Screws come in a variety of materials such as brass, stainless steel, nylon, aluminum, copper, titanium and ceramic. Screw driving shapes, which are located on the head of the screw, are used to determine the tools needed to tighten or loosen the screw. The thread of screws play an important part of their function and each type of screw has a variety of uses.
Wood screws are available in a variety of materials and screw heads, and are used exclusively for wood. These screws have a smooth shank and taper along the threaded portion of the screw. The smooth shank allows the screw to pull two pieces of wood together tightly and allows for the screw to go all the way into the wood so there is no screw sticking up above level surface. The tapering of the screw optimizes the screws holding power in wood. Wood screws are available in brass, silicon bronze, stainless steel and zinc plated steel. A variety of sizes and gauges are available for wood screws.
Sheet metal screws are highly versatile and can be used in wood, metal and fiberglass. These screws are available in pan head, flat head, oval head and washer head. Pan head screws will protrude above the surface of the material to be fastened and flat head sheet metal screws will create a smooth surface area. Oval head screws are similar to the flat head, but have a more finished looked and slightly round top. Washer head type sheet metal screws have a hex head and washer attached. This screws are available in zinc plated steel and stainless steel. Gauges available for sheet metal screws range from 4 to 14 and have lengths from ¼ inch to 2 inches.
Machine screws, also called stove bolts, are blunt-ended and mainly used to fasten metal parts together. The screws are manufactured with four basic head types; oval head, round head, flat head and fillister head. These are commonly available in steel or brass; however, can also be purchased with brass, nickel, galvanized, cadmium, zinc and copper coatings. The coatings help to deter rust. Available sizes are 2 to 12 gauge and ¼ inch to 3 inches. The diameters of machine screws range from ¼ inch to ½ inch.