# Threading chart



## J. Tranter (Mar 9, 2008)

Does anyone know where to find a metric threading chart? You know the ones that tell you what drill to use with what tap.
John T


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## mklotz (Mar 9, 2008)

Tap drill size = Major diameter - pitch

example: 6 x 1 mm tap

Tap drill size = 6 - 1 = 5 mm

This approximate formula will yield about 75% depth of thread.

BTW, it works for Imperial threads as well...

example: 1/4 - 20 tap

Tap drill size = 0.25 - 1/20 = 0.2" (#7 drill)


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## rake60 (Mar 11, 2008)

John

I keep this taped to the lid of my toolbox.


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