Friday, April 3, 2009

Fretting over polish and polishing the frets

Once the bodies, necks and other parts are finish sanded it is time to polish everything with shellac. I am hesitant to call my finish a French Polish, mostly because the technique did not truely arise in France (shellac is from the Far East), but also because I don't use pumice. But, here's the process I have come up with to get a nice shiny surface without the use of sprays or volatiles. Shellac, being the excretions of a beetle disolved in grain alcohol, is an organic, non-toxic and renewable resource. Applied thus it is the thinest possible finish and, if you believe the nuts, a tonaly superior finish.
A small piece of old wool sweater is dunked in the cut. I can't give you exact proportions, but the canned shellac is cut about 1-1 with alcohol to start. Along the way I add more alcohol for a thinner mix as the polish builds.

The rag is squeezed between two pieces of veneer to remove as much of the cut as possible.

The rag is then wrapped with soft cotton cloth.

This forms the rubber or tampon with which the shellac cut is applied to the wood. The object of this operation is to obtain a rubber that is almost dry. In this way only the tiniest amount of shellac is applied with each pass.
The process of polishing takes many, many hours, over several days. The shellac dries quickly, though, so by the time you make a pass over every thing, the first pieces are dry and you start all over. Rubbing, and rubbing and rubbing.

In between 'sessions' when the shellac has had a chance to cure, 1000 grit paper is used to buff out the surface. I think this is where the pumice came in for the original formula. I used to use 600; going to 1000 is new on these guitars. The upgrade is quite noticable in the finished gloss.At a point in the process things just start to shine. Towards the end you lubricate the rubber with a bit of linseed oil to keep it from sticking. There are several points at which you may stop. Satin sheen or soft gloss. These I took out all the way, high gloss. Probably the shiniest I've achieved to date, partly for the finer grit, but you get a little better every time you polish, a little stronger too.

I shellac the necks and oil the fingerboards prior to installing the frets. This provides the necks some protection against scrapes and dings during the rather violent fretting procedure. I reapply oil several times during fret up and polishing. The oil acts as a cleaner, removing debris and each application improves the finish. I use a three part oil, the same as for my furniture. It consists of one part each linseed oil, turpentine and fast drying polyurethane. It penetrates, rubs out nicely and drys in 24 hours.

The first task in fretting up is to clean out the sawdust, oil and dried glue in the fret slots. This is painstaking work, akin to a dental hygenist's trade, no doubt. I use the sharp edge of a flimsy metal rule and a straw to blow out the debris.

The frets are then cut to size and the nippers are used to undercut the ends to seat over the bindings.A flat file is used to clean up the undercut while holding the fret upside down in a block grooved to fit the crown. You need a really strong grip for this and even my fingers get sore after the 2nd or third neck.Using a shaped caul with a groove for the tang, I hammer the fret to shape.The objective is a curvature that is a bit sharper than the fingerboard radius as this will aid in keeping the ends down. Some folks advocate bending the whole piece of fret wire to radius before cutting. It is easier to file the ends if the wire is still straight at that point, however, and there is something to be said for hammering the frets into shape. By pounding on them they give up a bit of their "spring." Thus when they are pressed into place they have less energy to pop up at the ends. At least it feels this way to me.The saw I fashioned to cut the fret slots produces a slot that is very tight. The frets will stay put without glue, but they are much easier to drive when a bit of white glue is used. It acts as a lubricant for one, and there is some talk of a better tonal connection from string to neck when the slot is well sealed with the glue. The ends are hammered down first and with small gentle blows the fret is driven into the slot. Once driven far enough to cause glue squeeze out the excess is removed with a damp rag.If you wait just a minute for the glue to take effect, the fret can then be fully seated with the use of this specially shaped caul. That and a huge amount of brute force. By pressing in the final bit and not using the hammer, I ensure against any over driven frets.The ends are trimmed flush with the nippers, and the fret is carefully inspected all around under bright lights, repressing if needed to get a perfect seat. The ends are given a few taps to just slightly bend that overhanging piece down into the binding.Dressing the fret ends requires a great deal of patience. Each fret is masked with tape and a flat file is used to start the bevel.I've ground one edge of the file smooth as a safe edge. This edge is run against the fingerboard and the end of the fret is shaped round.Since I do each fret individually, I don't see any point to taking off such a severe bevel as you see on most factory necks. Instead, I endeavour to keep the crown all the way out to the end with a rounded bullnose shape just over the binding. Somewhere I read about a guy who "dressed frets all the way out to the end, to keep from falling off," this is my take on that idea. Once the shape is filed, I buff the ends out with 400, 600 and then 1000 grit.

Up until this point I have maintained a very sharp edge on the neck at the binding. I will now go over the edge with 400 grit and up; in between and around the end of each fret to produce a chamfer on the binding. This final shaping of the neck brings the dressed fret ends right to the edge and the neck has a nice broken in feel.

Leveling the frets at this point is pretty easy. My necks are nice and flat, and the extra care in fretting pays off. Instead of just filing down all the tops of the frets in one swoop, I work up and down the neck with a straight edge looking for high spots. It takes a bit longer than leveling with a stone, but it's not so messy, and not much material needs to be removed anyway.By lining with 200 grit, the same caul that I use to press the frets in, I can remove the tiniest amount of material from a single fret while maintaining the crown. Once they all check out, I line the caul with 400, 600, and then 1000 grit paper and polish the frets one by one. All the while checking against the rule. This is, once again, painstaking and tedious work. When you find a high spot at the finer grits you have to stop and repaper the caul and take that fret all the way out again.

Once the frets are dressed completely they get a final polishing. Now you may have noticed that I do things my own way. No exception here. I've seen all kinds of gadgets and mess making devices to polish up the frets, but none of them compare to what I have come up with. Check this out.

The day before polishing I smear some white rubbing compound on a piece of wood. It is allowed to dry. Using a wooden caul, shaped with a chainsaw file, I scrape some of the now powdery compound into the groove.The groove is blackened and smooth from previous polishings and the soft cherry is worn to the shape of the fret crown. Using a flat file, I continuously maintain the edges to just touch the tape on either side of a fret.With the frets taped off the caul is vigorously rubbed back and forth, initially scraping up the powdered compound as you go. Pressing very hard the compound impregnated wood polishes the frets to a high gloss. Rounding over the edges the fret ends get polished as well. The trick is to scrape off a little fresh powder for each fret. As the polish blackens it also gets finer and looses it's 'grit.' Starting fresh each time is the most effective.

Once the fret are polished the fingerboard is oiled a final time and allowed to dry. The shellac is then buffed out with the rubber eliminating any scratches and sealing up the chamfered edge of the binding. Drilling for the screws that secure the tuning machines and truss rod covers is all that remains.

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