Building a heat press: Nichrome question
Based merely on your questions I'd suggest you buy, rather than make, a heated platen. Or at least the heating part.

If making, you cut the 100 feet of wire (a resistor) into short enough sections (many parallel resistors) that a more suitable voltage drives it - or you choose something more appropriate for the task than 40 AWG nichrome. Industrial heating elements come in many flavors, lots of which work fine off 240 VAC. 







simulate this circuit &ndash; Schematic created using CircuitLab

Dunno about 20 tons, but a dry-mount press is a stock off the shelf (or off the used product) item with a large heated platen, for instance.

Silicone pad heaters are one stock item that would appear to work fine for your proposed use. Not associated with or even a customer of the place I found a picture of them...


If you heat by clamping them to the backside of the thick steel platen, 4 common 240VAC electric stove elements (per plate) will probably get the job done perfectly well  - ("as evenly as possible" is taken care of by 1.5 inches of steel.) You can also drill lots of holes and insert lots of cartridge heaters.

Be sure to carefully and throughly ground all parts of the press, especially if you home-brew the element. If something fails, you want the breaker to blow, not to electrocute someone.