Is Oak ever used as a tone wood in instrument making?
(answer at the end of this month's journal)
In June, the neck and headstock were roughed out with a sanding machine and various rasps and files. Essentially, that marked the end of the machining processes for these guitars... the rest of the work to complete the guitar is almost exclusively done by hand.
This month's work included the finish carving of neck, the heel cap, and the head stock. End pins were installed in the butt of the guitar, and the tuners were temporarily set in the head for final layout and dimensioning of the head. Also to be custom carved for each guitar is the bridge, the saddle and the nut. Then comes the final fret work and the set up of the guitar.
The finish line is in sight.
Finish Carving of the Neck
The finish carving of the neck should (at this point) only require light-weight, hand tools_ files and scrapers mainly. Pictured below is a gooseneck scraper that I use almost exclusively to work the neck down to its final dimensions. To do this work I pay strict attention to the total thickness dimensions of the neck and fingerboard at the 2nd, 5th, and 10th fret.
The finished curves and shape of neck are the result of continuously feeling the neck in my hand and under the scraper as wood is removed. One should also carefully monitor shadows on the curves of the neck to find flat spots. A high-intensity LED task lamp is great for this purpose. I also keep a finished guitar laying side-by-side with the guitar and neck that I am working on. This provides touch and visual reference.
The subtleties of using a scraper correctly are many and difficult to explain in words. Using a scraper properly is an art. The end result is a finished surface that is flatter and smoother than a sanded surface. I will note here that there are probably many good videos available online regarding the use of a scraper for finishing wood. The first thing that I would look for in these videos is an explanation of exactly how to sharpen the scraper. That is key.
When sharpened correctly, a scraper will hold a sharp edge for quite a long time... even years, if the tool is used exclusively in building guitars.
Gluing the Bridge
Next to gluing on the neck, there is no more critical component of guitar building than locating and cutting the saddle slot. First, however, the bridge must be glued in place.
The location of the saddle needs to be laid out on the spruce top with a light pencil line. A fret rule is essential here. Once marked, note where the pencil line crosses the center line of the guitar top. The front of the bridge should be located square to the top center line and approximately 8 mm forward of the intersection of the top center line and the pencil line which marks the saddle position. This should give you plenty of room to locate the saddle between the bridge pins and the front edge of the bridge.
The hole for the end pin can be drilled anytime after the butt strip has been installed. End pins, of course, are for holding a strap if the player wants to play while standing. Some players never play while standing and would prefer not to have an end pin. One can be added later if needed.
Measure and layout the center and middle of the butt strip. To do this, have the guitar clamped up so that the butt is up. I use the same set up that you have seen for installing the butt strip. This makes it easier to drill a hole that is perpendicular to the butt. Start with a 1/4" Forstner bit and then switch to a 1/4" twist drill. Try to advance the drill slowly into the wood but at maximum speed so that tear out will be minimized when the bit breaks through on the other side ot the butt block.
Remember, end pins come in various sizes and lengths, with a varying degree of taper from the shoulder to the toe of the pin. Be sure that the hole is dimensioned for the end pin that you are using. The end pins that I like are rosewood or ebony and are 0.30" in diameter at the shoulder and 0.25" at the toe. The shaft is about 0.75" long.
Head Stock and Tuners
Traditionally, the head stock of the guitar is a feature which can be used to display the luthier's creativity and craft. I find it to be a good idea, therefore, to install the tuners at this point, before finish is applied, in order to ensure that the presentation of the entire headstock speaks for the effort taken in creating the instrument.
Converging lines are a recognizable feature of my guitars. The issue with this geometry, however, is that asymmetrical or unbalanced patterns are easy to pick up visually. Extra effort must be taken, therefore, to get the geometry of the back, neck and head stock to be balanced around a common center line. That requires strict attention to symmetry throughout the construction process... and the head of the guitar will stand as a display of how well the maker has done in this regard.
In the headstock pictured, the chrome tuner shafts and washers must be symmetrically placed relative to the light-colored, maple strips which converge from the top to the bottom of the head. These maple lines are only as deep as the veneer covering the mahogany head stock. The back of the head looks quite different as its lines of symmetry begin at the heel of the neck and converge through the length of the neck and peg head. These are, essentially, 5-piece necks and the vertical laminates of mahogany and maple make the neck more stable as well as attractive.
Saddle and Nut
With the bridge glued in place, it is ready for the final marking of the saddle slot. To cut the slot with a router and a 1/8" (0.125") bit, I've built a simple template to align and guide the router. The template guide is clamped to the top of the guitar and the router slides across it. I will have some pictures and more words on this next month as I've not started routing the saddle slots yet. All that I will say right now is that setting up to cut the saddle slot is tedious and an effort that must be precisely executed. The same is true of drilling for the bridge pins and cutting the string slots in the nut. In a small shop, like Woody Strings, each and every part of the guitar is unique to this instrument. The nut, saddle and alignment of the strings at both ends is, likewise, unique.
NOTE: I just received from LMI a few finished guitar parts for relatively little money. The parts included a finished and polished ebony bridge complete with perfectly cut CNC saddle slots and bridge pin holes. Also received were sets of perfectly cut and polished bone saddles and nuts with string slots and saddle compensation already complete.
After trying the ready-made parts I concluded that they really do look nice and there is so little effort required to install them. The only problem is that they look machined, and polished and perfect when everything else on the instrument has the look and character of being handmade by one man. The machined parts stand out as inconsistent.
More on all of this next month.
P.S. Work in the shop was interrupted this month by another type of wood event... a 60' oak tree fell into my back yard__about 20' from the new finishing shop.
As it was my neighbor's tree, he paid to have it cut up into firewood lengths (~ 20") and Woody, being Woody, agreed to move it out of the neighbor's yard... and into my wood pile. In all, I received a gift of about 3 cords of oak firewood (8 tons).
It took 2 days to move the wood and 3 more days to recover. That brilliant idea killed a week.
Answer to this month's Woody Question.
Is Oak ever used as a tone wood in string-instrument making?
Almost Never. Oak has straight grain, but coarse, and uneven texture which complicates machining and fine tooling. Oak bends nicely and is commonly used in cabinetry, furniture and boat building where durability and flexibility are important.
The hardness of quarter sawn oak wood varies across the same board, so machine sanding often leaves the surface wavy. Likewise, this non-homogenous texture (hard, soft, hard, soft, etc.) leaves much to be desired in the transmission of sound.
Carving the Neck
Gluing the Bridge
Headstock and Tuners
Saddle and Nut