Axial load is free until it is not

Below a threshold e (roughly 0.22–0.44 of the radial load) thrust costs a deep-groove bearing nothing. Above it, the equivalent load jumps to 0.56Fr + YFa and life falls with the cube.

Why it works

The contact angle already carries a share of axial load, so small thrusts do not change the equivalent load at all — people over-design for them. The cliff is real though: e depends on Fa/C₀, and once you cross it the Y factor can be as high as 2, so a thrust equal to the radial load can more than double P and cut life to under a fifth. Find out which side of e you are on before sizing anything.

Do it exactly

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

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More in Mechanical

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• Torque mostly fights frictionRoughly 90% of tightening torque is lost to friction; only ~10% actually stretches the bolt.
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• Depth beats width, cubedDouble a beam’s depth and its deflection drops 8-fold. Double its width and it only halves.

Does a bit of thrust load hurt a ball bearing?

Below a threshold e (roughly 0.22–0.44 of the radial load) thrust costs a deep-groove bearing nothing. Above it, the equivalent load jumps to 0.56Fr + YFa and life falls with the cube. The contact angle already carries a share of axial load, so small thrusts do not change the equivalent load at all — people over-design for them.

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