New knife blades from Bullet Tools

So in my previous posts I showed what I was able to do with the box cutters and that seemed to be reasonable.  However I felt there might be better solutions.  With a little bit of research I found that Bullet Tools has a line of products for cutting insulation.  Their Magnum Rigid Foam cutter looks like it would be very useful for large scale installers. But it's way too big for me to find useful.  However the 7" blades for utility knives looked like they might hit my requirements exactly.  They're designed for foam, and require no other infrastructure.  Though they do also mount in a reciprocating saw if I need to do some more bulk cutting.

Here some pictures of the blades.

The new razor blades as delivered.  

It's quite impressive when mounted in my utility knife handle.  It doesn't quite fold up for safety anymore. 

We  were able to successfully cut the foam very cleanly with the new knife.  See below for the example.

A successful cut.

The key we found to making a good cut was to take advantage of the length of the knife to keep it running straight and iterate in the same slot.  With the long blade you can hit the same line relatively well so as to not get parallel cuts.  This was even good enough to shave off 1/4" from the sides of the foam.

Cutting the foam with a good low angle of approach.

Our first attempt we scored the surface a little and then sawed through it with the blade almost perpendicular.  In the picture below you can see the issue was that the sawing motion drifted side to side leaving rough edges where the knife cut parallel to the original scoring.

What you get if you saw instead of slice.

PS Thanks to Wim for helping me with this.  Several of the fingers in the pictures are his.  And luckily despite the large and sharp knife all of his and mine are still attached.