Side Bending

I have thicknessed and bent the sides for my guitar.  There really is no way of describing the bending process in words.  A person just has to do it to discover that it's not that difficult.  The tools I use for bending are pictured at left.   

The first step, however, is to mark the sides.  I put them side by side, as a book-marked pair, and marked the waist bend on both.  Do it with something that won't wash away as you soak the sides.  Because I begin with the waist, and I would encourage people to do that, if it's marked you will avoid bending two left sides and the two ends will align with grain patterns.

The stainless tray was fashioned for me by students at the college, and it has come in very handy because it is side sized.  I soak the sides to be bent in hot water and a cap full of Downy for about an hour or so before bending.   The Downy, or any fabric softner, does just that, it softens the fibers so they bend more easily.   The bending iron was a gift from my kids.  I had an elaborate pipe and blowtorch set up before, but I would encourage purchasing the bending iron.  I clamp it in my bench clamp, and let it heat up as the sides are soaking.  When all is ready, then just bend.  I wrap the bend in a wet cloth, press it against the iron, rocking it slightly, until I feel the fibers loosen and the bend taking shape.  I use the clamping jig as a template, and when it is right, I clamp it into place to cool and set.   I don't worry about a bit of spring back if the side can be clamped into the mold without excessive forcing.   I then clamp it in the mold, and mark the centerline to cut off any excess from each end of the side. 

You can see the sides in the mold in the photos to the left and right.  Before gluing up the sides, one needs to fashion the head and tail blocks.  The tail block is made from bass wood.  Other woods could be used, but I like bass wood, in part because it does not have a resonant overtone, and in part because it is light in weight.  The head block is made from mahogony.  Usually, I would use some left overs from the neck, glued up into a block of the right size, but this particular block I purchased from LMI.   You can see the mortise for the neck tenon in the photo below.  I cut it in multiple passes on the router table with a 3/4 inch straight bit.  I will cut away the excess side material later clear the mortise.

When I glue up the sides, I have the soundboard side flush with the top of the head and tail blocks.  That keeps everything at the right angles, no pun intended.   When the glue has dried, the next step is to arch the back.  In the photo below, you can see the preliminary arch.  I usually divide the guitar in half along the center line, and then plane along the side with my block plane, along each side, starting with short strokes near the block, then taking longer and longer strokes, until the side is planed flush with the block.  When I have glued in the kerfing, I will take away some of the peak as I level the kerfing. 

 

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. 

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.