I have been pulling my hair out trying to tap holes to get decent
threads. Instead they are always sloppy and oversized.

I use good technique.....tap absolutely square to the hole;
I use a good cutting oil; and I back the tap out to clear
the chips; etc.

But the fact remains that a 1/4-20 tap measures .255 diameter
while a 1/4-20 bolt measures .244 diameter (threaded portion)

That is .011 difference!!! I have checked my other taps and they are
all oversized.

How can this be and is there any solution?

Thank you very much