- Acoustic Guitar Bridge Replacement Parts
- Custom Acoustic Guitar Bridge
- Acoustic Guitar Bridge Repair Cost
- Acoustic Guitar Bridges For Sale
- Acoustic Guitar Cracked Bridge Repair
- Acoustic Guitar Cracked Bridge Lyrics
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Thing is, it’s not the best solution. The tailpiece is resting against the top of the guitar with isn’t the best for getting a good tone. Also, the guitar’s designed to have strings couple to the bridge for good transfer to the top. Here's the reason for that weird repair. This Takamine has a seriously cracked bridge.
Bridge Plate Overlay
© Frank Ford, 3/15/98; Photos by FF, 3/12/98
Here's a topic that usually sparks heated discussion (argument) in the guitar repaircommunity. I'm hoping to try to sidestep the controversy by stating from the outsetthat I'm presuming that the reason for performing this operation is a matter of survivalof the guitar. In many cases, we can perform a bit of delicate surgery and removea damaged bridge plate and replace it with one of appropriate size and style.
Here, we're talking about a guitar that's seen damage from heat and previous repair.This is not an uncommon situation. Quite a bit of my work consists of making thebest of a lousy situation. Maybe the instrument was badly abused in the heat of aparked car. Certainly a well intended (or maybe not so well intended) previous repairattempt left the guitar even worse off.
This guitar is a 1971 Martin D-28 which had obviously been subjected to the stressof high heat. The braces were loose from the top directly under the bridge. In myexperience high heat is the ONLY cause of this problem in a finely crafted guitar.The bridge had been sloppily reglued, the pickguard was curling up, and the fretends were sticking out where the fingerboard had shrunk a little.
Quick note: WATCH OUT FOR HEAT. Your car can get up to 175 degrees (F) out there parked in the sun. At 150, most glue is history! If you MUST risk this heat, slack the strings off completely. At least you'll save the bridge, top braces, neck and fingerboard joint. It really is a big deal.
Here's the reason this guitar came to see me:
The bridge is cracked badly right through the pin holes. When I look inside, I seethe smears of glue from the regluing of the braces right under the bridge, whereall the stress is concentrated. In this picture you can see the pickguard curlingup as well.
Looking at the bridge plate I see that the wood was mostly chipped out between theholes. Here's a view with the INSIGHT inspection camera. Notice how the woodis missing for at least half its thickness right at the holes.
I do not understand why virtually all makers run the grain direction of bridge platesparallel to the length of the bridge. With the grain running this way the bridgeplate can't do its job so well. The function of the bridge plate is to reinforcethe top for seating the string balls, and TO KEEP THE TOP FLAT SO THE BRIDGE STAYSIN PLACE. Without a bridge plate, the spruce top would have a much greater tendencyto 'peel' loose from under the bridge.
When the holes are drilled through the plate, most factory guitars suffer a littlechipping out. Then later, as strings are changed, more chipping. This poor guitar'stop began to fold right on the dotted line!
On to the business:
I'm heating the bridge to soften the glue underneath. My heater is one of those rubberheat elements like the ones sold by L.M.I. I specially ordered this one 1' x6' for regular steel string guitar bridges. The L.M.I. ones are 5' longand do the job well also. I wrap the element in aluminum foil for a little bettercontact, and weight the ends with lead and the cord with a sandbag to keep it fromshifting. The heater reaches about 400 degrees, so I have to keep close watch!
I reach inside to feel when I think the temperature is about right, take the heateroff, and start to lift the bridge with my flexible knife. The glue is very soft andthe bridge comes off cleanly.
Holy Moly! Look what I found:
The top is a real mess under that bridge. It's not the worst, but it's bad enough.Whoever took the bridge off last time ripped big holes in the spruce. Those inlaidpatches of spruce were an attempt to do the right thing, but they obviously cut rightthrough the spruce in the very area where the holes, grain direction and chippedwood of the bridge plate make it the top weak as well. The inlaid patches are welldone, and tightly glued. The bridge was tightly glued, too, but it cracked becauseeverything underneath folded on the line of the bridge pin holes.
The job is clear now. It's time to overlay the bridge plate to improve rigidity.
Removing the old bridge plate would be a big risk, what with all the damage rightwhere the bridge glues on. There's no big problem in gluing on a new bridge, butI don't want it to crack. Cost is also a factor. Replacing the big original rosewoodbridge plate is just too expensive for the owner, and for the value range of theguitar. Bridge plate overlays can always be removed, by the way, should there bea future reason to change the style of the repair.
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Steel string guitar
Examining Cracked Bridges
© Frank Ford 2006; Photos by FF
For most of the last hundred years, we've counted on flat top guitar bridges to resist the load of up to around 180 pounds of relentless string tension, to transfer the strings' vibrating energy to the top and to support a saddle that determines action height and intonation. The choice material for bridges has traditionally been ebony or rosewood because these two woods are among the most dense, stiff and strong in the world. But, sometimes they fail - either pulling loose from the top to which they are glued or actually breaking under the load of string tension.
A car parked in the sun can develop interior temperature in excess of 150 degrees Fahrenheit. At that temperature, the glue that holds the bridge may start to fail, and the bridge will become noticeably loose from the top:
Regluing loose bridges is standard fare for most guitar repair shops, and it's usually successful, resulting in a healthy guitar.
Structural failures of the bridge itself are often best addressed by replacement of the entire bridge. Unlike other structural parts of the guitar, the bridge must withstand a constant load, which, in the case of damage or poor design, may be concentrated in specific areas of the bridge, amounting to more than either the wood or any glue can handle. While a bridge may develop stress cracks in any position as a result of dryness caused heat and/or low humidity, the two most commonly seen structural failures of steel string bridges are cracks through the line of bridge pin holes, and cracks in the area that supports the saddle. Wood is most likely to crack along the grain lines, and guitar bridges are always constructed with the grain oriented lengthwise, perpendicular to the pull of the strings.
Here's a classic break. The forward tension on the saddle was simply more than the bridge could handle. Either a small weakness in the grain, or a poorly fit saddle may have been responsible:
As if the bridge weren’t vulnerable enough, it has a deep groove cut in it that must support a saddle against which the strings bear mightily. If the saddle is too high or the slot too shallow there might not be sufficient strength to handle the forward thrust of the saddle as it is pulled by six steel strings tuned to pitch. It’s a matter of leverage by which the saddle can simply split the bridge along its grain lines. Here's a too-high saddle, and it is really testing the strength of the ebony bridge:
Sometimes, the addition of an under-the-saddle pickup element is the last straw. Raising the saddle by the customary 1/16” may be just enough in some bridge and saddle combinations to increase the leverage against the front edge of the saddle slot, and the bridge may break catastrophically:
If the saddle fits very loosely, it will bear right on that upper edge of the slot, and the forward pull of the strings may be magnified enough to cause a similar crack. A bridge cracked at the saddle is hardly ever repairable. Most of the time the only logical course of action is to replace the bridge, preferably with one that has a better geometry – a taller bridge with a lower saddle or a deeper slot to accommodate the pickup element.
Some makers try to minimize the tendency to crack through the line of holes by orienting the holes in an angled or circular pattern so they don’t line right up with the wood grain:
The bridge above has an added bonus - since the pin holes are lined up parallel to the saddle there's a more even down pressure (break angle) on the saddle for each string.
Synthetic materials such as high pressure laminated phenolic (Micarta) or epoxy/carbon fiber composites might indeed make for a superior and indestructible bridge, but the acoustic guitar remains a traditional stringed instrument, so these materials have not accrued much favor to date.
A common misconception is that bridges crack between the bridge pin holes because someone has rammed the tapered bridge pins in too far, or that wooden bridge pins have swollen enough to exert the force necessary to cause a crack. In fact, there are a number of more likely explanations. Bridges that are very thin may be too weak to resist the string tension and may bend under the load. While the wood of the bridge is very strong, it is also quite brittle and can crack easily if subjected to this kind of bending. So, if your guitar bridge is thinner than about 1/4” in the region of the bridge pin holes, it may be thin enough to crack because it is simply too weak:
Another major cause for this particular crack is a failure of another important element. Under the top, roughly aligned with the bridge, there is a hardwood reinforcement called the “bridge plate.” Here's a cross section of a healthy guitar top, with a nice bridge and saddle configuration, a pickup under the saddle and a nice flat maple bridge plate under all of it:
The bridge plate has two basic jobs – to reinforce the tender spruce against the wear and upward pull of the string balls, which are held against it by the bridge pins, and to help keep the top stiff and flat under the bridge.
Acoustic Guitar Bridge Replacement Parts
This bridge plate is mahogany, a wood that's clearly too soft for the job:
Notice how the string balls have pulled right up into the plate. Now, they're starting to bear directly on the bottom of the bridge, increasing the possibility that the bridge will bend and crack between the holes.
Custom Acoustic Guitar Bridge
An older instrument may have undergone hundreds of string changes, and the bridge plate may have become worn or chipped along the line of the bridge pin holes:
Often enough this wear is enough to weaken the bridge plate significantly in this region, contributing to a bending force on the bridge, ultimately causing that familiar crack:
Or, the wear may result in enlarged bridge pin holes such that the string balls pull up directly against the bottom surface of the bridge itself, increasing the likelihood of bridge and/or top failure
Acoustic Guitar Bridge Repair Cost
In the excess heat of a car parked in the sun, the glue bonds between the top, bridge and bridge plate may weaken enough to allow the entire assembly to bend under the load of string tension. While this kind of heat usually results in a loose bridge, it is also a major cause of bridge cracks. Even if the result is only a loose bridge, it may be accompanied by a crack in the bridge plate that might go unnoticed when the bridge is reglued.
Later, the cracked bridge plate may contribute to the cracking of the bridge as the top flexes in that area, pulled by the string balls
Acoustic Guitar Bridges For Sale
A bridge cracked through the line of bridge pin holes may possibly be glued but it is important to recognize the original cause of the crack. So, most of the time, it’s a good idea to reinforce the bridge plate with a substantial layer of hardwood, about 3/32” thick. If the grain is oriented parallel to the direction of the string pull (perpendicular to the crack in the bridge) even such a thin layer will add tremendous strength to the whole assembly, while having little if any effect on tone:
Complete bridge plate replacement is another good alternative to correct the worn or damaged plate that can cause cracks, but it is a process with more complexity and possible risks.
Replacing the bridge is a more certain way to assure continuing support for the string tension, but even then it may be desirable to overlay or replace the bridge plate for extra insurance. The new bridge may well be free from a defect in the grain that may have contributed to the crack, too.
Acoustic Guitar Cracked Bridge Repair
A parting shot from the rogues gallery:
Screws are not a good way to try to fix anything on a guitar bridge!
Acoustic Guitar Cracked Bridge Lyrics
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