Estimation of screw diameters

according to VDI guideline 2230¹⁾

The following procedure allows a rough estimate to be made of the required screw dimensions for a particular screwed connection and temperature around 20 °C, in correspondence with the details in VDI 2230. The result should be checked mathematically in each case.

A Select in column 1 the next higher force to the work force F_A,Q acting on the bolted joint.

B The required minimum preload F_{M min} is found by proceeding from this number:

C The required maximum preload force F_{M max} is found by proceeding from this force F_{M min} by:

D Once the preload (force) has been estimated, the correct screw size is found next to it in column 2 to 4 underneath the appropriate strength class.

A joint is loaded dynamically and eccentrically by the axial force F_A = 8500 N. The screw of strength class 12.9 will be assembled with a manual torque wrench.
A 10 000 N is the next higher force to F_A in column 1
B 2 steps for «eccentric and dynamic axial force» lead to F_{M min} = 25 000 N
C 1 step for «tightening with manual torque wrench» leads to F_{M max} = 40 000 N
D For F_{M max} = 40 000 N thread size M10 is found in column 2 (property class 12.9)