Back & Binding Jig

Last Sunday, I had some time, and the scrap left from my molds, so I began my binding jig.  The construction is less complex than it looks.  I began with the plastic that would serve as the router mount, and cut it to size.  In the picture, the router is mounted backward, and I still have some work to do on the mounting plate, but it's width is correct and that was the crucial dimension.

Next, work on the interior box.  On the material for the interior box (3/4 MDF) I cut the groove for the mounting plate on the table saw with a dado blade.  It took a bit of fussing with shims to get the width of the groove correct, but I wanted a tight fit.  Next, I cut the sides to width, about 2 1/2 inches, and length.  The drawer glides determined the length.  With the mounting plate in the side grooves, used that to get the measure for the width of the back.  I used a simple butt joint, then glue and brads to build the box.  You can use the mounting plate to keep things aligned.

The next step was the exterior box.  Again, I cut the sides to width, about 2 1/2 inches.  Again, the interior box and the drawer glides determined the height.  It is set so the router, at the lowest level, will not bottom out its bit.   A word on the base.     You can see in the photo above and to the left, that it is flush with the front, but extends back.  When the jig is in use, I plan to clamp it behind to one edge of my bench, and you can see from the photo that it supports the weight of my router without the clamps.

I built the exterior box in the same way.  The width of back was determined by the interior box, with the drawer glides.  I then used a simple butt joint with brads and glue.  I cut and installed the base last.  When the glue had dried, and I'd rounded over all the edges, I installed the drawer glides.  Make sure you get the orientation right, but basically the interior box slides up and down like a drawer in and out.

Next, I need to fuss a bit with the router mount, and build the guitar cradle, but on the whole, this project went together better than I would have anticipated.

I had ordered the back and side plates from LMI.  I was side tracked a bit.  Originally, I had intended to use mahogany, but got side tracked by the idea of black walnut, a domestic wood.  It arrived on Wednesday, so I was able to get a start on the back of the guitar.

I brought the thickness down some with my toothing plane, and my thickness sander.  With the toothing plane, I only worked the interior surface.  It's quicker than the thickness sander alone.  There was a bit of tear out, but the thickness sander removed it along with the toothing plane tracks.  

The center stripe is maple from the local hardwood store, with black/white perfling on either side.  The stripe, as you can see from the back view goes all the way through, and is not an inlay.  I prefer this to an inlay, particularly since the joint is reinforced.  The assembly needs a little fussing to get it all lined up in the lattice jig, but then I don't need to worry about sanding through the inlay.  I used scraps from the soundboard redwood to make the reinforcement strip.  Once I had glued it in place on the on the go-bar deck (using every go-bar I had to insure even pressure along the length) I planed it level, then planed a slight bevel on either side, which is rounded over when I sand it.  Today, I will work on the bracing for the back, which I intend to make from walnut, also purchased from the local hardwood store. 

Sound Board Bracing

You can see the finished Go-Bar deck.  It took all of a half hour to build.  I cut two pieces of 3/4 MDF slightly larger than my radius dishes, nipped the corners off, drilled holes and enlarged them slightly on the top, then bolted the top and the bottom in place.  I used 5/16 threaded rods.  I could have used larger, and they would have had less wiggle, but the 5/16 are working quite well.  I didn't cut the rods, but left them at the full 36 inches.  The extra length will allow me to raise the upper deck, if I want to use it for projects other than guitars.  (My wife wants me to make some boxes for a variety of tea bags, something well crafted that could be used on the table.) 

The go-bars themselves, I made from poplar.  I had thought about ordering some fiberglass rods from McMaster-Carr, but frankly didn't want to wait.  Poplar is a stringy, hence springy, wood, so I cut some strips at about 1/8th inch thick.  Any thicker and they're too stiff.  At any rate, they work like a champ.

I have an order of precedence in gluing on the braces, and I won't outline it here.  It begins with the X-Bracing.  I begin the process by cutting them from lumber.  I'm cutting the bracing from a redwood 2 by 4 that I rescued from the Home Depot.  The first trick is the grain.  I wanted a piece with tight, even and straight grain.  It doesn't where that grain is on the billet (I'll call it a billet from here on out) but when the brace is cut, the grain should run the length of brace.  Looking at the end grain, it should be vertical to the soundboard.

I cut my X-Braces at 3/8 wide and 3/4 inches high.  They will lose a bit of that dimension when planed and sanded, but it also makes for a stiffer top.  To radius the braces, I do two things.  First, I begin by planing a preliminary radius on the brace.  Take a cut with the plane about one inch from the end, another at an inch and a half, another at two, et cetera, until you reach the center of the brace.  Do the same for the other end, then run a squiggly (technical term) pencil line down the brace.  I finish on the radius dish, as you can see in the photo, by laying sandpaper at the approximate place where the brace would lie on the sound board.  Using light downward pressure, and short strokes, I sand until the pencil lines are gone.  When I have done that, just to be sure, I put another squiggle down the brace, and sand that off as well.  I say "light downward pressure," because you don't want to bend the brace into the radius, you want to sand it into the radius.

I join the X-Brace before I glue them in place.  Layout is important.  The first step is to find the place where bridge will be on the top.  Using the LMI ruler, I measure and mark the bridge location.  I then mark the outside string locations.  The X-Brace should allow for about 1/2 inch on either side of each e string.  You want the pins that hold the strings to pass through the bridge plate, not the bracing.  The joint itself is essentially just a half-lap joint at the angle of the X.  After I have sanded the radius into it, I lay it on the soundboard, put the other brace over it, and mark the angle, then cut it with a razor saw.  I put the other brace over the other, so it covers the razor saw kerf, mark with a sharp x-acto knife, then cut the second kerf to the same depth, about half-way through the brace.   The waste between the kerfs should pop right out with a sharp chisel.


The trick is not to cut it too wide.  Better to cut the channel too narrow and take some shavings to get it to the point where the other brace slips into it snugly.  With the other brace in the channel, I mark it with the knife, cut two kerfs just inside the markings, make the adjustments for fit, and glue them together.   You don't really need to wait for the glue to dry before gluing the brace to the top, and in fact, I didn't.

You can see the go-bar deck in its full glory in the photo at left.  Here the trick is to get the brace in place with the first bar.  With the glue on the braces (and I do use Titebond) they have a tendency to slip around.  Once it is in place, then it is simply a matter of placing the go-bars so you get a nice even line of squeeze out along the entire length of the brace with no gaps.  This shouldn't be a big problem if a proper radius was sanded into the brace.  Although you can't really see it in the photo, I do have a sheet of poster board between the soundboard and the dish.  Although it isn't a big deal right now, eventually, when it comes time to adjust the kerfing on the sides, I will cover the dish with sandpaper, and so I thought I would get in the habit of protecting the show face of the sound board right from the start.

Before I glued in the bridge plate, I did scallop the X-Bracing.  The scallops on the ends of the braces start at about 1 and 1/2 inches from the sides of the guitar.  The secondary scallops are positioned so they line up with the bridge plate.

Cutting a scallop takes a little practice, but not much.  Start with the sharp chisel.  (Mine this morning were a bit dull, so I will need to attend to it.)   For the end scallops, start at about 1/2 inch back from the end.  With the back side of the chisel up, cut on either side of the brace to create a peak, then chisel then scoop the peak away.  Go back a bit on the brace, and repeat the process, cut away the sides until you have a peak, then scoop the peak away.  For the secondary scallops, at the center of the scallop, cut a kerf to the depth of the scallop.  Then do as above, just working from the center kerf to the mark.   

The next step is the bridge plate.  It is made from a block of (I think its cocobolo) that I found in the garage many years ago when we were living in Michigan. It is a beautiful piece of dense wood, and this is the first cut made into it.  I had in mind that someday, when the spirit moves me, I will make a morris style plane with the remainder of the block, but for the moment, I will let it serve as a bridge plate.  It is about 1/8th inch thick, and positioning is important.  Although I plan to make a pinless bridge, the bridge plate should be below the bridge and the pins should pass through it (not the braces!).    You can see the shaping from the photos, and the reason for the particular shape will be obvious when I install the next set of braces.  

Go Bar Deck & Molds

Yesterday, I fiddled around with a radius cutter, similar to the Lie-Nielsen tool, but I did not get anything approaching satisfactory results, so I set it aside.  The next big projects, though I won't likely work on it much until after the holidays, will be the Go Bar Deck, the Mold, and a clamping station.   

The Go Bar Deck should be a simple affair.  I visualize a plywood base and a plywood canopy of approximately 24 x 24 inches.  In the corner of each, a  3/8th or 1/2 inch threaded rod with a pair of bolts in each corner to hold everything together and allow for height adjustment.  LMI sells the go bars (CLGO), but they are a bit pricey at about four bucks a pop.  McMaster-Carr also sells 3/16 fiberglass rods at 5 foot lengths (8543K28) for about 2.50.  I will go with the McMaster-Carr, and if they don't quite work out, will order from LMI later.     

The base provides something to think about.  It's easy enough to have a 1/4 dowel in the center to capture the radius dish, and a second (not through the dish) to keep it from spinning like a lazy susan.  I have been wondering, however, should I make the base so it can serve as a sort of supplemental work station?  It's not an original idea, but what I have in mind is a two level base, with one side covered with carpet remnant, the other bare or covered with sandpaper.  The advantage would be a covered work surface that wouldn't mar the surface of the guitar while doing things like trimming bracing.  It would also, so far as the go-bar-deck itself is concerned, make it a bit more convenient to attach the base.  I will likely go for simplicity.

I have been procrastinating on the mold for a while, but have decided to press ahead at the next opportunity.  I intend to do it much the same way that I did the blanks for the radius dishes.  First, with a 1/4 spiral up-cut bit in my router, along with a brass bearing closest to that 1/4 inch diameter, I will trace the outline of the guitar into the MDF at approximately 1/4 inch depth.  That will provide two things, the inside contour of the mold, and the outside contour of a clamping station as well as the pressure pads for the mold itself once complete.   I will clean them up with the pattern bit.  Then do it again until I have enough pieces to stack 4 deep on each side, or a 3 inch thick mold.   I clean up the outside edges on the table saw.  I will talk about the design of the mold as I built it, so I can use photos to illustrate, but it too is a relatively simple affair.

I use the clamping station for a variety of purposes, not least as a test when bending the sides or binding.  It could also be used for a mold when bending sides with a heat blanket.  I have never used that method, so won't attest to it, but I have seen it illustrated a number of times.  I built my first on Sloane's advice, where the sides are essentially boiled soft, then quickly clamped in place.  I never found that workable, but like his model, I use spring loaded clamps when I want to use it for actual clamping -- e.g. letting a side rest after bending freehand.  Here again, it's a relatively simple affair, but I will talk more about the design as I build it.  I figure, if you're building the molds, might as well build the clamping station at the same time and save some scrap.

In the meantime, I have a piece of redwood that I have been using for guitar tops.  Since the parts have still not come in for my band saw, I have set up a time Tuesday to use the one at the school where I administer to re-saw some plates.  The responsible dean found it all very amusing, the Provost in the wood shop, and wanted to be there with camera should I happen to cut off a finger.  I can get a start on some sound-boards while slowly putting everything else together.   I've made the jointing jig, and I will likely use the zip flex pearl from LMI for the rosette itself, along with some perfling material.  I'll likely order all that after the holidays.