Hi, I have a small question. I am connecting two steel plates together with a self-drilling screw. I wanted to just drill the two plates through at once, but I was told that I should make a pre-drilled clearance hole at the top plate and then just drill through the second plate so that the two plates would stick together more tightly. Is that so? Which method is more common in real steel structure construction?
Great question! In steel construction, yes the second method (clearance hole in the top plate) is far more common. The fastener in your case is clamping the two plates together. By virtue of having a clearance hole, the screw pulls the bottom plate up as it tightens. If the threads are forced into both top & bottom plates, then their relative positions are set and they cannot clamp together without the threads "fighting" between top/bottom.
Hi Tuolite - terminology does vary from region to region and company to company, but these definitions are what I have found to be most standard. It is how they are classified in the McMaster-Carr catalog, for example.
