Bearing Torque, Load, and Life
Bearing torque, load, and life are the three pillars of mechanical design. Load dictates the forces acting on the bearing, torque defines the rotational resistance caused by friction and the load itself, and life estimates the operational duration before material fatigue occurs
1. Starting Torque
The torque required to initiate the rotation of one bearing race or washer relative to another stationary race or washer.
2. Running Torque
The torque required to prevent the movement of another bearing race or washer while one bearing race or washer is rotating.
3. Radial Load
The load acting perpendicular to the bearing axis.
4. Axial Load
The load acting parallel to the bearing axis.
5. Static Load
The load acting on the bearing when the relative rotational speed of the bearing races or washers is zero (radial or thrust bearings) or when the rolling elements are not moving in the rolling direction (linear bearings).
6. Dynamic Load
The load acting on the bearing when the bearing races or washers rotate relative to each other (radial or thrust bearings) or when the rolling elements are moving in the rolling direction (linear bearings).
7. Equivalent Load
A general term used for calculating theoretical load, under which, in specific cases, the bearing is subjected to the same theoretical load as if it were under actual load.
8. Basic Static Radial (Axial) Load Rating
The radial static load (central axial static load) corresponding to the total permanent deformation of the rolling elements and raceways. If, under zero load, the rollers and raceways (roller bearings) are or are assumed to be in normal generatrix (full-line contact), the total permanent deformation at the contact point between the rolling elements and raceways under maximum contact stress is 0.0001 times the diameter of the rolling elements. For single-row angular contact bearings, the radial load rating is the radial component of the load that causes pure radial displacement between the bearing rings.
9. Basic Dynamic Radial (Axial) Load Rating
A constant radial load (constant central axial load) under which the rolling bearing can theoretically withstand a basic rated life of 1 million revolutions. For single-row angular contact bearings, the radial load rating is the component of the load that causes pure radial displacement of the bearing races relative to each other.
10. Life (of a set of bearings)
The number of revolutions a bearing race, a washer, or a rolling element completes relative to another bearing race or washer before the material of that race, washer, or rolling element first shows signs of fatigue propagation. Life can also be expressed as the number of operating hours at a given constant speed.
11. Reliability (of bearing life)
The percentage of a group of nearly identical rolling bearings operating under the same conditions that are expected to reach or exceed a specified life. The reliability of a set of bearings is the probability that this bearing will reach or exceed its specified life.
12. Rating Life
The predicted life based on the basic radial dynamic load rating or the basic axial dynamic load rating.
13. Basic Rating Life
The rated life associated with 90% reliability.
14. Life Factor
A correction factor applied to the equivalent dynamic load to obtain the basic rated radial dynamic load or basic rated axial dynamic load corresponding to a given rated life.
15. Plummer Block
An assembly consisting of a radial bearing and a housing, with a base plate on a support surface parallel to the bearing axis for mounting screws.
16. Plummer Block Housing
A housing for mounting rolling bearings.
17. Flanged Housing
A housing with a radial flange and screw holes on a support surface perpendicular to the bearing axis for mounting.
18. Adapter Sleeve
A sleeve with an axial opening and a cylindrical inner bore, its outer surface being conical with external threads at the small end. Used for mounting bearings with tapered bores (using locknuts and lock washers) on shafts with cylindrical outer surfaces.
19. Withdrawalsleeve
A sleeve with an axially open cylindrical inner bore, its outer surface is conical, and the large end has an external thread. Used for installing or removing bearings with tapered bores onto shafts with cylindrical outer surfaces (using a nut).
20. Locknut
A nut with a cylindrical outer surface and an axial groove, tightened by a locking washer, one of its outer claws, and a ring wrench. Used for axial positioning of rolling bearings.
21. Lockwasher
A thin steel washer with many outer claws. One outer claw is used to lock the nut, and one inner claw inserts into the axial groove of the adapter sleeve or shaft.
22. Eccentric Locking Collar
A grooved steel collar with one end eccentrically positioned relative to the inner bore, installed on the equidistantly eccentric extended end of the inner ring of an outer spherical bearing. The eccentric collar is rotated relative to the inner ring to secure it, and then the set screw is tightened to secure it to the shaft. 23. Concentric Locking Collar
A steel ring mounted on the wide inner ring of an outer spherical bearing, screwed into a hole on the inner ring by a set screw and in contact with the shaft.
Post time: Jun-29-2026
