Trade Secrets!

Tune-O-Matic setup: is the trouble with the bridge or the neck angle?


Issue 93 August 06, 2009

Is this bridge set too high?
Is the tailpiece too low? Photo: Dan Erlewine
Is there a neck angle problem? Let’s see if these common
questions apply to your
Tune-O-Matic bridge, too.

Dan Erlewine, August 6, 2009
Photo: Blue Eagle Music Frank McDermott owns the Blue Eagle Music store here in Athens, Ohio. He does basic guitar setups right there in his shop, while sending repairs to my buddies at nearby United Lutherie.
Frank did a good standard setup on this guitar, but an unhappy customer brought it back. When I stopped by Blue Eagle, Frank asked me to help him figure out what went wrong.
The guitar is a 1979 Gibson “The Paul” flattop solidbody with a Les Paul shape. The problem: the strings were bending over the back of the bridge, instead of passing unobstructed to the tailpiece. (The arrow at left marks the trouble spot.) “The customer thinks this is killing the tone. Is that a real problem?” asked Frank.
The tailpiece was tightened down snug to the top, to solidly couple the hardware to the body for good tone. But when the strings touch the back of the bridge, I believe you’re losing tone because you're dampening the strings. It just has to reduce the natural, chimey, harmonic presence that we love to hear.* I always set the tailpiece high enough for the strings to clear the bridge.
“I've seen plenty of Les Pauls with the tailpiece down low, and the strings don’t hit the bridge. What’s wrong with this guitar?”
There’s nothing wrong with the guitar. Its bridge has to be high because of the angle of the neck to the body. The optimum neck angle for a Les Paul is about 4°, but they vary between individual guitars from about 3° to 5°. This variation in angle is why the bridge and tailpiece need to be height-adjustable. The steeper the angle, the higher the bridge.
*Leon Rhodes, of the Grand Ole Opry, feels that behind-the-bridge harmonics are important, too: he doesn't want them!
They interfere with his clean fast picking, so mutes that part of his strings with black electrician’s tape!
Image: neck set angle
At 5°, this one’s on the steep side. That’s why you can’t crank the tailpiece down low without the strings hitting the bridge.
Photo: measuring bridge height I’ll set it up the way I think it should be, and let’s see if Frank’s customer gets happy.
With a string action gauge, the top of the bridge measured about 11/16" off the body (to be fussy about it: 43/64”).
Dead Blow Fret HammerIf your fret hammer bangs and bounces against the
frets, it won’t keep those frets from springing back up.
Our new deadblow hammer’s shot-filled head (you can
hear the shot in there) strikes the fret with no bounce.
The energy goes to the fret, seating it with fewer
blows and less bounceback.
Photo: stop tailpiece With a stop tailpiece wrench, I raised the tailpiece until the strings cleared. (I always loosen the strings a bit before raising or lowering the tailpiece studs.) The guitar’s action over the fingerboard was set a little high, so I was able to lower the bridge slightly — and that gained a little more clearance.
Stop Tailpiece Wrench
Photo: using a bridge jack Under string tension, it’s hard to raise or lower a Tune-O-Matic bridge. Here I’m using a bridge jack to hoist the bridge up momentarily so I can turn the thumbwheels. I first saw this tool in the original Gibson shop in Kalamazoo, Michigan. They used it all the time, and it’s handy.
Bridge Jack
Photo: collapsed bridge
This bridge, a Nashville Tune-O-Matic, had caved in from years of tension. It no longer had the proper saddle radius. The top of the bridge body should be straight like the edge of gauge in this photo, but look at it sag. StewMac stocks replacement parts and saddles for a bridge like this, but I decided to start fresh with our Nashville T-O-M bridge (an exact replica). I saved the old bridge in the guitar case (not that it’s of much value).
Nashville
Tune-O-Matic
Photo: string spacing rule Using the string spacing rule as my guide, I laid the strings out on the saddles for proportional spacing — the way I like it.
String Spacing Rule
Photo: radius gauges Both the notched and understring radius gauges agreed that the saddle radius matched the 12" fretboard radius perfectly. To put string notches in the saddles, I used a shortcut I learned by visiting the Gibson shop:
Understring Radius Gauges
Photo: fret hammer making string notches I simply tapped each string with the brass face of my fret hammer. The strings make their own notch. (Only do this with an old set of strings, since it ruins them! I’ll be putting new strings on.)
Photo: measuring saddle positions Quick Setup Tip
This guitar didn’t have intonation problems, so I set the saddles in the new bridge to the same locations as the old bridge saddles. To do this, I quickly measured each saddle with a luthier's caliper and adjusted the new ones to match.
Photo: inserting a jam nut Lock down tight
The customer wanted the tailpiece tight against the body, believing it gives him “good sustain” (like “good tone,” that’s a highly subjective term, IMO). But there’s a way to get this kind of lock-down even when the tailpiece is raised up:
I installed “jam nuts” — short 5/16" set screws — in the bushings for the tailpiece studs to contact. I measured with the depth gauge of my caliper to set the right depth, then cranked the studs down onto these set screws. This makes the studs tighter-than-factory.
This new setup gave the customer what he was after — the strings don't touch the bridge any more. I can’t prove what getting those strings off the bridge did for the tone, but now he says he loves the way the guitar sounds. Frank’s happy now, too.
Luthier's Digital Caliper
Photo: top-wrapped tailpiece And here's a simple way to raise those strings off the back of the bridge while keeping all original hardware:
Lower the tailpiece back down to the body and run the strings through in the opposite direction. “Top-wrap” the strings up and over the the back of the tailpiece, and they’ll approach the bridge from a higher angle.

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