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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.

1) VDI = Verein Deutscher Ingenieure
Procedure

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

B The required minimum preload FM min is found by proceeding from this number:

Estimation of screw diameters

C The required maximum preload force FM max is found by proceeding from this force FM min by:

Estimation of screw diameters

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.

Example

A joint is loaded dynamically and eccentrically by the axial force FA = 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 FA in column 1
B 2 steps for «eccentric and dynamic axial force» lead to FM min = 25 000 N
C 1 step for «tightening with manual torque wrench» leads to FM max = 40 000 N
D For FM max = 40 000 N thread size M10 is found in column 2 (property class 12.9)

Estimation of screw diameters

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