Selftapping – vs. selfdrilling screws: what is the difference?

Self-drilling vs. self-tapping screws

Both screws are commonly used in steel- and general constructions. They also serve the same purpose as they are usually used to attach two pieces of material together when you only have access to one side of the material.

However, it is important to know the differences as both terms are often used interchangeable, which can lead to annoying situations.

Self-tapping screws

The name itself already suggest the main trait of these screws: a screw that cuts or forms its own thread in material like plastic, wood or metal. Self-tapping screws can basically be divided into two classes:

Thread forming: screws that displace material to form thread, so the material is not removed
Thread cutting: screws with sharp cutting thread that remove the material

Synonym(s): Parkers, Parker-screws, sheet metal-screws

Applications: fixing of one or two sheet metals, fixing aluminium profiles together, screws in plastic housing,…

Self-drilling screws

Also here the name predicts the main trait: these screws not only tap their own thread into the material, they also drill themselves into the material. This makes them very efficient, as you don’t need to pre-drill a whole, tap thread and install the screw separately. The screws can easily be recognized by the drill-like fluted tip that looks like the tip of a center drill.

When chosing self-drilling screws it is important to take the two following aspects into account:

Thickness of the material
What materials need to be joined together

The thickness of the material determines the diameter of the screw you should use. Below you can find an overview of the different diameters with their respective maximum plate thickness (G max.).

Table material thickness self-drilling screws

Applications: fixing roofplates, fixing HVAC ducts and brackets, skeleton construction, carports, platforms, garages,…

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