Variac or Rheostat for Hotwire Cutters?

General Discussion
1

I did a cursory archive search and can’t find any info on using a rheostat instead of a variac with a hotwire cutter. Is there any reason not to? I’ve got a variac, but my buddy just made a bow with a rheostat, and I’m just curious if anyone has used one with success (or failure for that matter).

2

If you’ve got the variac, use it. It works like a charm. Make sure to do some test cuts to get the voltage right before you get to cutting the real deal. If your hotwire comes off the template every now and then the first few times, no sweat. Do not go back over the area, unless you really know what you are doing. It is much easier to sand down a high spot than to have to thin out the whole blank or spackle due to a gouge.

JSS

3

A Variac is the best choice but you must be careful

or you could burn it out by putting to much amperage

thru the coils. It is imporant that you size your variac

for the resistance of the wire you are using. Hopefully

you are using a guage of Nichrome and not guitar strings.

Make sure that you are in the middle of the variac range

and it should last a lifetime. Mine is 21 yrs old and still

works like a charm.

4

They both do basically the same thing. Variac might even be considered a brand name that has become used generically for a type of variable transformer .

They both allow a user to adjust the output from an electrical source.

It is important that you recognize a couple of things…

  1. What is the source of your power?

  2. What is the rating of your controller, be it rheostat or variac? There should be a spec plate somewhere on the controller.

You would not, for instance, want to use a low current 12 volt DC rated rheostat with 110 volt AC current. It would fry in a fraction of a second.

Be especially careful with your hotwire device if using 110 current. It has been suggested here that for safety reasons, you route a 110 power source through a transformer and convert it to 12 volt before controlling the final output from there.

5

Great advice there,

The one about not going back over any lumps is important!

A smooth cut comes from even speed.

I use 21 AWG nichrome, and I have never snapped a wire! Perfect cut.

I bought 10 yards, so I think i’m set for life.

I started with 28 gauge, and it was only just useable, snapped a bit too much.

So anywhere inbetween that range will work.

I’d get one that is thickish, rather than thinner, so you can string your bow really tight (make it a strongly made bow) and you’ll get a truer cut without snapping.

But don’t max out your variac, as pointed out above!

Kit