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  • RTFM!

    I just spent two days converting my swing arm drill/tapping machine to an electric motor with brake controlled by a VFD to raise and lower the arm. It was previously raised and lowered hydraulically. The motor turned a trapazoidal screw. It worked really well and I was stoked. Then I mounted the arm on the sliding plate and raised and lowered it a few times after which I noticed some swarf coming out of the top of the nut. It looked like I was drilling a hole with a sharp drill and the two strips of metal swarf coming out the top.

    Then I went online and read more closely the specs on the screw and nut and it very plainly stated that they were not suitable for use to drive or be driven with a motor. Only for clamping by hand.

    The machining and getting everything aligned just right and running smoothly was a good job and I was quite proud of how it turned out. So now it is either mount a ballscrew or go back to hydraulics.

    So now I know to read the f....ing manual and know the specs.
    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  • #2
    NOPE! You can't be in the REAL MANS CLUB if you start reading the damn directions, they only send them to start the diesel fire to burn the machine when it doesn't work because you didn't read the directions. So suck it up & make it work
    "Let me recommend the best medicine in the
    world: a long journey, at a mild season, through a pleasant
    country, in easy stages."
    ~ James Madison

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    • #3
      I'm slightly confused. Why should a trapezoidal (30°) thread not be suitable for driving with a motor? I know that there is a 'centering' ACME thread form, which is the same as the normal (29°) ACME thread, but with reduced radial clearance, but even with the normal non-centreing form it works ok with a power feed?.. Do you need some sleeves to centre the male thread in the threaded bush?

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      • #4
        Too bad you are so far away I have some cold beer.

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        • #5
          In my experience, the third version of the prototype works pretty well.

          Only two more versions to go.

          And hey, you learned something....

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          • #6
            Originally posted by michigan doug View Post
            In my experience, the third version of the prototype works pretty well.

            Only two more versions to go.

            And hey, you learned something....
            There is a lot of truth in that statement!
            How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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            • #7
              Acme and Trapezoidal are both self centering.

              -D
              DZER

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              • #8
                Originally posted by michigan doug View Post
                In my experience, the third version of the prototype works pretty well.

                Only two more versions to go.

                And hey, you learned something....
                If the prototype works on the first try you never know if it was just dumb luck or if you did actually something right.

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                • #9
                  Originally posted by MattiJ View Post
                  If the prototype works on the first try you never know if it was just dumb luck or if you did actually something right.
                  But everyone else thinks you did it right

                  I just had a company prepared for several iterations at 10 day cycles per, but the first one was perfect. Now they want more immediately. I played that one wrong..

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                  • #10
                    Originally posted by Doozer View Post
                    Acme and Trapezoidal are both self centering.

                    -D
                    They have a tendancy to lock up with axial loads when machined to the standard tolerances. The self-centring version has less radial clearance and ensures that axial clearance is always maintained.

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                    • #11
                      So RTFM becomes RTFN

                      i.e. Re-cut The F'n NUT

                      You do have a thread cutting lathe available.

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                      • #12
                        Originally posted by Mark Rand View Post
                        They have a tendancy to lock up with axial loads when machined to the standard tolerances. The self-centring version has less radial clearance and ensures that axial clearance is always maintained.
                        Where is the specifications for your, "self-centering version"?

                        -D
                        DZER

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                        • #13
                          Are you talking about ANSI General Purpose Acme Thread Form ASME/ANSI B1.5-1997,
                          and Stub Acme Screw Thread Form ASME/ANSI B1.8-1988 ?

                          -D
                          DZER

                          Comment


                          • #14
                            I don't understand. I have never seen a screw and nut that would work by hand but wouldnt work by motor. I assume that you are NOT trying to raise and lower at super high speed,but only at a speed that is reasonable. Maybe you chose a screw that is too small for the load.If you can crank it up quickly by hand,then it should work by motor,the screw doesnt know what is turning it. Edwin Dirnbeck

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                            • #15
                              I am also confused. Just what is causing the problem. I can't see how a screw that is running in a matching nut can remove shavings/chips. I would think that with any screw/nut combination neither of them would have the clearance required to actually cut the other. What is happening here? Is the screw or nut made from something super soft? Lead? Pot metal?

                              And just what is different between the forces needed to raise something as compared with those needed to hand clamp something? Is the screw not properly aligned with the nut?

                              Perhaps a photo would help.

                              Just a reminder, it is not April 1st yet.



                              Originally posted by Mark Rand View Post
                              I'm slightly confused. Why should a trapezoidal (30°) thread not be suitable for driving with a motor? I know that there is a 'centering' ACME thread form, which is the same as the normal (29°) ACME thread, but with reduced radial clearance, but even with the normal non-centreing form it works ok with a power feed?.. Do you need some sleeves to centre the male thread in the threaded bush?
                              Paul A.

                              Make it fit.
                              You can't win and there is a penalty for trying!

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