Double the load, an eighth of the life

Ball-bearing fatigue life scales with 1/load³.

Why it works

The ISO 281 L10 relation: L ∝ (C/P)³. Even a 26% load increase halves the life — margins on load matter enormously.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

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More in Mechanical

• The bolt-torque shortcutTightening torque ≈ 0.2 × preload × bolt diameter (dry steel).
• Torque mostly fights frictionRoughly 90% of tightening torque is lost to friction; only ~10% actually stretches the bolt.
• Deflection limits: span/250Keep beam deflection under span/250 generally, span/360 where people will notice a bouncy floor.
• Depth beats width, cubedDouble a beam’s depth and its deflection drops 8-fold. Double its width and it only halves.

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