I'm in a class that is talking about screws (common everyday type of screws). The question came up with regarding exactly defines the power of a screw? We're sure that the smaller the space is in between the thread contributes to more clamping power. For the other factor, we're thinking that the length of the screw is also important. Some in the class think that it's the length of the "stick" that is required to go around the screw head (to tighten it) - in other words, the length of the screwdriver. Others speculate that it's the diameter of the screw head. What is the right answer? Thank you.