The reciprocating blades of an electric carving knife have always been my “go to” as I get a smooth cut even for curves or into corners. Just go carefully and keep knife vertical and not force the blades through the foam.I think he's talking about polyethylene foam, not polystyrene foam. All I've ever seen used is like an electric carving knife with the reciprocating blades. It's a specialized tool.
I've made my own for cutting styrofoam wings for R/C airplanes with nichrome wire using a battery charger for power.
I agree, just did not see any for sale at the time I bought the carving knife or I would have gone for one of those… Perhaps next time as they are cheap enough…An electric fillet knife works better than an electric carving knife. Fillet knives have plain edges instead of serrated. Keep it very sharp.




