Tech Tip: What About Those Point Sizes?
Self-Drilling/Self-Tapping screws must be matched to the material thicknesses they will be fastening to work properly. Unlike fasteners selected by length and diameter, these screws are specified by point size. The self-drilling must be finished before thread tapping begins, so the drill point must be longer than the combined thicknesses of the materials. The screw will cross-thread if the two materials are at all searated when tapping begins and will cause thread stripping or drive stalling. The #2 and #3 point sizes cover a wide thickness range and are most common. For a given screw diameter, the #2 point will drill and tap a combined material thickness of .035” to .100”; the #3 point will drill and tap material thicknesses from .110” to .210”.