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.
The escapement lever is then considered. The spring that governs it requires adjustment. It must be sufficiently strong to cause the hammer to dance and jump a little on the lever when the key is released. The escapement lever must also be regulated by means of the hook that is found at its rear end. There must be space enough between the hook and the lever to ensure that the catch of the hammer by the check is at all times free. The screw that regulates the rise of the escapement lever must also be attended to. It is necessary that the movement of the lever be arrested before the hammer has quite risen to the point of the trip up of the jack.
The after-touch under the front of the keys is regulated by means of paper punchings. If enough punchings are placed under the keys to make very hard pressure necessary to force a release of the hammer, then punchings of 1/32 of an inch in thickness must be removed to make the after touch correct.