Self-tapping screws are typically used to secure wood, plastic, metal and brick together. There are two types of self-tapping screws, thread-forming and thread-cutting. Thread-forming: Before you can use these screws you will need to drill a pilot hole as the screw itself does not contain a pointed tip.
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.
Self-tapping screws are also known as metal screws, sheet metal screws, or tapper screws. The primary difference between self-tapping and self-drilling screws is the pilot hole. Self-tapping screws cannot be used without a pilot hole being drilled beforehand.
