Calculator Torque (Click here to start counting)

Tightening torque to preload a bolt
Metric thread :	M1 M1.2 M1.6 M2 M3 M4 M5 M6 M8 M10 M12 M14 M16 M20 M24 M30 M36 M42 - 3.6 4.6 4.8 5.6 5.8 6.8 8.8 9.8 10.9 12.9
Initial tensile stress : σt =	·Rp0.2
Thread coeff. of friction : µthread =
Head - face coeff. of friction : µhead =
pitch P	mm
pitch diameter d2	mm
root diameter d3	mm
tensile stress area At =π/4 d02 ; d0=(d2+d3)/2	mm2
ultimate tensile strength Rm	MPa
yield strength Rp0.2	MPa
tensile stress σt = σ't x Rp0.2	MPa
torsional stress τ = MG / ( π/16 d33 )	MPa
equivalent stress σe = (σt2 + 3τ2)½	MPa
thread friction MG	Nm
thread friction MG-	Nm
head face friction MWD = Fi μhead 1.3 d/2	Nm
Total tightening torque MA = MG + MWD	Nm
Initial preload Fi = σt ·At	kN
Load at Yield F02 = Rp02 ·At	kN
Load reserve Pb=F0.2 - Fi	kN
1) stress by torsion is relaxed after tightening. 2) equivalent stress should remain below the yield strength (linear elastic).

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