Finally, The Holes Are Drilled!

I'm guessing I've broken the first rule of blogging by failing to post regularly. I got off to a flying start with a bit of preparation in the bank, but I knew from the start that there would be interruptions, delays and sometimes limited opportunities for consistent updating. After all, should I be spending my spare time working on the bass, or just writing about it? Nevertheless, just because there hasn't been a post recently, it doesn't have to follow that no progress has been made.

So where we left off was working out how to mark the positions for preamp control holes. There were a few false starts, but they all contributed to the result at the end. The aim was to align the controls in an arc that matched the curve of the lower bout. The first attempt of copying the arc was to trace out the profile onto plywood and then cut out this shape. The difficulty here was to get that profile translated correctly onto the internal cavity template so that it was parallel to the body outline. By marking the cavity width on the plywood I could position reasonably accurately and mark the curve on the template. The control knobs were put in place on the arc line and positioned to be equal distance apart. The result didn't look too bad, but when I checked by measuring the distance from the edge to the centre of the knobs, as in the picture, there was quite a variation from one to the other. Therefore, the arc could not be parallel with the body. And once I thought about it, that had to be right. If you think of concentric circles, the inner circle has to have a smaller radius. By copying the body arc, I did not get a smaller radius. I'm glad I measured twice!

In the end I used the arc as a guide and then measured with the small square and ruler the perpendicular distance from the outer profile to the centre of the knob. I marked a circle around the knobs and then marked the centre of the circle for the pilot hole.

Having the centre holes now marked on the template, and the template captive in the cavity, I drilled pilot holes of 1/16" diameter. Finally, I was committed, with no turning back. The 7 mm holes were next.

Another aspect of my paranoia regarding the holes was achieving a clean cut at the knob surface. I learned from my research that the Forstner bit is recommended to give a nice, clean cut. You can see from my test on a veneered panel the difference between the brand new Forstner bit and a not so new regular twist bit. To be honest, I expected more tearing on breakout of the twist drill. From this result, the surface would clean up OK with a light sanding. I think the key here is to have the workpiece very securely clamped over a sacrificial piece of wood, so that you do not drill out into fresh air. 

Finally, four holes drilled. Just one more, for the switch, to go.

Working out the best place for the switch was the next issue. In the end I decided to position it in line with the rear-most knob, mainly so that it didn't get in the way. In theory, it should lie midway between the knob and the bridge. The final result is shown below.

 

 Now the hard part is over. Getting to this point took, literally, weeks of agonising, measuring, checking and procrastinating. The holes are where they are. They can't be moved or corrected in any way, but to my eye, they look acceptable, and close to what I had in mind.

From here it should be full steam ahead!