Skip to main content
Disclosure: As an Amazon Associate, I earn from qualifying purchases.

Rolling Contact Bearings

Rolling Contact Bearings (Anti-Friction Bearings)

Rolling contact bearings use rolling elements—either balls or rollers—to carry applied loads with very low friction. Unlike hydrodynamic or hydrostatic bearings, rolling contact bearings do not rely on a fluid film to separate surfaces, allowing them to operate with minimal wear and reduced starting torque.

Because of their greatly reduced starting friction compared to conventional journal bearings, rolling contact bearings are commonly referred to as anti-friction bearings. They are typically manufactured with hardened rolling elements and raceways, and most designs use a separator (cage) to maintain spacing and minimize friction. Many variations are used throughout the mechanical and electrical industries.

Common Applications

The most widely used anti-friction bearing is the deep-groove ball bearing, usually supplied with a ribbon-type cage and sealed or shielded grease lubrication. This bearing is capable of supporting combined radial and moderate thrust loads and is extensively used in rotating machinery.

Sealed and shielded deep-groove ball bearings have become standardized components, ordered from manufacturers’ catalogs much like fasteners. Their simple design and elimination of external lubrication systems make them competitive with traditional plain bushings in many applications.

Standards and Interchangeability

Most major bearing manufacturers produce complete ranges of ball and roller bearings with standardized dimensions, tolerances, and fits as specified by the Anti-Friction Bearing Manufacturers Association (AFBMA). These standards ensure interchangeability across suppliers for many bearing types.

However, aside from deep-groove ball bearings, performance standards are less rigidly defined. Bearing selection and sizing must closely follow individual manufacturer catalogs and application guidelines. Consultation with bearing suppliers is recommended for critical applications.

Accuracy and Manufacturing Quality

Rolling contact bearings are manufactured to extremely high accuracy. Balls and rollers are commonly held to diametral tolerances of 0.0001 in (0.0025 mm) or less within a single bearing. In some cases, bearing balls are used as reference gage elements in precision toolroom operations.

This high level of precision is essential for limiting runout, maintaining correct internal clearances, and ensuring smooth and reliable operation. Low friction during both starting and steady-state operation allows rolling contact bearings to simplify machine designs that would otherwise require journal bearings.

Lubrication and Bearing Life

In addition to accurate shaft positioning, rolling contact bearings are valued for their low lubrication requirements and their ability to tolerate brief interruptions in lubrication. However, their service life is ultimately limited by rolling contact fatigue of the bearing material.

Bearing life is influenced by load, speed, lubrication quality, operating temperature, internal geometry, and mounting conditions. Because fatigue life varies statistically, bearing performance is expressed in terms of probability of survival, using life equations recommended by AFBMA standards.

Significant deviations from catalog life predictions may occur in extreme applications involving high speed, shaft deflection, misalignment, elevated temperature, or inadequate lubrication.

Design Considerations

  • Select bearing type based on load direction (radial, thrust, or combined).
  • Verify catalog ratings for speed, load, and expected life.
  • Ensure correct shaft and housing fits to avoid internal preload or looseness.
  • Provide appropriate lubrication and sealing for the operating environment.
  • Consult manufacturer guidelines for non-standard or critical applications.

Reference:

Robert L. Mott, Machine Elements in Mechanical Design, Prentice Hall, 2003. ISBN: 0-13-061885-3

Labels:

Comments

Post a Comment

Popular posts from this blog

The Engineer’s Guide to Precision Alignment: Dowel Pins, Diamond Pins & Fits

The Unsung Heroes of Precision: Dowel Pins & Locators In the world of Precision Engineering , the difference between a high-quality product and a scrap part often comes down to microns. While bolts hold parts together, they are terrible at positioning them. This is where Dowel Pins and Locating Pins become essential components in industrial tooling . What is a Dowel Pin? Dowel pins are precision-ground fasteners used to secure the relative position of two parts. They are typically machined to extremely tight tolerances (often within 0.0001 inches) and are available in materials like: Hardened Steel: For high-wear applications in CNC fixtures . Stainless Steel: For corrosion resistance in medical or food processing machinery. Plastic (Thermoplastic): For lightweight, non-conductive, low-load alignment. The "Play" Problem: Bolts vs. Dowels When mechanical design engineers create components, they cannot rely on bolts for alignm...
Post a Comment
Read more about this Mechanical Design Article »

Hoekens Linkage: Kinematics, Optimization, and Walking Robot Applications

Introduction to the Hoekens Linkage The Hoekens linkage is a specialized four-bar mechanism designed to convert rotational motion into an approximate straight-line motion. While it serves a similar purpose to other straight-line generators, its unique coupler curve—a "tear-drop" shape—makes it exceptionally useful for intermittent motion and walking machines. One of the most fascinating aspects of kinematic theory is the concept of "Cognates." The Hoekens linkage is actually a cognate linkage of the Chebyshev Straight-line Mechanism . This means that while the physical structure and link lengths differ, they can generate the exact same coupler curve geometry. Search for "Design of Machinery" Books Kinematics and Optimization Unlike the Watt linkage, which has a central pivot, the Hoekens linkage relies on a rotating crank to drive a floating coupler arm. The "straight" portion of the curve occurs when t...
Post a Comment
Read more about this Mechanical Design Article »

Ball Detent Torque Limiter: The Ultimate Guide to Precision Overload Protection

The First Line of Defense: Overload Clutches In high-speed automation and heavy industrial machinery, a "jam" is not a matter of if , but when . Whether it is a cardboard box getting stuck in a packaging machine or a tool crashing in a CNC lathe, the resulting torque spike can destroy gearboxes, twist shafts, and burn out expensive servo motors in milliseconds. A torque limiter (or overload clutch) is the mechanical fuse of the drive system. While electronic monitoring (current limiting) is common, it is often too slow to prevent physical damage from the massive kinetic energy stored in the system inertia. A mechanical torque limiter provides a physical disconnect that operates in a fraction of a second. Search for Torque Limiters & Safety Couplings Why Choose a Ball Detent Limiter? Not all torque limiters are created equal. In precision applications, the Ball Detent type is superior to friction or shear types for several reason...
Post a Comment
Read more about this Mechanical Design Article »