View Full Version : Gibson A model - adjustable bridges

Rob Gerety
Feb-21-2010, 9:31am
When was it that adjustable bridges starting appearing on these mandolins? Were they one foot or two foot? Did the pick guards attach to the bridge as they do on the earlier non adjustable bridges? Can anyone point me to a good picture these adjustable bridges in place on an A model showing some detail? Or to a site where I am likely to find some pictures.

Feb-21-2010, 11:07am
Hi Rob,

The patent date on the bridge is Jan. 18,1921 so that would imply when they were first used on Gibson mandolins. They are 2 footed and the pickguard support (little nail) goes right next to the treble side threaded post with the thumbwheel. Sometimes a small notch is removed from the base so the nail can fit easily. Here's a (somewhat blurry) shot of my 1916 F-4 with an adjustable bridge. I removed the pickguard so you can see the little notch on the treble side of the bridge base. It should work the same way for an A style as an F style. Hope this helps.

Len B.
Clearwater, FL

Rob Gerety
Feb-21-2010, 11:22am
Thanks for that picture - great help.

Yours is a 1916? With an adjustable bridge? Is it a modern bridge?

Feb-21-2010, 11:53am
It is not original to the mandolin, obviously. It was on the mandolin when I got it in 1975 so I don't know if it's a repro or possibly a genuine Loar era bridge. It looks pretty old to me so it could be an original. I don't know who may have been making repros way back then. Randy Wood perhaps?

Len B.
Clearwater, FL

Rob Gerety
Feb-21-2010, 11:59am
Does the bare nail from the pickguard sit in what looks like a little notch in the base just inside the adjuster? Looks like a similar but clearer notch is shown on the bass side? Right?

Do they have any sort of felt or other cushion on the nail to prevent vibration while playing?

Feb-21-2010, 1:02pm
I think CA has a replica date stamp... to make new replacements look authentic,

2 pins into the fingerboard would suspend the finger-rest , supporting the fingerrest with a brace into the bridge, would put some energy into vibrating the fingerboard.

Older pick-guard/finger-rests have a steel wire in them, for stiffness, on the top edge,
so if the older ones , be ready to cut plastic and steel.

I've been threatening to do that with my own, older mandolins , they got a felt plug under the corner closest to the bridge, for support in the meantime, It definitely vibrates when the string is..

so reduce, rather than prevent, is probably a better concept,
It's better to have the pickguard not supported near or on the bridge, keep it floating.

edge of the Fingerboard, and/or the bracket to the rim, alone, a better solution..

MHO, etc.. ~o)

Rob Gerety
Feb-21-2010, 1:17pm
I'm interested in seeing whether the original Gibson adjustable bridges were two foot or one foot. I'm also interested in seeing how Gibson dealt with the interface between the pick guard and the adjustable bridges when they first came on the scene.

Feb-21-2010, 8:15pm
Yeah, the adjustable bridge was invented and patented in 1921 by Gibson woodworker Ted McHugh. Here is a pic from a 1920s Gibson catalog


Tom Sanderson
Feb-22-2010, 8:03am
The first ones were the old style one piece bridge with the top sawed off for the base, and aluminum bridge top with double thumb screws. I had an F4 like that (67130). I also had an F2 (68991) that had the Loar style bridge, but with double thumb screws.

Bob A
Feb-22-2010, 11:14am
The "bare nail" fits into a hole in the one-piece bridge, which is larger than the nail, and used to have a ring of felt in it to keep the thing from buzzing. I've had both fixed and adjustable bridges on my F4, but the clamp-on pickguard had been swapped out long before I got it, so there's no nail. So long as you don't really lean on the pickguard there's little need for the nail-like extension, in my opinion. I wouldn't want it involved in any way with an adjustable bridge.

Darryl Wolfe
Feb-22-2010, 12:23pm
Earliest example

Rob Gerety
Feb-22-2010, 3:38pm
Did they start with the early adjustable one foot and then move to the two foot design early on? Do we know whether there was any testing or analysis done regarding the use of different bridge designs on different model mandolins?

Feb-23-2010, 3:13pm
Based on the originals I have seen the "single foot" version (like the one shown in a previous post) was the first.

Rob Gerety
Feb-23-2010, 4:03pm
I wonder why they went to a two foot design?