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Fret Measurement Accuracy?

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In Martin Koch's book Building Electric Guitars he suggests (in setting out frets) that if a fret position is more than 1/64" or 0.3m/m out from the calculated position it should be remarked. Questions:

1) I'm assuming this means +/- 1/64"?

2) What, in people's opinion, is the maximum tolerance allowable? My 24" rule has 1/100ths but only at inch 4 which makes it prone to error when trying to align something like 8.231 inches.

Any help/advice would be appreciated.

:D Dave

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Make it as perfect as you possibly can. Just cause you can get away with 1/64 off doesn't mean you should try. If your ruler can't measure accurately enough, get a new one, shouldn't be terribly expensive and it will save you the headache of screwin' up a fretboard.

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You could use a printed computer generated fret layout(look up online fret placement calculators, or use drafting software), then check it with your ruler. Things can go wrong with printed layouts (some printers scale 1-3% off, paper can distort), but as long as you have a good drawing to start with it can be more accurate than a ruler. You can also buy machine cut templates, which are usually extreamly accurate. I have found most marked rulers are hit and miss for accuracy at a very high level, etched rules sometimes are much better, slotted seem to be very accurate(but your slots only allow you a certain degree of accuracy, because you can only put so many slots in a ruler). Then you have to consider what you are marking with(it has a thickness) and how your slotting saw blade aligns with the mark you make. It is pretty easy to be off .03125" with ruler and marking unless you are really careful, That is close to the width of a fret tang (which is about .023"). If you did get it that close and you noticed a problem, you could shape the fret crown to counter some of that innacuracy(although I doubt most would notice if you were within a tangs width, since even spot on is not going to be perfectly intonated up and down the neck).

So accuracy is hugely important. 1/64" off may not be problematic, but it is not easy to hold that level of accuracy unless you use an accurate method of marking and cutting. :D

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