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  • GM thread standard?

    I have to make some custom 6.3mm x 1 bolts since i can't find them anywhere, so i started wondering why GM had their own treading standard.

    anyone know ?
    -Dan S.
    dans-hobbies.com

  • #2
    GM like lots of other company's made their own sizes so if you bought from them you were 'sucked' in. As Kodak made their own size film and virtually gave the cameras away for almost nothing as the only film you could buy was from them.
    These days it would be easier to make your own in house thread as cnc threading machines are quite cheap these days. I suppose the purist could always argue that GM want to keep the quality control in their hands but I reckon they just want the money!!
    Peter
    I have tools I don't know how to use!!

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    • #3
      now see the funny part is that the bolts aren't for a gm product, they're for a Chinese made dust collector that I'm converting from single stage to two stage.
      -Dan S.
      dans-hobbies.com

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      • #4
        All the funnier in that it shows that the chinese are just copying everything verbatum!!
        Peter
        I have tools I don't know how to use!!

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        • #5
          GM does plenty of stupid fastners just like everyone else in th automotive biz.

          Latest from them are odd sized metrics 7,9,11,13 mm thread diameters.
          I just need one more tool,just one!

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          • #6
            You probably won't believe this but 6.3mm x 1mm is a standard metric size. I have one from a tap & die set sold at Sears back in the 70's!

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            • #7
              Think 1/4-24 fellows

              Rich

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              • #8
                1/4" Bsf

                Or a 1/4" BSF at 26 TPI is even closer to 1mm pitch which is 25.4 TPI. Unlikely for a GM thread though unless its prewar Vauxhall.

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                • #9
                  Originally posted by fasto
                  You probably won't believe this but 6.3mm x 1mm is a standard metric size. I have one from a tap & die set sold at Sears back in the 70's!

                  actually, thats how I made the bolts tonight. I cut some long 1/4 -20 bolts to length, and then broke out the sears die and went to town.
                  -Dan S.
                  dans-hobbies.com

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                  • #10
                    Here's a clue. 6.35mm = 0.250". And a 1mm pitch is very close to 25TPI. Someone just translated the 1/4" English size to metric with a metric pitch. Probably lets them make "metric" serews with 1/4" stock.
                    Paul A.
                    SE Texas

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

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