Saturday, February 16, 2002

Mandolin #1: Body Binding

You know, looking at the assembled body with the neck in the dovetail, you might start to think, "Hey, a mandolin! It's almost done." You are so naive...

Repairing the Scroll
Well, before I could move forward with the binding, I had to spend some time on my little scroll issue. My first task was to trim away the overhanging scroll block with the coping saw (this time being sure it was perpendicular to the top and back). Because the overhang was on the body side of the scroll, the body side looked good (after extensive filing and sanding). The scroll button side on the other hand had the top overhanging the scroll block by 1/8 inch in some places. Thus, the next step was to find some way to take up this space. Using some Ash colored wood filler and some plastic as a funnel/mold, I just started stuffing as much filler down into the scroll as possible. I applied pressure into the void by slipping folded pieces of plastic between the plastic mold and the body side of the scroll. I was surprised at how much filler the void seemed to be sucking in but wanted to pack it in as tight as possible.

The inside of the scroll is not really the most visible part of the mandolin, but it's one of those spots you hear people referring to as a measure of the quality of an instrument. Every time I hear someone say "The scroll work on this mandolin is sloppy," I want to slap 'em. Then again, I would hope that the speaker is making the comment in comparison to the work of master builders. I just wish that they'd start with the qualifying statement, "Although if I tried to make a mandolin the scroll would have the curves of a train wreck, in comparison with the work of luthiers with decades of experience and fully equipped shops, the scroll work on this mandolin is sloppy."

Anyway, after letting the filler dry overnight, more sanding and filing resulted in a decent, though admittedly sloppy, scroll. I figured that once the the filler was stained and lacquered I would be able to escape ridicule from the average person.

Trimmed scroll Filling the scroll Filling the scroll 2

Filling the scroll 3 Filling the scroll 4 Repaired scroll 

Preparing for Binding
Routing the binding channel is one of the steps that really benefitted from the the aid of a special tool. As you will see when the binding ledge is cut on the scroll, it's possible to do it by hand, but it would be tough work to do the whole body this way. The tool I chose for the job was the Stew Mac precision router base for the Dremel tool. The base allows adjustments for the depth and height of the router cut and (sorta) keeps the bit square to the sides. You can see my routing set up in the picture at left. The Don MacRostie video suggested that setting the body on its side and holding the Dremel horizontally allowed for better control of the tool. That is, better downward control for an even depth of cut but also horizontal control to prevent runaways. As you move the tool along the sides, you can really feel the grain changes. Just when you are starting to notice how smoothly the bit is cutting, she'll make a break for it, and you'll watch helplessly as the whirling bit flails towards unintended surfaces of your masterpiece. The other fun surprise is the router bit threatening to grab a piece of end grain as you approach the points and rip the whole point off. The only solution involves chicken bones, a grass skirt, and a small straw doll in the likeness of Lloyd Loar. At the precise time (as indicated using the previously mentioned tools - available at Stew Mac in the Luthierie Essentials section), you need to stop your progress in the current direction, jump ahead a couple inches and cut back in the opposite direction.

Set up for binding routing 

Generally, the Dremel and router base performed admirably although a couple passes were sometimes necessary to get an even depth if I wasn't very careful about keeping the bit square to the sides. The colored pencil on the rim definitely made it easier to chisel any last maple or spruce off the rim. There were a few places that the router base could not fit into including the upper bout approaching the scroll where router base would ride up on the scroll ridge, thus decreasing the height of the ledge. I also needed to be cautious in area because the scroll is thicker than the rest of the top and the binding needs to rise up off the sides to maintain a consistent height. Because the top of the scroll is not flat, I had to abandon the Dremel and cut the scroll binding ledge by hand. Thus, the top and back were sanded flush to the sides using my wide sanding stick (same one used to level the lining and neck heel) and 60 or 80 grit paper and the outline of the binding channel was drawn in pencil.

The carving of the binding channel on the scroll turned out to be one of the most difficult steps on the whole mandolin. Getting a consistent binding height and depth while creating a smooth rise seemed like an exercise in deciding the fate of each splinter individually. The best method seemed to be tracing the curve from above with an xacto blade then coming in from the side with a chisel. A few specialized tools (right angled micro chisels) may have made it easier to work on the inside of the scroll and the button. I'm sure the second time would be easier, but I spent the better part of a day on each side of the scroll (remember, as soon as you're done with the top, you still have to do the back!).

Rough binding ledge Rough binding ledge 2 Flush sanded scroll

Flush sanded scroll 2 Binding ledge on scroll Binding ledge on scroll 2

The entire channel needed some degree of attention with a chisel though the remaining wood on the rim came up easily. I was not really sure how smooth the ledge needed to be and how much variation would be filled by glue. There were definitely a few places where the router bit caught some endgrain or the router guide drifted away from the sides leaving a thinner channel, but I was fairly pleased that I had managed to avoid completely ruining what I had done so far.

Back with complete binding ledge Back with complete binding ledge 2

Gluing the Binding

Okay, let's start out with the debacles. I had a couple "size" issues right off the bat. First, on a typical f-style mandolin, the back becomes thicker as it approaches the neck button. Whereas the scroll area handles this by having the binding rise up off the sides, on the back it is handled by routing all the way down to the sides and gluing together a higher piece of binding. Well, this is how it is handled by people who know what they are doing. I, on the other hand, could not get two pieces of binding to stick together to save my life. Despite what I thought was ample glue and a good clamping set up (clothespins), the pieces fell apart as soon as I tried to use them. I'm sure my results would have been better had I sprung the $10.95 for the Stew Mac Binding Laminator. Further, I was not happy with the rough edge when the pieces were trimmed down to width with my nippers. You know, on the MacRostie video, this step looked like a no brainer. I think he may have been using butter-based binding the way his chisel sliced through it. Anyway, it was a different story for me, and I quickly determined that, like the patent-pending "sound nooks" in the top, a sharp angle of the back at the neck as it slopes down to meet an abnormally low binding was going to be a Coydog Strings trademark.

And for my next blunder... well, it seems that when I grabbed some binding from the kit to do the first few body pieces, I grabbed the headstock binding instead of the body binding. No wonder it was sitting a little low in the binding channel. Anyway, after I ripped all that back off and ordered more headstock binding from Stew Mac, I realized that the pieces of white binding I had tried to use to increase the height of the back binding at the neck (refer to debacle #1 above) were intended for the fingerboard binding and I was left a couple inches short of what I needed. Okay, one more order from Stew Mac...

Gluing higher binding Gluing higher binding 2

With all the binding I needed, I set out to explore some options for bending it to the curves of the body. My first arrogant instinct was that I could just bend the binding cold. I quickly found that without heat, the binding does not bend smoothly and instead leaves straight sections connected by corners. With the binding with the black line on the top, this jagged bend really shows and subtly disrupts the curves of the body. I tried dipping the binding in hot water and even holding above a candle but found the first method ineffective and the second overly effective (damn that binding material is flamable!). Finally, after experimenting with my wife's hair dryer that would alternate between switching itself off, not allowing me to switch it off, and blowing the surge suppressor, I, being the thoughtful husband I am, suggested that my wife deserved a brand new hair dryer. You know, one of those high wattage ones with a concentrator attachment. They kinda look like... whatdya call those... oh yeah, heat guns. In hindsight, I wish I'd just bought a proper heat gun. Then again, my wife's hair looks fabulous.

I clamped a long bar clamp to my work table with the bar extending upwards and clamped the hair dryer to the bar allowing me to work the binding with both hands. Using a selection of dowels to bend the warmed binding and and a lot of trial and error, I was able to dry fit the binding pieces to the curves of the body. When satisfied, I filled the ledge with binding cement and held the binding in place with long rubber bands (available from Stew Mac) attempting to remove as much excess glue as possible with a paper towel. Once the glue was in the ledge and the rubber bands started going on, things could get pretty frantic. It must have been rather strange for my wife arriving home three or four days in a row to find the air thick with glue fumes and me wildly wrapping the misshapen little wooden box I'd been building with absurdly long rubber bands only to release expletives unfit for Hells Angels vocabulary readers when the whole bundle would explosively unravel when one band would slip or be dissolved by the acetone in the glue.

Binding the points Binding the points 2 

Binding the scroll Binding the scroll 2 Binding the scroll - long piece 

Mitering the Joints
Of course, just when I was happy with the bending process, I had to focus on mitering the ends so that the different pieces would come together cleanly in the corners and so that the black line on the top would be continuous. After a few corners, I started to be able to visualize how the two ends would come together and could thus cut the mitres pretty well. While some pieces could be cut before they were glued, some were better done after part of the piece had already been attached. Mitering the ends of these pieces required a delicate process of holding a cutting block beneath the end and coming down from the top with a chisel.

You can see in the picture on the right that this was one of the points that had been brutalized by my binding routing process. I'll fill this in later with some wood filler. Also, you can see that my mitre is not terribly tight. While I got better on some others, the joints can be acetoned and heated while being pushed together to create a fused joint. You'll notice on your nice mandolin at home that the seam is most likely indetectable.

Mitering the binding 2 Mitering the binding 3 

Mitering the Points
I came up with a decent method for clamping the mitres on the points together after adding acetone and heat. These little pieces of spruce were left over from the tone bars or the tabs on the top. With a little chiseled notch, they were used as cauls to redirect the downward pressure of the clamps into inward pressure on the binding pieces. Notice that I had to wrap the point with rubber bands to prevent the binding from bowing outward under the downward pressure. 

Mitering the points 2 Mitering the points 5 

Point Protectors
With a decent joint on the points, I could add the bone point protectors. A flat area was created with an xacto and a chisel and the bone was marked to width. Then with coping saw and sand paper, it was brought down to a snug fit between the binding pieces and glued in place. Once the glue was dry, the remaining material could be removed with a chisel and sandpaper. I was impressed by the end of the process at how well the binding joints were looking and how well the point protector blended in with binding.

Point protectors 

Bound and leveled body
With all the binding on the body, there were inevitably places where the binding needed to be leveled down to the top and back. My flat sanding stick could be used in some locations (see picture) while sandpaper stuck to bent plastic sheets worked well in the recurve. While this process resulted in a very clean, smooth transition between the wood and the binding on the top and the back, I ran into a problem when leveling the binding to the wood on the sides. I would use a my flat sanding stick and basically run it around the contours of the sides. However, depending on the depth of the binding channel, there were spots where leveling the binding to the side wood removed so much material that the outer white layer was sanded away to reveal the center black layer. Ugh. Definitely a rookie move. In the future, I will need to make sure the binding ledge is more precise, perhaps even erring on the side of making it too deep (but so deep as to make the side wood too thin when leveling!). The other option that would solve both my crooked black line from bending binding without enough heat and my sanding through problem, would be to use binding with the black line on the sides. Is that called reverse binding like on Bill Monroe's Loar? Well, if it is, I'll just claim I was trying to be true to the legend...

 Leveling the binding Bound body

Index of Project


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