and rattle. Hammer them just enough to tighten; too much might split
the key.

5. _Friction_.--Where different materials, such as wood and felt,
would rub together they are covered with black lead to lubricate them.
The point of the jack where it comes in contact with the butt, the toe
of the jack which strikes the regulating button, and the long wooden
capstan which takes the place of the extension and works directly on
the under side of the wippen, which is covered with felt, are
black-leaded. When a key squeaks and goes down reluctantly, the
trouble can usually be traced to these places; especially to the
wooden capstan, the black lead having worn away. Use powdered black
lead on these parts.

There are many things in this kind of work that require only the
exercise of "common sense." These we have omitted to mention, treating
only of those things the student does not know intuitively.


QUESTIONS ON LESSON VI.

1. When a key snaps or clicks at the instant it is let up, give
two or more conditions that might cause it.

2. When a key simply rattles, what parts of the action would you
examine for the trouble?

3. When a key is struck and there is no response, what may be the
cause?