Crankpin bearing Clearance:

.crank pin bearing clearence   .cpbc    .bebc    .bbc

→ Turn the concerned crank to BDC

Measure the clearance in the crankpin bearing by inserting a feeler gauge at the bottom of the bearing shell on both sides

The wear limit for the crankpin bearing shells is based on an evaluation of the bearing condition at the time of inspection. An average wear rate of 0.01 mm per 10,000 hours is regarded as normal

In modern shell bearings, the clearance is manufactured into the shells. When the clearance has reached a maximum value as laid down in the instruction manual, the bearing has to be changed.

Thick wall shell bearings fitted in some engines have the clearance adjusted by fitting shims between the bearing halves. The shims are of equal thickness on both sides of the bearing housing.

Crank pin measurement:

Crank pin measurement is done by outside micrometer at three different positions along the length of the pin. The measurement is taken at Port-Starboard and Top-Bottom positions. Handle the micrometer carefully to avoid scratching the pin while taking measurement.