The Physics Behind Bearing Life Ratings

Bearings do not "wear out" like a brake pad - they fail by rolling-contact fatigue: microscopic cracks initiate below the raceway surface and grow into spalling. Understanding this changes how you specify and maintain them.

Sub-Surface Origin of Fatigue

Under rolling load, maximum shear stress occurs just below the contact surface. Repeated loading eventually initiates a subsurface crack there; as it reaches the surface it flakes off a small pit - spalling. This is why material cleanliness (few non-metallic inclusions) and hardness uniformity are so important to fatigue life.

Rating Life and the Weibull Spread

Industry uses rating life L10: the life by which 90% of a population will still be running (10% may have failed). Because fatigue is statistical, actual lives scatter widely (some fail early, many outlast L10 many times over). Modern rating methods also account for contamination, lubrication and fatigue-load limits, recognising that a starved or dirty bearing dies far sooner than the catalogue number suggests.

What Kills Life Early

The usual suspects are contamination (hard particles denting the raceway and seeding cracks), inadequate lubrication (mixed/boundary contact raises stress), misalignment (edge loading), overload (exceeding the dynamic rating) and electrical arcing (fluting from shaft currents). Addressing these often extends life more than simply buying a "better" bearing.

How KMK Bearing Applies This

At KMK Bearing (SINO BEARINGS, KMK brand) these principles guide every order we manufacture in Chengdu, China. Our in-house process chain - forging, heat treatment, precision grinding, superfinishing and cleanroom assembly - is built to the standards described above, whether the part is a standard catalog bearing or a custom-engineered solution.

• 20+ years of precision bearing manufacturing
• Materials from chrome steel to 17-4PH stainless steel and full ceramic (ZrO2, Si3N4)
• In-house heat treatment and metrology to P4/P2 (ABEC 7/9) precision
• Custom designs and low-MOQ prototyping from drawings or samples

Discuss your application with kevin@sinoti.com or browse our bearing catalog.

SINO BEARINGS (KMK) - Perfect Quality -- Great Service -- Customized.

Source: SINO BEARINGS