Neck dovetail with a rounded body

Please put your pickup/wiring discussions in the Electronics section; and put discussions about repair issues, including fixing errors in new instruments, in the Repairs section.
Post Reply
Christ Kacoyannakis
Posts: 252
Joined: Sat Jan 07, 2012 8:58 pm

Neck dovetail with a rounded body

Post by Christ Kacoyannakis »

On a guitar where the top of the body is rounded, rather than completely flat, how do you route the dovetail into the neck portion? It seems to me that the body part of the dovetail routing would be easy enough, but on the neck side, if the body is round, rather than flat, you will have large gaps in the side of the neck. What is the solution?
User avatar
Barry Daniels
Posts: 3185
Joined: Thu Jan 05, 2012 10:58 am
Location: The Woodlands, Texas

Re: Neck dovetail with a rounded body

Post by Barry Daniels »

Determine the angle between the top and the sides (won’t be 90 degrees) and cut the neck heel to match.
MIMF Staff
Alan Carruth
Posts: 1264
Joined: Sun Jan 15, 2012 1:11 pm

Re: Neck dovetail with a rounded body

Post by Alan Carruth »

Don't feel too bad; this is always the hardest part of making the guitar for my students. The important thing is to make one surface (usually the shoulder of the guitar) to the final shape, and then fit the neck to that without taking more wood off the body. Do one thing at a time: align the neck with the center line by trimming the shoulders of the tenon on the end of the neck, then establish the back angle, and finally fit the neck so there's no gap on the sides of the heel. Then you trim the tenon (the dovetail) to drop the neck to the right level and have a good fit of it's gluing surface, particularly at the bottom.

You generally can't do this simply with one pass of a router. The shoulder of the tenon has to be fitted to the curve one way or another. I find the best sequence for me is to leave the tenon over size, and fit the shoulder first. Use this to get the angles right, with a good fit to the curve, and then trim down the tenon to get the depth right.

If you're devising your own shape it makes a lot of sense to have the upper edge flat for at least the width of the neck (say, about 2-1/2"), and round the shoulders off from there. Sometimes you can just flatten the end; the side thickness will taper out, maybe even to nothing, but it's easier to fit the neck and nobody will know once the neck is on. Alternatively, you can do it the way they do on Classical guitars built on a solera. You draw a straight tangent to the upper bout curve starting about an inch and a half from the center line. The surface peaks at the center line, but each side is flat so it's easier to fit. On the solera they're cutting a slot into the side of the neck and heel, but it's the same idea. In any case, if you can avoid having a concave surface to fit it helps.
Darrel Friesen
Posts: 264
Joined: Fri Jan 06, 2012 5:48 pm

Re: Neck dovetail with a rounded body

Post by Darrel Friesen »

Call me crazy but after doing my first few guitars using dovetails, I started doing bolt ons. Way easier for this, resets etc. YMMV of course but dovetails are declining IMHO. There's no magic sound gain or difference.
Alan Carruth
Posts: 1264
Joined: Sun Jan 15, 2012 1:11 pm

Re: Neck dovetail with a rounded body

Post by Alan Carruth »

In some cases, where the bolt-on hardware is heavy on a light body, the added mass can drop the 'neck' resonance pitch, and alter the feel, and maybe the sound. Using lighter hardware instead of cross dowel nut and 1/4-20 furniture bolts, can help.
Darrel Friesen
Posts: 264
Joined: Fri Jan 06, 2012 5:48 pm

Re: Neck dovetail with a rounded body

Post by Darrel Friesen »

I haven't tried the cross dowel attachment yet Alan as hanger bolts have worked so well for me. Even my old Stewmac 000 plan shows hanger bolts. Combined with furniture assembly nuts, they are likely somewhat lighter than using cross dowel nuts and headed bolts.
Carl Dickinson
Posts: 94
Joined: Fri Feb 08, 2019 5:38 pm
Location: Forest Ranch, California

Re: Neck dovetail with a rounded body

Post by Carl Dickinson »

I've been doing rounded shoulders on several recent builds. Recess the neck shoulder leaving 1/8" edge around the edge and heel bottom, then you can floss it flush a lot easier. Use a sharp chisel or a dremel rasp. If doing a dovetail, this is done before shimming it into place. It will effect the bridge saddle placement.
Post Reply

Return to “Flat-Top Acoustic Guitars and Bass Guitars”