Self-tapping screws and self-drilling screws are two of the most common types of fasteners. Both types of screws are heavily used in general construction, especially when it comes to metal fastening.
However, the differences between self-drilling screws and self-tapping screws can sometimes fly under the radar.
Let’s dive into self-drilling screws and self-tapping screws, how they work, and their individual use cases.
Self-drilling screws are easily distinguished by their drill-bit-shaped tip. They’re often called Tek® Screws after the brand that made the screw a household name.
The drill-bit tip of a self-drilling screw allows the screw to be used without a pilot hole, allowing the user to save time. It may not seem like much, but if many screws need to be used, drilling every pilot hole can eat up a considerable amount of time.
The drill points on a self-drilling screw vary in length and thickness. The screws use a number system of 1 through 5 to identify these characteristics. There are also variations in screw length and head styles, with common head styles including Phillips, hex, and square.
Self-drilling screws are capable of fastening alike materials, such as metal to metal, or two different materials, such as metal to wood. They’re typically used in lighter gauge applications. However, a #5 drill point self-drilling screw is capable of fastening heavier-duty materials, such as a half-inch steel sheet.
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. What a self-tapping screw can do is tap threads into the material being used, as the name suggests. The tapping action is an extra layer of protection to ensure that the materials remain fastened together.
Self-tapping screws have a variety of tip styles available, and these tips determine how the threads are tapped. For example, a pointed self-tapping screw cuts the thread into the material, while a flat tip screw rolls a thread into the material.
One of the most important aspects of using self-tapping screws correctly is the hole size. If the pilot hole is too big, the screw won’t fasten properly, won’t create an effective thread, and can’t secure the material. If the hole is too small, a self-tapping screw can actually split or crack the material.
Self-tapping screws work well in several applications, from metals to plastics and even some forged materials, such as aluminum or iron.