Tuesday, May 29, 2012

Cutting up a neck blank

Yesterday I made some more guitar building progress. Every time I work on them, I realize that it's not quite as tough as I sometimes make it out to be. I also decided that I like breaking the process into individual steps, and posting about each one. I think it helps pace myself, or process my thoughts, or something.
I drew out all the steps some time ago. Now I just have to stick to the plan.
The plan was to rip off a piece to use for the headstock. It comes from behind where the fingerboard will go. Ideally, the neck ends up about the right thickness, and I have a nice piece left over to use as the headstock. This way the headstock will end up matching the rest of the neck.

Unfortunately, I had set myself up for a challenge by making a really dumb mistake when I prepared the layers of the neck blank. The piece of cocobolo in the middle is not the full thickness. I tapered it off when I cut it out of a large piece, apparently attempting to save wood. This means that I have just barely enough wood for a headstock, and next to no room for error.
The middle layer of the sandwich doesn't reach the bench. D'oh!

In order to cut out a headstock piece without wasting wood, I needed accurate lines to follow, and before doing that, I had to bring the surfaces up to snuff, accuracy-wise.

There is foamy dried glue showing near the top, but it will get covered by the fretboard.
I planed the fingerboard-facing surface first, making sure to keep it perpendicular to the glue lines. Since the veneer layers were out of alignment, there was some dried glue where there should be wood. Wanting to conserve wood, I planed down far enough to get a completely clean surface only where it will show. There are a few glue bubbles visible in one of the narrow walnut stripes, but these will be hidden by the fingerboard. A relatively fine setting on my cambered jack plane was useful for focusing efforts on one end for a little while. This ebony is difficult stuff to plane, so anything that focuses energy in one area can make planing a lot easier. I finished up with my jointer plane, set as fine as possible because otherwise it's very difficult to push. A 90-degree fence on the jointer helped make planing the two sides easier. I didn't bother with pictures of planing because it's not unique to this project. I left the back and ends rough, and moved on to marking out some lines.

Before I actually marked anything, I wanted to sanity check the dimensions in my drawings. I made a full scale cardboard mock-up to make sure I liked the size. I didn't end up deciding to change anything significant, but I did end up deciding that I will need to beef up the headstock a bit. If the picture of the mock-up looks weird, that's because it's going to be a weird guitar. The whole thing will be tiny, and the body is not integral to the design.
The neck blank with hardware, tape & cardboard gives me an idea of what this thing will look like
The part of the neck blank that goes through the body will stay full-thickness. The rest needs to shrink down a bit to be playable. Since I won't be using a truss rod, all of the strength of the neck needs to come from the wood itself. This is why I've chosen very stiff species. Still, making it too thin now would be a mistake. I'm going to make a final decision on the thickness later, after I've seen it under string-tension. For now, I'm comfortable with 3/4" at the headstock end, and 1" where it meets the body. This leaves just enough excess to use as a headstock.

Chalkdust makes knife lines visible.
I used a marking gauge set for 1" and a 1/4" brass set-up block to mark both depth settings. A square and marking knife defined the other dimensions. These knife lines are great for accuracy, but they're almost invisible. Chalkdust fixes this. I scribbled over the marks with chalk, then wiped off the excess, leaving sharp white lines to follow.
This spacer might have been overkill, but I like not having to change a gauge setting until I'm sure I won't need it again.

I clamped down a ruler to connect the dots with a marking knife. This is important, because if I make two lines by accident, I will undoubtedly end up following the wrong one.
The chalked knife line is crisp and noticeable.
With the lines marked, all that remains is the straightforward task of sawing to the lines. I'm pretty sure I have Chris Schwarz to thank for putting the idea in my head that this is a very important skill. Being able to saw to a line is liberating, because you can draw a line almost anywhere.

I used my favorite saw for this, which also happens to be the only decent rip saw I own, an inexpensive ryoba made by Vaughan (no financial connection etc.). It was important for this step to use a saw that cuts a thin kerf, and to stay right on the line--for at least two reasons. For one, I need to avoid wasting wood. For another, because of the shape of the neck, it will be very difficult to plane the back. Better sawing means less work later.
Sawing to a line is the key.
The saw I was using has a pretty thin plate and only very minimal set. This means it's very hard to steer. This makes it hard to correct for errors, but also hard to make them in the first place. The key to doing a good job is simply vigilance. I watched the line every second I could, and when I got off track, I corrected immediately, before it got any worse. I flipped it a few times so I was always sawing the line I could see. This was easier than I thought it would be, because patience and vigilance make up for a lot of raw talent that I don't have.
Ripping exotics is a good way to work up a sweat. Good thing I had a sharp saw!
To fully liberate the headstock piece, I had to make a small compound-angle cut. This is where sawing to a line has such an advantage over say, a table-saw. I could have done this on my table saw, but it would have required quite a bit of error prone setup. I think it would have ended up taking 10 times as long, plus I probably would have made a stupid mistake along the way. Seeing the line as you cut is reassuring.
This begins to suggest what the back of the guitar will look like.
 After I got the pieces free, I was pleased to discover very little roughness, but still plenty of room for improvement. This is one of those things that just gets better with practice, I guess. The scrap I was left with does look big enough for a headstock, so I'll call this a success.
This scrap should be just big enough to make a matching headstock.
 Next time I have a chance, I will do the same steps on the other guitar. It's softer wood and without the missing chunk, so it should be significantly easier.

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