Theory and Practice of Piano Construction / With a Detailed, Practical Method for Tuning

by William Braid White

CHAPTER XIII.
REGULATION OF PIANOFORTE TOUCH MECHANISM.

We may presume that the reader is by this time quite familiar with the appearance and use of the various parts of the grand and upright pianoforte action, both as assembled and detached. We may therefore proceed to give general instructions for the adjustment of these within the instrument and the regulation of the various working parts into proper harmony with one another.

We say “general instructions” advisedly; for it is quite out of the question to teach action finishing and regulating by means of written directions. Experience and the practical routine of the shop must be gone through by anyone who hopes to be able to do this kind of work well. For there are few departments of mechanical endeavor that demand such skill, care, and patience as the regulation of pianoforte mechanism.

Nevertheless the directions that we shall give in this chapter will be sufficient to make him who reads and digests them a very efficient critic. It is much to the employer to be able to estimate correctly the value of each practical detail of the construction, and the correctness of the manner in which it is executed. This chapter is intended to provide as much of this knowledge as may be imparted by means of written words.

We shall begin with the grand action, following the method that has been pursued throughout this work.

The first step in the regulating and adjustment of the grand action is taken by the “action-finisher.” He receives the action and keys separately. The former is without hammers or dampers and the latter without rockers or capstan screws. The action has to be placed within the space destined for it in the instrument and the proper position for it noted. If the action has been well made there should be no difficulty in seeing that it fits its place correctly. The action is screwed on to the key-frame through its metallic brackets and the capstan screws are put into the keys at the proper points so that they engage with the cushions on the bottom of the wippens. When this has been done the weight of the action upon any one of the keys should be noted and the action may then be removed. A piece of lead should then be taken and fastened to the back of each key. This lead must have the same weight as the action has upon each key. The keys will then remain in their proper positions when the action is removed, and the work of leveling them may then be begun. Remembering the depth of touch that was prescribed in the last chapter, let the extreme bass and treble keys be adjusted to an equivalent height by wooden blocks through their front rail pins. Then run a straight edge over the keys and proceed to adjust their levels by means of the thin paper punchings that are provided for the purpose. These come in various thicknesses and are laid over the balance rail pins and under the cloth punchings that must first have been placed in position both on the balance rail and the front rail. When the leveling is accomplished let the action be screwed on again. Then let the hammers be glued on. The striking point of the hammers must be carefully measured and the directions already given as to the striking of the highest hammer must be observed. It will be remembered that one-tenth of the string was recommended for the highest hammers, graduating down to the ideal one-ninth and one-eighth. The scale draughtsman will prepare a marking stick showing the true hammer line. The hammers are glued on absolutely at right angles to the plane of the strings. After they are dry, they must be adjusted to the proper position by the capstan screws or rockers. They must lie just over and not quite touching the wippen cushions. Let them also be aligned to each other, horizontally, with great exactness. Be sure that the keys work easily and that the depth of touch is roughly adjusted as already provided for.

It next becomes necessary to fix the damper mechanism. This is chiefly situated in the back of the action and the damper levers are to be so adjusted that they rest a little above the backs of the keys, ready to be engaged with them when the fronts of the keys are depressed. The dampers must fit on to the strings straight and must drop with sufficient force to effect an instantaneous damping. The damper levers are leaded for this purpose.

The instrument is then taken in hand by the action regulator. His work is most important. He first sees that the level of the keys is perfect and that they are properly balanced when suspended without the action. If any defects are found here they are remedied by changes in the leading. The keys should be so leaded that they balance when tested on a scale and the weight of touch with the action fitted must not be more than two and one-quarter ounces.

The alignment of the hammers is then corrected and the length of the hammer stroke, as laid down in Chapter XII, is adjusted by means of the capstan screw or rocker. The jack is so regulated by its button and screw that the trip up of the jack occurs when the hammer is ⁵⁄₃₂ of an inch from the string. The checks must catch the hammers when they have fallen three-quarters of an inch away from the strings. The tails of the hammer-moldings must be roughened and the checks be so slanted that the catch is sure and tight.