RE: scratch built hot wire cutter
A little bit of knowledge is dangerous.
There is nothing wrong with using 115 volts as the input to the dimmer, unless you are stupid enough to place yourself across the input.
The output is very safe, unless you insist on doing the hot wiring in your bare feet while standing in a bucket full of salt water with copper ankle bracelets that lead to your grounding electrode system.
Then you might feel a tingle.
BTW....nichrome wire sucks, use stainless.