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Bolt Torque from Thread Pitch Calculator

Fastener and Screw / Bolt Design Formula Design Data
Strength of Materials

Fastener Relation Between Torque, Thread Pitch and Clamping Force Formula and Calculator

Relationship between the applied tightening torque and bolt preload F_f

Equation 1
T = F_f · { d₂ / 2 ( µ / cosα + tanβ ) + µ_n d_n / 2 }

Alternatively

Equation 2
F_f = T / { d₂ / 2 ( µ / cosα + tanβ ) + µ_n d_n / 2 }

Figure 1 Drawing nomenclature

Figure 2 Drawing nomenclature

Where:

T = torque, N-mm
F = axial tension, N
d₂ = Pitch diameter, mm
µ = Friction coefficient of threaded portion
µ_n = Friction coefficient of bearing portion
α = Half angle of screw thread, ISO screw 30°
β = Lead Angle

Reference:

"Theory and calculation of threaded fasteners" Akira Yamamoto (Yokendo Co., Ltd)

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