Tap drill sizes

[gman]

I'm not sure if this is the correct forum or has been discussed in the past. But here is a very simple formula on finding the correct tap drill size.

tap size-pitch=tap drill
example 1/4-20 tap is .201 tap drill
.250-(1/20)=.20

[zcases]

And this is even easier in metric......M3 x .5 thread, M3 - .5 = 2.5mm tap drill.