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D-7 spec on Metric tap?

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  • D-7 spec on Metric tap?

    On a 14x2 metric tap there is a D-7 specification, I have seen H3,4,5 etc but not D7, is that the same as H# but for use with metric?

    Thanks
    Ken

  • #2
    I dont know that spec but any tapped hole that has specs I would use a roll tap. they are stronger and tap a better hole to start with.

    Screw machines use them and tap good holes faster than any cutting tap ever will.

    form/roll taps rule...

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    • #3
      I agree on the form tap, these holes do not have a spec, I bought these high quality taps very reasonable and was just curious as to what the D-7 designated.
      Probably why they were so reasonable

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      • #4
        Cool when you get an answer I will learn too. Metric tap specs are beyond what I know but I do know roll taps are best for holes with specs.

        Im here to learn too.

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        • #5
          Ken.

          Yep, D numbers are the metric worlds way of tap thread limits.

          An M14 x 2 - D7 should have a pitch dia of 12.751 min / 12.792 max

          Its pretty close to what you guys would know as a 6H fit. And that’s fairly standard for that size.

          Regards Phil.

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          • #6
            ISO bolt & screw specs

            These might help. There isn't a lot about.

            http://www.boltscience.com/pages/screw8.htm

            http://mdmetric.com/tech/u19e2.htm

            http://www.americanfastener.com/tech...ings_steel.asp

            http://www.google.com.au/search?hl=e...d&start=0&sa=N

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            • #7
              Thank you for that Phil, good to know that D-7 is pretty much standard.

              Oldtiffe, thanks for the links, it was surprising how little, read nothing, that I found searching.


              Ken

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              • #8
                Ken - Is it a Form-tap or a cutting tap? Forming taps come with something like 6HX tol.. A cutting tap M14 x 2 - 7D would be a special oversize M14 +50/+68.
                (Tap tol. are designated with the number first and than the letter like in 3H etc.). Do not confuse this with class. In ISO you also have class 1 or 2 or 3 etc.
                Pitch dia for M14 x 2 is 12.701 add 7D tol. +50 /+68 and you come up with
                12.751/12.769 .
                Formula for theoretical pitch d2 = d - 0.64952p
                For the inch crowd - that is approx. 0.002 - 0.003 inch oversize.
                Wow!! Time for a beer.
                Last edited by juergenwt; 06-07-2008, 04:16 PM.

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                • #9
                  It is a cut tap juergenwt,

                  This is the exact text;
                  14x2
                  7336 HS
                  2552 G D7

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                  • #10
                    McMasters list this as the "Ground Thread Limits" for Metric taps, so Phil you are correct, so was I but mine was a guess

                    They listed two for the M14X2, D3 and D7 so looks like it is as mentioned a pretty standard tap.

                    They did not list what the limits were, juergenwt, I bet your calculations are more then close enough for Government work.

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