Section III. Alignments
27) Align hammers to strings
To facilitate this alignment procedure, install the action into the piano and make a rough check of the let-off measurement. If the let-off is very far from the strings, the hammer-to-string alignment will be very hard to make. So try adjusting the let-off by say one-half or one complete turn of the adjusting screw and see what number of turns it takes to get the hammer to let-off right next to the string.
At this point in the regulation procedure, if the hammer blocks on the string, it will be all the easier to make the alignment. Then remove the action and turn all of the let-off screws the number of turns that you found necessary to get the hammer closer to the strings.
Before starting to centre the hammer to the strings, make sure that the hammers have been filed, removing all traces of former string grooves. If the piano has agraffes, then your job will only be to align the hammers to the strings. If the piano does not have string aligning mechanisms throughout, then you must make sure that the strings are properly spaced and centred before attempting to align any hammers.
Normally, unless the plate has been repositioned or a bridge reglued onto the soundboard, there should be a straight line running from the hitch pin through the bridge pins and on to the tuning pin hole in the plate. The middle string of a trichord should run along this line, with the right and left strings having the same inward pointing angle, since the bridge pins are wider spaced than the spacing at the V bar.
Begin aligning the hammers to the strings by taking a wire hook and coming down from the strings, lifting the shank so that the hammer blocks on the string. Or, take a finger and lift the bottom of the whippen taking the hammer past let-off and pushing up until the hammer again blocks on the string. I prefer the latter method since the wire hook is slower and can cause the hammer to be pulled to one side if you are not careful.
Looking directly above the hammer, check to see, if it is properly centred to the strings. For a trichord, equal amounts of hammer should be seen on both sides of the unison. On single or double unisons, the hammer can either be likewise centred, or they can favour the bass side a little, depending upon how you want the hammer to strike when using the una corda pedal.
Any hammers which are properly centred on the strings, I mark with an “O” on the key with a piece of chalk. Those which are off to one side, l mark with a straight line on the key to the side which they need to go, varying the thickness of the chalk mark as the amount the hammer needs to be moved. Do one section at a time.
Pull the action out after chalking all of the keys, and compare the marks with the way the hammers look. All of the chalk marks must coincide with either a perfectly centred hammer or else a hammer that needs to be traveled, angled, spaced, or a combination of these three.
Place a long screwdriver blade or other object such as a spare pedal rod under all of the shanks in this section and check the hammers first for traveling. Even though a key was marked “O” the hammer may be traveling or have the incorrect angle. After correcting the traveling, heat the shanks of those traveled along with any others whose angle needs to be changed until all of the hammer angles look uniform. Lastly, space the hammer by slightly moving the flange sideways.
If the flanges are of the type where a screwdriver or flange spacer can be used, install the action into the piano and space the flanges directly by lifting up the hammer until it blocks on the string. If the flanges are not of this type, then they must be spaced outside of the piano. Use the width of the chalk marks as a guide to how far to move the flange, and try to use any keys marked with the “O” as a point of departure.  
I get two keys about five or six keys apart marked with the “O” and work from these, putting t action back into the piano and making any needed refinements.
Remember that some manufacturers have a two degree tilt hammer on the shank. The more the hammer was bored at an angle to match the angle of the strings, the more likely it is the hammers will have to be tilted on the shank to properly space the hammer to the string and to make sure the tails do not interfere with the adjacent hammers.
Centre all of the hammers in each section in the manner shown. If someone altered the plate sideways, for instance when installing a new pinblock, or if a soundboard was replaced and the bridges are a little off to one side, good luck!
28) Align and square whippens to the knuckle
Ideally, when the shank and flange assembly is made, the bottom of the flange should be perfectly flat and the birds-eye be drilled correctly so that the centre pin is perfectly horizontal. The shank bushings should be perfectly fitted so that the bisects the shank, and of course, the knuckle should be ungrooved and perfectly round, being glued onto the shank squarely. Such an assembly would have no need to be traveled, making the knuckle tilt the one side. Sweet dreams.
What happens when a tilted knuckle receives a strong blow from the jack? If the jack is also at the same tilt, very little power is lost, and rather little wear results. But when the jack is not on the same plane as the knuckle, power is lost and abnormal wear results. Every time the jack hits the knuckle, the power from the key is transmitted by the tip of the jack to the knuckle, not by the whole top surface of the jack. Power is lost here. Worse yet, the jack centre pin and bushing take a beating. Likewise, the knuckles wear at one spot since the corner of the jack inflicts the blow. The shank then is given a twisting motion at the centre pin instead of an even straight blow, again resulting in a loss power and abnormal wear to the shank bushing. The best relationship is when the whippen and thereby the jack is tilted to match the tilt of the knuckle.
Granted, tilting the whippen results in the capstan no longer hitting the whippen felt squarely, and the whippen centre pin and bushing get a little twisting motion. But remember, the capstan is rounded, so the whippen felt is not abnormally worn. Also, keep in mind that the arc of travel for the whippen is far less than the shank, and the whippen centre pin is further from the transmission of power than the hammershank centre. The lesser of evils is definitely to tilt the whippen.
Therefore, when spacing the balanciers to the knuckle, look at two things:
1) Does the tilt of the whippen need to be changed to match the tilt of the jack?
2) Should the whippen be moved sideways to keep the capstan centred under the whippen felt?
If tilting the whippen aligns both the knuckle to the balancier and the whippen felt to the capstan, all is well. But, if tilting the whippen puts the knuckle in line at the balancier and not the capstan at the whippen felt, then compromise. The balancier must always be centred with the knuckle, even if the tilt of the jack does not exactly match that of the knuckle. The capstan can be a little off to the centre of the whip much as to cause the capstan to be on the edge of the whippen felt.
To tilt the whippen, loosen the flange screw and tilt, then retighten the screw. Sometimes the flange must be papered underneath on one side. To space the whippen sideways, remove the flange and paper the flange on the side that you wish the whippen to move. This is the opposite to papering a hammershank flange. For ease in removing the whippen flanges, it is best to remove the hammer rest rail first, if there is one. 
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