At first thought the oil in gear
cases is there primarily to serve gear
sets. However, lubrication of bearings is often of equal importance. In
circulating systems an oil supply can be provided for bearings no matter what
the location. Bath or splash systems pose a different problem. Here troughs may
have to be provided to direct oil to bearings, or flingers dipping into the
oil, in addition to the gears, may be necessary.
If the gear runs
on a bearing and oil holes are drilled from the
roots of the gear teeth with the thought that
this will provide oil, Merritt^34 mentions that this will
be quite deceptive. Thus, the oil will flow outward due to
centrifugal force and will flow inward only if the gear is stationary. Such
holes, if they do not seriously weaken the gear
teeth, can be used to lead oil outward from
a supply at the center of a hollow shaft.
