Hammer Mating to the Strings

When the hammer top hits all strings of one note at the same time, the maximum power is transferred. To make the adjustment, the action must have been finely regulated and the piano freshly tuned. The cheekblocks are better in place to make sure the action is at the correct position. This hammer to string mating process is learned from Mr. Eric Schandall. 

First, the hammer must be lifted to the strings. Lift up the jack toe with two fingers until the hammer head meets the strings. Press firmly without triggering the let-off. If the let-off was set too low, this lifting method may not work. Pluck the strings of this note one at a time. When well mated, the hammer should block all three strings on a tri-cord note or all two strings on a bi-cord note, and give a muffled sound, not ringing. If one string rings, the hammer top surface against this string is too low. The higher surface of this hammer, or the non ringing side, must be sanded off. Sometimes two strings may ring and one string gives a muffled sound, which means the hammer top below the two ringing strings is too low, the surface below the muffled string should be sanded. With a chalk, mark where to be sanded on the wooden part of the keys. Every technician has his/her own way for the marking.

Pull the action out and sand down the marked location. Mr. Schandall does not use special any tools for the sanding process but a sanding block. When only the middle of the hammer top needs to be reduced, simply tilt the sanding block, sand and feel. After working on a few hammers, one can develop a feeling of the sanding angle, pressure, location, etc. The sandpaper used here is of 800 grits. When finished, push the action back and place the cheekblocks. Check mating on all marked hammers. If the hammer is well mated, erase the chalk marks with solid felt, such as hammer felt. Change the chalk marks if the mating is changed but not correct yet. The whole process takes many rounds. Be patient, take many breaks. It took me about 4 hours for this newly strung piano. An experienced technician will take way less time on it.

Retune the piano after the hammers are mated to the strings. One can hear the difference. The piano should sound more powerful. Gratitude to Mr. Eric Schandall!