Section 6.8.4 Glossary

Failure of aluminum components in an engine, contributing aluminum debris into the lubrication system; i.e. blower(s), intermediate camshaft bearings, flywheel housing, turbochargers, piston skirts, oil pump housings, and governor housings.‪

Any alloy that is used as a bearing lining surface.‪

The removable half of the housing that holds the bearing shells in place.‪

Chemical attack evident on bearing surfaces by metal loss or discoloration.‪

The cracking and eventual “chunking out” of bearing material associated with repeated loading in excess of the fatigue strength for the material.‪

Trimetal alloy mainly of copper with lead and tin for maximum fatigue strength.‪

The bearing half that is made for assembly in the bearing cap.‪

The housing into which the bearing shells are assembled.‪

The bearing half that is made for assembly in the engine block or connecting rod as opposed to the bearing cap.‪

The dimension of the bearing shell through the radial cross section as measured by a micrometer with ball attachment.‪

The inside diameter of the main bearing/connecting rod bore into which the bearing shells are assembled.‪

Bore diameter, roundness, taper, and alignment (main bearing).‪

Cavitation is the formation of bubbles in a fluid (lubrication oil) which may occur when the fluid is subjected to low pressures. The high energy dissipated when these bubbles collapse near the bearing surface causes gradual erosion and pitting of the surface. This condition is called cavitation erosion and is generally not harmful to bearing performance.‪

The difference between the bearing housing bore ID and the bearing journal OD.‪

The structural member that transfers the force from the piston to the crankpin.‪

The bearing at the big end of the connection rod in which the crankpin rotates.‪

A condition where the bearing shell has been worn through the overlay and into the copper bearing lining as evidenced by a copper color.‪

See Bearing Corrosion.‪

The enclosure for the crankshaft formed by the oil pan and the lower portion of the engine block.‪

The crankshaft journal around which the connecting rod bearing shells are installed.‪

The main shaft of an engine; contains the main bearing journals and crankpins.‪

The center area of a bearing shell.‪

The circumferential interference fit necessary to hold two bearing halves securely in the housing bore. In a bearing half, the amount of circumference in excess of a half circle.‪

Metal removed on the bearing surface at the parting faces extending the full width of the bearing.‪

See Foreign Material.‪

See Foreign Material.‪

Either fuel or coolant in the lubrication system mixing with the lubrication oil.‪

Unequal loading of a bearing shell evidenced by taper wear across the length of the bearing.‪

The ability of the bearing material to absorb foreign material without causing serious bearing damage.‪

The enclosure of solid particles into the surface of a bearing shell; i.e., dirt, shavings, metal grinding dust.‪

The possible forward and backward movement of the crankshaft in the main bearing fore or connecting rods on the crankpin.‪

The main casting of an internal combustion engine containing the cylinder bores and main bearing bores.‪

See Bearing Material Fatigue.‪

The ability of a bearing material to withstand the repeated loads during engine operation.‪

Any extraneous material not intended to be present, i.e., particles of steel, cast iron, dirt sand, etc.‪

See Spread.‪

This term is used to describe a condition where the bearing lining becomes unbonded from the steel bearing back because of an excessively high bearing temperature. The high bearing temperature is almost always a result of the heat generated during a scoring failure. This condition does not indicate an initial defective bearing lining to steel back bond. It merely indicates that a high bearing temperature was reached during a scoring failure to “hot short” or “melt” the bond layer.‪

The eating away of the bearing overlay by the action of the oil flow past the surface.‪

Inadequate flow rate of the lubrication oil for satisfactory performance.‪

The part of a shaft that revolves in a bearing.‪

A size dimension either plus or minus the tolerance (high or low limit).‪

To machine the crankshaft main bearing bores, creating bore centers which fall on a true center line.‪

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See Bearing Lining Material.‪

See Bearing Material Fatigue‪

A projection on a bearing back that locates in a machined slot in the bearing seat, used to locate the bearing in the housing bore and keep it from moving laterally.‪

A substance capable of reducing friction between mating surfaces in a relative motion through separation by an oil film.‪

A bearing that is used to support the crankshaft in the cylinder block.‪

A crankshaft journal that is supported by a main bearing.‪

The area in the cylinder block machined to receive the upper main bearing.‪

The amount of bearing wear experienced during normal engine operation.‪

A viscous fluid, insoluble in water.‪

See Clearance — Diametral Bearing.‪

The thin layer of oil that protects the journal and bearing surfaces by separating them and preventing journal to bearing contact while the engine is in operation.‪

The main oil supply line in the engine block, often referred to as the header. Oil flows from this major supply route under pressure to the many parts that are to be lubricated.‪

A canal machined in the surface of a bearing to spread oil on a friction area or to permit the transfer of oil to another part.‪

A hole drilled through the bearing wall or crankshaft journal to allow the passage of the oil.‪

A condition of inadequate oil flow or supply.‪

An inside or outside diameter, designed to be perfectly round, having varying diameters when measured at different points across the diameter. ‪

The bearing overlay cracking which indicates the beginning stages of overlay fatigue.‪

The cracking and eventual lose of overlay material associated with repeated loading in excess of the fatigue strength of the overlay material.‪

A bearing load in excess of the load the bearing was designed to carry.‪

Either an inside or outside diameter that is greater than the standard size.‪

The edge formed where the inside or outside surface of the bearing joins at the parting face.‪

The surface that is in contact with the other bearing half when the bearing is assembled.‪

The theoretical line formed by the contacting parting faces.‪

The excess of diameter at the outside parting edges in the free state over the housing bore into which the bearing is to be installed.‪

A bearing set which has adhered to the journal and turned in the bore for various reasons, i.e. dirt, lack of lubrication, or improper lubrication.‪

An acceptable range of dimensions to provide accuracy in finished parts.‪

A flat bearing used to control the crankshaft end play.‪

Either an inside or outside diameter that is less than the standard size.‪

The gradual decrease in bearing thickness.‪