I've turned a couple of side knobs to replace the missing ones of my MF No. 2 and GP No. 5 hand drills. And I've bought some 5/16" - 18 threaded rod. It seems, however, that the pitch isn't appropriate -- I'm able to screw it in about 1/4' before it starts to bind. I've done a bunch of internet research trying to find what the correct size/pitch is, but I'm not getting the definitive answer I'm hoping for. I've read about a couple of people guessing at 5/16" - 20, but they seem to be just guesses. Also, it doesn't seem that this pitch is currently made. McMaster sells a 5/16" - 24 which I could try, but I'm reluctant to spend $8 on shipping a $2 purchase without knowing if it's going to be an improvement. I've also read that an M8 - 1.25 might be close to what is needed, but again, this seems like a guess. Anyways, can anyone tell me what the correct size/thread is needed for the side knobs of these drills(they're both the same.)

Any help would be greatly appreciated. Thanks fro reading!