I’ve just tried to tap a 1” BSP thread in a piece of 50mm round bar (mild steel). I’ve got a Second tap, Presto, brand new. Bored out to 30.73mm 0.02mm under what the Zeus book says, thought that will be alright. got the tap about 6mm in and it is just solid. Got a 12” bahco on it! Took another 0.6mm out of the bore. Still mega tight managed to get about 10-12mm of threads in, just enough for the taper plug I want to use, to seal. What have I done wrong?