Everything You Always Wanted To Know About Acoustic Guitar Pin Bridges (but were afraid to ask)

Here is a question from a reader:

I have a guitar which is basically new from the shop, and I have not yet changed any of the strings. I recently noticed that the pegs in the bridge that hold down the low E, A, and D strings were not fully depressed (as the G, B, and high E strings are) and wondered if this could have an adverse affect on the guitar. I tried pushing them in with my thumb, but could not get them to move. Should I be concerned about the pegs that will not push all the way down?

Basic Pin Bridge Concepts

On a flat top guitar all the tension of the strings is focused at the bridge. From the point of view of how the strings are anchored, there are two types of bridge - the "pull through" type, and the "pin" type. On a pull through type bridge, the strings pass over the bone or plastic "saddle" and anchor at the back of the bridge, but do not go through the top of the guitar. On a "pin" style bridge, the ball end of the strings pass over the saddle piece, then into holes in the wooden bridge which go through the top of the guitar. Then, plastic, wood, bone, metal or ivory pegs are inserted into the holes to prevent the strings from pulling back out when they are tensioned. Inside the guitar, there is a thin veneer of hardwood ( referred to as the "bridge plate") glued under the bridge location of the top during construction. The addition of the bridgeplate approximately doubles the thickness of this area. Also, whereas the top wood might be spruce or cedar, the bridgeplate is made from a harder wood such as maple or rosewood. This helps keep the ball end of the tensioned strings from wearing out the underside of the top. When a string is properly inserted and anchored, the ball end of the string is wedged up against the bridge plate.This firm anchoring of the strings transfers the tension, and in turn vibration of the strings to the guitar top.

While there are debates about the nuances of the eventual transfer of the string energy across the top, one thing most builders and designers can agree on is that the ability of the area directly under the pin bridge to firmly anchor the ball ends of the strings is crucial to getting a clear tone and good volume from a guitar with a pin style bridge. Snuggly seated bridge pins are an important part of the correct operation of a pin bridge.

To get back to the question at hand- does the uneven look of the pegs mean there is anything wrong? The answer is- The position, or height, of the pegs over the acoustic guitar bridge, in and of itself, doesn't have any particular effect on the health of the guitar. Bridge pin aesthetics aside (some people just prefer it when they are even), the only important consideration is whether the ball end of a given string is firmly seated against the underside of the top. Sometimes a high string peg at the bridge is indeed a reflection of the ball end pulling up through the bridge, but not always. If you are unsure whether the strings are correctly seated- check, either with a mirror, or by hand.

Installing Strings Into Pin Bridges

Despite the added strength of a hardwood bridgeplate reinforcing the area under the bridge, improper stringing of a guitar with a pin bridge can slowly ruin it, eventually necessitating costly repairs. The best method for maintaining good bridge and bridge pin health (and, in turn, ensuring the best tone and volume from your instrument) is to pay attention and take care when re-stringing your guitar. Give the string a slight bend near the ball end before you insert it into the bridge. The end that you have bent should point towards the neck as you insert it. Figure that the string needs about ¾ of inch (19-20 mm.) of length to reach the bridge plate. Then insert the bridge pin loosely, keep your finger on it, and pull back up on the string. You should feel the ball end stop at the underside of the top as you pull. Once you sense this, push the peg in firmly. As you tension the string the ball end should pull up against the under side of the bridgeplate.

On most well made guitars the string pins will, when fully inserted, stand about the same height over the bridge. If a peg seems to stand higher than it ought to, or out of line with the others, and you can't depress it further with the string under tension, loosen the string and then push down on the peg. It may drop a little, it may not. If the peg does not drop to the level of the others, you should check to see that the ball end of the string has passed all the way through the bridge and is correctly seated against the bridgeplate. With an inspection mirror inserted into the sound hole you could check this. But if you don't have a mirror, loosen the strings until you can get your hand into the guitar, reach down to the bridge area. You should feel a peg and a ball end for each string. If you don't feel a ball end, loosen the string, lift the peg, insert the string further, re-insert the peg and pull the string back up until you feel it stop. At this point the ball end should be seated firmly against the underside of the top, and you should be able to feel it. You should not, however, feel any of the string, that is, you should not feel the ball end hanging on a length of string below the bridgeplate. If you can feel any amount of string, pull back up on the string until the ball end is firmly up against the bridgeplate.

Generally, on a newer or well maintained instrument changing the strings should be straightforward. The pegs will usually seat evenly, but as I say - it is what is going on inside the guitar that really matters, so a slight unevenness does not necessarily mean that the health of the guitar is being compromised. If you find that the ball ends are correctly seated inside the guitar, but the pegs are uneven on the outside and you would like them even- take the guitar to your guitar tech and he will use a special reaming tool to adjust the sizing of the holes.

On older instruments, particularly when attention has not been paid to properly seating the strings for many years, the area of the bridgeplate where the ball ends seat can wear out over time, allowing the ball ends to pull up through the bridge. Eventually, the ball ends can lift the bridge or even cause cracking in the string pin area. If nothing else, a gradual loss of clarity and volume will result.

One sign of the string holes in the bridgeplate wearing out is that the thicker part of the string, where it is overlapped to hold the ball end, becomes quite visible above the bridge behind the saddle. Over time this thicker part of the string may reach and then push against the saddle. If left to go long enough, this stiff part near the ball end can apply enough forward pressure against the saddle to crack it, or even the bridge itself.

Sometimes, particularly with older plastic or wood pegs, the pins have just worn out,and no longer serve to anchor the strings adequately. If this is the case( and there is no cracking or lifting of the bridge), replacing the old pegs with new might correct the problem, and re-anchor the strings at the bridgeplate.

In other cases, the bridge pins themselves may be in good shape, but the bridgeplate is worn, allowing the strings to slide up. In this situation, and it may take using a mirror inside the guitar while the strings are tensioned to discern this, the bridgeplate may need repair or replacement.

Bridgeplate Repair And Replacement

The are a couple acceptable repairs for a worn bridgeplate:

1. Fill the holes with a mix of sawdust and epoxy, then re-drill.

2. Fabricate and install a thin veneer of matching hardwood to cover the area of the worn string holes, then re-drill.

3. Remove and replace the entire bridgeplate, then re-drill the holes.

The end result of each of the above remedies will be a a renewed and stable seat for the ball end of the strings. Which repair is most appropriate for a given guitar is something to discuss with your guitar repair tech before the work is done.

Plastic v. Bone Bridge Pins

Lastly, while we are on the subject of bridges and string pegs, I am often asked my opinion about the impact of the composition of the string pegs on tone and volume. Do metal or bone bridge pins enhance tone and volume more than plastic?

My answer would be a very qualified -maybe. The qualifications are these:

1. I think the firm seating of the strings against the bridgeplate is the far more important than the material that the pegs are composed of. I can absolutely attest to the effect of re-establishing good anchoring of the ball ends on the improved quality of tone and volume in a guitar. If the strings aren't seating correctly because the bridgeplate is worn, simply replacing the existing pegs with ones of a different material will not make a difference.

2. If the pegs are fitted correctly, and the ball ends of the strings seated firmly against the bridgeplate, pegs that are of a dense material such as bone or brass may make a difference on a given guitar. The one advantage I can think of for using a peg of denser material would be the alleviation of the slight vibrational damping effect that any given softer material might have. But I would have to say- I can't think of many times when I replaced well fitted plastic pegs with bone or ivory and immediately discerned a pronounced impact on the sound of the guitar. And also in my experience, some guitars reflect such subtle changes more than others. I could speculate about why this is, but I won't.

3. Well fitted bone or brass pegs will wear less quickly than plastic or wood. So this factor alone may justify the switch, if you feel like spending the money.

THE BOTTOM LINE