Saturday, June 18, 2011

Hammer Shaping: The Neglected Hammer Set

The modern piano action and keyboard have some 8000 or more moving parts. This mechanism is subject to gravity and therefore wear upon regular use; without being maintained correctly at regular intervals, the geometry of the keyboard and action wear,  resulting in an instrument that does not respond to play correctly, or sound good.

Because the acoustic piano is mechanical not digital, this means that there are a lot of moving parts within the action and keyboard that have contact or friction points. These points must be checked, maintained, and lubricated on a regular basis. 

The technician will often encounter a piano where the tuning has been maintained by regular service while the mechanics of the instrument, the keyboard and action, have not been maintained, or serviced on a regular basis.  The result of this neglect is the often heard complaint that the instrument has poor touch control, and the tone of the piano leaves much to be desired.

One of the first places to reveal a neglected piano is to inspect the hammer set at the strike point. This is the area of the hammer that comes into contact with the strings of the piano and is the area of the piano hammer that is subject to the most wear.

 To improve tone and touch control, one of the first things to accomplish is to have the hammer set shaped back to the original contour when the hammer set was new.  Shaping the hammer set back to original specifications improves the way that the hammer comes into contact with the strings when the piano is played. This will improve the tone of the piano immediately.

At times this task is problematic, especially in older pianos that have suffered without regular maintenance. Many of the older tall uprights or vintage grand’s would require a new set of hammers; the cost of that restorative work is often exceeding the financial value of the instrument in question.
Here is a hammer set that is badly worn and really should be replaced. Because this is an older tall upright the choice is to shape the hammer set as the cost of a new hammer set exceeds the value of the instrument.  At the same time as the hammer shaping takes place, I also show other repairs being performed as the action is already dismantled.

First there is the rough shaping of the hammer set to remove all of the damage caused by the felt hammer head striking the metal string over years.

Following the rough shaping of the piano hammers, the entire set then must be gang shaped with a wide piece of sandpaper. When shaping hammers individually with a block sanding device, it is impossible to keep the strike line even and the same on each hammer head. Failing to gang file the hammer set will leave the strike line uneven from one hammer to the next; the result being that the tone quality will vary greatly from each hammer.

The following photos show the process of rough hammer shaping. There is a video short of the wrist technique required to perform this task.

 After rough hammer shaping there are  photos of gang filing to even out the strike point of the hammer set.

Following photo 21 there is a 5 minute video of one of the world’s top concert technicians using this technique to shape a new set of hammers.

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