Yamaha MM700A Manual page 34

28
a shaft and into a housing at the same time, a tight fit is re-
quired for both outer and inner bearing races. In this situa-
tion, install a spacer underneath the driver tool so that
pressure is applied evenly across both races. See Figure
58. If the outer race is not supported as shown in Figure
58, the balls will push against the outer bearing race and
damage it.
Interference f i t
1. Follow this procedure when installing a bearing over a
shaft. When a tight fit is required, the bearing inside diam-
eter will be smaller than the shaft. In this case, driving the
bearing on the shaft using normal methods may cause
bearing damage. Instead, heat the bearing before installa-
tion. Note the following:
a. Secure the shaft so it is ready for bearing installa-
tion.
b. Clean all residues from the bearing surface of the
shaft. Remove burrs with a file or sandpaper.
c. Fill a suitable pot or beaker with clean mineral oil.
Place a thermometer rated above 120' C (248º F) in
the oil. Support the thermometer so that it does not
rest on the bottom or side of the pot.
d. Remove the bearing from its wrapper and secure it
with a piece of heavy wire bent to hold it in the pot.
Hang the bearing in the pot so it does not touch the
bottom or sides of the pot.
e. Turn the heat on and monitor the thermometer.
When the oil temperature rises to approximately
120' C (248º F), remove the bearing from the pot
and quickly install it. If necessary, place a socket on
the inner bearing race and tap the hearing into place.
As the bearing chills, it will tighten on the shaft so
installation must be done quickly. Make sure the
bearing is installed completely.
2. Follow this step when installing a bearing in a housing.
Bearings are generally installed in a housing with a slight
interference fit. Driving the bearing into the housing using
normal methods may damage the housing or cause bear-
ing damage. Instead, heat the housing before the bearing
is installed. Note the following:
CAUTION
Before heating the housing in this proce-
dure, wash the housing thoroughly with de-
tergent and water. Rinse and rewash the
cases as required to remove all traces of oil
and other chemical deposits.
a. Heat the housing to approximately 212' F (100' C)
in an oven or on a hot plate. An easy way to check
that it is at the proper temperature is to place tiny
Shaft
drops of water on the housing; if they sizzle and
evaporate immediately, the temperature is correct.
Heat only one housing at a time.
CAUTION
Do not heat the housing with a propane or
acetylene torch. Never bring a flame into
contact with the bearing or housing. The di-
rect heat will destroy the case hardening of
the bearing and will likely warp the hous-
ing.
b. Remove the housing from the oven or hot plate, and
hold onto the housing with a kitchen potholder,
heavy gloves or a heavy shop cloth. It is hot!
CHAPTER ONE
Shaft