Acornhouseworkshop

After taking a week to recover from the trauma of having to remove the neck, I was finally ready to deal with the damage from the iron. The body was easy, a card scraper took care of most of the glue residue, and the paring chisel finished the job. Then I went through the sanding pads from 600 to 12,000 grit on the top of the body. Its not perfect, especially if you look in a raking light, but, for the most part, it is back as it started.

The burned/boiled cocobolo fingerboard took a little more effort, working around the frets, but it was essentially the same process. The worst part were the MOP dot inlays, which had lifted. Apparently the CA glue and cocobolo oils expanded enough to push them up. So the affected ones had to be refiled flush to the fingerboard. Even after sanding and polishing, the color is decidedly darker where the iron had been.

Then came the actual reset, changing the angle at the join. I used a chisel to get an approximate fix, and the reattached the neck with the bolts and restrung the guitar. Much better. Then it was a matter of taking it off, refining and sanding, bolting it back on, restringing, taking it off again, refining and sanding some more, bolting it back on again, restringing, etc. etc. etc. About six tests before I felt it was as good as it could be. Then, mustering up some courage, to glue the fingerboard back on; permanently, this time (I hope). At least until the far distant future when it needs a reset due to age and years of happy pickin’.

It sings! Especially in “terz” tuning, which is a third higher – in G – than the standard E tuning. It’s page is now up, and I plan on getting some video/recording posted at some point. Now I just need to find a good home for it.

Here is the finished guitar strung up.

And from the back.

And, from the side.

If you look closely, you will see that the strings are laying on the frets. That was the problem that I talked about in the last posting. Well, I got the new saddle blank and rough shaped it. Popped it in to test and, as I was beginning to fear, the strings were still too low. They were now able to hit notes, but they were still buzzing against the frets. And, no amount of truss rod adjusting was going to raise them high enough.

Unfortunately, there is only one solution for this problem. One that, hard as I tried, there was no avoiding. The neck would have to be reset. I got the angle wrong, despite my testing. (There is always a problem in a sophomore effort.) In order to reset the neck angle, the neck needs to come off. The good news: with the bolted tenon system, this is not as bad a job as with a dovetailed neck. The bad news: it still involves heating up the fingerboard to loosen the glue where the fingerboard is glued to the body. So, with fear dripping from every fiber of my being, I got out the iron (yes, just a regular clothes iron), plugged it in, set it on high, and placed it (shudder!) on the fingerboard above the body. I could hear the oils in the cocobolo sizzling and crackling. After about 20 minutes, testing periodically, I was able to start prying the fingerboard up. Once heated enough, it went fairly quickly, and came off without having to force it. The result? The body is not too bad, just some minor repair of the finish. And, of course, the old glue will have to be scraped off.

The fingerboard is a little worse off. Its going to require some major scraping, sanding, and leveling; in addition to changing the angle. It ain’t pretty. We’ll have to see how it recovers. This guitar may have to remain in my stable.

With the bridge firmly attached, it’s time to drill; not for oil, but for sound. Break out the trusty eggbeater and carefully penetrate the top; and be resigned to vacuuming out the chips from the inside, being guaranteed to miss a couple, which will rattle around, defying capture.

Can’t stop there, however. Bridge pins are tapered, for a secure fit (wouldn’t want the strings to pop out at in inopportune moment). So the holes need to be reamed out with a taper. In order to account for any variance in the pins, I’ll do each one individually, fitting until its just right (Goldilocks would make a good Luthier!), and trying to make sure I keep each pin with a particular hole. (More shavings to vacuum!)

Finally, we have all six, lined up waiting for strings. I selected rosewood-like (a wood called tintul, an Indian hardwood) pins with a Parisien eye insert to match the dot inlays in the bridge. Notice the saddle. (More on that momentarily.)

Then I calculated the strings spacing at the nut, or rather, used an online calculator to do it for me. The strings have to be spaced so that there is the same distance between the edges, which means that the thicker strings need to be further apart than the thinner ones. Digital calipers are just the ticket here. A small handsaw starts the slots, different sized files will work them down so that the strings are just the right height above the fingerboard. Now the strings go on and are brought to full tension, which is necessary to gauge the strings height. Now the saddle rears its ugly head. Instead of nice ringing tones, I have nothing but fret buzzing. I had worried that it would be the case when I got the saddle (which is a different one than the one I used for the first guitar), but now it was confirmed: IT’S TOO SHORT! It doesn’t raise the strings high enough off the frets. Going back and checking the catalog confirms it. I had gone with this one because it had a compensated b-string; i.e. a little bit longer length for the b-string. Like the nut, I am using a TUSQ product, which is an artificial ivory and has a consistent density. So, I’ll have to wait until I get a replacement in a couple of days.

ARGHHHHH!

The guitar is out of the finishing room(s) (I had to do the last couple of coats for the body at school, since it got too cold to do finish in my unheated garage). It got extended when I discovered that turner’s tape is NOT the tape to use, when a wiping varnish is being used. Last year I had used regular double sided carpet tape to attach my bridge mask, and had no problems. This year, I used double sided turner’s tape, which reacted to the varnish, causing a halo around the bridge mask that wouldn’t cure. I’m guessing they both use the same solvent (mineral spirits), and the adhesive was leeching out. So, I had to take off everything except the green painter’s tape, which was the bottom part of the mask, and sand down close to bare wood. Then, a few more coats, and the top was finally finished.

I gave the varnish a couple of days to cure, and then used my micro mesh pads to sand everything down to 12000 grit, putting a nice shiny polish on everything, and making the neck silky smooth. Not quite the mirror finish that a big buffing wheel and numerous polishing compounds will give, but ok. I like the more natural look with actual wood grain showing, rather than the plastic look of a filled and featureless surface. (Of course, I don’t have a big buffing wheel and polishing compounds.) The next step was to bolt the neck on and glue the fingerboard down. The tenon gets no glue. So when the time for a neck reset comes (which it will on all guitars), the only glue to deal with is under the fingerboard, which is no big deal. The nut was also cut to length and shaped and glued in with CA glue.

Then the bridge. Before glueing the bridge, it’s bottom has to be contoured. Remember, the top is not totally flat, there is a very slight arch. So the bridge, with its flat bottom, needs to match that arching, or it will not glue down solidly without creating a stress area for the top, acting against the arc of the bracing. Which will lead to premature failure. Some vigorous sanding with 100 grit paper takes care of the arch, and leaves a rough bottom to the cocobolo, suitable for glueing. (Since cocobolo is an oily exotic wood, it needs it’s oiliness tempered before glueing, with either acetone, or a fresh sanding with coarse paper. I prefer sanding, since it leaves a lot of tiny nooks and crannies for the butter…I mean, glue.) The top of the bridge gets its final sanding down to 12000 grit (never a finish on it for steel strings.) Then I put down some more green tape to get reference lines. The bridge has to positioned exactly, for good intonation, doubling the distance form the nut to the twelfth fret, and adding 2mm to the distance to the saddle slot at the high E string. Then its time for the last glueup on the guitar.

One of the challenges in building a guitar is dealing with curves, and finding a way to hold and clamp the irregular shapes. So, while general woodworking tools can be used for most of the work, some specialty items are a must. For glueing the bridge you MUST have some deep reach clamps like a deep reach C clamps, and (so useful during the entire build) wooden cam clamps. Especially since you are dealing with very thin material, which would be crushed by the usual woodworking clamps. The cam clamps give just enough clamping pressure to do the job. As you can see, there’s not a whole lot of room to maneuver, so doing a dry run first is a given. Once the glue is on, you better be ready.

Now I know what dentists feel like.

Now its just a matter of drilling and tapering the bridge pin holes through the top, filing the slots in the nut, getting the saddle height adjusted, and pickin’ and a grinnin’.

I had a “design opportunity” this weekend. I am currently working on a display cabinet for student art and awards for the Fine Arts building where I teach. The cabinet is made of walnut, and will have two locked display cabinets flanking an open area for award plaques. While routing out the rabbits on the door frames, the walnut’s grain was deciding to not cooperate and left me with some tearout in the visible edges. Design opportunity! Instead of going with a rather plain walnut door, I decided to add some molding. And, in keeping with my natural proclivity to use contrasting woods, I grabbed some sycamore from my stock and milled up a rounded molding to cover all of the ruined edges. A much more interesting look, now. As a side bonus, the added sycamore added a lot of strength to the 3/8″ thick doors. (pics will be posted upon completion.)

I finished the video stand with some Early American maple dye and blonde shellac. Trying to brush shellac in the tight confines between the two shelves was a challenge, but I can’t think that there is any easier way. Here is the finished product in use. Since there is a color change between the natural light pic and the pic using a flash, I’m posting both.

The guitar is almost finished in the finishing room. Then I just need to glue on the bridge, attach the neck, finish shaping and slotting the nut, and do the final (initial) setup. Then I can finally hear how it sounds!

The guitar is in the finishing room! I attended to the final details, in preparation for finishing, after the binding was done. The most important of these was setting the neck angle. The neck is not completely parallel to the body sides, there is a 3° angle, or thereabouts, that allows the strings to angle up towards the bridge’s saddle, while staying close to the fingerboard. Cheaper guitars don’t adjust for this and end with horrendously high action (the height of the strings over the fingerboard), making them a nightmare to play. Unfortunately, since this is more common in the cheaper instruments that beginning players usually have, it turns off a lot of them to playing. If they were able to start on a better quality instrument that they didn’t have to fight with, it would make learning a more positive experience, and they would stick with it. Setting the angle involves a lot of test fittings, sanding a little, maybe paring some, putting the neck back on, taking it off, sanding some more, putting it back on, and on and on and on.

Once that is done, it’s time to add the ramps in the headstock to allow the strings smooth access to the closest tuners.

Then, everything, neck and body, gets a final sanding to 320 grit. After that, the neck gets attached once more so that the bridge position can be finalized. In order for the guitar to play in tune, the bridge has to be positioned to the exact scale length (21 1/4 in this case), while allowing for the expansion of the string when it is pressed down behind a fret. That position then is masked off, so that there will be a clean glue surface after finishing. (On classical guitars, the bridges is finished along with the guitar, but on steel strings, the bridge is unfinished, and attached after finishing.) I use some cardstock attached to green painter’s tape with double sided turner’s tape, a little undersized.  Also, the area where the fingerboard will be glued down needs masking.

(Note the replacement neck. I thought I’d simplify and go with an oak board. Just kidding. That’s so I have something to hold during finishing.)

The fingerboard also needs masking. Cocobolo, and the other oily exotics usually used for fingerboards, (ebony, rosewood, etc.) never have a finish, just some fingerboard oil. A maple fingerboard, on the other hand, usually does get a finish. Otherwise, it get very visibly grimy, very quickly.

I am using a wiping varnish for my finish. Since I don’t have spray equipment, I decided against lacquer. The other choice is a French polish, although that is more traditional for classical guitars. Varnish is also a traditional finish; nowadays, lacquer is the most common commercial finish. due to its quick drying time, the guitar “factories” can do it on a production line basis, rather than the more labor intensive, hand rubbed varnish.

The key to any guitar finish is not which finish is used, but how it’s applied, and, most importantly, how much is left. You want just enough finish to protect the instrument, but not so much that it loses its resonance. So, as many layers as are put on, a good part of that is sanded off.

With the guitar in the finish room, I did a quick one day project. Less than 24 hours form conception to completed assembly. (Finishing will, of course, take longer.) After replacing a DVD player, which had a different footprint, I couldn’t stack my components on top of each other; so I needed some type of shelf, or cabinet. I decided on an open type shelf unit, to allow for maximum air flow. Grabbed a board of sycamore, worked out some curves, made a form, cut some dadoes, cut and routed the legs, sanded glued, clamped and pegged. Voila!

Now I just have to decide on a finish. I think I will go with an early American maple dye and shellac and oil. Any other suggestions?

The binding is done. As I’ve mentioned before, if you ever want to get a lot of hand tool practice, build a guitar. With binding work, a well-sharpened card scraper is a must. Its funny how the bends change the wood’s nature. Regardless of the wood’s grain, it wants to be scraped uphill. The top bindings turned out much better than the bottom bindings. Whether that was because of the practice I got doing the bottom first, or the purfling, which, being softer than the maple, acts as a cushion to conform to the top better, I don’t know. Maybe a combination of the two. Here is a close up of the binding/purfling combination. The purfling I used was w/b/w (white/black/white) which is made from a flexible cardstock type material, standard for the trade. Its gives a very subtle delineation between the maple and the spruce.

And the totally bound body.

The last steps before finishing are: add a filler to the fret ends (the slots are always a little deeper than the fret’s tangs); adjust the neck’s shoulders at the tenon, so that it sits at the correct angle with the body; do a final sanding  to 320 grit; and mask off the areas where the bridge and the fingerboard will be glued to the top after the finish is complete. This last step has to be last, so that the scale length (distance from the nut to the bridge’s saddle) is perfect. If the bridge is to close to the neck, or too far, the intonation will never be right – the guitar will always sound out of tune when playing anything other than an open string. Can’t have that, can we?

Of all the various tasks and challenges in building an acoustic guitar, this one has to be my most feared and hated: the binding. In order to hide the join of the top and back to the sides, and to offer some protection from the inevitable bump, guitars have bindings around the edges, with, or without, extra purflings (thin, decorative strips of white and black layers, or sometimes a herringbone or abolne inlay). In order to add the bindings, you have to rout out a channel, parallel to the sides, on a top and bottom that is not at a 90 degree angle to the side, and, in the case of the back, a changing angle. Also, since you are routing around the entire body, you end up routing against the grain a number of times. And that means dealing with tearout, and trying my best to avoid it. I put on a couple of wash coats of shellac, and that seems to have helped. Although, I did get a major grab on the end graft, and had to redo it, but that wasn’t too bad, and I like the new, wider end graft better.

The top actually has two routs for the binding and purfling channels. Routing spruce, especially against the grain (using a climb cut), leaves a rough surface that requires more handwork. I may try to handcut the top channel on the next one, using a specialist tool called a gramil (although, I’ve seen reviews that talk about the difficulty of doing it by hand). You can see why you need kerfing to glue the top and bottom on: after routing the binding channels, you wouldn’t have any side left to hold the top on, otherwise!

Since I am using maple bindings (as opposed to the plastic ones used by most of the big, mass market, companies), they need to be prebent on the bending iron. This is much easier than bending the sides. I taped three strips together (always good to have extras) for each side, spritzed them with a little water, and hit the iron. They were done before I knew it, and after clamping them in the form to dry, they were ready to go.

The shape of the guitar dictates another specialist tool to clamp the bindings after glueing: tape! Actually, this is a special tape, available at luthier supply stores, that is tearable by hand, but strong enough to stretch and hold fast, yet come off clean. Painter’s tape wont work here. Just make sure to tear off a lot of strips BEFORE glueing; time is of the essence.

Here in the mortise, you can see the ends of the binding and purfling strip. On the bottom, I just used the maple binding strip. On fancier guitars, made by people with a LOT more experience than me, they may add purfling beneath the binding, on both top and bottom, as well as fancier, and multiple, inlays on the top. I’m going to keep it simple, for now.

When it is dried I will scrape and sand it flush, and then prepare the guitar for the finishing room.

In the final stretch now!

I finished the bridge today. Actually, I finished the second bridge today. You ever have one of those moments when you’re trying to get something perfect; paying attention to every little detail; carefully laying out everything and thinking about every step. Then you get to a point and realize that you were so focussed on the details, that you didn’t notice a critical mistake.

What’s wrong with this picture:

Everything laid out carefully, just off center! I was so focussed on the pin spacing, that I never noticed that my initial layout lines weren’t in the right place.

So, on to bridge #2. After milling the cocobolo blank to size, I put it in a jig to rout out the slanted slot for the saddle.

Next, after triple checking my layout lines, I marked and drilled the holes for the string pins. Luckily (hah!), I still had everything set up from the first try: dividers, drillpress fence, etc. If you don’t have a birdcage awl and ever plan on marking holes for drilling, I would highly recommend getting (or making) one. They are the best tool for starting a hole.

With the holes drilled, I marked the shape from my template and headed to the scrollsaw, being careful to remember which direction the blade wants to drift. (Man, I wish I could figure out a way to avoid the drift. Maybe  something other than a cheap scrollsaw would be better. Ya think?) Then, to the sander to slope the ends. Notice the resin buildup on the sandpaper. If you ever want to ruin some sandpaper quickly, just do a lot of cocobolo sanding.

Then its a lot of hand work, with a block plane, carving knife and sandpaper to round edges and smooth lines.

Finally, I inlaid the MOP dots and did an initial polish. (I’ll probably go back and do some more sanding, to 12000 grit).

The color will deepen, as it’s exposed to air (it dulls and purples when it’s milled). Next up, the binding.

I am using a bolted mortise and tenon joint to join the neck to the body of the guitar. This system is becoming increasingly popular amongst custom builders. Aside form the ease of construction; it allows for much easier adjustment of the neck angle as the guitar ages and the wood adjusts and moves. This is common to all guitars, regardless of the maker and the neck joint. The more traditional sliding dovetail joint makes this a very complicated job; this joint makes it a piece of cake.

It also means, I can do as many test fittings as I want. So…

Here we are, all together now (all together now), all together now, (all together now…) (Ahem..sorry, been a lot of Beatles in the news lately.) Here is a pic from the side, showing the sloped back.