The following table shows the values of torque and preload at minimum yield strength for the thread sizes M4 up to M68.

Torque and preload for one thread size you can see one below each other for the property classes 8.8, 10.9 and 12.9.

 Five columns with values of torque and preload are shown for the different friction coefficients 0,08 - 0,10 - 0,12 - 0,15 - 0,18.

 Considered in the given values is the torsion stress generated by the thread friction µ-th.

 Because the yield values of torque and preload are given, in case of a torque controlled tightening the real assembling torque values must remain below this value !

Assembling torque = 80% .... 90% of given values e.g.

 The shown thread is coars thread.

Legend :

D                     : nominal thread diameter                                                  F         : preload

Acr.Flat        : width across flat                                                                    µ-tot : total friction coefficient

p                     : pitch                                                                                           µ-th   : thread friction coefficient

Prop.Class  : property class                                                                         µ-b    : bearing friction coefficient

T                     : torque    

given values without engagement

Instruction for the following calculation sheet for assembly preload and tightening torque acc. guideline VDI 2230

After the first opening of calculation sheet you will get a protected view, you have to activate / confirm the processing – otherwise a calculation is not possible. The files are virus checked.

Then please select with the black arrow keys :

Thread size                 : M 4 …. M 68

Thread pitch               : 0,5 mm ….. 6 mm

Property class            : 8.8 ….. 12.9

Friction coefficient     : µ_th 0,06 ….. 0,24

For standard thread under „Info to regular pitch“ (move cursor to F39) you can view a table of thread pitches for the thread range

M 4 … M 68.. For fine thread you have to select the corresponding value.

In the input field D_b you have to put in the mean bearing diameter of bearing surface. For standard hexagon bolts you will find a table in the range M 4 …. M 68 under „Info to D_b“ (move cursor to F 42)  from where you can take the value of D_b for the input in the field C44. For special bearing surfaces – flange or cone head e.g. -  D_b must be measured or calculated respectively.

The load factor „x-% R_p0,2“ (E3) is fixed to the value 0,9 because the tables A1 …. A4 in the VDI 2230 are given for load factor 90% also. When you select any other than 90% then this will not deliver an other result - 90% are fixed internally 

In the calculation sheet you will find the working-sheet „VDI-2230-A1_A3“, which has to be used for shank-bolts. Here the calculation is performed by the stress-area A_s of the thread.  

The working sheet „VDI-2230-A2_A4“ has to be used for necked-down bolts. Here the cross-section of the reduced shank A_T will be used.

The torsional load caused by the thread fiction (µ_th) – which delivers an additional stress beside the tensile stress - is considered in both working sheets already.

Beside the assembly preload (F2) and tightening torque (H2) you can see the values of stress-area A_S respectively  / cross section A_T (C48). additionally.

In field J2 you can see the tensile force at yield point.

 The following picture of calculation sheet is an example only, there is no calculation possible. Please download the calculation sheet below.

Please note !

When you set the cursor to any calculation field and then put in anything (character or number)  into the basic input line (above the calculation sheet), then you destroy the internal formula and this result can no more calculated in the right way. In such a case you have to download the file again.

The calculation is without engagement.