It's easy to set up a spreadsheet to calculate fret distances. Each fret is 1/17.817155 of the remaining distance to the theoretical saddle position, with no compensation. I actually wrote a small program in BASIC that I still use. It prints out both the distance from the fret to the saddle, and the fret to the nut. I find this really helpful.
When I'm laying out the 'board, I use three clamps to hold the steel ruler down; that way, when I move one there's no chance for it to slip. I start with the nut location at zero, and use the 'nut to fret' numbers and a knife point to mark each fret location to within .2mm (.008", which is about as close as you can see them). These days I use a magnifier. When I have all the fret locations marked, I remove the ruler and use a square and the knife to strike the lines.
NOW COMES THE IMPORTANT PART! Clamp the rule back onto the board, but reverse it. If I'm using a 650mm classical scale length, the zero of the rule will be where the bridge will go, the 12th fret at 325mm, and the nut at 650. Check the scribed lines against the 'saddle to fret' table. Any that are off by more than .2mm I mark with a little arrow, to show which side of the line to cut on. If they're off by more than .5mm I re-mark, and re-check them. I slot 'on' the line; with the marked line being in the center of the slot. Since the kerf is .5mm, cutting to one side of the line moves the slot .25mm to that side. Remember to cut the nut slot to the side of the line.
What I've found is that if I use the same table to both mark and check the fret locations there's a tendancy to read the numbers wrong the same way both times. Reversing the rule gives you an entirely different set of numbers, and you're less likely to see what you remember, rather than what you're looking at. You'd be amazed at how easy it is to get something a full 5mm off, just because you fixed on the wrong line on the ruler. Looks pretty stupid, too, AND it's hard to fill in.
I've used the old 'Blitz' backsaws for years. They don't make them any more, but you should be able to find something that cuts the same kerf. Those little saws can't really be set to provide clearance for the dust, and tend to bind in ebony after a few cuts. The burr left from sharpening acts to increase the kerf enough to provide clearnace, and once it's gone things get difficult in a hurry. I have found I can sharpen the saw pretty quickly and restore it to smooth cutting.
You'll need one of those little 3-square (tiangle) diamond needle files. I get them from Micro-Mark or the local hobby shop. Clamp the saw in a vice, so that there is very little of the tooth side of the blade clear and it's nice and stiff. Roll the side of a black felt tip pen along the teeth, to blacken in the gullets. Now use the diamond file to take one or two light strokes across every other tooth. I hold the file level, and perpendicular to the blade, as if I was sharpening a rip saw. Match the file angle to the rake of the teeth. It's easy to see which ones you've hit: the gullets are shiny. When you have hit every other tooth turn the saw around in the vice and get the other ones. Filing every other tooth in the opposite direction makes the same burr on each side, and keeps the saw cutting straight and smooth.
I've never used a miter box, but I can see where it would be handy so long as you can dress one edge of the board off parallel to the center line. Sometimes I used to get one that was too narrow for that, and had to use a protractor to scribe the lines instead.
Slotting a freboard is not hard, but it is fussy. So are a lot of the other things you ned to do to make a guitar. Knowing how to lay out and cut a board frees you up in some ways, and it's a good thing to learn.
|
