The first time tapping threads into my tapered gear shifter didn’t go all that well. This time around I made a proper fixture for holding it before tapping it without a problem.
I designed and 3D printed a gear shifter for my car. An engineer experienced with direct metal laser sintering wanted to to make his own out of titanium. In exchange for the model, he made me one as well. Read about how I barely managed to tap threads into it and see how you can do it yourself in a stainless steel version.