bottle cutter, further update

On Mon, 19 Dec 2005 21:31:20 -0600 in rec.crafts.glass, "Mike Firth" wrote,

I think that you should include the caution that variac transformers do not provide isolation between the power mains and the output. Touching the wire or any metal part connected to the output can give you a dangerous shock.

I like to use a large car battery charger plugged in to the variac. That provides isolation and a big current step-up to better match the low resistance heating wire. That may not work with a modern automatic charger but works great with an old simple-minded one.