6/30/2015

Workshop: Fixing Worn Bridge Pin Holes & Worn Bridge Plate


So, this is a 70s Martin D-28 that's been having tuning stability issues related to worn bridge pin holes and a somewhat worn bridge plate. Basically, the ball-ends are slipping all over the place. Normally the "solution" is to install a new bridge plate. Well... this one has its original plate intact and a rosewood "plate cap" added already. Neither of those are helping to solve the problem of worn pin holes that have also been mucked-about by a half-round file at some point in their life as well.

Want a quick way to fix this that'll last for a long, long time? First tape the underside of the bridge plate with some blue painter's tape (see how it's blocking the holes above)...



Next procure some wood dust via a sanding job. I like rosewood or ebony.


Here's StewMac's #20 super glue -- slightly thicker than super thin stuff but not gelatinous like #30. I'm using a "wick" cap on the end of it to precisely locate a few drops of glue where I want it in the pinholes. In this case I want to build up tiny layers of glue+dust over time and get it seated in all of the little worn areas, especially.


#20 glue is fast-drying so I can put a little dust in and then "pound it down" with a piece of scrap softwood...



Then I blow off the remaining dust that's not grabbed by the glue/pounding job and start the next layer.


This stuff makes the job go more quickly on a rainy off-day repair session.


I'm half-way, now!


...and that's high enough for gov't work. I've removed the tape to show how the glue doesn't stick to it on the bottom while it's drying (which would be super annoying).


Inside you can see that my fill job has made short work of some quite worn pin-holes that were letting the ball-ends slip around a lot and "dig" into already-worn slots along the sides of the holes.


Now to drill and ream those holes to fit some new ebony bridge pins.

Note the saddle's out: I'm making my own new replacement because that was part of another tuning stability problem: the "as supplied" bone saddle leaned over under tension and that's never an ideal situation. It was cut just a bit too thin. My new (since installed) one fits tight and "straight" in the slot.


Here I'm stringing it all up and guess what? The ball-ends are snug and tidy on the underside of that bridge plate just as they should be.

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