I'm purchasing drill bits

[avbill]

I bought the bock 5mm & 6mm taps so after reading:i need the following drill bits

6mm feeder tap = ( 7.9 - 0.2 ) = 7.7mm or 'N'

5mm feeder tap = ( 6.4 - 02 ) = 6.2mm or "C"

Is my understanding correct in this matter?

thanks bill

 

[mredburn]

no the rule of thumb is diameter minus pitch. 7.9-.6 and 6.4-.6

 

[mredburn]

Then you may have to use a slightly larger drill bit since most taps are not cutting 100 percent threads. so I would start with 9/32 and B or C I use a C drill bit. for the #5 and it works fine. If you find that your cross threading threads go down to a B Cut Your tenons 7.7 and 6.3mm for the dies