I bought a 1/8" nipple and want to tap an oil pan for its use. I found a 3/8"-24 bolt and it fit into a female 1/8" fitting. When I tried to put the nipple into a 3/8"-24 nut it wouldn't thread. Anyone know why, or know what I should tap the pan with? thanks

 

The brass fitting has a different thread pitch, you need to find out what the exact pitch is. Option #1: barrow a friends tap&die set. #2 barrow or buy a thread pitch gauge, then just buy the die you need. #3 Go buy a good tap&die set.

 

thanks for the quick response. I just noticed that my tap and die set has a 1/8' npt specific tap and die. It is actually 27 pitch, thats why it was so close to 3/8"-24.

 

Pipe nipples are tapered NPT threads, not SAE threads. You can't put an SAE nut on a pipe fitting. To attach a part through the oil pan, you need what is called a "bulkhead fitting". That has a longer, SAE male thread that is long enough to project through the bulkhead, and a matching nut to put on the other side.