Tune-o-matic

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Typical Tune-o-matic bridge with stopbar

Tune-o-matic (also abbreviated to TOM) is a name of fixed bridge design for electric guitars. It was designed by Ted McCarty (Gibson Guitar Corporation president) and introduced in the Gibson Les Paul Custom guitar in 1954^[1]. In 1955, it was used on Gibson Les Paul Gold Top. It was gradually accepted as a standard on almost all Gibson fixed bridge guitars, except the budget series^[2].

1 Function
2 Construction
3 Varieties
4 Spelling
5 References

[edit] Function

Guitar strings, especially steel strings, are not ideal vibrators. Generally the thicker the string, the shorter the effective length. This refers to the length of string involved in producing a sound, as opposed to the length between the nut and the bridge. Many guitar designs with fixed bridges have the bridge slanted or stepped so that the distance from nut to bridge is larger for thick strings. The Tune-o-matic extends this idea to make the distance adjustable for all the strings, within limits.

The most common way of determining correct adjustment for a string is to compare the note at the 12th fret with the harmonic at the same position. The two should be as close as possible.

[edit] Construction

Tune-o-matic with "strings through the body" construction (without stopbar)

The Tune-o-matic bridge consists of 2 adjustable posts that are screwed into the guitar body and a bar between these posts. The bar has 6 saddles, one per string. Each saddle has a small groove that matches string gauge and shape — it's where the string would be held by the saddle. When fully assembled, each string sits astride a saddle and the saddle thus "marks" the end of the vibrating string. Each saddle can be adjusted (moved back and forward) with a screw to control intonation. To prevent saddles from falling out of the bridge when no strings are installed, most models usually hold the saddles with retainer wires.

After the saddles, each string is passed to the tailpiece. Some guitars have a stopbar to hold strings, others have "strings through the body" construction, thus holding the string by whole body.

The Tune-o-matic bridge is not absolutely flat, and standard Gibson Tune-o-matic bridges have a 12" radius^[1]. Ideally, the radius should match the radius of fretboard for the most comfortable playing experience.

It is possible to fit the bridge either way round on the two body posts, which leads to a certain amount of confusion when changing strings, should the bridge fall off. Conventionally, the string length (intonation) adjustment screw heads should face the neck although, provided the screws do not foul the strings between the bridge and stopbar and the saddles are identical in string groove depth, it can be used with the screw heads facing the stopbar, as in the photo. Unless the player wishes to completely reset the action and intonation, it is important to refit the bridge in the same orientation as before a string change, regardless of which way round it was to start with.

[edit] Varieties

Since its invention, different versions by Gibson and other companies have emerged. Gibson has introduced at least 3 versions that has minor differences in construction^[2]:

Standard Tune-o-matic is the first version that appeared in 1954. It used slim posts, but lacked slots for adjustment with screwdriver. The only way to adjust it was using a thumbwheel that was accessible only after loosening strings. Adjusting the bridge height required retuning of the whole guitar.

Modern Tune-o-matic is the second version. It featured a much larger post with a threaded pot. It could be adjusted using a slotted screwdriver instead of a thumbwheel, but the posts were too large to be used in Fender guitars. It also required drilling to install.

Refined standard Tune-o-matic is the third version of the Tune-o-matic. It featured both slim posts (as in "standard" version) and a screwdriver adjustment (as in "modern" one).

There are multiple widely known Tune-o-matic models that differ in the following parameters:

Model	1st-to-6th distance, mm	Between posts, mm	Post, diameter × length, mm	Thumbwheel diameter, mm	Saddles, mm
Model	1st-to-6th distance, mm	Between posts, mm	Post, diameter × length, mm	Thumbwheel diameter, mm	width	height	thickness	hole
Gibson BR-010, ABR-1 ("Vintage")	52	73.8	M4×30	15	8.8	6.5	3.0	M3
Gotoh GE-103B^[3]	52	74	M4×30	18	8.8	8.0	3.0	M2.5
Gibson BR-030 ("Nashville")	51.6	74.3	M3.9×25.1	11	8.8	10.0	2.55	M3

[edit] Spelling

There's no general consensus on "proper" capitalization of bridge name. Gibson's official site usually spells it as "Tune-o-matic"^[1], while "Tune-o-Matic" and "Tune-O-Matic" are frequently used in advertising and promotional material.