Tapered Roller Bearings

Tapered roller bearings are classified into three types:

· Single-row

· Double-row

· Four-row

The main parameters of tapered roller bearings have been optimized, increasing the number of rollers and their effective length. The meticulous design of the rollers and raceways significantly improves geometric contact, stress distribution, and lubricant film formation, enhancing roller motion conditions. Consequently, compared to earlier models of the same size, these bearings offer higher load capacity and extended rated service life.

Double-row tapered roller bearings can withstand combined radial and axial loads (primarily radial) as well as bidirectional axial loads. A spacer is placed between the two inner rings, allowing clearance adjustment and uniform load distribution by varying the spacer thickness. These bearings are suitable for medium to low-speed applications.

Single-row tapered roller bearings are available in both metric and inch series, both widely used.

· Metric series bearings conform to ISO 355:1977.

· Bearings with prefix F-J comply with AFBMA Standard 19.1.

· Inch series tapered roller bearings comply with AFBMA Standard 19 (1974).

The maximum allowable misalignment between the inner and outer rings of single-row tapered roller bearings is 3 arcminutes. Therefore, during installation, strict concentricity between the bearing bore and the housing bore must be ensured. Otherwise, bearing service life may be compromised.

For tapered roller bearings of the same designation, the inner rings (with roller and cage assemblies) or outer rings are interchangeable. After swapping inner or outer components, the total bearing width T must remain within tolerance limits.

· Metric Bearings:
Standard metric tapered roller bearings are manufactured with normal tolerance. Products with tolerance classes P6X, P6, P5, P4, and P2 are also available. Bearings with P5 tolerance or higher are primarily used for machine tool spindles. Chamfer dimension tolerances comply with ISO 582:1979. F-J series bearings are generally produced to P6X tolerance, with chamfer dimensions adhering to inch series bearing chamfer tolerances.

· Inch Bearings:
Standard inch series tapered roller bearings are manufactured with normal tolerance. Products with tolerance classes CL2, CL3, CL0, and CL00 are available upon request.

Internal clearance in single-row tapered roller bearings is established only after mounting and adjustment against a counter-oriented bearing. The radial clearance for double-row tapered roller bearings follows the values provided in the table below.

Cages for tapered roller bearings are generally made of high-quality stamped steel. For larger bearings, machined brass cages are used. For special applications, injected nylon 66 cages may be employed.

To prevent destructive sliding between rollers and raceways caused by inertial forces and lubricant friction during high-speed operation, a minimum radial load must be applied. This can be estimated using the formula:

F_{rm} = 0.02C

Where:

· F_{rm}: Minimum radial load (N)

· C: Basic dynamic load rating (N)

Dynamic Equivalent Load

· When \frac{F_a}{F_r} \leq e:

P = F_r \quad \text{(kN)}

· When \frac{F_a}{F_r} > e:

P = 0.4F_r + Y F_a \quad \text{(kN)}

Where:

· e and Y are provided in the bearing tables.

When calculating the dynamic equivalent load, the axial component force generated under radial loads must be considered. The formulas on the next page account for various mounting configurations and load conditions. These formulas apply only when bearings are adjusted to zero clearance without preload.

In the illustrated configurations, Bearing A always carries radial load F_{ra}, and Bearing B always carries radial load F_{rb}. Both F_{ra} and F_{rb} are treated as positive. Radial loads act at the pressure center (denoted as a in bearing tables). Additionally, an external axial force K_a acts on the shaft or housing. The axial load factors for A and B can be found in the bearing tables.

Static Equivalent Load

P_0 = 0.5F_r + Y_0 F_a

Where:

· Y_0 is provided in the bearing tables.

Double-Row Tapered Roller Bearings

Dynamic Equivalent Load

P = F_r + Y_1 F_a

Static Equivalent Load

P_0 = F_r + Y_2 F_a

Values for e, Y_1, Y_2, and Y_0 are provided in the bearing tables."