Take a close look at the threads on the bolt. The tops are probably
"flattened" a little. This is why the bolt "appears" to be undersized.
Are the bolts really sloppy in the hole or is your concern solely
based upon the measurement differences?

Pete Stanaitis
------------------------

wrote:

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