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‘O’ Ring Groove Sizing

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‘O’ Ring Groove Sizing

Home › Forums › Workshop Techniques › ‘O’ Ring Groove Sizing

Viewing 6 posts - 1 through 6 (of 6 total)
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  • 26 August 2023 at 19:55 #658097
    Colin Heseltine
    Participant
      @colinheseltine48622

      I have a hand pump on a Stuart 504 boiler. The pump does not seal over well. It used to have graphite yarn as a seal but this had dried and gone brittle so replaced with an 'O' ring. Still not a very good seal. I am thinking of putting an 'O' ring on the piston itself.

      The piston is 0.624" dia. and the bore is nominally .625". I have silicone 'O' ring which is .625" OD and .4375 ID.

      Is this a good idea and if so what groove dimensions should I use (width and depth).

      Many Thanks,

      Colin

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      26 August 2023 at 19:55 #16468
      Colin Heseltine
      Participant
        @colinheseltine48622
        26 August 2023 at 20:30 #658099
        JasonB
        Moderator
          @jasonb

          Is that actual size or nominal size?

          My thought s are that it is a nominal 3/32" ring with actual cross section of approx 0.103.

          Typical size for model use from Model Engineers Handbook would be groove width of 0.125" and depth from cylinder 0.098" which is approx 5% compression

          26 August 2023 at 21:36 #658107
          Colin Heseltine
          Participant
            @colinheseltine48622

            'O' ring is 5/8" OD and 7/16" ID Macc Models no. 111.

            Colin

            26 August 2023 at 22:13 #658115
            Huub
            Participant
              @huub

              I use the this PDF/handbook for o-ring & groove dimensions

              Parker O-ring dimensions

              27 August 2023 at 06:50 #658132
              JasonB
              Moderator
                @jasonb

                That's the nominal sizes then and nominal 3/32" section

                So my sizes will be OK of model use.

                The thing with many makers/suppliers charts is they are for much higher pressure use which results in far too much friction for our use in things like model engine cylinders and feed feed pumps. The figures I gave are based on tests done by Arnold Throp (Fleet Coreliss fame)

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