Acoustic Guitar Construction

With the exception of a few specialty models the nut sits on the fingerboard plane. Actually the models that have the nut on the headstock plane don't have a slot either. For both the slot is formed by the FB and HS veneer. I thought you were correcting an unforced error.

I was correcting an unforced error - got it solved now with a wee shim glued to the nut, thanks!

Cutting the headstock veneer to make space for the nut and getting the edge of the veneer parallel with the end of the fb is what usually drives me a little nuts. So to speak. I wondered if Martin and/or others use a fixture to keep everything just perfect, level, parallel, and all that stuff.

I am sure Martin has a whiz/bang automated fixture of some kind, I don't recall seeing it.

I normally cut off the veneer a little shy and use a file to tweak the gap.

Here's a response from Frank Ford. Sounds like a good approach?

"Permalink Reply by Frank Ford on January 15, 2015 at 4:05pm
OK, here's the deal. You may want the nut slot to be perfectly flat, but you don't need to have it that way.
In cutting or trimming the bottom of the nut or the nut slot, I always try to make it very slightly "hollow" in the center, so that the nut fits absolutely tightly right at the ends where you can see it from the edge. (By "very" slightly, I mean just a few thousandths of an inch - not something measured with a ruler.)
In the center section, it doesn't quite touch completely across. Same goes for the interior corners. I try to cut the slot with sharp corners at the bottom, but when I make the nut, I "break" the corners just a bit except for the last 1/16" at the ends. Trying to fit a perfectly square and sharp corner into a perfectly square and sharp corner for the full length is a procedure for CNC machining, and a monumental waste of time for hand work.
That way, I get a nice fit, and the nut is well supported. Nuts get glued in place along the end of the fingerboard, not at the bottom.
As to tooling for trimming the bottom of the slot, a narrow chisel works best for me.
And, before you ask, NO I DO NOT THINK THE NUT NEEDS TO FIT SOLIDLY ON THE BOTTOM FOR ANY TONAL REASON.

Common sense has me respectfully disagree --- its damping science not opinion.

Understood.

I set my belt sander to the neck angle and bevel the veneer before installation. I use a stock nut to set the distance. The final nut is thicknesses to fit the slot.