Friday, July 24, 2009

The Butt-Wedge

Got your attention, didn't I?

It's technically called an end graft, but it's commonly referred to as the butt-wedge, and, admit it, butt-wedge is more fun than end graft, isn't it?

It's extremely difficult to get the two ends of the sides to meet perfectly at the bottom or butt of the guitar. As you can see, the sides don't even come together on the end block on this guitar. No worry, however, for this is where the end graft comes in.

The butt-wedge gives you a great margin of error, but also serves as a decorative piece. It's one of those parts of building where you get to use some creativity. It's a great merging of form and function.

I'm going to use rosewood for the wedge to match the rosewood bindings, so I find a suitable scrap that's both long and wide enough. I cover it with masking tape so that the pencil lines are easy to see, draw a centerline, and square up lines at either end. I want the top of the wedge to be about 1/2" and the bottom 1", so I draw these dimensions and connect the lines.

After cutting this out at the band saw, I put some masking tape on the end of the guitar and trace this wedge shape onto it, matching the centerlines. I then saw down to the end block just inside these lines using a block of wood as a guide to make sure that the saw blade stays square to the bottom of the guitar. Once these cuts are made I chisel out the zebrawood between the lines, and sand everything smooth.

Now, I'm a dork, and now realize that I made my wedge too short; I should have extended the lines on either end so that the wedge is both too narrow on one end and too wide on the other. That would give me more wiggle room. As it is, with the cut I've made, the wedge is actually too tight before going all the way to the top.

Also, I plan to have two purfling strips on either side of the wedge, which just makes the problem worse. So I find another piece of rosewood, cut a masking tape template from the actual wedge cut and transfer that to the rosewood, extending the lines much further than actually needed. Cut that out, and here's what I get:

Now it fits in the cut with room to spare on both ends. When I do a dry fit of everything I realize that the purfling strips sit just barely below the level of the sides and I want them to be just proud of the surface, so my first step is to glue a thin piece of wood veneer to the bottom of the graft.

I spread glue on this, making sure to get some on the sides of the graft, and then put the purflings in.
Then I slide the butt-wedge in, making sure the purfling strips don't slide forward too much or slip up over the surface. Because it's a wedge shape it serves as it's own clamp; just a couple of light taps with a hammer, and it's in. I use a damp paper towel to clean up the glue squeeze out.

I want to make that the wedge is seated tightly in the cutout, I clamp it down for a few minutes using a wood caul.

After about an hour it's ready to be trimmed and then scraped and sanded flush to the surface.

1 comment:

  1. I remain amazed at how much woodworking is like quilting. I'm not talking your "grandmother's quilt", but rather the intricate set-ins that are done to make a quilt an original.

    I'm sure enjoying watching a guitar being made from pieces of wood, just as a quilt is made from pieces of cloth.

    Lou Ann