Hammer Head Filing-an in depth look

Hammer Head Filing

See our article at http://brighamspianoservice.com/depth-look-hammer-head-filing/ for a brief introduction to hammer head filing.

The hammers in a piano are somewhat like the mallets used to play a xylophone, except that in a piano each of the 88 notes of the instrument has its own separate mallet, of hammer. When a key is played, the chosen hammer swings on a pivot point and strikes the strings, resulting in a tone. Hammers, strings and soundboard are the three vital factors in the quality of this tone.

Of these three components of tone production, the hammer heads over time often become the weakest link. The hammers of the acoustic piano receive more punishment than any other part inside the action of the piano. They take a beating, day-in, day-out basis. Over time, they will begin to wear out. It is a slow but steady process.

However, there is good news! Frequently a set of hammers, even on many older piano, can be given a new lease on life with a careful filing. While in cases of severe wear and tear, hammers sometimes must be duplicated and replaced (a more costly procedure), usually hammer heads can be improved and returned to service.

In the picture below (to the right), you will notice the outer surface of the hammer head is rounded smoothly. The striking surface has no indentation. Over time, as the hammer repeatedly strikes the steel strings of the note it is matched with, the metal strings begin to bite into the stiff felt of the hammer. As more and more fibers in the hammer are broken over time, the cuts become deeper and deeper.

When a hammer with deep cuts from years of hard playing strikes it has a mushy feel. The felt of the hammer, instead of delivering a clean blow to the strings, wraps around the strings upon point of impact producing an unsatisfactory tone. Compare the tone made by a hammer in this condition to that which would be produced by an accomplished violinist trying to play her instrument while wearing a wooly mitten on her left hand. No matter her level of skill, the results would be poor. The good news is that this outer wear layer is covering good felt underneath. If enough of the original felt remains, a skillful reshaping in combination with careful voicing can return much of what has been lost in the tonal quality of the piano.

These cut marks will effect the tone negatively because the broken fibers in the hammer head have no tension, and the hammer over time becomes encased in a mushy, dead layer of felt, which does not have the resiliency, or bounce, of its original surface. What's more, if the cuts are allowed to deepen, the hammer does not impart a clean blow to the strings, but instead wraps around the strings, producing a tone that is inferior in comparison with how the piano sounded when new. Skillful shaping of hammers done by a professional can produce very positive results, if enough of the original felt remains to work with.

A hammer that has been carefully will strike the strings with a clean blow, delivering maximum power to the strings without producing the weird overtones created by a worn hammer as the felt "fingers" wrap around the strings. When skillfully done, reshaping a set of hammers by filing off the wear layer may produce a drastic improvement in tone. There are other considerations which need to be accounted for, such as a slight lessening of the mass of the hammer and a change in the distance of the hammer line to the strings plus the voicing that should be done in conjunction with shaping,and this work should only be done by a professional piano technician. By hiring a qualified technician to do this work, you are making a wise decision in keeping your piano performing up to its potential.

Not every set of hammers can be reconditioned by filing. If they have suffered extreme wear and tear resurfacing would be impossible. Although it is at times a judgment call whether there is enough felt left to work with, there are times in which there is no use in trying to do anything with a set of hammers that has long out-lasted its usefulness. The hammers on your instrument  are probably not in such a sorry shape and may be successfully filed, a more economical repair than total replacement.  The work could be done either in your home or in a workshop, whichever suits you the best. While it is necessary to remove the action from the piano, it is at times possible to work on the hammers in a client's home.

Is this a job that someone could do themselves? While there are a few simple maintenance chores that every piano owner should know how to perform (such as knowing how to adjust the sustain pedal), filing hammers would definitely not be on the list of projects for a do-it-yourselfer to try. A badly done filing of a set of hammers would do far more harm than good to the tonal qualities of a piano. Gauging exactly how much felt to remove to achieve the best results takes a skillful hand and eye that come with experience.

The sanding technique involves a great deal of practice to perfect and should only be performed by a professional. In addition to filing, voicing the hammers will be needed to complete the job. This involved using special tools to adjust the hardness of the hammers.

If you would like to learn more about hammer head filing, or would like to schedule a tuning or repair from one of our expert technicians, please give us a call at 801-701-0113 or visit our website at brighamlarsonpianos.com. We would love to discuss the best maintenance program for you and your pianos to get it sounding its very best! We also carry a variety of new and used pianos if you are looking to upgrade the piano you already have.

#piano #pianorepair