Stainless Steel DIN7504n Countersunk Csk Philips Flat Head Self Drilling Screws Flat Self Tapping Screw

Some self-tapping screws such as the Tek screw brand, are also self-drilling, which means that in addition to the thread-forming section there is also a fluted tip much like the tip of a center drill. These screws combine hole drilling, threading and fastener installation into one driving motion (instead of separate drilling, tapping, and installing motions); they are thus very efficient in a variety of hard-substrate applications, from assembly lines to roofing. Some types incorporate a sealing washer, for fastening roofing sheets to purlins.