Need help with binding ledges - strange angles

[Chris Lounsbury]

I've started a prototype of a new body shape and decided to make my venetian cutaway flush to the (straight) tapered heel of the neck. Unfortunately I jumped right ahead to building before considering the tooling I've been using for cutting binding/purfling ledges.

What I have been using is a Fleishman-style setup which is a telescoping & rotating arm with a parallelogram fixture on the end which allows the router to travel up and down, always remaining plumb. This is great when the body is held in its cradle so the sides are plumb all the way around the body. BUT in the area of my cutaway the treble side (rib) is angled to match the heel when the rest of the body is plumb. As far as I can see, it is not possible to use this setup to route all the way around the body and get the correct width ledge in the cutaway area.

If I were using tooling that registered the cutter to the guitar side, the channel would be the proper width and angle but would vary a small and manageable amount in height, but I don't have that setup.

I'm hoping that someone on this board can suggest to me the best way to cut my ledges by hand in this area.

I do not plan to repeat this configuration unless I change my tooling first.

Chris Lounsbury

[Randy Roberts]

Chris,
Could you tape shims of thin wood along the path your bearing rides? This would get you back plumb.

Several layers of tape laid on top of each other, on top of the shim, would let you gradually walk up to your final depth of cut by starting obviously too shallow and then removing one strip of tape at a time where the bearing rides. This would let you walk up at about 2 thousands at a time (depending on the thickness of your tape).

Assuming you are binding along the neck edge as well (the vertical edge), that can be done free hand with the router and the bearing I would think.

[Bob Gramann]

Wow! What a cool idea! If you want to cut the ledges in that area with a chisel, it's not too hard if you have patience. It kind of like mortising a door hinge with a chisel. (http://www.todayshomeowner.com/video/ho ... -a-chisel/ ) Us a gramil or some other guided cutter to cut the outside edge of the ledge on the side. You may have to repeat this two or three times as you get the ledge to its final depth. Use the same guided cutter to mark the inside of the ledge on the top or back. Unlike the description of mortising the door hinge, don't plan to go to the final depth in one pass. Two or three passes or more is appropriate for a binding ledge. You don't want to be quick but rather accurate. Don't get greedy--only work to an easy depth on each pass. Sharpen your chisel before you start. Using hand pressure, make cuts the width of the ledge on the side (across the grain) about a third of the depth and an eighth of an inch or less apart. (I'm assuming your binding is in the .080 to .090" range.) With the chisel bevel down, you can scrape out the little chips you have just made. After you finish one pass, do it again. On your last pass, make your cross grain cuts just a hair shy of what you want for your final depth. After you clean up this pass, use your chisel, held at right angles to the side, as a scraper to work your binding channel to the final depth. Pay attention to grain direction when you cut and scrape--the direction you go relative to the grain makes a difference. It doesn't take nearly as long as it might seem to do this. Doing a clean job this way is a skill, so it is worth the time to practice for a while on scrap wood. Your chisel needs to be sharp and you need to pay attention to what might happen if the chisel slips and don't risk your hands or any good wood (like the top--a slip landing on the top could be very unfortunate).

And, wait until you hear from others. There may be a better way that I would be happy to learn myself. I've never had to do a whole guitar like this, only some sections, but I would imagine a whole guitar would only take a couple of hours. The process is actually kind of fun (but not so fun that I put away my router). Good luck.

[Michael Lewis]

And I will reiterate, "sharpen your chisel"! This is a good opportunity to take a few deep breaths and slowly exhale, settle into slow breathing and focus your attention on the ledge and the cutting edge. Don't get in a hurry, get it right.

Sometimes I spend hours getting the binding ledges ready. It's wonderful when you can just run a router along the edges and put your binding in, but it doesn't usually work that way for me. The preparation is most of the work, and it really does help make the job come out "perfect".

[Mike Mahar]

I have the same Williams/Fleishman style machine. What I would do is to use it to cut the binding channel everywhere except part of the cut away that is at an angle. I would then adjust the cradle so that the remaining portion of side is vertical and cut that. There would be a bit of cleanup with a chisel at the point where the transition between the two cuts was made.

[Mark Judd]

Make a jig like this one, which keeps the router parallel to the sides......

[Alan Carruth]

I used a jig more or less like Mark's for years. It works, but essentially does the same thing that the other jigs do. After all, they work by keeping the router perpendicular to the bench top, and run on a box that's held so that the sides are kept perpendicular as well. That's not the problem.

The problem is that with a domed top or back the binding has to bend vertically as well as horizontally, and it doesn't want to do that. Particularly on the upper bout on the back there's a tendency for the binding to tip away from the back surface around the upper bout. That's one reason I put on bindings with a rubber rope and wood glue: they give enough pressure to twist it in. If you put on bindings with CA and hand pressure you might not be able to get them tight.

[Bob Gramann]

One of the tricks on getting the bindings to fit tightly is to glue them on immediately after you bend them--one piece at a time immediately after you bend that piece. They are much more compliant before they fully cool and set. I use hot hide glue and the green high-stick 3m tape (2060) and sometimes take the whole guitar back to the bending iron when I have a recalcitrant section after the rest of the piece is taped. The next day, the bending iron and a bit of moisture can be used to coax a gap closed.