Monday, August 3, 2009

In a Bind

Pam and I were gone all of last week to the Eastern Shore, so that's why there haven't been any posts. No cable TV, no Internet, cell phones barely worked. Being disconnected from the world for a few days isn't so bad.

This week of vacation was supposed to last through Sunday, but Pam realized she needed to be back in town on Saturday for an all-day meeting, so we came back on Friday night, but since I already had someone to preach for me Sunday morning, I continued my vacation at home, spending almost all the time in the garage workshop.

Now that the body is assembled, it's time to install bindings. The bindings protect the end-grain of the top and back from being crushed, and really dress the guitar up.

They can also be a pain in the butt-wedge. I have to rout ledges where the sides meet the top and the back, and if anything goes wrong you can really mess a guitar up. Ever see a bad binding job on a guitar? Nope, neither have I, because if you mess it up, you either fix it or you just start over. That's how much a bad binding job can mess a guitar up.

Things are complicated by the fact that, because they are radiused, the top and back are not perpendicular to the sides. If this isn't taken into account, the router will make a cut that isn't square to the sides, leaving the bindings thin at the top and thick at the bottom.

There are a variety of ways to deal with this. Earlier this year I bought a jig that holds the router square to the sides. Here it is:

The guitar is held in a carriage and adjustments are made so that it is square to the table at the neck and butt ends. The router is attached to a platform which rides freely vertically on a metal post.
The bit extends below a smooth plastic ring, which rides just on the edge of the top or back, discounting their radii. The sides are narrower at the neck than at the butt, but the router simply moves up and down as the sides are rotated under it.

The depth of the cut is determined by how far under the ring the bit is extended. The width of the cut is controlled by bearings--the smaller the bearing, the wider the cut. Here is the bit with one of the bearings attached, and the different bearings that can be used.

There is a lot of trial and error here--but not on the guitar. I take a piece of the binding and change out bearings until I get one that allows for as flush of a cut as possible. The depth is such that the binding is just proud of the surface. The I test it on a piece of scrap wood. I make a cut, place a piece of binding in it and determine what adjustments must be made.

Adjust depth, change out bearings, test the cut, make more adjustment. When I'm satisfied, I rout the ledge, first on the back.

Look closely and you can see the ledge, and look closer and you can see a piece of the rosewood binding that I've place in the ledge. Here's a closer look:

Seems straightforward, huh? But I have to rout not just for binding but for the decorative purflings that are on the top and back surfaces. And, because my life isn't complicated enough, I've decided to add a purfling line under the bindings. Remember the black/white/black that bordered the butt-wedge? I'm going to use that same purfling under the bindings.

Sooooo....I have to first rout for the binding. Then, because this purfling is going to be mitred to that of the butt-wedge, I have to adjust the depth to accomodate it, stopping just short of the butt-wedge, and finish by hand with a chisel.

You know what? This will be clearer when I install the bindings and purflings, so let's just leave it for now.

After making those two routs, I have to make a third rout for the back purfling. That's three routs, testing and adjusting for each one.

Then I have to do it all over again with the top. This takes time. Plus I had to assemble the routing jig, which took most of Saturday morning. Finished the routing Monday night, and hope to have all the binding installed by the end of this weekend.

But stay tuned. This part is never easy.


  1. I've thoroughly enjoyed following your build. I have built one guitar (Englemann spruce, Sapele OM) and am planning to start my second this fall. I am a worship pastor so I also enjoy your interspersed thoughts on the Christian life. How do you like your binding machine? Did you get the kind of results you were looking for? I'm planning on building a similar one based on the Ribbecke design for this next build.
    Fred B

  2. Hi Fred,

    Anytime you use something for the first time there is a learning curve, but the binding machine works as advertised. Here's one thing I learned, though: some people say that it doesn't matter if you make the binding cut before the purfling cut or vice versa, so on the back I made the binding cut first. However, the purfling cut is so shallow that the bearing rides on the fresh-cut binding channel at the upper bout but then moves to the side just under the rout at the lower bout, changing the width of purfling cut.

    Now, it probably shouldn't do this, and it's probably caused by something I didn't do exactly right, but now I have had to tape some binding in the channel to achieve a consistent purfling cut. So on the top I cut the purfling channel first and then did the binding.

    It's good to hear from another builder. Are you located near frederick? From your screen name it appear that maybe you are. I'd love to talk some more with you about building and ministry. Shoot me an email if you are so inclined.