Self-tapping Screws

Self-tapping screws are characterized by their ability to produce their own hole. All screws require a hole. To install a screw, you’ll have to insert it into the hole of a workpiece or surface. Self-tapping screws produce their own during installation. When turning a self-tapping screw with a screwdriver, it will dig into the workpiece or surface while simultaneously producing its own hole.

They are known as “self-tapping screws” because they “tap” into the workpiece or surface with which they are used. In other words, self-tapping screws create their own internal threading. They either dislodge or remove material from inside the workpiece or surface, thereby creating a threaded hole. There are thread-cutting self-tapping screws, and there are thread-forming self-tapping screws. Regardless, they all capable of producing their own hole during installation.

Self-drilling Screws

Self-drilling screws can be identified by the drill bit shaped point of the screw and are designed for a variety of applications such as fastening metal to metal and metal to wood. Self-drilling screws do not require a pilot hole, which accelerates installation time and lowers the cost and need of additional drill bits. This extra functionality and cost saving feature makes self-drilling screws the clear choice for metal building construction. The drill points are numbers #1 through #5 and the amount of steel they can drill through increases as the numbered point increases.  Typically, self-drilling screws are used in light gauge applications but a #5 drill point can drill through and fasten up 1/2" of steel. During installation, self-drilling screws will also tap threads to a degree.

In conclusion

All self-drilling screws are also self-tapping screws, but all self-tappers are not self-drillers. Self-drilling screws eliminate the need for a pilot hole, but can tap as well. Self-tapping screws tap their own threads, but cannot drill through metal and require a pilot hole. These screws are not interchangeable, and mixing up the two can cause many headaches or possible failures in the field.