With regard to plastic buttons, there is a risk of snapping the tap wire
when running them on, so I took the following precautions.  Firstly I
pre-drilled the hole to a size less than the diameter of the rolled
thread.  I then had a hand drill mounted in a bench vise with a small
sample length of tap wire with a gentle point, and would run the buttons
on and off by hand.  This would put an impression of the thread into
the button.

Paul Camps