Classical Bridge Repair

This nylon strung guitar had suffered a nasty bridge failure - the bridge had split through the string holes, and the whole tie block had come off. As well as the split, the bridge was badly warped, and had been re-glued once already (not by me), and was starting to peel up at the back again.

broken_bridge01.jpg broken_bridge02.jpg broken_bridge03.jpg

There was no chance of salvaging the old bridge, and it was a pretty crude bit of dyed maple, so I planed it down to make removal easier. You can see the back edge is a good 1.5-2mm off the top, and there are some sinister looking splinters of spruce visible under the raised edge!

planed_down01.jpg planed_down02.jpg planed_down03.jpg

I masked off the top with cardboard and aluminium foil to protect it, and heated the bridge with an iron to soften the old epoxy. Then, using a hot spatula and a gentle prying action, I worked the bridge off the top. I took note of the grain run out in the top so that I always worked in the direction of run out. This is different on each side of the centre seam due to the bookmatched top (or in this case, the bookmatched to leaf of veneer).

top_masked01.jpg top_masked02.jpg bridge_removed01.jpg

With the bridge removed, I turned my attention to making a replacement. The old bridge was dyed maple, and very crudely shaped, but I decided that the work of replacing the bridge meritted decent materials and some more elegant shaping, so I used East Indian Rosewood (EIRW) and a classic bridge design. I bandsawed the EIRW bridge blank down to rough thickessm and planed it smooth, then shaped it with my neck shaping rasps and files. No pics of the shaping process I’m afraid.

blank_sawn01.jpg blank_planed011.jpg

With the new bridge shaped, I fine tuned it’s position, and marked it on the guitar top with masking lo-tack tape. Then, I traced the bridge outline onto a piece of paper, and used magnets to transfer the brace positions underneath the top. I will need these to create a clamping caul with notches for the braces.

bridge_positioning01.jpg bridge_positioning02.jpg brace_marking01.jpg

The bridge had torn up lots of fibres from the top when it lifted, and the first reglue had introduced a lot of epoxy into the voids where fibres were missing. To ensure a good joint, I needed to get as much clean, wood-to-wood contact as possible, so I used a router to remove the top in tiny increments, until I had a clean area to work with. I compromised between removing all the old glue, and taking the top too thin, but was able to remove 90% of the old epoxy (compare this image to the image after removing the old bridge, and the image where the bridge position is marked out). I cleaned up the edges of the area with a very sharp chisel. In the closeup you can see why so many fibres were torn out as the bridge lifted - whoever scored the finish around the bridge at the factory was a bit heavy handed, and cut most of the way throguh the first ply of the top! I made the new bridge a fraction larger than the original to conceal this damage, you can see the old bridge outline about .75mm inside the newly cleaned outline.

top_routedclean01.jpg top_routedclean02.jpg

Since the top was still no 100% clean and level, I opted to use epoxy to attach the new bridge. This is a good choice where voids may be present in a gluejoint, and though I would have preferred titebond, it simply wasn’t appropriate for this repair. I clamped the bridge with a maple cam clamp and notched interior caul made for the purpose, and allowed it to dry for 48 hours before stringing it up. I also fitted a new bone saddle, since the original plastic saddle was pretty cheesy.

Better than new!

bridge_attached01.jpg bridge_attached02.jpg bridge_attached03.jpg