An overview of self-drilling screws and self-tapping screws

One of the most often used industrial fasteners is self-tapping screws. Self-tapping screws were one of the first engineered fastener products, made of hardened steel, and its use fueled the Industrial Revolution. Self-tapping screws come in a variety of designs and varieties, each designed for a unique fastening function.

Unlike aerospace or military fasteners, the terminology employed in the commercial fastener industry can be vague and cause confusion. The distinction between a self tapping screw and a self drilling screw is a good example of this imprecision.

A self-tapping screw is more appropriately defined as a tapping screw, although it is also commonly referred to as a sheet metal screw due to its widespread use in the sheet metal industry.

It is so named because it contains form mating threads in a pre-drilled hole into which they are driven, regardless of the name.

A self-drilling screw has a drill point and is a form of self-tapping screws. In a single action, the sharp drill point will drill a hole and produce the mating threads.

So, where does the ambiguity between terms arise? Many times, when mentioning this sort of screw, the phrases self-tapping screws and self-drilling screws are interchanged, however a screw is only self-drilling when it drills its own hole.

Other self-tapping screws that are comparable to self-tapping screws include:

Thread-Cutting Screws (TCS) - Thread-cutting screws are screws that can be used to cut threads in a pre-drilled hole. Thread-cutting screws are divided into several categories based on the thread-form used to complete the thread cutting.

Thread Rolling Screws (TRS) - Thread rolling screws are screws that roll or extrude threads in a pre-drilled hole in the substrate without removing any material. These screws produce a very strong bond.

To summarize, the terms "self-tapping" and "self-drilling" are not synonymous. Self-tapping screws are all self-drilling screws, however not all self-drilling screws are self-tapping screws. Both of these screws are widely utilized in the commercial, industrial, and construction areas and come in a variety of configurations.