Tapered Heel

 

The above assumes that you intend to make a jazz heel, where the vertical sides of the heel run parallel to each other. If on the other hand, you are making a tapered heel, notice that this changes the geometry. In this case, the two knife edges taper towards one another from the fretboard to the heel cap. This means that the knife edges will automatically assume a slight backset, even if you cut them at 90 degrees to the top of the fretboard. The amount of this backset will be determined by how much you taper the heel and also by how much you have undercut the tenon shoulders. My recommendation is to make detailed plans for your heel design. By way of illustration, on a 12-fret 000, the heel tenon shoulders need to be undercut by about 10 degrees, so that the tenon shoulders clear the curved body at all points except the tenon knife edges.  In the case of a body 3 1/8 inches in depth at the heel, and a heel tapering to 3/4 of an inch at the cap, the taper alone will give you a little less than 2 degrees of back set, which is too much. In this case, make the knife edge taper in the opposite direction (giving a negative backset, or - if you will forgive the expression - an upset), Make this upset about 1 degree, which corresponds to removing about 1/16 of an inch of material from the top of the knife edges (and of course removing zero material from the bottoms of the knife edges. To summarize, a heel designed to fit right into the body (fret board parallel to the sound board) will likely result in an action that is too high, forcing you to make the saddle too low for best sound.

You want the neck rotated with the head end down about 1 degree. This is achieved by removing about 1/16 of an inch from the bottom of the heel knife edges tapering to zero material removal from the top of the heel knife edges. This can be done on your table saw when you cut the tenon shoulders. Cutting the shoulders at a 1 degree angle gives you the 1/16 of an inch of material removal.

All of this works fine if you are using a jazz heel, which does not taper. It also works on a 14-fret guitar where the body at the heel joint is almost flat.

In the special case of a tapered heel on a 12-fret model, additional considerations enter due to the curvature of the body at the heel joint. As explained above, in this case I recommend starting with one degree of upward neck rotation (removing 1/16 of an inch from the top of the heel knife edges). This will automatically be converted into about 1 degree of downward rotation (which is what we want) when the heel is tapered.

The result of this adjustment is only an approximation, but it should get you in the ball park. And because the neck is easily removed, you can make further modifications using the methods explained.

Conclusion

 

Assuming you have done all the above to your satisfaction, your strung up guitar should have good action and good saddle height, and no fretboard extension lump. The fret board extension will be resting with light pressure on the soundboard. In the photo of guitar #1, I have not glued the fretboard extension down at all. After a year of heavy playing, this appears to have caused no problems (such as buzzing) and means the neck is completely detachable. On guitar #2, which was for a client, I glued the fretboard extension to the soundboard by applying a thin line of fish glue around the perimeter only. It didn’t buzz prior to this treatment either, but I wanted to be sure. If down the road the neck needs to be taken off, a small amount of heat and moisture at the edges of the fretboard extension will do the trick.

 

<-- Previous Page

The New England Luthiers is an association of professionals and amateurs brought together by a common love of making stringed instruments