Depends ion who you ask. I use the so called 3/8-10 modified, which pretty much means nothing except that it has a flat minor(bottom) rather than a normal V. Most have a .308" minor. The ones I use have a .312" minor. I drill shafts with a 5/16" bit and they'll fit any 3/8-10 in the world that I know of. Shafts with a smaller hole won't fit mine, and some won't even fit the .308" minor.
I use a .308 minor but drill with a carbide "N" bit, like the tighter feel.
Mario
I'm glad this works for you but the numbers don't make sence. N drill is .302 and the minor on your screw is .308. ?????
Thanks Mike, no wonder it didn't work..change that to .302 LOL