engine you will find that these two halves do not meet on the wrist pin
by at least one-eighth of an inch. They are brought up to the pin by
means of a wedge-shaped key. (I am speaking now of the most common form
of wrist boxes. If your engine should not have this key, it will have
something which serves the same purpose.) As the brasses wear you can
take up this wear by forcing the key down, which brings the two halves
nearer together. You can continue to gradually take up this wear until
you have brought them together. You will then see that it is necessary
to do something, in order to take up any more wear, and this "something"
is to take out the brasses and file about one-sixteenth of an inch off
of each brass. This will allow you another eighth of an inch to take up
in wear.

Now here is a nice little problem for you to solve and I want you to
solve it to your own satisfaction, and when you do, you will thoroughly
understand it, and to understand it is to never allow it to get you into
trouble. We started out by saying that in a new engine you would most
likely find about one-eighth of an inch between the brasses, and we said
you would finally get these brasses, or halves together, and would have
to take them out and file them. Now we have taken up one-eighth of an
inch and the result is, we have lengthened our pitman just one-sixteenth
of an inch; or in other words, the center of wrist pin and the center of
cross-head are just one-sixteenth of an inch further apart than they
were before any wear had taken place, and the piston head has
one-sixteenth of an inch more clearance at one end, and one-sixteenth of
an inch less at the other end than it had before. Now if we take out the
boxes and file them so we have, another eighth of an inch, by the time
we have taken up this wear, we will then have this distance doubled, and
we will soon have the piston head striking the end of the cylinder, and
besides, the engine will not run as smooth as it did. Half of the wear