Every deep-groove ball bearing carries a catalogue rating, C — the constant radial load under which 90% of an identical batch will survive one million revolutions before fatigue. Push a bearing harder than its rated load and life falls off fast: the ISO 281 formula L10 = (C/P)³ × 10⁶ revolutions means doubling the load doesn't halve the life — it cuts it to an eighth.
A 6205 bearing (25 mm bore, C ≈ 10.8 kN) carrying a 2,000 N radial load at 1,800 rpm is rated for about 157 million revolutions — roughly 1,450 hours of continuous running. Halve the load to 1,000 N and the same bearing is rated for over 8× longer, purely from the cube relationship — no other change needed.
They share a bore but not a cross-section. The 6300 (heavy) series uses larger balls in a bigger outer ring, giving substantially higher load ratings for the same shaft — at the cost of a larger housing bore and more radial space.
C (dynamic) governs fatigue life under rotation — it's what the L10 formula uses. C₀ (static) is the load a stationary bearing can take before the balls permanently dent the raceway. A bearing can be adequately sized for running duty and still be damaged by a heavy shock load while parked.
No — it's a statistical rating. 90% of an identical batch, under identical conditions, should reach or exceed this life; 10% will fail sooner, and some will run far longer. It also assumes clean lubrication and normal temperature — contamination or heat cuts real life well below the catalogue number.
Deep-groove ball bearings also tolerate moderate axial (thrust) load, but combining radial and axial loads into a single equivalent load requires load factors (X, Y) specific to each bearing's internal geometry, published per size in a manufacturer catalogue — outside what a general reference tool can responsibly embed. For pure radial loading, this calculator is exact to the ISO 281 method.