That's the neck joint described in Cumpiano and Natelson's book. Very difficult to execute. I wonder how many people got frustrated and gave up in that section of the book. In the early 90's I used CN book for a couple guitars and have more or less adopted that open style of building, but used a dovetail instead. Later he updated it on his online accompaniment to the book saying the following:
Quote:
I learned the system in the Gurian workshops during the early seventies. The system was reportedly adapted by Michael Gurian and Walter Lipton from post-and-beam barn construction. In this ancient joint, oak pins are hammered through holes in the mortise into holes holes drilled in the tenon, holes drilled slightly offset, thus drawing the two tightly and permanently together. On the barn, both mortise and tenon were massive, and the pin was knocked in with a hammer.
The joint's guitar counterpart requires much greater finesse and precision. An offset of one to two sixty-fourths of an inch is correct: much more and the pin simply refuses to enter the tenon or, if it does, mayhem can ensue: the neck shaft can be drawn forcibly away from the fingerboard. This rarely happened at the Gurian shop: we all learned how to install it without problems. But, alas, hindsight has shown that it is not a good neck joint to learn to do from a book or expect to get it right the first time every time. I've become aware over the years that although some students seemed to handle its challenges pretty well, other people using were stymied by the precision required for it to work properly—if not the number of special gadgets, fixtures and implements that have to be fashioned to handle its assembly.
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https://www.cumpiano.com/an-improved-neck-body-joint