Friday, May 7, 2010

Bridge Building

The last week has been spent putting the oil finish on the neck and headstock of Clark's guitar. No pictures for you, because there's really nothing to see. Clark decided to go with an oil finish, as many players do, because it maintains the feel of the wood under the thumb, which a lot of people like, and it will not grip the thumb or the hand when sliding up the neck as really glossy finishes can do when the hand gets a little sweaty.

I use Tru-Oil, which is a polymerized linseed oil with other natural oils added that is made for gun stocks. It is easy to apply, dries quickly, and is completely safe to use since it does not emit toxic fumes like lacquer.
It is not as hard or as protective as lacquer (the traditional finish for steel string acoustics) or the acrylic urethane that we used on the body of this guitar, but it is still a beautiful finish that can be used on the entire guitar. In fact it is what we used at Vermont Instruments on my first guitar since we only had two weeks to complete the entire guitar. Lacquer, on the other hand, has to be applied over the course of three days, you must wait at least a month for it to cure before it can be buffed.The process is simple: just squeeze a little on a lint-free rag, rub it on, then wipe off the excess with another rag and let dry. It'll actually be dry to the touch in less than an hour, but I like to give it several hours between coats so that it really gets hard. The first application I let dry over night, then used 0000 steel wool to level any grain that might have been raised and applied another coat. After this dried overnight I used 600 grit sandpaper to smooth and level it, then for the rest of the week I would put a coat on in the morning, then another in the evening. One or two days I'd put a coat on as soon as I came home from work, then another right before bed about six hours later. By the end of the week the neck and headstock were beautifully shiny. I may polish the headstock even more, but maybe not; it already looks really nice.

OK, to the bridge. The bridge blank is a rectangular piece of ebony. First I use the belt sander to make sure the glue surface is smooth and completely level and that the front edge--the one toward the neck, is also completely level. Then, using double-stick tape, I attach a plywood template of my bridge shape onto the blank, aligning the front edges.

I use the band saw to cut close to the shape, and draw lines around the template, remove it, and use a drum sander on my drill press to bring the blank down to the lines.

(I have since bought a sanding drum with a bearing on the bottom that can ride against the template and sand an exact duplicate of the template.)

Then I use the belt sander to bring the blank close to my final thickness of 3/8".

I mark off a rectangle 4" x 1", which is where the saddle will be. This also delineates where the wings and back will be tapered.

I use the round edge of the belt sander to shape these areas:

I hand sand with 150 grit to smooth these top surfaces, then work through 220, 320, 400, and 600 grit papers to really make the ebony shine. Ebony is an extremely hard wood, but it's also a little oily. It's a mess to sand, and you have to use a mask, but at 600 grit with the natural oils the wood is being polished. I finish off with 1200 grit paper, and the bridge really shines, almost like a finish has been applied.

All right, time to glue this baby on!

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