saber saw keyway cutting

[Frank S]

Clever but wondering if you also mount more than one blade in the jigsaw to increase the cutting width..?

My Dewalt has a collet type blade lock that will only open wide enough to accept a single blade other brands may have a different means of securing the blades.
I found that making 2 cuts at just under the finished keyway width then slicing out the remainder from between them worked very well. then I finished the keyway with a small file. I always try to make my keyways as near to dimensionally true as possible.
Even when I has a broaching machine I would finish the cuts with a file. I have made a statement before about files. I love them and they hate me. New files get treated like precision instruments old dull files become scrapers or knives I can mill a head or deck an engine block and set the fit of a V8 intake manifold with a large file to almost the same precision as a CNC mill or surface grinder it just takes me a while longer.