How it's calculated

BPFO = (N/2) × f × (1 − Bd/Pd × cos θ) BPFI = (N/2) × f × (1 + Bd/Pd × cos θ) BSF = (Pd/2Bd) × f × (1 − (Bd/Pd × cos θ)²) FTF = (f/2) × (1 − Bd/Pd × cos θ)

Defect frequencies tell you which part of a bearing is damaged when you see a peak (or its harmonics) in a vibration spectrum. Outer race defects (BPFO) are the most common. Inner race defects usually show sidebands at 1× running speed.

Bearing makers publish exact geometry; the default values are for a 6205 deep-groove ball bearing.