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A Cookie Cutter Classical Bridge

4/1/2014

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1. A Well Traveled Guitar.  This student model Yamaha has been around the world 3 times and is covered with stickers that speak of the owners friends, family and travels.  The bridge has broken in two and needs to be replaced. 2. Sentimentality is the only thing saving this guitar from the scrap heap; the owner isn’t ready to part with this guitar.  Check out this sticker, I think Woody Guthrie would approve.  I’ll replace the original bridge with a cookie-cutter rosewood bridge from Stewart MacDonald.
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3. Heating Things Up.  I’m using a heat lamp to heat the bridge.  This is S.O.P. for a professional grade guitar where the bridge is attached with a glue such as hide glue that allows for safe disassembly.  An imported plywood guitar like this isn’t usually manufactured with future repair work in mind. 4. Removing the Bridge.  The heat liquified the bridge’s finish but it hasn’t appreciably softened the glue.  I can feel that my offset spatula is taring into the wood grain.  I’ll work my way around the perimeter of the bridge.
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5. Not as Bad as it Looks.  Near the center of the bridge, a few chunks of the plywood guitar top veneer remain stuck to the bridge.  There are some small pieces of the bridge still attached to the guitar top. 6. Cleaning Things Up.  I’m cutting away the pieces of the bridge that remain glued to the top with a sharp chisel.  The upper-most veneer is impregnated with some sort of white colored grain filler/sealer.
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7. Bridge Geometry.  It’s important that the saddle slot of the new bridge remain the same distance from the nut as the saddle slot of the old bridge.  The distance from the back of the bridge to the saddle slot is the same on both the old bridge and the new bridge.  The back of the new bridge will be my reference point for fitting it to the guitar. 8. String Spacing.  The string spacing on the new bridge is a little wider than the string spacing on the old bridge.
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9. The Footprint of the new bridge is larger than the footprint of the old bridge.  I’ll block-plane the front of the new bridge to the same width as the old bridge before I move on. 10. Locating the Lateral Placement of the new bridge is very important, especially since the new bridge has a slightly wider string spacing.  The relationship of the E strings to the edge of the fretboard will dictate the lateral placement of the bridge.
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11. Layout is Key.  I’m marking the lateral location of the bridge with a small pencil mark at the 6th string for future reference. 12. Marking the Bridge for Length.  The new bridge is longer than the old bridge.  I’m marking the new bridge at the end of the old bridge’s footprint on the top in order to maintain the footprint of the original bridge.
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13. Cutting the Bridge to length with my bench hook and a Japanese pull saw. 14. The New Bridge looks a little funny after I’ve made my cross-cuts.  I’ll need to re-taper the wings of the bridge in order to maintain the original look.
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15. Re-tapering the Wings of the Bridge.  A sharp chisel does the trick. 16. The Wings are just about ready.  I’ll clean up the saw and chisel marks with a couple of light passes with a block plane, then oil them with linseed oil to match the rest of the unfinished bridge.
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17. Scraping the bottom of the bridge gets rid of the oxidation which could hinder the glue joint. 18. Scoring the Upper Veneer of the top around the edges of the new bridge is the first steep in top preparation.
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19. Removing the Upper Veneer of the plywood is a must.  There is no way that my hide glue is going to stick to the sealer-impregnated veneer.  A sharp chisel cleanly removes this .006″ thick veneer. 20. Scraping down the high spots and remaining glue with a razor blade with a burr leaves a flat and clean gluing surface.
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21. Lightly Scoring the top and the bridge improves the glue joint, maybe.  I suppose it’s more of a habit or superstition but I’ll continue to lightly score gluing surfaces until I learn of a compelling reason not to. 22. Outside Clamping Cauls.  These little pieces of cherry are my classical guitar bridge reglue clamping cauls.  They are cork-lined to protect the bridge and have the same contours as the clamping surfaces of a classical guitar bridge.
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23. Inside Clamping Caul.  The guitar top has 3 small holes in it, I used those to center a block of wood to which I had taped a thin piece of styrofoam.  Some clamping pressure caused the off-center fan-bracing to indent the styrofoam.  I transferred these indentations to the block of wood and hand cut them as channels to accommodate the fan bracing. 24. Hot Hide Glue is my glue of choice for guitar bridges.
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25. Clamping.  The long cam-clamp holds down the center of the bridge and two deep-throaghted c-clamps clamp the wings.  The c-clamps have built-in leveling screws which I prop up with a cork-lined block of wood.  I’ll leave the bridge clamped for 24 hours. 26. A New Bone Saddle completes the repair.
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27. A Cookie-Cutter bridge isn’t always appropriate but for this student classical it makes sense. 28. A New Bridge.  This guitar is ready to rock until the cows come home!