I have a bit of a problem, my 2002 cat 500 temp switch(the one screwed into the head by the t-stat), was bad. I attemped to unscrew the old switch to replace but the old switch being aluminum and obviously siezed in the head striped but left the threads in the head I believe,anyway does anyone know what size threads or tap rathe to use to chase those threads????? please help

 

well just to answer my own question in case someone else runs into this they are 1/8 inch by 27 thread pipe tap.