MIMF

Thanks, Brian. It's a riff on an old idea. Standing on it sounds like fun! And yes, I do need the full inch. I want the inch at the heel, but it's also necessary to get the flange to reach to the end of the tenon, plus a little more for truing up the fingerboard gluing surface.

EDIT: Stood on it. My heel right at the nut. Nothing. Not even a creak from glue cracking. I think I weigh about 175 right now. I didn't jump or bounce on it, but this is good enough for me.

Back from our Spring Break trip south to warmer weather, and went out to the shop intent on destroying this joint.

I stood on it, and again nothing. I put a clamp on it and tightened it as far as I could, until I got hickies on my palms. That piece of wood is some 15/16" 17-ply plywood on edge, and it deflected over 1/8" (pic taken before I torqued it). Nothing. Then I put it in my end vice and cranked it down. The headstock wood split down the grain on one side... ... and cracked down the floor of the pocket on the other side, allowing just a bit of the tenon to lift out. This joint is stronger than the wood. If the headstock is being struck hard enough to break it, then that guitar is experiencing some destructive motivations far beyond accidental knocks, bumps, or falls. I'm calling this a successful solution and will continue to refine the jig and construction process.

That's pretty impressive.
Was it glued together, or was this all just the mechanical strength of the mortise/tenon??

Fish glue, all the way. And while the tenon fit snugly in the mortise (tapped in with a dead blow mallet), there were still gaps around the flange and shoulder.

Nice work Jason!

Thanks, David. This has been fun.

Hey, folks, here's a general question about dovetail templates that I wasn't able to find an answer for on the interwebs: are the tenon and mortise outlines supposed to mate perfectly when lined up? That's how I made mine initially, but found that my first cuts didn't result in parts that fit (only about half way). Instead of shaving the tenon, I changed the template and tried again. After a few tries, it turned out that I needed to cut about 3/32"-1/8" off the female template, and then the resulting parts fit almost completely (except for that final 1/16") or so that needed a mallet tap).

I made the templates out of 1/4" hardboard for ease of tweaking on the test version, but will duplicate them in 1/2" ply for the final jig. Do dovetail templates need some space, some sort of relief gap, to fit correctly?