Support the crankshaft in V blocks and use a dial indicator to check full length alignment (A, Figure 9-39), short
bend alignment (B), and nose section and flywheel pilot runout (C).
If the TIR for full length alignment exceeds 0.002 inch (0.05 mm), straighten the crankshaft in accordance with
step e, below.
If the TIR between adjacent main bearing journals exceeds O.002 inch (0.005 mm) correct for short bend
alignment in accordance with step e, below.
If the TIR of the nose section or flywheel pilot exceeds 0.001 inch (0.03 mm), correct the runout in accordance
with step e, below.
If the crankshaft gear was not removed, position the dial indicator on the gear teeth and check the runout. If the
TIR exceeds 0.001 inch (0.03 mm), remove the gear in accordance with paragraph 9-18, and check the gear step
in accordance with step (6), below.
Visually inspect the gear step for physical damage, and measure the step size (A, Figure 9-40) and keyway width
If the step size and keyway width are not in accordance with the dimensions given in Figure 9-40, the step shall
be chrome-plated and ground to size in accordance with step f, below.
Inspect the counterweight capscrew holes and pipe plug holes for damaged or stripped threads. The repair of
stripped threads shall be limited to three repairs per crankshaft. Repair stripped holes in accordance with
Inspect the front and rear seal surfaces for grooving caused by the seal lip. If grooving exceeds 0.005 inch (0.13
mm), install a wear sleeve in accordance with paragraph 9-28.
Using an outside micrometer, measure and record the connecting rod and main bearing journal diameters
(Figure 9-41). Using these measurements, determine the feasibility of using the crankshaft as is, or grinding to
one of the standard undersizes given in Figure 9-41. Grind the journals as necessary in accordance with step f,
If any journals show a blue or straw discoloration, heat damage may have occurred. Test these journals using
scleroscope hardness tester ST-1196. Crankshaft surface hardness should be 40 to 52 Rockwell, and core
hardness is approximately 26 Rockwell. Make several tests in different areas of the suspected journal until
consistent readings are obtained. If any area tests below 40 Rockwell, mark that journal for a trial grind and
retest. In many cases heat damage is restricted to the surface and the crankshaft can be saved.
Inspect the crankshaft using fluorescent magnetic partide inspection in accordance with MIL-1-6868. Use
magnetic inspection unit MIL-M-6867, Type Ill, having a contact head opening of 96 inches (243.8 cm) and a 20
inch (50.8 cm) coil. Mount the crankshaft between the contact heads and inspect as follows:
Apply at least three successive head shots of 1800 amperes for a duration of 1/2 second each.
Examine the crankshaft under black light for longitudinal cracks in accordance with A, Figure 9-42. The
limits of acceptability shall be in accordance with Figure 9-43. Replace the crankshaft if it is defective.
Apply at least eight coil shots along the length of the crankshaft using 4500 to 5000 ampere turns.
Examine the crankshaft under black light for transverse cracks in accordance with B, Figure 9-42. The
limits of acceptability shall be in accordance with Figure 943. Replace the crankshaft if it is defective.
If the crankshaft is acceptable, degauss it by activating the demagnetizing cycle before removing it from
the inspection unit. Test for residual magnetism at several locations using a magnetic field indicator. The
residual magnetism shall not exceed 3 oersteds (239 A/m).
If the crankshaft is to be returned to service at this point, dean it thoroughly in accordance with step c, above.