Search:

Martin D-35: Bridge Reglue


1. A Lifting Bridge is serious business. As the bridge/top glue joint becomes smaller, the string tension is distri- buted through an ever more concen- trated area of the top. This will even- tually cause damage to the top, bridge and bridge plate if left unattended.	2. Scoring the Finish. Most contemporary guitar manufacturers actually leave about 1/8th" of finish underneath the bridge all the way around the outside perimiter of the bridge. When regluing a bridge that was built this way, I believe that the finish beneath the bridge must be re- moved in order to ensure a strong glue joint. I'm using a sharp exacto knife to score the lacquer without actually cutting into the softwood fibers beneath the finish. This will make removing the finish under the bridge easier after the bridge is removed. Since the bridge must be reglued in the same location as the factory originally glued it for purposes of intonation and aesthetics, having no finish under the bridge doesn't pose any problems.


3. Removing the Bridge with a Spatula. I'm starting disassem- bally from the back of the bridge. I'll first free the rear of the bridge pushing the spatula only as far as the pin holes. Then I'll work my way around the bridge. In order to remove the bridge without damaging the spruce I heated up the bridge in order to soften the glue. Also, I'm always mindful of the runout as the grain orientation of the top will help determine how best the glue joint should be approached with the spatula. If a top exhibits too much runout, the top will splinter if the proper precautions are not taken.	4. Bridge Removed. The bridge came off nice and clean. Note the finish around the perimiter of the bridge's footprint.


5. Shaping the Bottom of the Bridge. This vice does a great job stabalizing the bridge while I contour the bottom of the bridge to fit the top. I start this process with a block plane frequently checking the bridge against a straight edge. Next I'll spot scrape the ebony with a scraper. I want the bottom of the bridge to be ever so slightly concave from end to end. This will help stabalize the top with- out flattening it too much. If a top is too flat the tone will change.	6. Scoring the Bottom of the Bridge. This improves the strength of the glue joint.


7. Clearing the Glue from the Top of the Guitar. I like to do this with a chisel, but a scraper or razor blade also works. I'm using the chisel as a scraper to remove the old glue and finish. The bevel of the chisel is facing away from me and I am pulling the chisel toward myself.	8. Bridge Reglue Clamping Cauls. Cauls help distribute the force of clamps to both protect the workpiece and ensure even clamping pressure (this is the same general purpose that washers serve when used in conjunction with a bolt). The inner caul is made of hardwood and has notches cut into it to accomodate for clamping around the top braces.


9. Clamping the Bridge. The two thumbscrews on the outer caul ensure that the bridge is under even clamping pressure. I've reglued this Martin guitar's bridge with hot hide glue because it won't tend to creep as alaphatic resin and polyvinyl glues can.	10. All Done. A meticulously fitted joint glued with hide glue ensures that this bridge will stay put for many years to come.


11. A Reglued Bridge with a new bone saddle.