The strike point is determined, (not designed), by the placement of the action, the angle the hammer is installed on the shank, and the length of the boring. Some pianos ,in the top section ,have the string rising up from capo bar to the bridge at such angle that hanging angle AND bore distance must both be used in order to bring the angle of attack to 90 degrees. In these situations, having the hammer contact the string at ninety degrees is not possible by altering just the bore distance, ( with extremely short bore distances, you often run into regulation problems concerning the let-off buttons and stop screws, not to mention the alteration of the arc coincidence of jack and knuckle). If hammer 88 is leaned proximally in order to improve its angle of attack, the distance it must be hung out on the shank will have to be increased to keep the strike point the same. There is often room for the attendant back-check alteration in this part of the piano, though lower down will at times cause problems with Sostenueto rods. Just a few thoughts. regards Ed Foote
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