Please see the previous 5 posts.Looks to me like it should be 3/8-24. See the link below (reference 31)
You said that you encountered resistance after threading in the 7/16-20 bolt a couple turns. Then you were able to force a couple more turns before encountering high resistance. Have you tried running a tap into the hole to see what comes back with the tap? If you are getting 4 turns into the hole, it seems like the bolt and threads are correct and that you have crap in the threads. You can feel the difference when running in the tap if you are cutting metal (cross threading the existing threads) or removing debris. Don’t cut metal with the tap. Another method is make a chaser with the 7/16-20 bolt. I use a 3-corner file to undercut the threads. I tried to upload a picture but I get a msg that it’s too large to upload from my iPad. Good luck
I have several tap and die sets. The one that is from HF I only use to chase or clean up threads. I don’t feel it’s strong enough to cut new threads. If I need to cut new threads (tap or die) I use my old craftsman set. Best of luck.I don't own a tap kit, I've been asking around to borrow one but coming up empty so i'll probalby go buy a HF kit after the holidays.
I also had the idea of getting a stick of hot glue or a crayon, an slightly melting it into the threads. The once it cools, popping it off and then comparing the threading of the glue stick to the threading of the bolt itself.
As far as dirt in the threads, it looked clean and it didn't feel like i was binding on dirt, it felt like the threads were wrong. But who knows.
I would not waste my money on the HF taps and dies. I brought two set and both were junk and had to return them then I got a couple Vermont American set. NOw of course that was 15 yrs ago and have only replace one tap so far.I don't own a tap kit, I've been asking around to borrow one but coming up empty so i'll probalby go buy a HF kit after the holidays.
I also had the idea of getting a stick of hot glue or a crayon, an slightly melting it into the threads. The once it cools, popping it off and then comparing the threading of the glue stick to the threading of the bolt itself.
As far as dirt in the threads, it looked clean and it didn't feel like i was binding on dirt, it felt like the threads were wrong. But who knows.