Press fit / interference
Interference fit calculator using thick-wall cylinder equations: contact pressure, hub hoop stress, press force and the torque a press fit can carry.
Press fit / interference
Contact pressure, hub stress, press force, and how much torque the fit can carry. Bearing seats, bushings, gears on shafts, inserts in aluminum housings.
Contact pressure from the radial interference, Lamé thick-wall cylinders:
p = δ / ( d · [ (1/E_h)·((D²+d²)/(D²−d²) + ν_h) + (1/E_s)·((d²+d_i²)/(d²−d_i²) − ν_s) ] )
Hub tangential stress at the bore: σ_t = p · (D²+d²)/(D²−d²), compared against the hub yield.
Press and holding force: F = p · π·d·L · μ. Holding torque: T = F · d/2.
D is hub OD, d the interface diameter, d_i the shaft bore (0 for solid), δ the diametral interference, L the engagement length.
Lamé thick-wall equations with smooth, concentric parts and dry, unlubricated contact (μ 0.10 to 0.20 steel on steel, lower with oil). Surface finish eats some of the interference, and temperature changes the fit when the materials differ; check both before you trust the torque number. Hoop stress is the hub tangential stress at the bore, the first place an aluminum hub cracks.
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