TM 5-3805-281-24-2
Crankshaft, Main Bearings, and Flywheel
CRANKSHAFT GRINDING GUIDELINES
blend smoothly into the journal and
IMPORTANT: Crankshaft grinding should be done
crank cheek. Check the radii with a
ONLY be experienced personnel on
fillet gauge.
equipment capable of maintaining
crankshaft size and finish
Care must be taken to avoid
specifications.
localized heating which often
produces grinding cracks. Cool the
Crankshaft rod (pin) journals have
crankshaft while grinding by using
an undercut fillet radius. DO NOT
coolant generously. DO NOT crowd
grind within this undercut area when
the grinding wheel into the work.
undersize bearings are used.
Grind crankshaft with journals
In addition to the standard size main bearings, 0.292
turning counterclockwise, as viewed
mm (0.0115 in.) and 0.552 mm (0.0217 in.) undersize
from the front end of the crankshaft.
bearings are available for main bearing journals. Rod
Lap or polish journals in opposite
(pin) journals have only 0.292 mm (0.0115 in.)
direction of grinding.
undersize bearings only. If journals are tapered,
out-of-round, scored, or damaged, grind the crankshaft
3. Polish or lap the ground surfaces to the specified
and install the proper undersize bearings.
finish to prevent excessive wear of the journals.
IMPORTANT: If undersize bearings are used,
NOTE: Production crankshafts are induction hardened
check bearing clearance after
and shotpeened at the factory. Field
bearing caps have been tightened to
shotpeening is not recommended due to the
specified torque. If undersize
equipment required and part geometry.
bearings are too tight and clearance
is not within specifications, the
journal and bearing will be wiped
4. If the thrust surfaces of the crankshaft are worn or
clean of all oil. This would result in
grooved excessively, regrind and polish. Maintain
premature wear of parts.
the specified radius between each thrust surface
and the bearing journal. An oversized thrust washer
If the crankshaft is to be reground, use the following
and two 0.18 mm (0.007 in.) oversized washers are
recommended guidelines:
available. (See THRUST BEARING NEW PART
SPECIFICATIONS, earlier in this group.)
1. Compare the crankshaft journal measurements
NOTE: When thrust surfaces are reground and an
taken during inspection and determine the size to
oversized washer is used, crankshaft end play
which the journals are to be reground.
specification must be maintained to within
0.038--0.380 mm (0.0015--0.0150 in.). (See
2. Grind all main journals or all connecting rod
CHECK CRANKSHAFT END PLAY, earlier in
journals to the same required size. (See
this group.)
CRANKSHAFT GRINDING SPECIFICATIONS next
page.)
5. Stone the edge of all oil holes in the journal
IMPORTANT: All main journal (tangential) fillets
surfaces smooth to provide a radius of
radii must be free of any sharp grind
approximately 1.50 mm (0.060 in.).
marks or scratches. The fillet must
Continued on next page
RG,RG34710,1175
1923OCT971/2
