Fret Cutting Saw

Some years ago I bought a saw from Stewmac. It is a lovely little saw but it is a pig to use. The blade it 0.021 inches thick and the required kerf width is 0.023 inches. The leaves 0.002 inches clearance, consequently it binds horrendously. I have struggled on with it through about 10 fretboards but could stand it no longer so set about modifying it. I decided that the blade would have to be about 0.005 inches thinner. It would never be needed to saw deeper than about 5mm so I chose to "thin down" the last 10 mm. That way, the blade would retain its stiffness and it would allow some set to be imparted to the teeth. I used my drum sander to remove most of the material, taking  great care to ovoid overheating the blade and spoiling its temper, and then a coarse oil stone followed by a water stone to refine it. Straightforward enough but time consuming.

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Here the saw is clamped under a block of wood with just the 10mm showing. A Japanese water stone is shown here being worked backwards and forwards to refine the thickness. I removed the saw several times to measure the progress. It was very slow but eventually I achieved 0.015 to 0.017inches along its whole length as measured with a micrometer. Following the thinning, The teeth were set using a saw set, no easy feat for a man with less than perfect eyesight. To aid the process, I marked alternate teeth with a marker pen and performed the operation under an illuminated magnifying glass. I set the teeth three times, testing on a block of wood and measuring the resulting kerf with feeler gauges after each pass. On the third pass 0.023 inches of the feelers was a tight fit. Job done.

I used the rejuvenated saw to deepen the fret kerfs in my Jazz Bass fretboard. It cut them with ease, a great improvement at a cost of about 4-hours work.

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