I screwed up the other day working on my Bronco project. I welded in a O2 sensor bung to my header reducer and got it a little too hot. The threads look ok but have kind of a mill scale look to them. I could probably force the sensor in, but I would rather clean up the threads.
So, my plan is to make a cleaning tap. I'll turn some stock to M18x1.5 and then mill 3 slots length wise and then heat treat. Since I have never did any heat treating before (I'll watch some YouTube first) will it distort the threads? The other thing is, I'm not sure what I have for stock, will 12L14 work? Other than that, I probably only have mystery metal. Or maybe a larger US bolt that I could turn down.
I don't think it will take much to clean up the threads, maybe even turning an M18x1.5 and a couple slots would do it without even hardening.