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27. Piano Hammer-
Reattaching Hammer Head Felt


We sell all your repair needs for Hammer Repair in the Catalog.

Repairing a broken hammer is now covered at:
25. Piano Hammer- Broken Shank

Reattaching the felt head of the hammer
to the wood molding

Suggested tools:

Small "C" clamp
Strong but not too thick steel wire (not piano string)
1/16 inch drill bit and battery operated drill motor

The problem under discussion is when the felt of the hammer breaks loose from the wood molding, and it pops up and hangs away from the hammer at an angle. It is rare for the hammer felt to come clear off, but this can happen. In this case, the felt may be in the bottom of the piano.

When hammers are made, a long piece of lamb's wool felt, about 48 inches long, is laid on a work table and shaped. This felt is extremely compacted when it is made. The craftsman tapers the felt piece so that the final desired taper from bass to treble hammers is shaped into the piece of felt. The felt piece is placed into a large powerful machine. Then an equally long piece of tapered wood is placed in the machine. The machine squeezes the felt into a "U" shape around the long piece of wood. The curved slab of wool is attached to the wood piece with glue. "T" shaped staples are then popped into the thing vertically, all along the way, at precise intervals.

The wood and felt piece is then taken to a jig saw type machine, and the long piece is then sawed into 88 individual pieces. The end result is the hammers you see in your piano.

Now, what happened to your hammers is that age took a toll on your piano. The glue deteriorated and let go. Also, some companies had trouble with the staples, which were not done in graduations enough, and some staples did not go through far enough to hold indefinitely. Some companies even decided to not put staples in all 88 of the hammers. This is very stupid, for a little more effort on their part might have kept you from having this trouble.

Now, we know what happened, but what do we do next? The sound of the hammer is terrible, and a replacement would be in order. The problem is, a new hammer might be almost as much trouble as the fix. So, here goes.

Take the hammer assembly out of the piano by removing the bridle strap, and take the screw out which holds the hammer butt flange in place. Fish the hammer assembly out.

Put a generous layer of Elmer's carpenter's glue between the felt which broke off and the wood molding. If the whole felt popped off, put glue on both top and bottom of the wood molding where the felt was attached.

Use a bench vise, small hobbyist's vise you can hold, or a small "C" clamp to compress the hammer felt back down into place. Position the clamp so that it is centered in the approximate middle of the hammer felt, and leave some room at the back end of the felt to work. If the whole felt popped off, keep pressure on the front of the felt hammer as you tighten the "C" clamp so that the felt is back into the wood molding as tight as possible. If attaching a felt piece which came clear off, it would be best if you had a third hand. This is being developed in the basement at MIT by a mad PhD :-)

With a maximum 1/16 inch drill bit, and a smallish electric drill motor, drill two holes in the felt side by side. a Dremel drill would be ideal for control if you have one. Just be sure not to also drill through your finger. This is not necessary at all really. The holes must be about one half to 3/8 inch back from the end of the back end of the felt. They also must go all the way through the top felt, the wood, and the bottom felt VERTICALLY. I try to space them so that they divide the hammer, viewed from above, into thirds from side to side.

Now, make a "U" of a piece of thin piano wire, or use a rather stiff piece of regular wire of some sort. Copper is not strong enough. Fish the "U" or wire down through the two holes so that a tail hangs out underneath. Figure this out for total length of the wire before you cut the wire in the first place. Once the wire is hanging out underneath, grab the two tails with heavy pliers, and twist the tails together. Twist until you figure you are pretty close to breaking the wire. A little crush into the felt on top is in order to be sure you really are helping by doing the wire trick. If the wire does not break though, don't twist so much that you cut through the felt. This is to replace the staple that was not done well or is completely missing on some cheap pianos.

Once you have twisted the wire, cut off the excess, and leave about 3/8 inch of the tail. Then push the tail to the side flat against the felt-- bend it so that it lays down out of the way. At this point, the wire will often break, and you will get to start over. This makes the job so much more interesting, and you get to groan and moan and seek sympathy and cups of tea or coffee from anyone nearby who has any decent sympathy for you :-)

Here is a little song which you can hum to and calm your nerves as you break one of those twisties three times in a row.

The thing is done now. It is not 100% as to sound, but close, and I have done many of these. Don't let your tuner tell you this is not a good plan. It works, and it will at least get you through to a formal repair later.

  On to task 29