What kind of cutting knife are you using for 2" foam?

[Jay Batson]

Hi -

Building my first HYurt, and have been reading all the right stuff / watching all the right videos (e.g. appropredia & Danger).

BUT - I'm puzzled about one thing: what kind of tool to cut with?

The only Rmax available in my region is the 2" stuff, and that seems pretty thick to cut through. I'd have thought to buy one of those utility knives with the retractable / extendable blades, but the only ones I see at Home Depot are the ones that have a tip-snapoff to give you a new sharp bit at the front, and I'm thinking those might just break when trying to cut a rounded door / window corner.

I'm also assuming that:

- A bigger knife might be too thick in trying to cut through the foam, and bind up when cutting;

- A drywall saw will take away too much material, nor will it make a nice clean cut.

So, what do people use for the 2" foam?

Call me curious.

-jb

[Vladimir Khodel]

Fine Homebuilding magazine had a reader tip a few years ago :) which was to take a 4" putty/taping knife and sharpen its outside curved edge - then you hold it like a kitchen knife and pull towards you along a guide such as bevelled at 60 degrees 2x4, and it cuts polyiso like butter in a couple of passes :)

This can probably be used even on the playa, since there is no moop at all (well, I guess there are polyiso bevels to get rid of)

When making sharp or rounded corners there is still some need for a snap-off type knife of course, but very minimal.

Good luck!

Vladimir

-jb

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[Steve Upstill]

I was very concerned about using my hands to cut a straight line at a consistent bevel angle, so I took the trouble to haul my table saw out to my build site. I was glad I did. Set the blade at the correct angle, mark the diagonal cuts and away you go. The edge bevels in particular are no-brainers, since the fence can be set once (right next to the blade) for dozens of cuts.

For the diagonal cuts, you do need a steady hand and good eye to cut a straight line 9' long in the middle of one of those panels. That's a situation where it might be better to use a long-bladed jigsaw and a long (> 9') straight piece of board, metal or angle-iron for a guide--the problem being where to rest the panel and still give the saw clearance on the underside.

Makes a pile of nasty poly-iso dust (DO NOT try to cut poly-iso edges on-playa. There WILL be flyaways, to say nothing of the anguish of such work in that situation), and isn't too kind to your saw blade (get a disposably cheap one), but for sweet manufacture it's hard to beat. 

Cheers,

Steve

[Kevin Fischer]

I used a table saw for cuts on 2" board. If you don't have a proper vac setup, make sure you are using N99 masks (or at least N95, per US government recommendations) and vacuum with a HEPA filter vacuum. Vacuuming with a non HEPA filter vacuum spreads microscopic dust particles everywhere.

[hal muskat]

I use a very good kitchen knife that get's sharpened after several cuts! Less moop & toxic shit in the air!