I was on a job site a year ago or so and saw this groove cutter:



I think what the carpenter did was he got a longer bolt for the saw arbor and just used standard saw blades, then offset them so the teeth went in between the teeth of the adjacent blades.

It seemed like a simple solution to making a wide blade cutter.

I don't know all the fine details but it shouldn't be hard to do if you can find the right thread bolt for your standard skill saw.

Jim Rogers

Whatever you do, have fun doing it!