The term “self-tapping” is often misused when describing a fastener. Many people think a self-tapping screw creates it's own pilot hole. This is a common misconception, in fact, self-tapping screws require a pre-drilled hole prior to installation. Self-tapping screws are categorized as either thread-cutting or thread-forming.
Thread-cutting screws are normally used in wood or metal applications where internal stress is undesirable. Sharp cutting edges of the screw make threads in the mating material. The chip cavity on a thread-cutting screw provides space for the material removed when cutting.
In contrast, thread-forming screws form threads by pushing the fastened material outward. This creates a tight fit which increases the screw’s pull out strength. Sheet metal screws, u drive screws, thread-rolling screws, self-piercing screws, lag screws, deck screws, and wood screws are all common types of self-tappers we supply at Shamrock Express.
Self-drilling screws, also called by the brand name Tek® screws, perform double duty reducing both installation time and cost. They have the ability to drill their own pilot hole and form mating threads during installation. Self-drillers have tips in the shape of a drill bit which come in types 2, 3, 4, and 5 and vary by length.
When choosing the best screw for your job it is important to choose a tip that is long enough to clear the material before thread engagement to avoid thread damage. If you have questions, ask an experienced member of the Shamrock Express team for technical assistance. A full line of thread-cutting screws and thread-forming screws ship daily nationwide.
By Allen Wajda