What have folks found the best way to make straight cuts in the pink foam (I’ll be using the 2" thick variety).
For example, I’ll need to cut quite a few of the 2’ wide sheets down to 1’ width…
I’m hoping score-and-snap is effective as that would be easiest, but would still like the input of those experienced with it…
You’ll really have to score deeply to get clean snaps in the two inch stuff. It works better in the thinner sheets.
The best would be to use a long straightedge, maybe a large carpenter’s square. Failing that, a good piece of 2X4 that you know is reasonably straight, maybe a cedar stake.
Thanks, Selector. That’s what I feared.
But even with a straightedge (I have a 4’ level that will work nicely), what to cut with? My initial thought (boxcutter) also won’t work with the 2" stuff (and with supports every 16" I’d like to use 2" and skip the plywood underlayment entirely).
Should I use a hotknife (yuck, fumes), a sharp kitchen knife??? I’m not quite sure how to proceed - my experience is all thinner materials…
I’ve used knives similar to these. You get the benefit of having a sharp cheap replaceable knife with an adjustable length. Just extend the blade to slightly longer than the thickness you are cutting. I would recommend using a straightedge to keep things nice and straight. Also, be sure to keep the knife perpendicular to the foam.
HD
You could use a small carpenter’s saw for this purpose.You don’t need the top quality professional tool and probably could find one for a minimal fee in a Walmart tool dept.It will last you forever doing this and can also be handy for other layout building chores.
Score and snap - use a utility knife and a long metal straight edge. It ends up being as close to a smooth edge as you’re gonna get - fairly clean. If you need it perfect then you need something like a hot wire cutter, or perhaps a very fine tooth saw blade in a table saw - although that will DEFINITELY make a mess.
–Randy
I use my table saw for cutting 2" blue foam. I set up in the driveway and have very little mess.
Chuck
If you measure carefully, you can score BOTH sides and then snap it. I get a pretty good edge that way, but I’ll mostly be covering the seams with various kinds of scenery anyway, so the quality of the edge isn’t that important to me.
I make a series of cuts for 2" foam, extending the knife blade each time. Biggest problem is holding the blade vertical.
I usually use 1" or 1/2" foam for bases and 2" for added height. That means the edges aren’t as critical.
The knives HoosierDaddy suggested work pretty well for 2" foam. Fully extended, they are a little over 2" long when new. The blades are pretty thin, which means that it will cut easier than a thicker blade, but being thin, the blade sometimes has a tendency to wander and you may not get a good vertical cut. I use a drywall framing square for a straight edge, but your 4’ level is almost as good. Remember, you want to stay vertical with your cut and the thickness of the level may interfere with that.
MisterBeasley suggests measuring on both sides and cutting to the center on each side. I use that procedure often and it works as well as your measuring is accurate. Foam is easy enough to work with to clean up a rough cut, so don’t worry too much about a little roughness.
Like Crandell said, 2" foam doesn’t scribe and snap well. It’s too thick to do it reliably, although if you can cut it deep enough and only snap about 1/2" or 3/4", it should work okay.
Great idea to use 2" foam and ditch the plywood! You will be happy without the plywood.
Darrell, quiet…for now
I forgot to mention that you can ask at the home center where you buy the foam if they can cut it for you. They do this with other sheet goods and the charge is usually small. That would give you really nice, straight, vertical cuts and leave the mess for THEM to clean up! LOL
Darrell, forgetful, butquiet…for now
I generally use the knives HoosierDaddy showed for all foam cuts, from cutting them down to scenic carving. They work great, but dull fast when cutting through foam, so be sure to have a LOT of fresh blades on hand.
I use the score & snap technique all the time with foam, and it generally works well. If there’s a slightly rough edge, a Surefoam tool and sanding block will take care of the edge in a minute or two.
Food for thought-probably would have used the “snap” method had I read this forum before but this is the way I did it.
Scribed a line on the 2" foam with a straight edge. Bought a fine tooth metal cutting blade for a Saber saw and beveled the tooth edges to a near knife-like serrated profile using a dremel tool with a grinding disc. Set the blade position so that the longest stroke of the saw was just under 2". Cut the foam folowing the line. Straightness depends on how meticulously you follow the line. The foam snaps easily after the cut. Some trimming may be needed with a Surefoam tool. Clean cut no mess. Saw motion needs to reasonably constant as hesitation will cause heat build-up due to friction. Needed to cut curves which is why I used this method. Also cuts perpendicular. You can use a scrap piece if needed to support the other side of the saw.
JEB
Score it on both sides for long cuts, using a cheap but straight six foot level for a straightedge, or use a standard crosscut handsaw for smaller pieces.
Well, I think everyone got the knife part down, but her is a another tip. (I have done ALOT of foam work)
Get a peice 1x4, maybe a 8, or 10ft, and use that for a straight edge. You can clamp to secure, and cut away without haveing to worry about missing the cut paths, or getting nasty double cuts in the foam. Good luck.[:D]
John K
Create a hotwire with ni-chrome wire (available from the hobby store) and run it with an old power pack (more speed = more heat!). Use a 1x3 on each side as a straight edge (secure them with long screws right through the foam).
OR, cut on a table saw. The foam cuts surprisingly well, with very little mess. Go fairly quickly, but don’t force it. Works well.
Andrew
For what it’s worth I use a mini hacksaw with a strong blade and make the cuts with the extended portion of the long blade.
I’ve also heard of others using a serrated bread knife from the local Dollar store!
Thanks,
Doug
[:D]
I use what I know as a boot knife, used for cutting leather. I have never seen them in North America, but they are common in England and Australia.
I used to take a 1" wide power hacksaw blade and gut a piece about 6 or 8" long. About 1" protrudes fomr the handle at full width. Then for 3" reduce the width in a straight line to about 3/8" at the tip. Grind a rounded counter on the ‘back’ side of the tip.
When properly ground, hardened and honed they will hold an edge for an inordinate period. Sorry, I cant upload a photo of one. The 'box cutter / craft knives" shown earlier in the thread are far too flimsy and thus dangerous. In fact I would countenance against using any type of snap-off blade for any purpose. They are cheap, but the injuries I have seen them cause are far from cheap to repair.
John
You might check at a hobby shop for long Xacto blades. I know I’ve bought some that are about 2" long back when I was doing model airplanes. They were great for carving thick balsa blocks.
John M
when i install the stuff professionally, i usually have two basic methods, depending on the need for accuracy, and who might be watching.
if time is more important than accuracy: i snap a chalk line down the center and cut with my utility knife as i exhale slowly in a zen like trance while following the line precisely. i do this on both sides, and snap it apart.
if accuracy is the important factor: i mark the center at three or four points, and use my four foot drywall square to span the marks and guide the cut. i do this on both sides, and snap it apart.
the drywall square is the right tool for the job because of its thinness and length. it allows you to control the cut/knife so potential damage to you or the material is minimal. if you have to fake it; minimally tape a metal ruler or yardstick to the foam and take your time. and keep your thumb out of the way. cut depth is what is comfortable. make several strokes if necessary.
your knife is your basic utility knife that all carpenters carry around; it says stanley on the side and has spare blades in the handle. it also makes a great hobby knife. i like this knife because it is comfortable to grip, and allows me the control i seek.
-rrick