Quote Originally Posted by npcan2 View Post
True, however if I only tap the thread lower, won't the length of the thread inside the gear knob restrict how far down it could go?

I think that if I only tap the thread, then the gear knob will still sit at the same height as it won't utilise the extra thread created.
You can measure the depth inside the knob using a stick and compare that to the thread height on the gear stick. But from experience, you probably need to both tap and trip the stick. Be careful as to how you cut the stick because if you ruin the thread, you might not be able to screw the knob on.