I've recently been running many jobs with bastard sized threads that are not found on most Tap Drill Charts. As you may know, finding the tap drill size for a #10-64 tap may be a bit of a challenge.
My solution? Create a 'chart independant' application that will calculate the required tap drill size given the tap's major dia, the desired percentage of thread, and the TPI or Pitch of the tap.
It will calculate for Inch Cut and Inch Form, as well as Metric Cut and Metric Form taps.
There are 2 different downloads; The small one is just the executable, for those that already have the VB6 Runtime libraries, and the larger one has an install program. They can be found at cadcam's FTP site under Unspecified Uploads as Tap Drill Calculator.zip and Tap Drill Calc Setup.zip.
Enjoy it and please post a comment if you try it out.
'Rekd