bridge with screws???

[AJ Ray]

I just discovered that my 2000 model j50 with undersaddle pickup has a screwed down bridge. Is this normal??? I noticed them when feeling inside for a bridge pin. They seem to be under the MOP dots on the bridge. Is this good or bad? Does it offer extra support for 13s etc?

[Bob Marsh]

Quite normal AJ Ray - Gibson's been doing it for years - more than for support it makes it possible to attach the bridge over a finished top without fear of it pulling loose - usually the finish is removed from the top in the area underneath the bridge before the bridge is glued on so the bond is bridge wood to top wood rather than wood to lacquer finish - Schools of thought on the screwed down bridge vary in their approval/disapproval of this technique - I'm sure lots of forum members will chime in and you can draw your own conclusions.

 

Welcome to the forum!

 

BG

[dhanners623]

I've heard of people removing the screws in search of better tone. I've got them on my '98 J-45, but I've never looked into getting them taken out. The size of the gluing area behind the bridge pins seems so thin that I'm thinking that, at least on my guitar, the screws may serve an important structural purpose.

 

That said, here is Frank Ford's take on the issue and his feature on upgrading a Hummingbird's bridge:

http://www.frets.com/FRETSPages/Luthier/Technique/Guitar/Bridges/HumBirdBr/hbirdbr1.html

[j45nick]

I just discovered that my 2000 model j50 with undersaddle pickup has a screwed down bridge. Is this normal??? I noticed them when feeling inside for a bridge pin. They seem to be under the MOP dots on the bridge. Is this good or bad? Does it offer extra support for 13s etc?

Gibson has been using machine screws--not screws, since they are threaded like bolts and have nuts and washers on them--since the late 1930's. Originally, this was to make up for the very small gluing area of the rectangular bridges, and provide mechanical attachment to augment glued attachment. Coincidentally, the machine screws--which are very small, and add little mass to the bridge--provide a simple means of positioning the bridge accurately and repeatably during construction.

 

It is not uncommon to see older Gibson bridges where the glued joint has failed, and the machine screws are the only thing keeping the bridge attached to the guitar.

 

As any engineer will tell you, the loading on the bridge is almost totally shear loading, and that shear load comes from string tension, which increases with increases in string gauge. The strings are trying to "shear" the bridge from the top of the guitar, to put it simply. Machine screws are very good in shear, and can help hold the bridge on particularly if the glue fails. Traditional glues, such as hide glue, are pretty brittle, and get more so over time, as I understand it. They strength of a joint made with a glue of this type depends on a thin glue film and a near-perfect wood-to wood contact, as the glue itself brings little strength to the table.

 

Modern bridging adhesives such as epoxies actually benefit from poor surface-to-surface contact, but if you put a bridge on with a glue of this type, it's almost impossible to remove the bridge without damage to the top.

 

If you have enough gluing area--that is, a large enough bridge surface in contact with the bare wood of the top--you don't really need the machine screws, but they are a traditional part of Gibson construction, and I doubt if they have a measurable impact on the sound output of the guitar.

 

Martin has always just glued the bridges on, but they went to the larger surface area of belly-style bridges long before Gibson, I believe.

 

Despite the larger "visual" footprint of belly-sytle adjustable Gibson bridges, the actual gluing surface of these bridges is about the same as a rectangular bridge. In the way of the adjustable saddle, the bridge is completely routed out. If you remove the adjustable saddle, you will see the top wood of the guitar through the opening.

 

I could go on about the engineering of bridges, but it would bore the crap out of you. The bottom line is, the machine screws are nothing new, the don't hurt, and you remove them at your peril.