I know this is a longshot but I am hoping someone has a non-standard tap that I could borrow. I guess prior to World War II the standard threads per inch on a 1/2 inch threaded bolt was 12 not 13 like it’s common place today. I purchased several drill press clamps and need to create backing nuts to hold them to the drill table. If anyone has one that they are willing to loan me I will get it back to them in a few days. Thank you.