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. 

A Bit More Progress

Another bad weather day -- about a foot of snow, but I was able to make a bit more progress.   In the photo at left, you can see the bending mold, now on a stand with the clamps installed.  I made them from scrap oak, but just about any wood will do.  The clamp at the waist has been contoured on the bottom to fit the waist snugly.  I did this on the bench sander, just rocking it back and forth, and checking it against the mold until it was about right.  Although it is not visible, the far post passes through a slot, not simply a hole.  When I had drilled the holes for the posts, I simply cut down with a gents saw into the hole.   This allows one to position it more quickly, a necessity if you are using the Sloan method of bending -- essentially boiling the sides until they are pliable, and clamping them into a bending mold like the above.  I have cracked several sides attempting it, and wouldn't recommend it, but then again Sloan has built more guitars than I will likely ever build. 

In the photo at right, you can see the completed mold.  I decided against the strap clamp for a couple of reasons.  First, they were too stretchy.  As I would tighten the extenders, it opened up the mold.  Second, the arrangement visible in the photos gave the mold greater stiffness.  Basically, it is simply a piece of 1/2 birch ply, tacked and glued on one side, bolted on the other with a 3/8th inch bolt.  Perhaps not the most aesthetically pleasing arrangement, but it works like a champ.

You can see the extenders below.  It is a simple arrangement as well, and a number of luthiers use something similar.  Essentially, it is a 3/8th by 16 threaded rod inserted into a 1/2 steel tube.  Both are available at the local hardware store.  At either end, the rod and the tube are epoxied into the blocks.  When the wing nut is tightened against the steel tube, it extends and puts pressure against the side in the mold. 

To make them, I laminated three scraps of 3/4 MDF, and from that cut six blocks to size.  Using the mold, I marked the contour on each block, and again shaped them on the bench sander to match the contour of the mold.  I then drilled the 3/8 inch hole on one side, the 1/2 inch hole on the other, about 2/3 of the way through the block. 

I then epoxied the steel rod into the 1/2 hole, and cut it off at about the center line of the mold, or where the two halves of the mold come together.  Since the holes were not precisely to the same depth, this worked well, and kept a sense of symmetry.
For the threaded rods, I did the same.  I epoxied one end into the block, then marked it at about one inch in from the opposite block.  In other words, the rod extends into the tube to about one inch in from the tube-side block.  This allows for enough rod in the tube to keep it straight, but also enough in and out play to remove the extenders when the kerfing has been installed on the side. 

The contoured end of the blocks were covered with cork.  The inside contour of the mold was also covered with cork.  It not only makes it all prettier, but smooths out some of the differences between the three layers of the mold and provides a protective cushion.  It's probably not necessary, but I do it regardless.  The cork comes in a roll and can be purchased in places like hobby lobby.  I cut the strips over-sized by about 1/4 inch.  Although the cork came with an adhesive, I still sprayed the interior of the mold with contact cement, waited for that to dry, and installed it carefully.  I then trimmed the excess away with a sharp exacto knife, and rounded it over with a file.        

A Wee Bit of Progress

Yesterday, I spent on yet another household project.  My wife does not like the arrangement of the living room, so I spent the day hanging a cabinet and the TV from the wall to free up floor space.   the challenge was not so much the hanging as the hiding of all the cords that support the electronics.  I have to admit, it looks much better, and she seems pleased, which is good enough for me. 

Today, however, is not a good weather day, so I couldn't move the vehicle out of the garage into the drive so I could get access to most of my tools, particularly the table saw.   I did make a bit of progress over last week on the bending jig.  In the picture above, you can see the hardware set for the upper bout and waist clamps, and the picture below, you see the hardware set used for the lower bout hold clamps, and in the last picture, the half-finished jig.  The stand is a piece of black pipe with two flanges.  The lower flange will be attached to a base.   I needed access my table saw in order to make the base.  

The upper and lower bout clamps are spring loaded, the waist clamp is shaped to fit the waist and is brought down with the two wing nuts.  As I said, I bend the sides first, freehand, then put them in the jig to rest, so speed isn't particularly crucial.  I do like to let the sides rest over-night, particularly if they are still wet from the bending process.

Next week-end, I hope I will have access to my table saw, and I will make the base, the clamps for the bending jig, and the spreaders to complete the mold.  More details to follow.

The Assembly and Bending Molds

I had a little more time to work this weekend, because my wife is out of town with the kids and grand-daughter.  She was a finalist in her school spelling bee, and grandma had to see it.  I'm a bit disappointed that I didn't get to see it, but we have an aged dog that doesn't travel well, so I am dog-sitting.  At any rate, the soundboard is as complete as I can make it for the moment, and I  don't have the plates for the plates for the sides and back.   So, wife away and at am impasse on the guitar itself, I decided to make the molds.  Since it involves MDF, it's also a hellacious messy, dusty job, something my wife fusses over the whole time.  What she doesn't see won't bother her, so long as I clean up well before she returns, all will be golden.  SAFETY NOTE:  wear a respirator. 

To be honest, I forgot to take pictures when I made the primary pieces of the mold, but the idea is fairly simple.  I used my router, a 1/4 upcut bit, and a brass bearing.  I took my initial template, clamped it first to a piece of 1/4 MDF on top of a piece of 3/4 MDF.  I clamped it my bench, tightly -- that's important, tightly -- and cut around the perimeter of the template.  I set the depth so it cut through the 1/4 inch MDF on the first cut, then another 1/4 inch into the MDF below.   Since there is a slight off set between the brass bearing and the initial template, the 1/4 MDF becomes the new template.  I set it aside, and cut around the template five more times, just 1/4 inch into the 3/4 MDF.

A couple of notes of caution.  When you cut left to right following the template, the router has a tendency to drift away from the template on the right side of the cut -- in the picture above, on the lower bout side.  Position yourself so you can keep good pressure between the brass bearing and the template.   

On the 3/4 MDF with the guitar shaped groove, I used my jig saw and cut along the groove, being careful not to cut outside the groove.   You should have twelve pieces, six for the outside perimeter of the guitar, six for the inside perimeter of the guitar.   Each of the six pieces should have a smooth contour left by the router bit, and a rough contour left by the jig saw.  I used my pattern bit, mounted in my router table, to trim off the excess left by the jig saw, running the bearing against the smooth contour, the blade against the rough contour.  I glued them up three at a time, trimmed the edges to make everything neat, and installed the dowels. 

Another couple of notes of caution.  My initial template extends a couple of inches beyond the center line.  Mark the center line.  When trimming the ends where the two halves of the mold come together, you want to hit the center-line mark precisely so the two halves of the mold come together symmetrically.  The dowels are there to keep things aligned and to keep the mold from folding up like a book when the band clamp is tightened around it.  There are a variety of ways that one can bind the two halves together, but after considerable experimentation in the past, this works well.  I have the band clamp.  It provides sufficient resistance for the extenders that hold the guitar against the mold.    So there you have it, an assembly mold.  Next weekend, I'll make the extenders. 

I did get a start on the bending mold.  I'll explain it in more detail, but you can see that it is basically the pieces that are cut out of the center of the mold.  You can see where I've drilled for the hardware.  Since it is six sheets of 3/4 MDF thick, I don't have a drill bit that will penetrate that far, so I carefully clamped two together, and drilled through them.  I glued up the bending mold, three sheets at a time, first using one drilled piece, then the other drilled piece.   Next week end, along the with extenders, I'll install the hardware and make the various hold down for the bending mold.  By the by, I do not actually use this for bending, though if one had a heat blanket, one could.  I bend freehand, but clamp it into the mold to finish drying and to rest.  It's also useful for holding bent binding while it's waiting for installation.