TM 5-3810-300-24&P-3
1.3 Crankshaft
Conn. Rod
Main Bearing
Bearing
Journal Dia.
Journal Dia.
Sizes
"A"
"B"
Standard
2.750"
3.500"
.002" Undersize
2.750"
3.500"
.010" Undersize
2.740"
3.490"
.020" Undersize
2.730"
3.480"
Fig 7. Crankshaft Journal Fillets
.030" Undersize
2.720"
3.470"
TABLE 2
wear on crankshafts on which regrinding
is unnecessary.
As previously mentioned, most of the indications found
If the crankshaft is to be reground, proceed as follows:
during inspection of the crankshaft are harmless. The
two types of indications to look for are circumferential
fillet cracks at the critical areas and 45 cracks (45 with
1. Compare the crankshaft journal measurements
taken during inspection with the dimensions in
the axis of the shaft) starting from either the critical fillet
Table 2 and Fig. 6 and determine the size to
locations or the connecting rod journal holes as shown in
which the journals are to be reground.
Fig. 5. Replace the crankshaft when cracks of this
nature are found.
2. If one or more main or connecting rod journals
require grinding, then grind all of the main
Crankshaft Grinding
journals or all of the connecting rod journals to
the same required size.
In addition to the standard size main and connecting rod
bearings, .002", .010", .020" and .030" undersize
3.
All journal fillets must have a .130" to
bearings are available.
.160" radius between the crank cheek and the journal
and must not have any sharp grind marks (Fig. 7). The
NOTE: The .002 " undersize bearings
fillet must blend smoothly into the
are used only to compensate for slight
journal and the crank cheek and must be free of
scratches. The radius may be checked with a
fillet gage.
4. Care must be taken to avoid localized heating
which often produces grinding cracks.
Fig. 8. Standard Dimension at Crankshaft
Fig. 6. Dimensions of Crankshaft Journals
Thrust Surfaces
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