Common Bridge Issues

Over time, the tension on the strings causes the holes in the bridge to become enlarged. Note the pin in the center of the photo with the hole on its left side.

Does your piano have a section of keys that just sound terrible? Do the strings make clunking or rattling noises? Do single strings have a warbling sound to them? These are common symptoms of issues with the piano's bridges. There are two bridges in a piano: the short (bass) bridge and the long (treble) bridge.

Bridges in a piano have two jobs to do. The first is to provide a termination point for the speaking length of each string (this refers to the section of each string that is struck by the hammer, vibrates, and produces the desired sound. There are several non-speaking sections of each string that are usually muted with strips of felt). The termination point is achieved by the use of iron “bridge pins.” These pins are sturdily embedded in the wood of the bridge and provide the lower end point of vibration for the strings. The second purpose of the bridges is to transmit the vibrations of the strings to the soundboard where they can be amplified to produce the volume that we expect from a piano.

The most common issue with the bridge is that of loose bridge pins. Over time, the sideways force exerted by the string causes wood surrounding the bridge pin to be crushed. This causes a loose fit of the pin in the bridge and can cause the noisy issues described above. There are other ways that a bridge can fail that will also cause these issues, but I won't get into those here.

The way to fix this problem is to remove the offending strings from the bridge, pull out the loose bridge pins, fill the enlarged holes with epoxy, drill new bridge pin holes, insert the bridge pins, and reinstall the strings.

The strings that pass the offending bridge pins must be loosened slightly.

After identifying the bridge pins you want to work on, follow the strings up to the tuning pins. Before working on the bridge, you need to loosen each of the tuning pins that correspond to the strings over the target bridge area. If you are working in the tenor section, take a closer look at the three strings. One of them will loop around a hitch pin at the bottom and double as a string for an adjacent note. The tuning pin for this string must be loosened as well. Turn the tuning pins in small amounts while lightly pulling the strings towards you. This will keep the coils tight around the tuning pins while they unwind. Keep loosening the tuning pins until the strings have enough slack to pull them away from the hitch pins and the bridge.

If there are enlarged holes in the long bridge in the area underneath the bass strings, you will have to remove several of the bass strings to gain access to that part of the bridge.

Holding tension on the strings while turning the tuning pins. I wear gloves to prevent any moisture on my hands from causing the strings to rust.

The loosened strings after being pulled away from the bridge.

Using a lineman's pliers, note the angle of the pins, and pull them straight out along that angle. 

Pulling out the bridge pins.

A removed bridge pin.

Use a piece of cardboard or styrofoam to keep the bridge pins in the correct order.

Keeping the bridge pins in order. Note how the right-most string of the note next to the one being worked on has also been removed.

Once all of the offending bridge pins have been removed, cut and mix a small amount of PC wood epoxy putty and fill the enlarged bridge pin holes. After the epoxy has hardened, sand it flush with the bridge.

The bridge after filling with epoxy and sanding.

Measure the diameter of your bridge pins with a micrometer and acquire a drill bit of the exact same diameter or of the closest wire gauge size on the smaller side (an overly tight bridge pin is better than a loose one). Drill new bridge pin holes while trying to duplicate the angle of the surrounding bridge pins as closely as possible. Push and twist the bridge pins back into place, reinstall the strings, and pull them back up to pitch.  Any buzzing, warbling, or clunking will hopefully be eliminated.  If not, you may have more serious bridge problems.

The bridge with one pin re-installed and a second hole drilled.

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Replacing Loose Tuning Pins

Every once in a while, I go out on a tuning job only to find that the piano in its current state is impossible to tune. Some tuners throw this sentiment around whenever they encounter a piano that is worth anything less than a few thousand dollars. “Impossible to tune” to these kind of tuners just means that the piano is incapable of sounding like a nine-foot concert grand. That's not what I'm talking about. These pianos of “lesser value” are in many cases much more important than the ones in the concert halls and auditoriums. These pianos are seen and heard every day. They bring warmth to homes and joy to the people in them. So, when I say “impossible to tune”, I mean it literally. The piano is physically incapable of making music. The most common reason for this is because the tuning pins have lost their grip.

Bass tuning pins in a Kimball upright. The shiny pins on the left are slightly larger replacement pins. The dull pins on the right are the originals that no longer are able to do their job of holding tension on the strings.

In my post “Loose Tuning Pins CA Glue Repair” I described a procedure that is used to tighten-up  tuning pins that are slightly loose. Sometimes the pins have gotten so bad that CA glue won't do enough to make the piano functional again. In these cases, it is necessary to replace the tuning pins with slightly larger ones.

The way that a piano holds tension on its strings is by having one end of each string looped around a stationary iron “hitch pin” and the other end wound around a tuning pin. These pins are between 2 and 2-1/2 inches long, however only about an inch of them is visible. This is the part that the string is wound around, as well as the part that a tuning wrench is placed over in order to turn the pin (changing the tension on the string and consequently changing the pitch of the string). The other inch and a half of the pin is tightly embedded in a laminated block of wood called the "pinblock". The pinblock is made of several sheets of wood that are glued together so that the grain of each layer runs in a different direction than the layer next to it. This layering adds a lot of strength and resilience to the wood. This is vital when each of the 200+ pins has about 150 pounds of tension on it.

The tuning pin and coil after loosening 3/4ths of a turn.

Over time, the wood fibers in the pinblock get slightly crushed and start to loose grip on the tuning pins. When this happens, the pin requires significantly less force to turn, and in bad cases the tension of a string at the proper pitch is enough to turn the pin all on its own. This is what I am talking about when I say “impossible to tune”. The string can be pulled up to pitch, but as soon as the tuning wrench is released, the tuning pin slips in the pinblock and the string goes out of tune.  In these cases, the best solution is to remove the tuning pins and replace them new, slightly larger pins.

If you plan in replace a large number of tuning pins, you want to be sure that the larger pins are actually going to help your problem. If the pinblock of your piano is severely cracked or has delaminated, it needs to be replaced before any other work is done. If you are unsure as to the condition of the pinblock, it may be worth it to just replace a pin or two here and there across the length of the piano, pull the strings up to pitch, and wait for a few weeks while occasionally giving a firm strike on each of the corresponding keys. If the strings with the replaced pins haven't drifted far out of pitch at the end of this test period, you can go ahead and replace the rest of the pins.

Before you start, you will need a tuning wrench, new tuning pins, a tuning pin setter or punch, a hammer, a thin flathead screwdriver, and a few different sets of pliers. 

Tuning pins come in sizes ranging from .276” to .306” in diameter and in .005” increments. To determine the size you need, remove one of the loose tuning pins by turning it counter-clockwise until the string is loose enough to remove from the pin (about 3/4ths of a turn). The string has a tight bend at the end (called a becket) that is inserted into a hole in the center of the pin. Pry the becket from the hole with a flathead screwdriver. 

Prying out the becket.

Releasing some tension by pulling the string off of the termination pin.

In the bass of many upright pianos, you can release a bit more tension by pulling the string over the termination pin just below the tuning pins. The coil can now be pulled all the way off the tuning pin. Using a tuning wrench or a string crank, turn the pin counterclockwise until it comes free from the pinblock.  Using a micrometer, measure the diameter of the pin. Find your size here: http://www.vandaking.com/s-210-piano-tuning-pins.html. If your old tuning pins loosened instantly under proper string tension, order new tuning pins that are two sizes larger. If the old pins loosened slowly over time under proper string tension, order one size larger. Make sure you get new pins that are the same length as the originals.

The coil fully removed from the tuning pin.

Spinning the pin out with a stringing crank.

The tuning pin has been removed.

At this point, there is a bit of disagreement between piano technicians as to the proper technique. Some technicians will drill or ream out the tuning pin hole to a size just slightly smaller than the diameter of the new pin. Others will clean out the hole with compressed air, a vacuum, or a long slender brush. Some technicians don't prep the tuning pin hole at all. In this case, the pins were already so loose that the holes did not need to be re-sized, and so I went right ahead and hammered the new pins in.

The tuning pin setter and the new tuning pin ready to be hammered into the pinblock.

In order to install the new pins, use a tuning pin setter and a hammer to tap the new pins straight into the pinblock. Only tap the pin in until it sticks out just slightly further than the original pins around it. The goal is for the bottom of the string coil to end up 3/16ths of an inch away from the plate (or the pinblock if the plate doesn't cover the full height of the piano). Pull the coil onto the new tuning pin and insert the becket into the tuning pin hole. If you pulled the string off of the termination pin earlier, place it back along its original path. Make sure that the string is still following its path through the bridge pins down below the keyboard. From this point, you will follow the same directions in my “Replacing a Broken String” tutorial.

The new pin after hammering.

Placing the coil on the new pin.

To see more photos of this procedure, take a look at Chuck Behm's instructions in this helpful PDF.

Checking to make sure the strings are all still following the correct path over the bridge.

The pin after bringing up to pitch.

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Cleaning Out an Upright

If you own an old upright piano, every few years, you ought to open up the base of the piano and take a look. Often times you will find rodent nests, broken pieces of the piano action, decades worth of dust and old pencils, or anything else you can imagine. This process only takes a few minutes and can give great insight about any ailments that may be affecting your piano.

I was recently called out to diagnose an old spinet that had survived Hurricane Katrina. The water had risen a few inches above the floor of the house and the water line could still be clearly seen at the lower end of the cast iron plate inside the piano. The reason I was called in was because, in addition to the piano being out of tune, many of the keys were either sticking or just moving very roughly. The first thing I did when arriving at the owner's home was to remove the lower panel of the piano (looking for a clue as to the piano's history). I saw the water line on the plate, but I also saw what looked like small piles of cat food along the bottom board inside of the piano. To me, this immediately implied a past or present rodent infestation. At some point, these critters had made this piano their home, found an open bag of cat food, and had stashed some of it for later. This definitely gave me an inkling as to what was going on with the keyboard. There is usually large enough gaps in the keyframe under the keys for mice to squeeze through and move around underneath the keyboard. However, this inkling didn't fully prepare me for what was to come.

After my quick check inside the lower cavity of the piano, I decided to pull a few keys out of the piano to see if there was anything underneath that could be jamming them, as well as looking at the condition of the bushings inside the keys that usually allow it to move smoothly up and down. After removing the top panel and fallboard, I lifted a few keys off the keyframe. What I found was that during the storm the mice that had been storing their food in the bottom of the piano needed to look for higher ground and, finding the cavity underneath the keys, had completely packed it with partially chewed cat food. The entire length of the keyframe had served as their emergency food storage. The food was so tightly packed and stuck together that it had to be chiseled out with a spoon and screwdriver.

The piano's owner and I spent a little over an hour removing all of the keys (and numbering them to ensure they were replaced in the proper order), scraping, scooping, brushing, and vacuuming all of the cat food out of the keybed cavities, and replacing the keys. Once the keys were back in, I was able to play all the way up and down the keyboard with only two keys showing any signs of sluggishness. These were quickly remedied by slightly easing (compressing) the balance rail bushings inside the offending keys.

This piano provides a great lesson about being vigilant about maintaning your piano. Open up the lid and the bottom panel every once in a while and take a look inside. If you see broken wooden parts, missing screws, or piles of small debris formed by rodents, you should take action quickly to prevent any small problems from becoming a serious issue that will prevent your piano from having to undergo expensive repairs. If you find that there are rodents moving in and out of your piano, be careful when cleaning up the mess they leave behind. Rodent feces can contain harmful viruses, so you should wear a dust mask and gloves. If you think they have caused damage to your piano, call your local piano technician to perform repairs and advise you on how to prevent similar damage in the future.

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How to Use a Wire Brake

Piano wire tends to be very springy and hard to control.  New piano wire comes in long lengths that are wrapped into tight coils.  Piano wire manufacturers package these coils in a few different ways: canisters, sheet metal brackets, zip ties, and wire brakes.  Each method has its advantages and disadvantages.  I definitely prefer to use wire brakes, as they offer the most secure hold on the wire as well as the most control when unwinding a length of wire.

When these wire brakes come in from Schaff, the center bolt is usually overtightened to keep the wire from potentially unwinding during shipping.  The first thing I do is loosen the bolt a little bit until the arm can rotate around the coil with some friction.  This is done by holding the thumbscrew with one hand and turning the wing-nut on the other side just a bit with the other hand.  Sometimes the wing-nut is so tight that a pliers is needed to turn it.

When working with piano wire, I wear some thin cotton gloves to keep the oils from my fingers off of the wire.  These oils will cause the bare steel wire to rust very quickly.

To use the wire brake, hold the arm of the brake in between the thumb and index finger of one hand.  Make sure you are not hanging on to the round part of the brake. Grab the end of the wire with a pliers and pull a length of wire out of the brake.  The round part of the brake will spin as the wire unwinds.

Once I have pulled as much wire as I need, I use the pliers to squeeze the wire against the bend at the tip of the arm.  This causes a tight bend in the wire that will catch in the small hole in the arm and keep the wire from unwinding.

The wire brake can now be put away until the next time it is needed.

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Re-gluing Damper Felts

The glue holding the bass damper felts on my Milton Player Piano had degraded to the point that the felts were falling off on their own.  They were still in good enough shape, so I decided to pull the remaining felts off and re-glue all of them.  

I start by holding the damper head firmly with one hand, while rotating the damper felt with the other until it comes free.  I work my way along until all of the old damper felts have been removed.

If I were re-gluing the treble damper felts, I would keep them in order, but for these bass felts it doesn't matter if they get mixed up.  Just keep the single-string dampers with the single-string notes and the doubles with the doubles.

To reattach the felts, I use Titebond Liquid Hide Glue.  Since the damper springs will provide the clamping action to hold the felts and damper heads together, I don't need the quick set that hot hide glue offers.  The liquid hide glue is much easier to work with and requires less set up time as well as less clean up.  

Some of the damper felts are not horizontally symettrical, so make sure that you keep them in the same orientation as they originally were.  The easiest way to do this is to keep the dirty side of the felt up and the clean side down.

Top side

Bottom side

Apply a small amount of glue to the back of the damper felt and then, using the strings as a guide, slide the damper down behind the corresponding damper head.  Allow the spring-loaded damper head to clamp the felt against the strings.

Try not to apply too much glue as it will squeeze out and fall onto other parts of the action where it doesn't belong.

Keep working along from left to right.  Going this direction will allow you more working room as well as better vision of the glue joint.

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