Simple cab groove cutter.

[Allen]

The second picture shows the stone against the wood and the blade.
 
The groove is being cut but the stone can only be pushed onto the blade until it hits the step now protruding on the wooden guide. Depth of cut is set by the adjustment screws.
Just place the stone against the blade and gently turn.

I expect a sintered or smooth blade would give a better result than those that are notched.

Some material is better than others, but yesterday I did some bolder opal (congealed mud) for good results.

[finegemdesigns]

OK I think I see it. Check out this photo:

[Allen]

Got It.

The vertical line is curved the same as the blade.

Hope you have a grooving good time this new year. 

Allen.

[finegemdesigns]

Very cool and innovative and the fact that the stop is the same profile as the saw blade makes it even better.

This allows basically any shape to be rotated into the blade and give a consistent groove depth.

Really pure genius.