I need to cut 2x2 ft square pieces from a sheet of memory foam. Not sure what tool is best for this. Any ideas? In the future I'd like to cut circles and eventually sculpt irregular shapes, I don't know what tool can be used for this sort of job.
For thicker pieces you might find you get better results by compressing the foam before cutting it. You could make a simple straight-line clamp out of a couple of 2x4s linked with a door hinge -- just put your foam in between, clamp the open end shut with a C-clamp, and use one edge of the wood as a guide for your cut. For your curved cuts it might make more sense to make a plywood die to match the final shape and press it down by hand or with something heavy before cutting around it.
I used a sharp razor knife on my memory foam. You can make a line and just make long cuts. Do not try to cut through it all at once. Start by making your first cut deep enough that you can follow it through and make a straight cut. Just keep cutting down your line until you are through. Take your time and be careful and you will have a clean cut. Don't use a saw or hot knife you will just ruin your topper.
A razor knife is your best tool for this.
If this were styrofoam, I'd recommend a hot knife (basically a wire stretched taut on a frame similar to a jigsaw, and electrified to heat it). However, visco-elastic foam will behave differently and you probably don't want to be breathing in the fumes produces by melting it.
In this white paper from the Polyurethane Foam Association regarding visco-elastic ("memory") foam, the PFA states that most conventional tools including saws can be used to cut VEF. However, care must be taken to go slowly and not deform the foam too much with the cutting action, because the slower recovery of VEF to its original shape will cause defects in the kerf line and possibly cause the saw to bind more easily.
I strongly recommend you let the mattress chill outside on a flat surface that maintains its original shape. The mattress becomes very hard when cold, in the same way warmth causes it to soften.
I would then follow the PFA recommendation; "that most conventional tools including saws can be used to cut VEF".
P.S. I do not know what the PFA thinks about having soft or hard memory foam, but I know which of these I prefer.
I used a pair of Cutco scissors. They worked great. The foam I cut was about 3" thick. I tried some other scissors first but they didn't even think about cutting it. I think the reason the Cutco scissors worked so well is the serrated edge they have. This made them bite into it instead of pushing back out like the other scissors I tried to use.
Well the best option is to clamp the memory foam between the 2 x 4' s.mentioned before.on top off a sharpy marked line, which is a marker.adjustable wood working clamps would work great for this. no matter how thick, which will decide the length of your knife. a good brand new razor utility knife preferably one that is disposable the kind that when you extend it you can break off the used dull portion. By using this kind of . razor knife when new you can extend it long enough to make a deep good clean cut through the thickness. without having to buy or use one of your wife's or husbands kitchen knives or just something that just won't do a good job Wright off the bat, and wind up with something that looks like A person having a nervous break down did it . the cost of a new razor knife like this is at the most $5 bucks at the dollar General store.