It happened recently that I broke the head off two screws, once by using an electric drill and once by tightening the screw by hand. For example, it can happen that the pilot hole in the wood is too small and I reach the maximum torque.
I am sure that the maximum torque which a screw can withstand before the head breaks off depends on the material and on the shaft diameter (without the threads obviously).
How can I calculate or where do I find a table with the torque admissible? I would like values from 3 mm shaft up to 8 mm shaft and a relationship between material strength (which I can look up myself) and calculated or listed values.
This is not about knowing the torque I need to apply to secure something, I'm interested in values which should not be reached to avoid damage.