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Replacing a Gibson
adjustable bridge
Martha had this classic Sixties Gibson B-25, with the plastic bridge and the porcelain saddle. She liked the size, and the small neck was also good for her. We've all seen these guitars, but we've often had a hard time hearing them. This bridge was not Gibson's finest moment.
The bridge is injected molded plastic,
and is held down by four sheet-metal screws. The saddle is porcelain,
its height adjusted
by screws that rest in studs set into the top. It must have seemed like
a good idea once, but
all the adjustable-bridge Gibsons, even the all-wood ones, sound much
better with
a simple bridge with a bone saddle. There's no question that the thing
to do is lose
this whole plastic thing and put on a new real wooden bridge with a
bone saddle. So, the thing
to do is first get rid of the old one.
Start with the saddle. Out it comes. Good riddance.
Next, you take a little socket like this and remove the four screws that hold down the bridge itself.
Now you have this. See, it's hollow inside. What a plus for tone!
Next you take a little
adjustable wrench
like this and quickly loosen the nuts on
Then you put the adjusting bolt
back in
for a moment and use a pair of
Easy does it...out they come. Now you have this little mess:
A lot of weight. And a lot of holes that need to be filled before you can go much further. It still has lacquer on it - the difference in color is a suntan line. Step One is to cover all the holes on the inside.
Sorry for the shadow here, but
what I have
is a thin maple patch big enough
Since the new bridgepin holes
will precisely
line up with the old ones,
To glue this patch in properly, you need to make precise marks you can see from outside through the holes. Always doing a dry run makes sure you have it right when you actually glue it.
Since the top is old a bit
bulged, this
patch will go down with a cork-faced caul. They
Here's the bridgeplate patch
double-stick
taped to the caul which is in turn taped to
Note: if
you were
doing a bridgeplate patch on a more normal guitar,
You apply the glue after you do a dry run, right? Now put the above rig in through the hole until the marks (see them?) line up with the holes, like this:
You want to make sure it's going in without hitting braces or anything else. Use a mirror and a light to check inside. Then you clamp it like this:
OK, now you take it all
apart, put the
glue on, and do it again. You can now see why the first clamp is off to
one side. Before the actual glue-up, I always put a layer of paper
inside
the guitar to catch any glue drips.
Now we have this. It still has lacquer on it, and lots of holes. At this point, I use the masking tape to define the precise edge of the backside and ends of the bridge, for later reference. You have to fill the holes. I use spruce dowel (ex-violin soundpost) for the four smaller ones, and two layers of spruce - some larger dowel and then a hand-cut disc - to fill each of the stud holes. A bit of spruce gets laid into any chipped-up places too. You want this surface smooth. Then I level the filled holes
with a chisel,
like this:
Here's another look at it.
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