tap-like flute in the leading threads, there is also a preliminary drill-like fluted tip that looks much like the tip of a center drill. These screws combine a threading-like action and the fastener installation itself into only 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. Brands such as the Tek screw integrate a self-drilling screw and sealing washer to quickly stitch together, for example, roofing sheets. Sheet metal screw Sheet metal screws (sometimes called "sheet-metal self-tappers", or P-K screws from the brand name Parker Kalon - who pioneered the manufacture of, but did not invent, these screws) are a type of self-tapping screw despite the thread created in the sheet of metal being small. Pan-head PK Self-tapping screws are common in electrical equipment, while flatter-headed truss or flat countersunk headed self-tapping screws are more common in aviation applications. Winged self-tapper Winged self-drilling have thin wings wider than the thread formed just behind the self drilling head. These cut a clearance hole in soft materials (such as wood or plastic), but are destroyed by more robust materials (such as metal). Thus, to clamp some material to metal, the clearance drilling, tap drilling, thread tapping, and fixing itself can happen in a single operation from one side, with the materials in their final position. Applications Self-tapping screws are used in a variety of applications ranging from DIY carpentry to surgery. Surgical Dental implants and orthopedic bone screws are both examples of self-tapping screws used in surgery. Different thread profiles are used for either denser cortical bone or the spongy cancellous bone. See also Fasteners with a tapered shank Tap References External links "Hold Everything", February 1946, Popular Science bottom of page 151 Screws