Diagnosing the Sticking Piano Key

Diagnosing the Sticking Piano Key (Piano Tuning and Repair)

Welcome to our Series on Piano Tuning and Repair.

One of the most common issues with pianos is having a sticking key. There is a list of things that could cause the sticking key. The video above walks you through the steps of checking the most common causes of a sticking key. Once you have determined what the cause is you can then move forward with the right solution or repair. We offer the parts and tools needed to make piano repairs in our online store which can be found at the address above.

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Video Transcript:

One of the most common issues in pianos are what some would call a sticky or sticking key. That particular symptom or what some would call a sticking key, there could be a number of different reasons that could cause that problem. This video will go through some of the more common or major things that you would come across that would be solutions to fixing a sticking key. It's not just necessarily always one thing that is causing that. This will kind of walk you through the steps to check if you have a sticking key to figure out what the problem is. Now we are going to start at the front of the key here.

Piano Keyslip

Probably one of the more common and easier to fix problems is often times if it's just white keys that are sticking. It could be that this board right here that sits in front of the keys which is called the key slip. This could be too close to the front of the keys.

So what happens is if this is too close when you push the key down, it gets stuck. The front the key gets stuck up against the key slip. You can kind of tell that if you look down in between the front of the key and the key slip. You can see that there is no space there.

The other thing is if you just pull back just a little bit and the key comes up then you know that the key slip is too close. The way to fix that is to take the key slip off. There are some screws under here or sometimes they just slip right off. Most of the time in most cases with the upright or vertical piano, they have screws underneath the key slip that you take out , and then the key slip will slip off. Then what you do is put a little shim to figure out where it's the closest. You can just make a shim out of either a piece of thin cardboard or something. You can ever tape it to the key frame. Then you put that up there to push the key slip out just a little bit because it doesn't have to be very much.
Just enough so that there is a little bit of space between the front of the key and the key slip. Now that is the first possibility.

Key Bushing and Key Pins


The other thing is that I have taken some the keys out here. It could be that the key bushing which is underneath the key and that sits on these key pins right here. This one back here is the sharp key and these ones up front are the white keys. This bushing right here could be tight because that is felt which sometimes swells. It may need to be replaced or eased. They have a video that shows replacing the front rail key bushings. So sometimes that needs replaced. Or it could be that the balance rail felt is too tight. So there is also felt in this hole and that sits on these pins here which are the balance rail pins. So if either of those two felts are too tight you will push it down and because it is too tight the key will not want to come back up. So you may need to replace that or just ease. There are some tools available to iron the felt to make it a little bit looser on the pin.


One of the other possibilities could be this front rail pin or the balance rail pin are corroded. As I tool the keys off of this I could feel that they are not nice and smooth. They are rough because they have corrosion on them a little bit. If they are really badly corroded you will have to replace the pins. In most cases you can just use some metal polish and polish those up so that they are nice and smooth so the key can move freely up and down on the pin. Okay the same with the balance rail pins. These are pretty smooth so those probably don't need polished. But these front rail pins have caused some sticky keys on this piano and that seems what the problem is with this particular piano.


The other thing is the front rail pins in most cases are oval shaped. So the dimension side to side is not as wide as the dimension front to back. Sometimes if a key is too loose if it wobbles side to side then some technicians will take and turn that pin just a little bit so that it tightens it up and that over time can actually cause the key to be too tight. So you want to make sure that it's not turned so that it makes the key too tight on the pin. Or the pin could be bent. If it's bent then it's not going to slide freely up and down on it.

Check Spaces Between the Keys

Another thing that could be happening with the keys: sometimes objects (coins are the most common thing) or paper clips can fall down between the keys and get wedged in between the keys so it can't go down and won't come back up. So you will want to check that sometimes by lifting off the key to see if there is anything lodged in between there which is a possibility.

Broken Key Sticks

Another option or problem with what they call a sticking key is if the key stick is broken. This is the whole key stick here. Sometimes you will see that there is a break and it's usually right at the balance rail in most cases. But if there is a break in that key then the front will be going down but the back won't be going up at the same time because the key is broken. It won't push the back of the key up by pushing the front if the key down. Now those are the things that have to do with action or for the keys for the most part.

Whippen Jack Spring

Some other things that could cause a sticking key would take place in the action and this is the whole action of the piano. Including the whippens, the hammer butts, and the hammers. So we are going to take a look at what can cause some problems with keys in the action. One of the things could be the jack spring. Okay now this is a whippen which is the part that goes right in here. This one is not from this piano but it is a very similar size. This piece right here is the jack spring. What that does is this piece here is the jack and that goes forward when the key is pressed down. It has to be able to return back to it's position and so it's that spring that causes the jack to go back. So it goes forward when the key is pressed down and it returns back when the key is released. Okay if this spring is broken or sometimes over time it can get weak then you need to replace those jack springs.