this was new to me
here is how the tool helped me...you can comb out the threads if they have been hammered on..the po hammered on the broken bolt of the steering shaft...the metric thread file allowed me to get a 10mm X1.5 tap started so I could rethread the few remaining broken threads..
it is square..a different pitch on each side...
I previously had run a 1/4 bolt douwn the center..so now I should be stronger than original