Taper roller bearings are designed such that cup, cone and
rollers have tapered surfaces whose apexes converge at a common point on the
bearing axis. Along with metric series bearings, inch series bearings are also
available. This type of bearing is suitable for applications that involve heavy
or impact loading.
Taper
roller bearings consist of an inner ring (cone), an outer ring (cup), a cage and
rollers which are profiled to distribute the load evenly. They have high radial
and axial (thrust) load capacities at low to intermediate speeds. Taper roller
bearings are available in single-row, two-row and four-row designs. With
single-row bearings, the thrust load capacity is about 60% of the radial
capacity. Double-row bearings have a greater radial load capacity and can handle
thrust loads from both directions. The rollers can be configured so that the
contact lines to the races converge or diverge towards the axis of rotation.
Diverging double-row bearings increase the rigidity of the shaft mounting, but
converging bearings do not. Other configurations for double-row bearings feature
a single outer ring and two inner rings, or two outer rings and a single inner
ring. Four-row tapered roller bearings consist of four rows of alternating
converging and diverging rollers.
Most taper roller bearings are made of alloy steels or low-carbon steels. Some
applications require the use of case-hardened or thorough-hardened, high-carbon,
bearing-quality steel. High-carbon grades of steel do not require carburizing
and can be case-hardened by induction heating or thorough-hardened by
conventional heating methods. When low-carbon, carburized grades of steel are
used, carbon is introduced after the cylindrical roller bearings are machined to
a depth sufficient to produce a hardened case that can sustain bearing loads.
The addition of carbon and alloys ensures the proper combination of a hard,
fatigue-resistant case and a tough, ductile core.
Bore size and outside diameter (OD) are important specifications to consider
when selecting tapered roller bearings. The bore size is the bearing's smallest
dimension. The outer diameter includes the bearing housing, but excludes the
flange. Other important specifications for taper roller bearings include overall
width, rated speed (oil), static axial load, static radial load, dynamic axial
load, and dynamic radial load. Static axial load and static radial load are,
respectively, the maximum axial and radial loads that bearings can withstand
without permanent deformation. Dynamic axial load and dynamic radial load are,
respectively, the calculated axial and radial loads under which a group of
identical bearings with stationary outer rings can endure for a rating life of 1
million revolutions of the inner ring.