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How to Repair Broken Piano Keys

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So you found a nice piano, but it has some broken keys!

So you found a nice piano, but it has some broken keys!

Piano Key Repair Guide

If you are looking for a used piano to buy and don't want to spend much money, chances are there is a used piano in your city or region either waiting to be tossed away or sold for a meager price. Sellers are usually up to negotiate the price due to major/minor repair requirements, so you will probably find some good pianos for your budget.

Apart from the casual tuning after moving the piano to its new home, you might need to do some repairs and adjustments. Although these services might be considered specialized instrument repairs and may cost you money, a piano is a finely manufactured mechanical instrument, and with some basic skills, you can make some of these repairs on your own, save money, and get acquainted with your new instrument.

Simply put, each key on a piano translates the force to a wooden hammer, which in turn hits a string to sound the note. In this tutorial, I will show you how to repair a broken key.

A broken piano key

A broken piano key

A broken key like this is something you don't see very often. Judging from the fact that there were two broken black keys side by side, I would conclude that it might have been a heavy object (like a vase) that had directly fallen onto these keys. The mechanism of a piano relies on the physical weight of each key and the associated hammer construction, so in order to remedy the friction and ensure a smooth touch, light materials are chosen.

Although it is very rare that normal piano-playing would cause such damage, the wood might have veins from within, or rapid changes in relative humidity might cause cracks to form. If you have a key, broken, and as pictured above, this is an easy but solid fix. Below is a list of what you will need.

Supplies Needed

  • Carpenter's glue
  • Toothpicks and your fingers to apply the glue to the key
  • 2 pressure clamps
  • No. 100 and No. 400 (one coarse and one fine) sanding paper
  • scissors
  • 2 very, very thin pieces of wood for each key
  • 2 pieces of thicker wooden pieces to help the clamps to press on the applied patch
Materials needed for this recipe

Materials needed for this recipe

Here is a brief walk-through so you understand what we are going to do:

We will be applying 2 patches on both sides of the broken key, using a strong carpenter's glue. The most important thing is to find or make very thin patches to prevent friction with the neighboring keys and which will also be thick enough to withstand force when the key will be played later. I recommend making the patch around half a millimeter thick.

The repair should be barely visible after the patches are applied. This way, the repaired key will not touch the adjacent, and it will move freely. Another important point is the weight balance of the key. Notice that the break is formed through the hole on the key. This hole is the balancing point. When the key is inserted on its corresponding metal pole, it lays evenly balanced. Since adding a patch will also be adding a minute amount of weight, you should apply the patch to have an equal distance from each end to the hole.

Step 1: Prepare the Patches

Find a piece of wooden plank. I happened to have old furniture, and I simply ripped a small piece from one piece. It was thicker than it should be, so I used a coarse sandpaper to make it as thin but still solid as possible. After you are done with sanding, the patch should be lightweight and flexible.

Use scissors to cut it to a rectangular shape that will fit the side of the key.

Step 2: Apply the Glue

If the key has a crack but has not completely separated, try to apply the glue carefully with a toothpick. If the key is almost two pieces, carefully break it into two before applying the glue. This will ensure the patch to hold better. Try to use a minimum amount of glue, and keep in mind to clean up the excess glue when the pressure is applied.

Gently, apply and clean up excess glue

Gently, apply and clean up excess glue

Press firmly with your fingers for a minute, and align the two pieces of the key before applying the patches to the sides

Press firmly with your fingers for a minute, and align the two pieces of the key before applying the patches to the sides

Step 3: Apply the Patches

Use your fingers to apply a very thin coat of glue on each side of the key, maintaining equal distance from both ends to the hole to ensure balanced weight. Apply the patches, and use two pieces of wood to apply pressure homogeneously, then fix with the clamps.

Lay the key aside, with the clamps holding patches in place for about 20 minutes to half an hour minimum. After this, remove the clamps. The curing time for the carpenter's glue is usually from 6 to 8 hours. Do not replace the key before it is sufficiently cured; this will ensure a strong bond that will withstand force when the key will be struck.

After a successful curing, your key is ready to be put back in place. Notice that the patches are thin enough so as not to add too much width and are well-balanced and strong enough to withstand force.


More Useful Advice

  • How to Open an Upright Piano
    This article will show you how to open an upright/studio/vertical piano, to give access to the hammer action mechanism, keys and the strings for examining/repair/maintanence purposes.


Dale Anderson from The High Seas on September 05, 2020:

We had a piano in our living room when I was growing up (a stand-up piano) and my grandmother used to play it sometimes. It was a magical experience that I will always remember.

Steinway Restoration on June 10, 2013:

Good write up and a valid repair!

Cam on May 26, 2013:

Hi Ruth, I have 2 which also stay flat at the Jack Spring requires replacing on mine to fix them. You may have the same problem.

ruth on August 02, 2012:

my piano have several keys that are flat... they won't stay do i fix this? it is upright older piano

Anna on December 19, 2011:

I wounder, how to move this thing it is pretty heavy. LOL. My piano was small and I still had to hire guys to help with moving. That was a scene.

John on October 04, 2010:

I performed this repair, the crack was in the same exact area as you indicate there. One thing I found (which required me to redo this) was you had to clamp the keystick down on a flat surface like a glass table, something you know to be flat. I found after performing this repair, the key had a slight bend it it. After clamping the key down to a table (so clamping it down horizondally as well as vertically. I was able to prevent any keydip on the finished product.

Nasah on September 03, 2009:

Very fine job