As previously mentioned, most of the in-
dications found during inspection of the
crankshaft are harmless. The two types
of indications to look for are circumfer-
ential fillet cracks at the critical areas
and 45 cracks (45 with the axis of the
shaft) starting from either the critical
fillet locations or the connecting rod
journal holes as shown in Figure 11B-72.
Replace the crankshaft when cracks of
this nature are found.
Crankshaft Grinding
In addition to the standard size main and
connecting rod bearings, 0.002", 0.010",
0.020" and 0.030" undersize bearings are
available.
Figure 11B-72. Crankshaft Fatigue
NOTE
Cracks
The 0.002" undersize bearings are
6. If the thrust surfaces of the crank-
used only to compensate for slight
shaft
(Figure
11B-76
on
page
11B-50)
wear on crankshafts on which re-
are worn or grooved excessively, they
grinding is unnecessary.
must be reground and polished.
Care
must be taken to leave a 0.130" to 0.160"
If the crankshaft is to be reground, pro-
ceed as follows:
1. Compare the crankshaft journal meas-
urements taken during inspection with
the dimensions in Figure 11B-73 and de-
termine the size to which the journals are
to be reground.
2. If one or more main connecting rod
journals require grinding, then grind all
of the main journals or all of the connect-
ing rod journals to the same required
size.
3. All journal fillets must have a 0.130"
to 0.160" radius between the crank cheek
and the journal and must not have any
sharp grind marks (see Figure 11B-74 on
page 11B-50).
The fillet must blend
smoothly into the journal and the crank
cheek and must be free of scratches.
The radius may be checked with a fillet
gauge.
4. Care must be taken to avoid localized
heating which often produces grinding
cracks. Cool the crankshaft while grind-
using coolant generously.
Do not
ing,
crowd the grinding wheel into the work.
5. Polish the ground surfaces to 8-12
RMS finish.
The reground journals will
be subject to excessive wear unless pol-
F i g u r e 118-73. Dimension of
i s h e d smooth.
Crankshaft Journals
E n g i n e (Less Major Assemblies)
