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  • Next Question: Threading Disaster

    Okay, what happened here?

    I wanted to use a die, and thread this aluminum rod to 1/2-20. (NF).

    I found the rod size here https://littlemachineshop.com/mobile/die_threading.php, and I reduced the rod to .4950. No good.

    I chamfered the hell out of the end, then I even chopped the diameter way down, and still it wouldn't start. All it does is grind the rod away.

    Any suggestions?

    Click image for larger version

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    Attached Files

  • #2
    Be sure that you are using a thread cutting die, as opposed to using a thread restoring die. Yep, I've been bit by that one before.
    Modern hardware stores and sales generally don't distinguish between the two types very well, if at all.
    I ended up tossing out two complete sets of new Irwin dies for that reason.
    Not to mention, starting it from the correct side -- but I'm sure you're smarter than me.
    25 miles north of Buffalo NY, USA

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    • #3
      Started with the writing on the die facing the direction I was going...

      Never occurred to me I have the wrong dies. How would I check?

      Comment


      • #4
        Rethread dies are most often hex shaped. Post a picture of both sides of it. One side is flared more open, that is the side you start with.

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        • #5
          Originally posted by Jammer Six View Post
          Okay, what happened here?

          I wanted to use a die, and thread this aluminum rod to 1/2-20. (NF).

          I found the rod size here https://littlemachineshop.com/mobile/die_threading.php, and I reduced the rod to .4950. No good.

          I chamfered the hell out of the end, then I even chopped the diameter way down, and still it wouldn't start. All it does is grind the rod away.

          Any suggestions?

          Click image for larger version

Name:	E57CA7D2-FD47-473A-8AC8-E3ABFB810C10.jpg
Views:	780
Size:	807.5 KB
ID:	1975426
          Go here: https://www.practicalmachinist.com/v...reader-331563/

          Comment


          • #6
            Are you sure that the spindle is rotating in the correct direction for the die in use.

            Comment


            • #7
              I will say now is the time to start playing with those change gears and start cutting some threads.

              Comment


              • #8
                The way to determine the direction is not the printed stuff, but the side with the lead-in on it. The bigger chamfered lead-in will also have some partial teeth, usually.

                As for re-threading dies, the way to determine them is NOT the shape, but to look at the cutting edges. Re-thread dies have no "hook" and do not cut. They are more typically deliberately "blunted", so as tp push material back to the correct shape.

                The wrong size rod, a bad die, bad chamfer, dull die, all those things can cause what yu have. Also press the die against the part to get it to start cutting. Once it has some threads, it will lead itself.

                The re-threading die in this pic is the one at the front. The others cut threads, they have a "hook".


                CNC machines only go through the motions

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                • #9
                  The last time that I threaded using a die in a lathe was well over 15 years ago.
                  24" of 5/8-11 threads in steel, held the die in a 3 jaw chuck and held the 40" long stock in the tool post, worked a charm.

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                  • #10
                    In my experience, even the correct die can start crooked and you wind up with a drunk thread.

                    Again, in my experience, the best way to cut a thread with a die is to single point it first, leaving only about 10% of the cutting for the die. The single point threads provide an excellent start for the die.

                    And then, apply all of the above suggestions as well.
                    Paul A.
                    SE Texas

                    And if you look REAL close at an analog signal,
                    You will find that it has discrete steps.

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                    • #11
                      In addition to the above, pushing the die against the work using the tailstock will both help with alignment and also help push the die into the work to help out start

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                      • #12
                        Just double check your OD on the piece is correct. I’ll admit I’ve played the .100” off game before while not paying attention on reading a mic.

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                        • #13
                          Assuming you're cutting a right hand thread..... You're not using a left-handed die are you??

                          JL....

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                          • #14
                            Originally posted by Jammer Six View Post
                            Started with the writing on the die facing the direction I was going...

                            Never occurred to me I have the wrong dies. How would I check?
                            You could check it against a bolt.

                            JL...

                            Comment


                            • #15
                              Originally posted by Jammer Six View Post
                              Started with the writing on the die facing the direction I was going...

                              Never occurred to me I have the wrong dies. How would I check?
                              Post a pic of the die you are using. I’m not sure the writing means anytime other than the ones I’ve seen that said “start this side first”.

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