The primary started out being wound between wooden
teeth cut in pine.
Then, on the list I read that wood may not be the best
insulator for the currents involved, so I drilled holes for nylon bolts,
inserted the bolts, then popped out what was left of the teeth.
Next time, I can skip making the teeth altogether and
start out with plastic bolts.
It uses 16 turns of 1/4" fridge tubing spaced 1/4" apart
The bolts are 1" long x 1/4" diameter.
The bolts... predrilling 1/4" holes made inserting
these things a breeze! I couldn't quite push them in, and didn't
want to bother turning them, so I hammered them and it went very quickly.
They came from http://www.fastenal.com/.