How Deep To Tap??

Also, don't get carried away tightening a pipe thread. The sensor can split the aluminum, like a wedge if you force it in too tight. I have been coating the threads with gasket sealant (purple stuff that dissolves in ethanol). Teflon tape seals well, but I don't like the little bits that get into things when you unscrew the sensor. Also, your sensor must cut thru the sealant to get a good ground.