If you’re using a serrated knife, you may need to make a gentle sawing motion with the knife blade as you cut through the foam. As long as the blade stays straight up-and-down, you should still get an even edge. If you’re using a hot wire cutter, carefully push the wire through the foam in a steady, even motion.
I’m not sure exactly what you mean by a “clean cut” but if you can tolerate a little fuzz and roughness then fred is correct about power tools being useful. A serrated knife like you might use in the kitchen for bread cuts foam effectively. So do the wavy knife-edge jigsaw or recip saw blades like these:
Another thing – lightly compressed with the straight end device – jig saw with blade – and wizz wizz on though at full tilt it appeared. again I wasn’t doing it – but dude was making foarm blocks for tool box drawers with it. Think snap on 42 inch job – drawers were I don’t know 28 or so on one side and 3 inch thick – whatever it is. foam block was 2 piece one red the other yellow so it had a witness color layer.
So supposedly they make a T shank jigsaw blade for cutting foam that acts like that foam cutter Fred posted about. I’ve seen a guy in the hangar use one not sure where it came from. it’s like 6 or so inches long and is wavy not serrated. as best as I remember.
I’ve only tried a hot knife on soft foam once and it was messy for me as well. I have never tried it on foam rubber, but I imagine it wouldn’t work. Hot knives/wires work by melting the material. Rubber doesn’t melt, it burns, so even if it could cut the foam rubber it would necessarily leave a nasty burnt edge.
I have had good results making straight cuts in most kinds of foam rubber and memory foam uncompressed using a snap-blade utility knife with a brand new, full-length blade. I extend the blade all the way and cut at an angle so as much of the blade is in the cut as possible. Brand new is important, if the blade has been used even a little it probably won’t cut well. With a very sharp blade there is no “sawing” motion required.
One of the things I neglected to mention in my banquette-building post was how to cut the foam. Having no money, I cut through five-inch-thick foam sections by making repeated swipes with a cheapie utility knife like the one above. It was time-consuming, messy, far from accurate, and doing the curves was a real pain. Its the dumb way to cut foam.
Theyre also fairly expensive, ranging from about $160 to over $500 for commercial grade tools. Hercules makes a nice-looking one for about $389.
If you dont have that kinda cash but have some building skills, check out this awesome DIY foam saw by YouTube user Designsbyg. Youll kick yourself when you see, midway through the video, what he actually used for the cutting device.
This foam cutting saw has a base that rides on tiny wheels to prevent friction, and the large area of the base keeps the blade straight up and down. Heres a similar one in action:
Don’t Cut Foam With A Bread Knife! A Better Way! #upholstery #doityourself
FAQ
What is the best method of cutting foam?
What tool do you use to cut foam?
What is the best tool to cut memory foam with?
How do you cut foam without a foam cutter?
How do you cut foam with a knife?
Hold the knife at a slight angle and apply steady pressure as you cut through the foam. Cut in one smooth motion: To achieve a clean cut, it’s best to cut through the foam in one smooth motion. Avoid sawing back and forth, as this can result in jagged edges. Instead, use a slow and steady motion to guide the knife through the foam.
How do you cut upholstery foam?
Apply just enough pressure to draw the line so you don’t tear into the foam with the pen. Step 2: Use a sharp, serrated knife to score along the mark. Although tutorials on how to cut upholstery foam recommend both smooth and serrated blades, smooth blades, such as those on carving knives, can bind or drag in the cut.
How do you cut foam board?
The best way to cut foam board, by contrast, is to use a sharp craft knife or box cutter, with a straightedge as a guide. Don’t rush: Cutting too quickly can cause the blade to jump the straightedge and cut your fingers. New upholstery is an attractive way to update old seating, but cutting foam can sometimes be tricky.
How do you cut a foam ring?
Make dots at your desired length every few inches down the foam, then connect the dots using a straight edge. Tip: Measure and cut the short edge first to get the length you need, and do the long side second. This way, you’re cutting the shortest possible length each time. Take your serrated knife and line it up with the cut line you drew.