Fret Slotting Jig
I have seen articles that describe cutting the fret slots freehand, following a scribed line with the saw. I have done it myself but I would not recommend it. Many years ago I made a fret slot cutting jig, a bodge of a job, done in a hurry when time was limited. I would have used it on the Jazz Bass project but for the fact that it was not long enough for a bass neck. So I made a bigger and better one. It features a bed of hardwood about 85 mm by 35 mm 1 metre long, an under-slung carriage that slides along the bed and carries the saw guides, a millimetre scale (steel rule) and a vernier scale.
The bed and carriage rails were made form a single piece of hardwood, rebated each side 10 mm * 10mm with a hand held router. The table router would have been better because the bearing surface of the edge of the board is not particularly wide and there was a risk of running off, spoiling the piece but I could not be bothered to set it up. Fortunately, it went OK. A 180mm length was cut off the end and the carriage rails were cut from this section using the band-saw. Making the rails and bed in one assured that the routed slots would align perfectly and it avoided routing fiddly little pieces. Slider strips, 19mm * 10mm were made and installed in the bed section with a few dabs of PVA. The steel rule was let into the beds surface such that it was flush with the top and the edge. The carriage was made by screwing the two slider rails to a base board of 20mm deal. The screw holes in the base board were made slightly oversize so that any slack can be taken up to give a good sliding fit on the bed. A little candle grease was applied to reduce friction and wear. I had to shave a little off the bottom of the bed to allow the carriage to slide freely, after that it slid without too much force being needed but it was tight enough not to need clamping whilst sawing the fret slots.