L10 Life • Dynamic Load Rating • Equivalent Load — Ball • Roller • Angular Contact • Thrust — Simulate • Explore • Practice • Quiz
A rolling-element bearing is one of the most critical components in any rotating machine. Bearings reduce friction between a rotating shaft and its housing, support radial and axial loads, and maintain precise shaft positioning. Correct bearing selection is essential for machine reliability, and it depends on understanding load ratings, equivalent loads, and bearing life calculations defined by international standards such as ISO 281.
Deep groove ball bearings are the most widely used bearing type. They accommodate both radial and moderate axial loads in either direction and are suitable for high-speed applications. Their simple design makes them economical and low-maintenance. Cylindrical roller bearings feature line contact between rollers and raceways, giving them much higher radial load capacity than ball bearings of the same size. However, standard designs like the NU type can only carry radial loads. Angular contact ball bearings have raceways offset in the inner and outer rings, allowing them to support combined radial and axial loads. They are commonly used in machine tool spindles and automotive wheel hubs. Thrust ball bearings are designed exclusively for axial loads and are used in applications such as crane hooks, turntables, and automotive clutch release mechanisms.
Bearing designations follow ISO standards. For example, in the designation 6205, the first digit "6" indicates a deep groove ball bearing, "2" denotes the width and diameter series (medium), and "05" is the bore code. For bore codes 04 and above, multiply the code by 5 to get the bore diameter in millimetres: 05 × 5 = 25 mm. Special codes apply for smaller bores: 00 = 10 mm, 01 = 12 mm, 02 = 15 mm, and 03 = 17 mm. Cylindrical roller bearings use prefixes like NU, NJ, or NUP to indicate the ring configuration.
The basic rating life L10 is the number of revolutions (or hours at a given speed) that 90% of a group of apparently identical bearings will complete or exceed before the first evidence of fatigue appears. The fundamental formula is L10 = (C/P)p in millions of revolutions, where C is the basic dynamic load rating, P is the equivalent dynamic bearing load, and p is the life exponent (3 for ball bearings, 10/3 for roller bearings). To convert to hours: Lh = (L10 × 106) / (60 × n), where n is the rotational speed in RPM.
When a bearing carries both radial load Fr and axial load Fa, these must be combined into an equivalent dynamic bearing load using the formula P = X·Fr + Y·Fa. The factors X and Y depend on the bearing type and the ratio Fa/Fr. For deep groove ball bearings, if the axial-to-radial ratio is below a threshold (e), the axial load has negligible effect and P simply equals Fr. Above that threshold, typical values are X = 0.56 and Y = 1.63.
In Simulate mode, select a bearing type, set radial load, axial load, speed and desired life, then watch the animated bearing cross-section while readout cards display the equivalent load, required dynamic load rating, selected bearing series, and actual L10 life. Use presets for common applications like electric motors and gearbox shafts. Switch to Explore mode to study 12 bearing concepts with formulas and worked examples. Practice mode generates random calculation problems with step-by-step solutions, and Quiz tests your knowledge with 5 questions per session covering both conceptual and numerical topics.
This bearing selection trainer is designed for mechanical engineering students, maintenance technicians, machine design engineers, and anyone studying bearing technology. It provides an interactive, visual understanding of bearing selection without requiring physical components or laboratory equipment, making it ideal for classroom instruction, self-study, and exam preparation.