# METRIC BOLT TORQUE CALCULATOR

Metric bolt torque calculator according to VDI 2230 standard for shank bolts with metric standard thread according to ISO 262;  hexagonal bolts according to DIN EN ISO 4014 to 4018, hexalobular external driving head bolts according to DIN 34800 or cylindrical bolts according to DIN EN ISO 4762 and hole ”medium“ according to ISO 273 (DIN EN 20273).

Based on theory given in VDI standard, it's aimed to utilize the bolt strength to the greatest extent. Normally 90 % of minimum yield point (Rp0.2min) is allowed to be utilized. The default value for utilization factor is therefore set as 0.9 but can be changed.

### Metric Bolt Torque Calculator

 INPUT PARAMETERS Metric Thread M4 x 0.7 M5 x 0.8 M6 x 1 M7 x 1 M8 x 1 M8 x 1.25 M10 x 1 M10 x 1.25 M10 x 1.5 M12 x 1.25 M12 x 1.5 M12 x 1.75 M14 x 1.5 M14 x 2 M16 x 1.5 M16 x 2 M18 x 1.5 M18 x 2 M18 x 2.5 M20 x 1.5 M20 x 2.5 M22 x 1.5 M22 x 2.5 M24 x 1.5 M24 x 2 M24 x 3 M27 x 2 M27 x 3 M30 x 2 M30 x 3.5 M33 x 2 M33 x 3.5 M36 x 2 M36 x 4 M39 x 2 M39 x 4 Property Class 8.8 10.9 12.9 Utilization Factor of the Yield Point Stress during Tightening Coefficient of Friction in the Thread and in the Bearing Area of the Head 0.08 0.10 0.12 0.14 0.16 0.20 0.24

 RESULTS Parameter Value Designation --- --- Property Class --- Screw Thread Series --- Utilization Factor [v] --- Assembly Preload [FM,Tab] --- kN Tightening Torque [MA] --- N.m

### Metric Bolt Torque Calculation Formula:

 Parameter Equation Tightening Torque [MA] $${ M }_{ A }={ F }_{ Mzul }\cdot [0.16\cdot P+0.58\cdot { d }_{ 2 }\cdot { \mu }_{ Gmin }+\frac { { D }_{ Km } }{ 2 } \cdot { \mu }_{ Kmin }]$$ Permissible Assembly Preload [FMzul] $${ F }_{ Mzul }={ A }_{ 0 }\cdot \frac { \upsilon \cdot { R }_{ p0.2min } }{ \sqrt { 1+3{ \left[ \frac { 3 }{ 2 } \cdot \frac { { d }_{ 2 } }{ { d }_{ 0 } } \cdot (\frac { P }{ \pi \cdot { d }_{ 2 } } +1.155\cdot { \mu }_{ Gmin }) \right] }^{ 2 } } }$$ Effective diameter for the friction moment [DKm] $${ D }_{ Km }=0.5\cdot \left( \frac { { d }_{ h }+s }{ 2 } \right)$$

Note: P - Pitch, d2- Pitch diameter of the bolt thread, d0- Diameter at the relevant smallest cross section, dh- hole diameter of clamped parts, s- Width across flats, μGmin-Coefficient of friction in the thread, μKmin-Coefficient of friction in the head bearing area, Rp0.2-0,2% proof stress of the bolt according to DIN EN ISO 898-1, DKm-Effective diameter for the friction moment at the bolt head or nut bearing area, A0-Appropriate minimum cross-sectional area of the bolt.

### Reference:

• VDI 2230– Systematic calculation of high duty bolted joints - Joints with one cylindrical bolt