Martin OM16DBM String action re set

This Martin OM16 DBM came to me in need of a fret dress and string action adjustment.

on closer inspection I noticed that the bridge was beginning to separate from the sound board.

I removed the bridge with the help of some heat and a spatula.

Typical of almost all mass produced guitars I've seen with this bridge problem, the bridge is glued into place with inadequate preparation.  Commonly the gloss finish is found to extend under the bridge by at least 5 mm. This prevents the glue from adequately adhering the ebony bridge to the gloss finish on the soundboard. There is also a noticeable lip created by the film build up against the bare wood under the bridge creating a void so that the bridge does not make perfect contact with the unfinished surface of the sound board 

My solution is to carefully cut around the bridge with a sharp exacto blade into the sound board to create a perfect margin marking the extreme edge of the bridge in its exact location. I then remove the  bridge after which I take a sharp scraper and remove the excess gloss finish to the  cut margin and scrape all traces of the old adhesive away as well.

This leaves me with a slight cavity into which the bridge sits perfectly. I always prep the underside of a wooden bridge with a scraper, then sandpaper then with acetone to remove all traces of resin from the wood which might otherwise prevent a perfect glue bond. I then scratch the under surface of the bridge with a razor saw to etch the surface prior to applying Tightbond glue. Replacement of the bridge requires 3 deep throat C clamps with wooden cauls above and below. I apply as much pressure as possible when clamping.

While I was at it I levelled, crowned and polished the frets. I also re set the neck relief, the first adjustment of the truss rod since the guitar was new in 1999.

I re strung the guitar and found the string height to be too high by 1 mm per bass E string and treble E string. I shaved 2 mm off the bottom of the tusk saddle which restored the string height back to ideal for my client, (2mm at the 12th fret on the low E and 1.6 mm on the high E string)

There was also a compression ding at the margin of the lower bout so I decided to apply some spot heat with my soldering iron through multiple layers of a wet cotton cloth. This has the effect of swelling the wood where it is compressed. With multiple applications the ding gradually disappeared. I then refinished the damaged lacquer with multiple coats of aircraft dope using an airbrush.

the repair is virtually invisible.

3 deep throat clamps apply pressure to the bridge until the glue has cured (a minimum of 12 hours)

Another view of clamps and cauls.

The finished guitar.