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machine compound curved surface

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  • machine compound curved surface

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    The rib on this barrel assembly was an investment casting attached to the barrel and barrel extension. I want to make and install a rib on a replacement barrel and extension.

    The extension is a simple curve. The barrel has a radius feeding into a taper.

    The only thing that comes to mind is to buy a surface probe and let Mach3 find the shape of the upper, mirror it, and then cut the curves with a ball mill. For a brazed joint, .002-.003 of waviness would be acceptable.

    Presumably, the factory sent an upper off to the investment caster and let them figure out shrinkage and the like. I'm stuck with machining. The prototypes were machined on manual equipment, and so were some of the third-party uppers made later.

    So how would you make the rib without CNC?

  • #2
    Well, I'd shape a grinding wheel, make a fixture, and grind it out. But I do grinding for a living and 'if all you have is a hammer'.......


    • #3
      You'd need a wheel about a foot long and a bit over an inch in diameter to grind it. I haven't ever seen a grinder that took anything like that.


      • #4
        Lol, or one .500" wide and 8" in diameter. Shape the angle on one side and the internal radius on the other. Take a few passes down the long axis and there you go. Just dont grind into the receiver.
        Might look a bit 'funky' at the receiver where the top rail radiuses out, but it would work. I think
        Last edited by All12Huskies; 11-08-2012, 02:01 PM.


        • #5
          How are you going to grind a hollow wineglass shape with a step in it, if you're running the wheel lengthwise?