of the hammer butt, producing a sharp click, which is very annoying,
to say the least. This click is heard at the instant the key rises to
its rest position. Sometimes, however, a similar click is produced by
the top of the key striking the board which is set over the keys, due
to the cloth being eaten off by moths, or a pencil or some other
article lying on the keys back of this board.

The center pin in the butt of some cheap actions is not held in the
butt by metal clip and screw, and if it gets loose so that it works
out, must be replaced by a larger pin. The size of center pins
generally used in the factory, is .050 of an inch in diameter; the
size for repairing should be .053. All of the best actions have the
set screw with which to make the pin fast in the butt.

Hammers stick when the center pin is too tight in the flange. The
bushing in the flange often expands. Some tuners oil at the ends of
the pin with kerosene or wet it with alcohol, which is very good; but
a better plan is to shrink the bushing with a drop of water on each
side so that it will penetrate the bushing. After this is done, the
piano cannot be used for a day or two, as the water first swells the
bushing, making all the hammers stick; but when they are dry again,
they will be found free. This may seem a curious method, but you need
not be afraid of it; it is the most effective.

Before leaving the hammer butt, see that the hammer spring is in its
place.

8. _Hammer Stem_.--These sometimes warp, split, crack, or come unglued
at the butt or hammer. If twisted so far that it does not strike
properly on the strings, or that it binds against the next hammer, the