A metal screw with a sharp point designed to attach two pieces of wood together. Wood screws are commonly available with flat, pan or oval-heads. A wood screw generally has a partially unthreaded shank below the head. The unthreaded portion of the shank is designed to slide through the top board (closest to the screw head) so that it can be pulled tight to the board to which it is being attached.
Similar to drywall screw except that it has improved corrosion resistance and is generally supplied in a larger gauge. Most deck screws have a type-17 (auger type) thread cutting tip for installation into decking materials. They have bugle heads that allows the screw to depress the wood surface without breaking it.
Machine screws are uniformly threaded screws of ¼ inch nominal diameter or less that are designed to be threaded into uniformly threaded nuts or threaded holes in the parts they are intended to fasten. Machine screws are available in a wide array of configurations, materials, driver head types and sizes. As their name implies, machine screws are used to fasten various components together in machines, tools, appliances, electronic devices and vehicles of every description.
Self-tapping screws have a wide range of tip and thread patterns, and are available with almost any possible screw head design. Common features are the screw thread covering the whole length of the screw from tip to head and a pronounced thread hard enough for the intended substrate, often case-hardened.
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.