Self drilling screws are ideal for fastening materials made from different types of substrates

Self drilling screws are ideal for fastening materials made from different types of substrates. This makes them perfect for projects like metal roofing, HVAC ductwork and steel frames.

The Wire

Self drilling screws, also known as Tek screws because of their drill bit-shaped point, eliminate the need for predrilling a pilot hole by drilling through and cutting threads in one action. The sharp point and mating threads cut through wood or metal to keep materials fastened together.

Stainless steel is used to create the screw head, shaft and thread. Heated treated versions are available up to 40 Rockwell C, allowing the drill point to penetrate hard resilient materials.

The Head

Unlike tapping screws, self drilling screws are designed with a drill point that eliminates the need to pre-drill a hole. Also known as Tek Screws, these steel fasteners have a point that creates its own hole and thread in one action. They also do not require a drill bit and are a faster option than traditional screws.

Drill points can fail if they are drilled into materials that are harder than the screw material. This can be caused by the application of too much force, using a screw that is not the correct size for the material being worked or due to improper placement.

Self-drilling screws with flat heads land flush with the surface and can be easily hidden with a screw cover. This type of head provides a low profile and decreases driving torque. They are used to frame structures and connect wood to metal including curtain wall and glazing applications. Stainless steel self drilling screws are available for use in harsh environments.

The Point

The point of a self drilling screw is shaped like a drill bit and is used in various fastening applications. It eliminates the need to pre-drill a pilot hole for the screw, making it more time and cost-efficient.

The length of the point determines the material thickness that the screw can reliably penetrate. The unthreaded portion of the drill point should be able to fully drill through the working material, either metal or wood, before the thread gets engaged. Otherwise, the fastener can bind or break.

The tip of the point also comes with wings that help enlarge holes in the fastened materials. This prevents the screws from separating from their base metal and helps the screw maintain its threads in the fastened materials. This feature is especially important for sheet metal work.

The Drilling Process

Like any cutting tool, the performance of a self drilling screw is determined by its basic parameters. These include point geometry, point length and the working material being fastened.

As with a drill bit, the point of a self drilling screw must be able to drill the initial hole into the working material before the threads engage. Failure to do so can result in the point becoming stuck or breaking.

The points of self drilling screws come in both coarse and fine options depending on the application and are available in different diameters and lengths. Coarse, designated as Type BSD, are tapping screw spaced threads and fine, designated as Type CSD, are standard right-hand threads that approximate the Unified series of machine screw diameter/pitch combinations.

In order for a self drilling screw to be effective, it must be inserted at the speed specified by the manufacturer. Failure to do so will cause the drill point to overheat which can shorten its life.