Fixed bridges can be lumped into two general categories; flat mount and tremolo (Fender style) bridges and stud mount (Gibson style) bridges and bridge/tailpiece combinations.

Problems arise because these two different families of bridge types are each designed to work with a different neck/body joint.

Flat mount bridges need to be used with the Fender style bolt on neck. These necks join the body with the fretboard surface parallel to the top of the body with the fretboard is about 3/8" above the top. Not coincidentally the flat mount bridge sits 3/8" above the top at its lowest adjustment.

Stud mount bridges are made for guitars with an angle between 2 and 4 degrees where the neck and body join that causes the fretboard to slope upward where it meets the body and requires a taller bridge. The stud mount bridges are 5/8" high at the lowest adjustment.

You can see from the measurements and drawing that the stud mounted bridge will not work on a guitar designed for the flat mount type. Used on a Fender style instrument without modification, the tune-o-matic bridge will be too high for comfortable playing action. Conversely, the flat-mount bridge cannot be raised high enough to avoid string buzz when used on guitars with a neck/body angle.

When planning an instrument or hot rod job you must know which type of neck joint the instrument will have to choose a compatible bridge.

String spread also plays a role in choosing a bridge. The string spread is the distance (center to center) of the outside E strings. Pickups are built with different polepiece spacing and the bridge and pickup measurements must match well enough to ensure that the strings will be over the pickup polepieces. Strings that do not pass directly over the pickup?s polepieces will be quieter and won?t balance well with incorrect spacing. This is an especially common problem when putting a humbucker in the bridge position of a Strat or Tele. The Gibson polepiece spacing is narrower than Fender?s. Some pickup companies address this problem by selling "F Spaced" (F for Fender) humbuckers. Pickups with blade style polepieces, of course, eliminate this problem.

Another common dilemma occurs when players decide to trade in their tremolo bridge in favor of a fixed bridge. To make this conversion you?ll have to fill the tremolo cavity with a solid block of wood. This glued in block is necessary for the mounting screws and string-through-body holes. Even with a pre-made block like the one shown this is a can of worms often better suited to a replacement body than a permanent conversion like this.

Tone, of course is another consideration in making your bridge selection. Here, it is much more difficult to give you concrete information to go on. Different players will swear by different bridges and it all gets very subjective.

Part of the bridge?s function is to transmit vibration from the string to the body wood so it makes sense from a physics point of view that the fewer parts in the bridge, the more vibration will be transmitted. Screws, springs, and other moving parts (roller saddles, special bushings, etc.) all dissipate string energy before it reaches its final destination affecting tone and sustain. I know players who can hear the difference between tune-o-matic bridges mounted on the old style studs (direct to the body wood) and the newer ones that use the threaded inserts to hold the posts. I don?t have that kind of hearing (anymore) but there is a difference. This is why the Tone Pros bridge has gained such a following. With the bridge locked onto the posts string energy is more effectively transferred and you can hear the result.

The same goes for flat mount bridges that string through the bridge rather than through the body. This doesn?t make one better than another, it just makes them different. In the long run your ears, instrument design, and woodworking skills will all play a role in choosing the right bridge to get your project off "The Drawing Board".