If you are looking for a used piano to buy and don't want to spend much money, chances are, there are probably a great number of used pianos in your city or region, either waiting to be tossed away or sold for a meager price to free some household space. 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 to no skills, you can make some of these repairs on your own, save money and get acquinted with your new instrument.

On how to open an upright piano to reach the mechanism and the keys, please read this article:

To simply put it, 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, - in its literal sense-, a broken key. Check the image below:

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) which has directly fallen onto these keys. The mechanism of a piano much 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 vains 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. Here is a list of what you will need:

• 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
  

Here is a brief walk through for you to 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 neighbouring 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 adjescent keys 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 equal distance from each end to the hole.

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

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

If the key has a crack but has not completely separated, try to apply the glue carefully with a tooth pick. 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 minimum amount of glue, and keep in mind to clean up the excess glue when the pressure is applied.

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 insure balanced weight. Apply the patches, and use two pieces of wood to apply pressure homogeneously, then fix with the clamps. Lay the key aside, wtih 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 insure 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 not to add two much width, well balanced and strong enough to withstand force.

Enjoy!