Saturday, June 11, 2005


Cocobolo Parlor: Spruce top and soundhole

This post has a lot of pictures, you people on dial-up are going to hate me.

For a long time now I had planned on using a nice redwood top, I'd already joined it and cut it to shape and posted pics of it here months ago. But I started noticing that visually it didn't seem to me that the color matched well with the cocobolo sides. I asked the opinion of a graphic designer friend and he agreed, so I decided to go with a spruce top and save the other redwood top for something else.

So here's the new spruce top, I joined it and cut it to shape last night.

Now it's time to inlay the decorative ring around the soundhole. It's going to consist of two 1/32"-wide strips of thin black/white/black purfling. Here's my soundhole cutter attachment and dremel router jig from Stewmac. The thumbscrew used to lock in the adjustment wasn't tight enough, so I used some spray adhesive to stick some 600 grit sandpaper so everything would stay solidly in place.

Here's the first channel routed out. I'm using a 1/32" downcut spiral bit.

Here's right after the second one is done so you can see how the circle cutting jig works. It pivots around a 3/16" pin which goes into the workboard underneath. Since it's a downcut bit, it tends to leave sawdust in the channel, so it might be hard to see the second ring.

I ran superglue in the channels, worked the purfling into the channels, and clamped everything down.

Here it is after the glue is dry and ready for scraping.

And after the soundhole is cut out.

That's a mighty fine soundhole, right there.
Looking really good! Seems like after much jig and piece building there is now something rather guitar-like to see!

I do have a question: the radiused back thing from the June 6 post--is that "normal"? I mean, does the average guitar have that? Why not just go flat... or even tapered but not radiused, since it's your first one and all? Must you tempt fate like this?
Yeah, most guitars are slightly arced in the back and top. The reason is that wood shrinks and expands perpendicular to the grain as it takes on or loses humidity. If you build it flat, you risk the guitar top or back going concave and things start to pop loose. If you build it slightly convex, it allows you to control the movement a bit so the thing doesn't "turn inside out" if that makes sense.
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