The procedure I use is similar to Ed's. The .0030 punching (or whatever your target is) is cut so that it can be slipped in and out from under the key easily. The permanent punchings are built up until one achieves escapement (hammer just falls) with moderate pressure on the key. Thus the aftertouch (key travel after escapement) will be equal to the thickness of your removable punching. David Love www.davidlovepianos.com -----Original Message----- From: Fred Sturm <fssturm at unm.edu> Sender: caut-bounces at ptg.org Date: Mon, 13 Dec 2010 14:48:01 To: College & University Technicians<caut at ptg.org> Reply-To: caut at ptg.org Subject: [CAUT] aftertouch (was Re: F..riction) On Dec 13, 2010, at 2:00 PM, David Love wrote: > This system is a good one and gives very uniform AT. I like .030 but > you do need to stay on top of the blow distance. With this kind of precision in measurement, it is important to know exactly from where you are measuring. I assume it is from the very moment of (or really barely before) escapement, or when the jack reaches its very highest point. The point of contact of drop screw and jack tender comes a little earlier, as another possible place to measure, and one can also measure from the point at which the jack has just finished escaping. With a gauge under the key, the key hits the gauge and the jack is at its highest. Squeeze the punching and escapement starts immediately. At least that is how I do that when I do it (which is rarely). For myself, I like to feel through the contact point, compression of springs, rubbing of the jack along the knuckle (all of which are tactile resistance of one kind and another), and then feel a free drop of key of a certain range of size, which is really a tactile judgment (and negotiable within limits). With a relaxed and sensitive hand lay the fingers on a series of keys (3 - 5, naturals separately from sharps), with damper pedal depressed, lower the keys until you feel the contact point (observe how high the hammers are, something like 4 - 5 mm from the strings). Now press through each finger in turn, feeling for an even "bump." With practice, you can feel variations of . 005-.010". It's a good way to even naturals and sharps. Final check is to take each key through escapement (slowly and controlled) and then press to the bottom and compress the front punching a bit. The hammers should each rise from drop the same amount, not much but definitely some (1 mm?). Regards, Fred Sturm fssturm at unm.edu "Travel is fatal to prejudice, bigotry, and narrow-mindedness." Twain
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