Section III. Alignments
29) Align jack to knuckle core
In order for the power to be transmitted from the whippen to the hammershank efficiently, the jack must be properly aligned under the knuckle.
Looking at the action sideways, the rear of the jack (the surface towards the hammer) should line up perfectly with the rear of the knuckle core. Normally, this alignment is easy to see. The knuckle should be glued on perpendicular to the shank, and if the hammer is new and was bored correctly, the shank should be perpendicular to the jack. Sighting along the rear of the jack, it should be easy to tell when the jack is in line with the knuckle core.
However, if the shank is not perpendicular to the jack this alignment is hard to see. Two things can cause this:
A. The hammer has worn resulting in the capstan being turned up to keep the blow distance close enough. The shank then becomes more than 90 degrees from the rear of the jack. In such cases, imagine a line drawn from the rear of the knuckle core down to the point on the knuckle leather where the jack would touch it. Then line up the rear of the jack to this point.
B. The other reason, which is fairly common, is that the hammer hole was not placed correctly in the molding. This results in the top of the hammer, either, being too high, or too low in relation to a line drawn down the middle of the hammershank.
Boring the hammer wrong of course results in the shank not being perpendicular to the jack as in cause A. If this angle of the shank to the jack becomes too great, then either the hammer has worn excessively so that it should be replaced, or if the hammers are new, then the hole in the molding should be plugged and rebored.
Why was the hammer bored incorrectly? Have you ever noticed when regulating the hammer-blow distance, that when the tops of the hammers are adjusted so they all are, say, 1 3/4” from the strings at rest, that the hammers in each section vary as to their heights measured from the keybed to the top of the hammers?
We should expect the bass hammers to be higher since the bass strings are higher so they can cross over the tenor strings. But notice that if the agraffes are not the same height as the capo d’astro, the hammers will also vary in their heights between these sections.
If the original or duplicate hammers were not bored taking into account these different string heights, then the hammershanks will not be perpendicular to the jacks with the hammers at rest.
We will discuss this problem further in a later post on hammers, but let me add here that some pianos have a different string height for each section!
An easy way to align all of the jacks is to align the end hammers in each section, and then by using a straightedge or a thread, align the jacks in the respective sections to the end samples.
Note that some manufacturers mark a line on top of the balanciers. This line serves as a guide only when the action parts are being assembled in the factory. If it is necessary to deviate from this line, don’t hesitate.
To test the jack alignment, hold the hammer with one hand to keep it from coming up, and with the other hand, give the key a strong blow. If the jack is too far in or out in relation to the knuckle core, the jack will slip out from the force of the blow given to the key. This test should be given to all 88 keys.
When the knuckles are all in a straight line, and if all of the jack tops are also in a straight line, this test should prove out on every key.
But many pianos made today do not have all of the knuckles lined up perfectly, some being out of line by an 1/8“! For these pianos, the jacks must be individually aligned to their respective knuckle cores.
Remember in replacing a whole set of shanks and flanges, the knuckles must be the same size as the original, and the distance from the centre pin to the centre of the knuckle core must be identical.
30) Align and square backchecks to hammer tails.
To facilitate this regulation, turn the action around so the backchecks are facing you. Individually lift the end of the key and wait for the hammer to come into check. Don’t lift the key so forcibly that the hammershank is marred by hitting against the drop screw, or actually broken off from the impact! Look to see if the hammer tail is caught in the middle of the backcheck and that the backcheck is square and aligned to the hammer molding.
To correct the side-to-side alignment, first bend the backcheck wire at the bottom to the right or to the left as needed, then bend it at the top to square the backcheck with the tail. This procedure is the same as when bending damper wires.
Check to see if the backcheek is turned or if the hammer tail was not filed properly on angled hammers. The two should be adjusted or filed so the stress on the key when the hammer goes into check is in line with the key itself.
Some imported pianos from Asia were made with the backchecks turned to meet the angle of the tails in the bass and tenor sections. This stressed not only the key bushings but also the hammer centre.
File these tails square to the ends of the keys as they should be, and turn the backchecks so they are square to the tails. If the tails are not filed properly, the protruding corner of the tail will cut into the backcheck leather in no time.
While aligning, make certain that the tails are roughed up enough to keep the hammer securely caught by the backcheck. I use 60-grit, open-coat sandpaper glued on to a hand file for roughing up old hammers. New hammers I rough up before they are glued onto the shanks. I would caution use of coarse files or moto-tool saw blades to roughen up tails, as these make the tails so rough they wear the leather out prematurely.
This ends the third section of our 50-point procedure. At the beginningof this series of posts about grand regulation, I mentioned that section IV, The Touch, was the most variable part of the regulation, and that depending upon the needs of the action, the sequence may be changed.
In the first post on grand regulation, I included a chart which shows how the different regulations of The Touch affect or are affected by the others. A quick glance at this chart reveals that three steps: A. the key height, B. the key dip, and C. the blow distance affect or are affected by the others the most.
Before we begin talking about all the steps in section IV, let us discuss how to get the correct relationship of these three steps. Without doing this first, the regulator can waste many hours on section IV trying to figure out why the action does not play at its peak performance.
Way back in step 12 in section I, we adjusted the keyheight. All that remains here is to adjust the blow and the dip. l will explain two methods to regulate a grand piano. One is the blow-priority method; the other is the dip-priority.
I contend that once the keyheight is set, one only needs to set the dip or the blow, and the remainder of the action can be regulated to peak performance, straight through, with little or no doubling back to alter previously set measurements. In the next post, we will continue with a discussion of these two methods.
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