TM 55-1930-209-14&P-21
(3)
Refer to Table 1-1 and measure all connecting rod journals at several different places on circumference in
order to determine smallest diameter.
NOTE
If runout is out of limits on main or connecting rod journals, replace crankshaft.
(4)
Used crankshafts sometimes show a certain amount of ridging caused by a groove in upper main bearing
shell. Remove ridges before new bearing shells are installed. Slight ridges may be cleaned up with 120 grit emery cloth,
followed by 240 grit emery cloth. Rotate crankshaft at intervals to avoid polishing in flat spots. Finally, polish surface
with a fine crocus cloth with fuel oil. If grooves cannot be removed in this manner, crankshaft must be reground or
replaced.
(5)
Inspect surface of crankshaft for evidence of cracks. To be effective, this inspection should be performed
using magnetic particle, fluorescent dye penetrant or a similar inspection technique. Demagnetize crankshaft following
use of magnetic particle inspections. Inspection must be performed if engine has experienced catastrophic failure such
as piston or connecting rod failure. Inspection should also be performed in course of engine overhaul. Replace a
crankshaft that is cracked.
(6)
Inspect crankshaft for excessive binding or twisting. Certain areas are critical and sustain most of load.
These areas are indicated by arrows in Figure 6-31.
(7)
Inspect crankshafts for circumferential fillet cracks. Check all fillets for smoothness. Journal fillets should
have a 0. 130 to 0. 160 inch radius.
(8)
Inspect crankshaft keyway for evidence of cracks or worn condition.
(9)
Inspect crankshaft in area at front and rear oil seal contact surfaces for evidence of roughness or grooving.
Slight ridges of more than 0. 0002 inch must be removed. Use crocus cloth, dampened with fuel oil. Ridges of more
than .0005 inch must be removed with 120 grit emery cloth and finished with 240 grit emery cloth followed by wet crocus
cloth.
(10)
Excessive wear or grooving on front and rear crankshaft oil seal area may require use of an oil seal sleeve.
This sleeve can be pressed on crankshaft. This sleeve provides a replaceable wear surface for lip type oil seal.
However, an oversize oil seal must be used with this sleeve.
6-72
