h bushing tried in
the space between the tail-pieces of the plates. It will probably be
found that the bushings are not of the right length, due to the
alteration of the form of the steam chest by heat. It will generally be
found also that the bushings are too short, and that the length can be
corrected by very thin washers of sheet metal. It has been found in some
instances that the thin bands coming with sectional pipe covering were
of the right thickness.

After the length of the bushings is corrected the shield-plates may be
assembled, made fast and tested by rocking them up and down, searching
for signs of sticking. If none occurs, the work has been correctly done,
and there will be no trouble from poor regulation due to friction of the
shield-plates.

The Baffler

The water which goes to the step-bearing passes through a baffler, the
latest type of which is shown by Fig. 23. It is a device for
restricting the flow of water or oil to the step- and guide-bearing. The
amount of water necessary to float the machine and lubricate the
guide-bearing having been determined by calculation and experiment, the
plug is set at that point which will give the desired flow. The plug is
a square-threaded worm, the length of which and the distance which it
enters the barrel of the baffler determining the amount of flow. The
greater the number of turns which the water must pass through in the
worm the less will flow against the step-pressure.

[Illustration: FIG. 23]

The engineers who have settled upon the flow and the pressure decided
that a flow of from 4-1/2 to 5-1/2 gallons per minute and a
step-pressure of from 425 to 450 pounds is correct. These factors are so
dependent upon each other and upon the conditions of the step-bearing
itself that they are sometimes difficult to realize in every-day work;
nor is it necessary. If the machine turns freely with a lower pressure
than that prescribed by the engineers, there is no reason for raising
this pressure; and there is only one way of doing it without reducing
the area of the step-bearing, and that is by obstructing the flow of
water in the step-bearing itself.

A very common method used is that of grinding. The machine is run at
about one-third speed and the step-water shut off for 15 or 20 seconds.
This causes grooves and ridges on the faces of the step-bearing blocks,
due to their grinding on each other, which obstruct the flow of water
between the faces and thus rais