Reference — standards, factors & tables

Standard numbers follow the selected language.

Standards in force

Applicable standards	ISO 281	ISO 76	ISO 15	ISO 286
—	—	—	—	—

Equivalent-load factors X, Y, e — deep groove ball

Angular contact ball 15° (X=0.44 when Fa/Fr>e, else X=1)

Angular contact 25° / 40° & tapered roller

Style	e	X (Fa/Fr>e)	Y
Angular contact 25°	0.68	0.41	0.87
Angular contact 40°	1.14	0.35	0.57
Tapered roller (e≈0.4)	0.40	0.40	Y1 (catalog)

Load factor fp

Condition	fp	Examples
No / light impact	1.0 – 1.2	motors, turbines, fans, pumps
Moderate / inertial impact	1.2 – 1.8	vehicles, machine tools, cranes, paper, metallurgy
Strong impact	1.8 – 3.0	crushers, rolling mills, drills, screens

Temperature factor ft

Required static safety S0

Bearing / condition	S0,req
Ball bearing, rotating	0.5 – 1.0
Roller bearing, rotating	1.0 – 1.5
Shock / static duty	≥ 1.5 – 2.5

Required life reference (h)

Key formulas (ISO 281 / ISO 76)

P = f_p(X F_r + Y F_a) · P₀ = X₀F_r + Y₀F_a
L_10h = 10⁶/(60 n) · (C_r f_t/P)^ε · ε = 3 (ball), 10/3 (roller)
C_req = (P/f_t)(60 n L_h/10⁶)^1/ε · S₀ = C₀/P₀