Gluing the Dovetail
When the neck is close to its final dimensions, especially at and around the heel, the neck is glued onto the guitar body. Gluing the dovetail is a critical point in the assembly of the guitar as no more alignment of the neck and neck angle can be done after the dovetail joint is holding the neck to the body.
Alignment is the keyword here as the angle that the neck makes with the body determines the height of the bridge and saddle and that, in turn, influences playability of the guitar. Likewise, we have previously discussed the importance of keeping the centerline of the guitar aligned with the centerline of the neck. All of this alignment becomes fixed once the dovetail joint is glued. The truss rod and the fretboard are attached to the neck after gluing the dovetail joint.
Checking Alignments: Placing a straight edge on the surface of the neck while attached, but not glued, to the guitar body, check the neck angle as indicated by the clearance of the straight edge above the spruce top at the saddle position. (see April journal) On my guitars this should be about 3 mm.
Also, with a piece of black thread, check that the centerline of the neck is in line with the centerline of the guitar. By tweaking the dovetail ever so slightly, minor adjustments can be made to the final fitting. Then, when satisfied, glue the neck onto the body. This is a significant point in the creation of your guitar.
Finally, epoxy fill the gap between the top to the truss rod and the neck surface after the rod is epoxied into the slot. Sand the epoxy flat with the neck surface when cured. That way, the neck and fretboard form a solid mass except for the operating part of the truss rod which is encased in the steel truss rod channel. … making sense?
Oh, one more thing. Wear surgical gloves when messing with epoxy. Otherwise, you might be looking at black epoxy under your fingernails for a week or so..
Finally, The Tail Strip
The butt strip can be installed any time one is ready after the guitar body_ top, back, sides, and bindings are assembled. For some reason, I usually end up installing the butt strip after the neck and fingerboard are on. I guess this is a simple matter of procrastination. For one thing, this inlay is in an awkward spot on the guitar. The butt of the guitar requires a bit of ingenuity just to hold in a workable position. There must be other ways to do this. Every butt strip is designed to complement the bindings on the particular guitar, therefore, inlay of a particular butt strip is only done once… ie., one-off design and execution… That's a beauty of hand-made instruments.
In May, the fingerboards were sanded to dimension and the fret slots were cut. Most of the fingerboard inlays and fretting was completed this past month (June).
Fretboard Inlays (Position Markers)
Before fretting, position markers need to be installed in the fingerboard. This can be a chance to exhibit some artistic taste and inlay skill, or just go with ¼” dots (as CF Martin has done for years). If dots are to be installed, it’s very easy. Be sure to inlay the markers before the frets are installed and be sure to use a forstner bit.
If some other shape of position markers are to be used besides dots, one can either purchase pre-cut perfectly identical markers, or more elaborate precuts with a theme (like leafs, or bear tracks, etc.). Just remember, these shapes need to be carefully routed into the fingerboard (by you). If you have never done this, I would start out with dots.
Returning to the Necks
Back in September 2015 we began the process of building 5 new guitars. To start, the laminated necks for all five were blocked out, i.e., glued up in blocks and trued to the centerline. Then work began on the guitar boxes and the necks were laid aside. In the spring of this year, the blocked-out necks were back on the work bench. The truss rod channels were routed and the process of cutting and fitting the dovetail joints was begun (as discussed in the April journal entry). Now, with the body built, the neck needs to be carved before it can be joined to the body.
When the dovetail joint is fitted to the guitar (but not glued), the necks are ready to be shaped to approximate finish dimensions. Before taking the blocked-out neck to the sander, however, it is important to mark carefully the “stop” lines for the sanding including all three dimensions and curves of the heel and the width, length and thickness of the neck from the 14th fret to the nut.
I use a Rikkon table sander with attached exhaust and a ventilating window fan (2 feet away) which draws a stream of air directly over the sanding machine. This works... be careful... work scant.
The last thing that you want to do is take off too much wood by sanding the neck down too far… particularly in the nut-to-third fret region. Part of my history is working with aspiring luthiers (apprentices) and over-thinning the neck is not an uncommon mistake. The end result will be a cracked neck when the truss rod is tightened and applies force to the back of the neck. At that point, there is no “fix-it” solution except a new neck.
Bottom Line: Know when to stop before you start… and check often. When in doubt, leave the wood and take it down later by hand.
Carving the Neck by Hand
That brings us to the next step in carving the neck and that is contouring from the heel to the nut with hand tools. I’ve built a simple jig to hold the neck while being carved. It allows the carver good angles to attack the curved surfaces.
Pictured below are the tools that I use to finish carving the neck. I think that they are all available at your local hardware store.
Shaping the Neck
Gluing in the Dovetail
The Truss Rod
The Tail Strip
By taking the vise and attaching it to a small workboard, I can turn the fretting vise 90 degrees in the Versa Vise and (with gravity on my side) press the frets in vertically. This helps.
Pressing in Frets
First, I put a little super glue at the ends of the fret slots (last quarter inch or so) and then place the pre-cut fret into the slot. The fretwire that I buy comes on a 50-foot, 12-inch roll so it is already curved to the approximate radius of the fretboard surface. If a fret is going to come loose, it will be at an end. That’s what the super glue is for. If the fret needs removal for any reason, a little heat applied to the fret with a soldering gun will break down the super glue cleanly and completely.
With the fret sitting on top of the slot (and the super glue setting up), put the fingerboard into the press. Carefully place the fret caul so that it is aligned and slightly engaged with the fret. Crank the vise down slowly and press the fret into the board. If your board has been shaped to the same radius as the caul, you will have a perfectly seated fret. Now... do this twenty times and the fretboard is just about ready to be glued in place.
On the left in the photo is a file card… for keeping the file clean. Mahogany is a relatively soft wood. It carves easily but clogs the file or rasp in a hurry. To do good work, keep your tools (and your wits) clean and sharp.
Three Surform tools are pictured and they are great for removing a lot of wood quickly (that should also be a caution). Pictured are flat, rounded and circular Surform cutters. Together these tools can rough down curves of the neck quickly. The kerf marks that the Surform leaves can be removed with files as the final contours of the neck are being shaped. The three styrofoam gauges represent the target radius at the 2nd, 5th, and 10th fret.
Remember, the fingerboard is not glued onto the neck yet so leave a couple of millimeters extra on each side of the fretboard, which, at this point, should be marked on the top surface of the neck. This will help later if the final positioning of the fretboard needs adjustment... as it sometimes does.
When installing the truss rod, be sure that the it will be completely buried below the surface of the neck when epoxied in. Also, the allen wrench adjustment at the nut end should not extend above the peghead veneer. An alternative is to access the truss rod thru the sound hole of the guitar. That means turning the truss rod around, obviously. But it also creates challenges in access and/or structural integrity… too much for us here.
Once the truss rod has been positioned in the dry, remove it and apply epoxy to the sides only. Quickly embed it back into the truss rod slot. Clamp as needed. One does not want to get epoxy on the rod itself which is inside the steel channel housing. The rod that I use comes with masking tape covering the open side of the 3-sided steel channel. The truss rod pictured here is with the tape side up, but it is actually installed with the tape side down.
So, that’s the story of June, 2016 at Woody Strings in Bon Air, Virginia. Building instruments that make music is great fun and very satisfying for a tools-and-wood kind of person. That’s Woody.
Have a great month.
Last month we discussed shaping the fingerboard so that the surface has a radius of 12” and the fret slots are cut to a 25.4” scale (common dreadnaught scale). When the position marker inlays are complete and final sanded, twenty (20) frets are cut from fretwire stock to the approximate finished length plus about a half inch. Next, they will be pressed into the slots.
Fretting a fingerboard is a specialty operation and I have fashioned an inexpensive, hardware-store vise to do the job. I find pressing the frets in with a contoured brass caul is much more controllable than hammering in frets which I did for years.
The truss rod channel in the neck was already routed to dimension before gluing the dovetail to the guitar body (see April journal). The routed channel might need to be extended into the heel block. Personally, I do this after gluing the dovetail.