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vice thread efficiency

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vice thread efficiency

Home › Forums › General Questions › vice thread efficiency

Viewing 7 posts - 1 through 7 (of 7 total)
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  • 12 January 2020 at 18:41 #446185
    gerry madden
    Participant
      @gerrymadden53711

      Hi All,

      I'm just calculating the clamping force I can get using my large but ancient vice. Its mechanical advantage comes out at around 260 which would give some theoretically big forces but there must be some losses. Does anyone here have an experienced-based suggestions as to what this might be ? 10%, 50% 80% ?

      12 January 2020 at 18:41 #27066
      gerry madden
      Participant
        @gerrymadden53711
        12 January 2020 at 18:56 #446191
        Vidar
        Participant
          @vidar

          If it is a vice screw it can't be very efficient as that would not work for a vice. If it was more than about 50% efficient it would just backdrive instead of keeping something clamped.

          So less than 50%, and probably not even close to that as vice manufactureres likely wanted to be able to work up pressure and keep things stuck.

          12 January 2020 at 19:27 #446206
          Anonymous

            The manufacturers data for my machine vice shows that the clamping force (lbs) is very roughly 90 times the torque (ft-lbs).

            Andrew

            12 January 2020 at 19:56 #446209
            gerry madden
            Participant
              @gerrymadden53711

              Thanks all. Vidar you put me on the right lines and got me thinking. I found lots of data for screwjacks and it comes down to lead angle of the thread and CoF at the thread. So in my case its going to be about 20%. And when plug this figure in I end up in Andrews ball-park ! Clever stuff, maths

              Gerry

              12 January 2020 at 19:57 #446211
              not done it yet
              Participant
                @notdoneityet

                Look up ‘fireball tool’ for videos on testing vises. I expect there are others, too. Then work backwards…..

                12 January 2020 at 23:05 #446246
                Nick Hulme
                Participant
                  @nickhulme30114

                  Your choice of friction modifier can make a difference.

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