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Climb Vs Conventional for Thread Milling

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  • Climb Vs Conventional for Thread Milling

    I'd like to know the rationale for one vs the other. It seems to me that conventional would mill slightly under size depending on deflection and backlash, and that climb might mill slightly oversize depending on details.

    That being said I just conventional thread milled a 10-32 hole with a 0.120" 4 flute single form thread mill. I programmed it as 0.190" (major diameter) and the machine screw just barely fit. It threaded in, but required a wrench. Just one finger on the wrench (short arm 5/32 hex key), but it needed it. A spring pass made little difference. I could hear it rubbing just barely, but I don't think it took off any practically measurable material. I went back in at 0.193" and threaded in like it had been tapped with a nice fresh tap.

    *** 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.

  • #2
    I wouldn't expect much difference in dimension unless there is cutter flex. IF its flexing the climb might pull the cutter in a bit deeper while conventional would push the cutter away a bit from the stock. Naturally, the quality and grade of the screw you are using will change the fit too, different dimensions for different class threads. Of course, the only real way to know if the thread hole dimensions are in tolerance for a given class thread would be a go/no-go gauge, trying the screw is the poor mans gauge.

    .190 should not have been tight IF the screw dimensions were proper AND if the major diameter really CUT at the .190 you programmed and the cutter diameter was properly comp'd.
    Last edited by Sparky_NY; 03-13-2020, 09:21 PM.

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    • #3
      Originally posted by Sparky_NY View Post
      ....190 should not have been tight IF the screw dimensions were proper AND if the major diameter really CUT at the .190 you programmed and the cutter diameter was properly comp'd.
      Also, IF the thread mill had properly-flatted tips

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      • #4
        I've never had a thread mill cut an on-spec thread right out of the box based on calculations. I always have to tweak the cutter compensation or wear offsets. I always climb mill, for best surface finish. I have no need to think about climb or conventional milling causing different deflections, because I always climb cut and tweak to get the proper pitch diameter.

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