I recently purchased a “project bass”. It came in pieces in a Wal-mart bag, as the previous owner had disassembled it and scraped all the finish off before giving up and selling it to me for peanuts. It’s a Samick Saturn Series 5-string.
I started with a Photoshop mockup. I drew lines on about where I wanted them, then figured out a formula for laying them out. The focal point for the lines is about 6 inches above and to the left of the bass. This mockup has 9 lines, but I thought the ones at the top were too close together. I liked the locations of the top line and the bottom line, so for the real thing I just equally spaced 6 lines between them for a total of 8 lines.
I designed this table saw jig to cut the slots in the guitar. That chunk of wood in the middle is my “test bass”. It’s about the same size and thickness as the guitar so I could get the setup right. The slots are one narrow-kerf saw blade wide, so almost exactly 1/8″. I set the depth purely by eye, to what “looked good”, and I even re-cut the one that crosses the curve at the very top because it wasn’t deep enough on the beveled edge of the guitar.
FULL INSTRUCTIONS FOR THE JIG: https://www.youtube.com/watch?v=ZJYQLz4SG_0
USING THE JIG TO CUT THE SLOTS: https://www.youtube.com/watch?v=A6nVFaj7Wds
I was so nervous about making the first few cuts, but it turned out very well. I spent hours setting up the jig, so the actual cutting of the guitar only took about 20 minutes. You can see the whole process in the video linked in the last step. You can see that there was a tiny piece broken out in between the two front pickups, where the cut crossed a sharp corner. I kept the little broken out piece and glued it back later. You can’t tell. 🙂
Here’s a side view showing the depth of the cuts. I basically wanted the cuts to be deep enough to wrap around the edge of the corner of the guitar so the ends wouldn’t be visible from the front, but shallow enough that they didn’t weaken the guitar until I got the inlay wood in.