On Wednesday, October 7, 2020 at 9:03:35 PM UTC+1, Dave Liquorice wrote:
On Wed, 7 Oct 2020 16:59:42 +0100, newshound wrote:

To cut the Celotex floor insulation into joist gap panels, I
bought
some of these jigsaw blades which should be good for up to 100mm.

Once you put any sideways force on a jigsaw blade it will bend and you
won't get a square cut any more.
+1
Cut by hand using a panel saw?
+1

Or score and snap. Works at 25 mm not tried 75 mm that might be to
thick or require to much force over a too long a distance.

--
Cheers
Dave.

I used an old bread knife - works well.

The best are those with actual serrations, and a mix of serration pitches: f f f f m f f f f m f f f f m f f f f m f f f f m f f f f m f f f f m f f f f m IYSWIM

The more modern wavy edge ones are less good for this.