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Roll Taps (Flute-less Taps)

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  • #46
    Originally posted by Rich Carlstedt View Post
    The void (?) is a function of the tap drill size

    I have done rolled threads down to 00-90 and in steel

    That's very impressive, did you do it in one pass CNC, or peck cycle? What kind of steel was it?

    Not to play the one up game, but the smallest tap I ever used was a .055mm x 205 microminiture thread.

    Hand tapping with a microscope. The young bucks can have it ! ! Your one of the few that can do that kind of work. Kudos~
    Last edited by Fasturn; 10-15-2021, 03:31 PM.


    • #47
      Originally posted by Rich Carlstedt View Post
      The void (?) is a function of the tap drill size

      unfortunately drill sizes are too broad to get it exactly right, but regardless of the criticism, Rolled threads are stronger
      I have done rolled threads down to 00-90 and in steel

      Even if it were to exactly match the volume to be displaced and the volume available, there would seem a guarantee of a "cold shut" at the thread crest.

      Originally posted by lbender View Post

      Almost all the strength of a thread is in the root, with the tip contributing virtually nothing.
      Having a defect in the tip, or even the tip removed completely doesn't weaken the bolt.
      On the other hand, the cold work from forming can increase the strength by several percent.

      Of course, it is cross-section. And 75% threads, yada yada.

      But that goes for both. Equal strength threads ought to fail at the point on the flanks where both have the same cross-section through the thread. The void created by the forming should modify that point, one would think.

      What you are arguing, and quite possibly correctly, is that the work-hardening adds more strength than the voids remove.
      CNC machines only go through the motions.

      Ideas expressed may be mine, or from anyone else in the universe.
      Not responsible for clerical errors. Or those made by lay people either.
      Number formats and units may be chosen at random depending on what day it is.
      I reserve the right to use a number system with any integer base without prior notice.
      Generalizations are understood to be "often" true, but not true in every case.


      • #48
        Originally posted by JoeLee View Post
        So do these taps work with a tapping head at those RPM's ? I can't imagine stopping on time especially threading a blind hole. On a CNC yes, but that's still a pretty abrupt stop on the down feed.

        generally in an albrecht drill chuck(gasp) they are fast, easy and cheap to rebuild, sometimes a collet. Tapping head has a bunch of dust on it and generally not worth messing with. We have mitutoyu quill dro’s on all the bridgeports, bring the tap down on top of the work, zero and run it in, turn it off when its close and engage the brake at depth, sometimes finish turning the drill chuck by hand and take the tap a little deeper if needed, then reverse out. If the tap hole is real shallow, I just hand tap it with a guide.


        • #49
          Originally posted by JoeLee View Post
          How does that happen ? I would think it would be a clean V angle.

          Kinda weird right? What about the vally in the crest of the thread point?

          That was an extreame photo of what happens very quickly. The vally and peak are made at the same time. The metal has to move and it does. With the pressures much of it is moved downward where we want it.

          The evcess is pushed up and out the top, the peak. Sometimes it gets folded which that pic looks like is what is going on..

          In real time the machine is so fast that the "fold" never developes. So its a "seameless screw. Or not..

          You dont ever want to see how your chicken, beer or cheese is made. Just enjoy it. JR