The flutes allow drilled material to exit the hole. Once the flutes become completely embedded in the material, they can no longer remove the chips cut from the work material. Since these chips contain approximately 80% of the heat created by the drilling process, this can cause the point to over-heat and fail. The length of the drill point determines the material thickness which the screw can reliably penetrate. The unthreaded portion of the point, known as the pilot section, must be long enough to completely drill through the material before the threads engage. Since the threads advance faster than the drilling process, if they engage before drilling is done the fastener can bind and break. The integral washer recess is to accommodate a resilient watertight sealing washer. The washer surface provides bearing surface to the drive socket.
- No drilling or thread cutting tool required
- No centre punching
- No pre-drilling
- No thread cutting
- No hole offsetting in the component
- High drilling performance
- More economical
For hard substrates such as metal or hard plastics, the self-tapping ability is often created by cutting a gap in the continuity of the thread on the screw, generating a flute and cutting edge similar to those on a tap. Thus, whereas a regular machine screw cannot tap its own hole in a metal substrate, with a self-tapping screw one can. For softer substrates such as wood or soft plastics, the self-tapping ability can come simply from a tip that tapers to a gimlet point (in which no flute is needed When selecting a self-drilling screw design, it is important to consider the material thickness and type of materials to be joined. There are key design features to consider when selecting a suitable fastener for Roofing application.