Have used table saw, circular saw, scoring with ut. knife and snapping, sawing with a steak knife, used an old (but sharp as a razor) boning knife. There has got to be a better way. I’ve heard of “hot” knives, and seen DIY plans for making an electrically heated “cheese cutter” type knives. Do these hot methods work with polyiso foam or just EPS and XPS?
Anyone have another method for making clean, accurate cuts?
Replies
I think a hot wire cutter will work with almost any sort of foam, though probably some better than others. You basically need a nichrome wire, a frame of some sort to hold the wire (eg, bow saw frame), and a low voltage power supply.
http://en.wikipedia.org/wiki/Hot-wire_foam_cutter
Another option is an electric carving knife.
At first I thought you were asking about soft foam (mattress)). We use a cheap electric carving knife for that. Maybe your wife has one you could try out on the rigid stuff. ; ^ )
It works great on soft foam.
Mike
Trust in God, but row away from the rocks.
Hot wire systems are used mostly by set builders to cut EPS foam. I have no knowledge of how well it cuts other insulation since set builders are not doing permanent construction . Hot wires can cut curves, so if you have alot of scribed to fit work this may be the way to go.
As for myself, I prefer to cut with an old skilsaw fitted with an abrasive cutoff wheel. More accurate than the "score and snap" method and alot less messy than a traditional sawblade. I've also used an angle grinder fitted with a sanding disk to do final shaping. Gaps can be fixed with a shot of expanding foam.
toolman65
Keeping things simple, I've always had good cuts with the filleting knife (boning) or a bread knife.
I've sharpened an old, thin 6" taping knife on the curved edge. That works pretty slick.
-h
Wearing a glove and using a bare hacksaw blade works pretty well--can actually sort of push and saw the blade through to start the cut. Pointy drywall saw works too.
For neat, sharp cuts, I cut foam board with a box-cutter/razor knife, with a new, sharp blade extended full-lengthm, and it works as well as anything else I've tried for all sorts of board, including polyiso, XPS, etc.
The trick is that you need to keep the blade at a very shallow angle to the foamboard surface. Don't try to cut the whole thickness in one pass; go two or three times, keeping the blade at as low an angle as you can. Let the knife do the work; don't muscle it any more than absolutely necessary.
Pull straight, or you'll snap the blade. Also, change the blade when it gets dull. I might go through about 10 blades per 100 sheets of foamboard from the combination of those two factors.
Dinosaur
How now, Mighty Sauron, that thou art not brought
low by this? For thine evil pales before that which
foolish men call Justice....
RedfordHenry
I do repeated cuts on my table saw both EPS and Polyiso. That's how I made my ICF's curve, I cut each block on my table saw at 7 1/2 degrees. The secret to a table saw is spray the blade and table well with WD40 and do it quickly! slow will melt.
Keep your hand well away I take the guard off
Single cuts I do with a sawzall (spray with WD40) or if straight cuts are critcal use a circular saw (sprayed with WD40) because it's faster than melting. I do have a melter but haven't used it on Polyiso.
I just finished doing EPS foam in a room.
I grabbed my japanese-style pull-saw, and found that it worked nicely. I used it at a shallow angle to scribe along the line, and then cut through.
Fast, but still with a bit of dust.
I use my old circsaw, and also lately I've been using my insul knife as well.
The house I'm building right now has 3 inch thick wool insulation for walls/ceilings. The wall wool insulation is 100% wool, and my insul knife is the only thing that will cut it. I keep my sharpener handy though as the blade dulls pretty quickly.
SS
What is this insul knife you speak of? I cut 2" pink foam board with a serrated steak knife... no chips and a pretty clean cut... but something better would be, well... better If dogs run free, then what must be,
Must be, and that is all.
True love can make a blade of grass
Stand up straight and tall.
In harmony with the cosmic sea,
True love needs no company,
It can cure the soul, it can make it whole,
If dogs run free.
http://www.cepcotool.com/insulknife/
Check it out, they have a demo video, etc. on their website.. I'll vouch for it anyway, its a decent tool.
SS
Yeah man, that is sweet... and it does lunch. too! If dogs run free, then what must be,
Must be, and that is all.
True love can make a blade of grass
Stand up straight and tall.
In harmony with the cosmic sea,
True love needs no company,
It can cure the soul, it can make it whole,
If dogs run free.
Thanks all for the suggestions. I think that I've tried almost all of them except for sharpening the back edge of an old taping knife. I have a bunch of 2" Thermax to cut in the next two days, might give that a whirl. In the meantime, I'll keep the boning knife close by.