floating tenon

[peter havriluk]

I will be using on my next guitar neck a 'floating tenon' so that I can avoid hacking a tenon out of a heel/tenon made from one piece of lumber. I think I can more easily achieve squareness by doing that. So far, so good. Neck now exists, neck angle of 1.5 degrees has been cut into the heel. The face of the heel is at right angles to the neck itself.

So - - - how far to cut into the neck for the floating tenon (which will be Finnish birch plywood, 3/4" thick.)? My notion is to relieve the neck 3/8" deep for the tenon, and extend the tenon 1/2" into the mortised slot in the neck block.

I have no idea whether my guesses as to dimension make sense. I've never seen this documented.

I'd love to have some advice and feedback.

Thanks very much.

[Dave Bagwill]

I usually, for a regular m/t neck, make the mortise 3/4" wide, 9/16" deep.

[peter havriluk]

I missed by 1/16"....

I don't think I've missed the point by much. Now as for how deep to slot the neck...

[peter havriluk]

I missed by 1/16"....

I don't think I've missed the point by much. Now as for how deep to slot the neck...

Thanks, Dave.

[Kevin in California]

Hey Peter. What is a floating tenon? A separate piece from the actual heel that just has holes for the bolts to pass through? What is the reason for this?
The dimensions of the tenon/mortise are really not that important, but deal more with how wide is the finished heel (at the bottom/cap area) and how deep and wide is your neck block that the mortise is cut into.
Can you put up a pic of this floating tenon? I'm curious.
Thanks

Kevin

[peter havriluk]

Kevin, let's see if I can create a word picture of this....There's no pictures available by virtue of my having not done this yet, and I've never seen anybody else do it. I will send you pictures when I've got some work product to show.

Imagine a normal mortise/tenon neck attachment. The neck block is routed to accept the protrusion of the tenon, and there's usually a couple of threaded inserts or hangar bolts that fasten the neck to the body.

To fabricate a 'floating tenon' the body preparation is unchanged. The difference is with the neck. The neck is cut flush at the correct angle (and here it's dead easy to control that angle, as there's no tenon that needs to be worked around). The neck is then routed to accept the tenon which is a separate part, in my case a piece of 3/4" Finnish plywood (nothing exotic, I bought a bundle of it from Woodcraft a couple of years ago). The 'floating tenon' extends into the neck and half inch and protrudes a half inch, making the neck look a whole lot like a regular m/t neck, but the tenon is plywood and glued in. And the threaded inserts can be installed with the help of a drill press to drill accurate holes in the plywood for the fasteners and also to install the fasteners square to the tenon, before attaching the tenon to the neck. All kinds of opportunities to fine-tune the neck angle and neck alignment without having to work around a piece of wood sticking out into the way.

So I hope, anyway. I ran this idea past my consulting luthier and he thought it could work, and in my geometry-challenged state, I thought it worth a try. And when I described what I wanted to do, the luthier (Kevin LaDue, maker of guitars that sing with the angels) said, oh, you are describing a floating tenon. Okay.

Mechanically, I think there's some merit in having a tenon that won't split while the fasteners are being installed, and I like the idea of controlling the accuracy of the fastener installation in the tenon. All this without the complexity of custom jigging to make the tenon and more exotic jigging to hold the neck while fasteners are installed.

We'll see soon.

[Dave Bagwill]

Sound like a good idea. If I may ask - why not use a piece of hardwood in lieu of the Finnish ply?
The method sure has some advantages. I like it and can't wait to see how it works out.