I was assembling my new Delta tenoning jig (the first I've ever owned)
and reading through the usage tips they offered a brilliant technique.
I love precision. Maybe everyone else uses this technique but it was a
revelation for me. I had always made home made jigs to cut my tenons
and never happy with my precision.
The suggest to make the first cheek cut with a shim piece between the
part and the jig. The shim thickness should be equal to the intended
thickness of the tenon plus the saw blade width. So a 3/8" tenon with
an 1/8" blade would be a 1/2" shim. Then make the second cheek cut by
removing the shim piece leaving the part in the same orientation and
you have an exact 3/8" thick tenon. Regardless of material thickness
you end up with a tenon the exact thickness of shim minus the blade
thickness. It is just up to the you to aling the first cut so you end
up with a centered tenon.
Using an 1/* blade and 1/2 baltic birch ply for a shim one can get
this exact thickness.
As long as you flip the piece end for end you will end up with aligned
tenons even if they are slightly off center. Other methods could end
up with a perfectly centered tenon but the width may very if the part
I really like this. Like I said maybe it is a duh moment for otthers
but I was pleasantly