Magnatone Giveawya

September 2014
more... GearHow-TosJuly 2008

New Sound, Old Guitar

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New Sound, Old Guitar
Photo 3: A saddle template with silly putty
Before I began cutting the bone to shape I took several measurements of the adjustable bridge at the optimum height. I lowered the bridge until it began rattling the strings and then raised it just a skosh. After a bit of hard strumming, I was satisfied. Then I took my string height measurements looking down from the bottom of the guitar, across the ebony saddle, transferring my sketch with measurements to my solid bone mass. Next, I placed a 12 degree radius contour block for fingerboard sanding across the top of my bridge pattern to confirm the radius of the top.

At this point in my adventure I began considering the following conundrum: do I restore the guitar to original condition or do I alter the rascal from its original, poorly designed specifications? I can still imagine some worker at Gibson going to his superior and saying, “You know, if we just altered the top bracing a little and added a little more to the bridge plate, we might be able to still use the pin bridge and make a better sounding instrument.” In my imaginary scenario I can hear the supervisor reply, “We don’t do it that way. We’ve had so many warranty repairs for that pin bridge that my boss wants it done this way.” Not working for Gibson four decades ago, I press onward.


Bridgeplay
I then enlarged my X-ray photo of the guitar’s top so that the image of the bridge measured exactly 7 1/2” from side to side. I made three 16”×20” prints, varying the contrast and exposure between them. When dry, I had an exact, 1:1 ratio photo of the top with the bracing structure revealed. This trick needs to be done with black and white film and an enlarger so you can tweak the enlargement proportions. In case you’re wondering, I’ve been a professional photographer since the seventies. I’m the guy who took Clapton’s photo in the Tulsa Jail, but I called Dick Sims’ mom to get him sprung (perhaps another story for another time).

I positioned my new-old-stock Gibson pin bridge over the photo of the existing bridge and determined that I would need an additional bridge plate underneath to both strengthen my new bridge and allow for a base for the new bridge pins to snuggle into. I started with a corrugated cardboard template cut out with a razor blade and carefully shaped it to fit between the existing bridge plate and the cross braces underneath. After staring at the mahogany bridge placed on top of the photo of the old bridge, I determined that I needed to add two small additional braces going top to bottom underneath the ends of the bridge saddle and joining the existing lateral cross-brace under the top. I remembered the words of my friend, the late Stewart Mossman, “Nothing is stronger in top bracing than the triangle.” I gazed with delight at how I had created three additional triangles under the top at the end of the bridge with the addition of my two braces glued to the lateral brace. I imagined my luthier friend from Kalamazoo up in heaven giving me a big “OK” with his right hand.

New Sound, Old Guitar
Photo 4: Using the old bridge to drill new pin holes
Returning to the rosewood bridge, I carefully measured the existing bridge and enlarged my template for the new bridge to be about 1/16” larger all-around to cover any unsightly footprint that may be left after pulling up the existing bridge, which was glued down unnecessarily. I selected a slighty thicker than needed piece of Indian rosewood from my “stash” and traced the new footprint out on the perimeter. Next I clamped the old Gibson mahogany pin bridge to my rosewood slab to begin drilling into my blank, one hole at a time and using the old bridge as a guide [Photo 4]. I used another bit to fit the inner end of the adjustable bridge slot and make the holes at either end of the bridge opening.

Afterwards I began cutting out my new bridge blank by hand with a hacksaw and a coping saw. Mechanical saws move too fast for this delicate process, although it took many hours to hand-file and sand the new rosewood bridge to shape, plus another four hours to fit the new bone saddle into not only the new bridge base but the old one as well, in case I reinstall the adjustable ebony saddle at a later date. Luthier Don Teter once told me to dig out the bridge adjustment nuts in the top and take out the old bridge plate; since the bridge adjustment nuts in this instrument were sunk slightly below the top, I decided against both courses of action and chose to leave the nuts in place and keep the existing bridge pad. I cut a solid piece of maple for an extension of the bridge pad underneath to match my cardboard template and saved the bridge adjustment nuts in case I needed them in the future.

I began volleying ideas back and forth with Don Kendall of Bridge Doctor fame. I had returned my Bridge Doctor after deciding it wouldn’t work under the cluster of 12 bridge pins [Photo 5]. Initially, I thought of making my own modified Bridge Doctor with two dowels going down to the guitar’s butt and a suspension strap at the end of the dowels to keep the pressure transferred to the endblock inside the guitar. This seemed to work, but I had to carefully countersink the “all-thread” into the outer edge of my new bridge without coming through the top, since I had determined that the feng shui of the bridge would be unbalanced if I had inlaid rosewood or pearl dots over the new bolts. I thought about the same bolts going through my soon-to-be-added spruce top braces for additional strength and then began thinking about what this would do to the flutter capacity of the top.

New Sound, Old Guitar
Photo 5: The Bridge Doctor at work
Although guitar tops need to be strong, they need to be free to vibrate as much as possible. I have been carving out and sanding guitar braces for better bass response for over 30 years, learning the process from Mossman Guitars. They would cut out scallops in the braces to allow the top to flutter more on the bass side, resulting in more bottom-end. I did this and then sanded my cuts down, first with coarse sandpaper, then with finer and finer grades, sanding through the soundhole. Once I sanded the braces with 400 grit dry paper, the guitar was ready for a lesson in rock n’ roll. I taped the guitar to the front of a speaker with a washcloth to keep it from scratching or falling over and placed a piece of carpet under the guitar. I then played some loud music for about four hours, making sure the bass wasn’t turned up high enough to cause damage. With the bass down and the treble and midrange up you can simulate about ten years of playing in only four hours, opening up a stiff and unresponsive top.
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