I admit that I would’ve got to this point of our Martin kit build a lot sooner had I not been distracted by making a fingerboard. I’m quite excited at the prospect of finishing the neck and setting it into the body – so let’s dive straight in.
On your marks, get set
Setting the neck correctly is fundamental to the tone and playability of acoustic and archtop guitars. In addition to conforming perfectly to the guitar’s centre line, it has to have just the right amount of back angle to achieve a playable action. Too little angle, and the action will be too high; and too much will require excessive saddle height, and the fingerboard tongue will ramp down like a ski jump beyond the 14th fret.
Martin’s neck joints are cut on a CNC machine and they’re very accurate. The neck drops most of the way into the joint, with about 5mm proud of the top. I apply chalk to the angled sides of the neck block and when I push the neck in and then remove it, chalk marks on the neck’s dovetail reveal the high spots. Using a very sharp chisel, I shave wafer-thin slivers of wood away at the high spots and refit the neck. The process is repeated several times, and it goes a little deeper on each test fitting. The fit also gets tighter, requiring a firm tap on the heel to knock the neck back out of the joint.
Eventually, the top of the neck sits about 1mm above the body and attention shifts to the line where the heel meets the sides. There are some small gaps on both sides, so I tap the neck out again, place a strip of 320-grit paper between the heel and the body – with the abrasive side touching the heel – and lightly press the neck back into the joint.
So long as you don’t force the neck in too tight, the paper can be pulled out, following the line of the heel. If the paper won’t move or it tears, the neck is in too tight and you should tap it out to try again. Also, take care to pull the paper dead straight, or even at a slight angle towards the body, to avoid sanding a curve at the exit point.
After two or three passes, the gap begins to close and I do the same on the other side of the heel. It doesn’t take that long before the gaps disappear. If you find that you have gaps in the area where the heel cap will eventually go, take the neck out and check for a raised section on the heel. You can remove this with a chisel, or by using the paper at a different angle.
Removing the last of the high spots from the dovetail, the neck goes in fully – with a bit of persuasion from a G clamp – and it’s time to check all the angles are right. I begin by establishing the approximate bridge position and mark the body’s centre line at that point. With the neck’s centre line also established, I place a long metal ruler along it and gauge where that line ends up on the body. The neck is fractionally off-centre – by 2mm towards the bass side – but I’m more than content with that.
Taking the same metal ruler, I hold it tight to the neck along its length and extend it over the bridge area. The manual suggests you need a gap of 1/16 inch, but I have found the action ends up a bit too high with that measurement. I’m closer to 1/8 inch and again, I consider that a bit of a result.
With all three of my previous builds, setting the neck was the most difficult and time-consuming process. Each one took me several hours and the results were never perfect. This neck-set took me less than an hour and as I contemplate the next step, unless something goes badly wrong when the glue is applied, I don’t think this one will require many excuses…
Since I haven’t done this for over a decade, I have to conclude that all the effort that went into keeping the neck block and sides square during the body construction has paid off. I had been apprehensive about this part of the build, but it turns out to be one of the most enjoyable bits so far.
Get on ’board
I showed you how to radius fretboards when I was doing my Gretsch 6120 conversion, and I do the same here. 180-grit paper is taped to a radius block and the ’board is taped to a flat surface, with runners for the block on each side.
The runners keep the block square and you just keep sanding until you have an even radius all along the fretboard. Later, I swap to 320-grit paper to remove any sanding marks, and I polish up with 1,000-grit sandpaper, followed by ever-finer grades of Micro-Mesh. Well, I did say I was flying by the seat of my pants – and in guitar building, you only learn by doing. Before radiusing the fretboard, I was concerned I might have cut the fret slots too deep, but they were actually too shallow.
Fortunately, the slots still had sufficient depth to guide my fret saw, so I set the depth stop on the saw so the slots will end up slightly deeper than the tangs of the Martin fretwire, and finish them off without using the mitre block. However, next time, I’ll install the marker dots after radiusing the ’board, because I must have come close to sanding through them.
With the dust and debris removed from the slots, I set about installing the frets. There’s nothing here we haven’t covered previously and everything goes smoothly. Martin’s fretwire comes pre-bent, but since I radiused the ’board to 12 inches rather than Martin’s usual 16 inches, I run the wire through my home-made wire-bending tool to tighten the curve.
Martin supplies just enough wire with the kit to complete the job, with a little extra that enables you to get three or four frets wrong. When you’re cutting the wire, allow for 3mm to 5mm overhang on each side of the fretboard and you should be okay.
I would also recommend getting a good set of end nippers and the one I’m using came from Crimson Guitars. They make a clean cut fairly close to the ’board edge and you can quickly bring the fret ends flush with an edge file or sanding block. After bevelling the fret ends, I set the ’board aside.
Suss the truss
Our kit comes with a two-way truss rod, which fits snugly into a slot that’s pre-routed into the neck. The instructions are a touch on the ambiguous side, however, because they were written for an earlier-style truss rod, but I find updated instructions stapled to the notes page at the back of the booklet.
Before installation, I verify that the rod is functioning in both directions, and then set it to a neutral position. It’s the area where the adjustment bolt feels a bit loose. The rod is installed with its rounded side downwards in the slot, and a test fitting reveals it will end up about 2mm below the neck surface.
This was normal with the old truss-rod design, and a filler strip was provided to close the gap. However, no filler strip is deemed necessary with the two-way rod. The rod must be held securely in the slot to prevent unwanted vibrations and allow it to function properly. The manual’s suggestions are either wood glue or epoxy, and I decide on the latter.
I apply masking tape along the edges of the slot to keep the epoxy away from the mahogany, and mix up some Araldite to line the sides and bottom of the slot. When the rod goes in, I realise it’s now sitting above the slot, which will prevent the ’board from seating properly.
I place short lengths of matchstick lengthways along the rod and apply three clamps to press it deeper into the slot. Very little pressure is needed, and I use a paper towel soaked in isopropyl alcohol to wipe away any glue squeeze-out.
Over the top
Martin’s tradition is to veneer the headstock face, but I’m less than impressed with the piece of black plastic sheet supplied with the kit. Instead, I find a piece of ziricote veneer on eBay. Similar in colour to rosewood, ziricote often has spectacular grain patterns and I feel it adds visual interest. A paper cutout of the headstock is moved over the veneer to select the section of ziricote I want to use. The veneer is quite brittle and prone to splitting, so I place a piece of masking tape onto it, just beyond my pencil lines, and cut out the piece using a fresh X-Acto knife blade.
With a protective layer of plastic tape on a flat gluing board, I position the veneer and secure it to the board with masking tape lipped 1mm over the top and bottom ends. This holds the veneer flat and prevents it from sliding around. With Titebond Cold Press For Veneer glue spread evenly across the headstock face, I position it over the veneer and apply several clamps to press it down. After a couple of hours, I remove the clamps and carefully sand the excess veneer flush with sides of the headstock.
The kit includes a full-scale template for locating the tuner holes; however, I discover the actual headstock shape differs slightly and the template markings don’t correspond with the stated measurements. I decide to make my own template based on the dimensions of my headstock and the measurements shown on the Martin template. Having traced around the headstock and established a centre line, I mark the post positions and verify that each string will run from nut to post unimpeded.
With my template taped to the headstock, a pin nail is placed over each post hole centre and lightly tapped with a hammer to mark the position onto the wood. Using a drill press and an 8mm brad point bit, I drill each hole until the point of the bit just breaks through the back of the headstock.
Flipping it over, I have six tiny holes and I drill back to front to finish the job. Doing it this way prevents the wood from chipping out at the back and I’m left with six perfect post holes.
Off the bone
I was unsure about the herringbone rosette from the start – and as my vision for how I want this guitar to turn out is becoming clearer, it’s really beginning to bug me. Herringbone is made from wood, so it seems reasonable to assume Martin uses wood glue to install it.
Wood glues such as Titebond will release when heat is applied, so I decide to see if the herringbone will come out. Using a damp scrap of cotton and a soldering iron set to 275°C, I place the cotton over the herringbone and heat a 1cm section that I know will end up covered by the fretboard.
After 20 seconds or so, I use a dental scraping tool to pry up the herringbone and I’m pleased to find it pops out cleanly. Better still, the black/white/black strips around the outer edges of the slot remain intact. It’s fiddly work, but an hour later, I’m left with a clean and empty rosette channel that I fill with fibre black/white strips from Small Wonder Music. With the excess scraped and sanded flush, the rosette turns out pretty well.
Finishing work on the neck and gluing it onto the body are the quickest and easiest of all the tasks featured in this month’s workshop. After drilling 2mm holes and using Super Glue on some pearl side dots, I apply hot hide glue to the neck, place the fingerboard onto the index pins and clamp it together overnight. The neck is wider than the fingerboard, so I use a rasp and sanding blocks to bring it flush and soften the shoulder along the line at the bottom of the fretboard. I also carve the area around the diamond volute in the vintage Martin style.
Any remaining chalk-dust residue is brushed off the dovetail and, with the hot hide glue brought up to temperature, it’s then applied to the underside of the fingerboard extension and the dovetail.
Working quickly, I press the neck into the body with a G clamp and add three more clamps to the ’board. The neck clamps are left overnight and I now have a guitar that is almost ready for bridge positioning and spraying. But these finishing touches will have to wait until the next instalment.
Read part seven here.