

                        Something I forgot to mention, overall length is 10", grooved length is 8".

                        Comment


                        • #13
                          Originally posted by Hawkeye View Post
                          What material is the tube?
                          I was hoping to use DOM tubing steel or brass (if available), copper as a last resort.
                          The shortest distance between two points is a circle of infinite diameter.

                          Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

                          Southwestern Ontario. Canada

                          Comment

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