re: Compression Release Valve Adapter

Hi Bruce. what happened is I bought a pair of taps for 22mm x1.5mm. One is a taper tap and the other is a bottom tap. I ran them in 1" and the new plug would only screw in half way. The 22 mm plug out of my 1928 McCormick Deering engine did the same thing. I'm thinking maybe the pitch diameter of these taps is about .004 too small. It did not take much to run the die over the plugs and they want right in. I had to buy a die to make the male end that will screw into the engine. I can't chase metric threads on my lathe...unless they have a 2 mm pitch which is almost the same a 13 TPI.