"Bill Stock" writes:
This is somewhat OT, but you appear to be the biggest suppository of
knowledge when it comes to NiChrome.

REpository.

I want to build a Hot Wire to bend some Acrylic. The wire in
question is #22 and approximately 1 ohm per foot.

Let's assume you need 3 feet for the sake of the math below

Most of the temperature tables I've seen for NiChrome wire show the
relationship between Amps and Temperature. But shouldn't this really
be Watts?

When resistance is fixed per foot, and the manufacturer doesn't know
how many feet you have, they can't use watts. They could use watts
per foot, but that's essentially amps. Constant amps gives a
predictable watts/foot regardless of the length of the wire. For the
same amps (and thus temperature), and twice longer wire uses twice the
watts (and needs twice the voltage).

For example the tables show that I need about 3 Amps for the 400°F
that I require. The tables I've seen don't actually show temps that
low. But assuming the tables are referring to 120V, that would mean
360 Watts or 15 Amps at 24 Volts? This can't be right?

3 amps for a 3 ohm (3 foot) wire is 9 volts (E=IR). You choose the
voltage in order to create the appropriate current.

If you put a 3 ohm wire on a 120VAC outlet, you'll get 40 amps (4800
watts) for a few seconds. If you try this, use a movie camera so we
can all share the excitement ;-)

The second problem is the power supply. Assuming I'm confused about
the Watts and 3 amps at 24 Volts will suffice.

You want a variable voltage power supply rated at, say, twice the
amperage you'll actually need, and high enough volts to generate the
amperage your project will call for. You adjust the voltage to result
in the current needed. Make sure the supply has an ammeter on it, or
use your own.

The average light dimmer will only handle about 500 Watts,

The average light dimmer is a pulse width modulator suitable only for
120VAC circuits.

If you want 3 amps across 3 ohms, with a 120VAC circuit, 3 amps at
120VAC is 360 watts. You'd need a couple lightbulbs in parallel to
get that, or a floodlight. I suppose you could build a box with, say,
3-6 100W bulbs each with their own light switch, to provide variable
current. Each bulb adds ~ 0.8 amps.