Fasteners - Screws

Screws are most often used to fasten materials such as wood and metals; however, they can also be used with other materials. This article provides information on screw types.

Screw Composition

Screws are metal fasteners that have a threaded shank, which is driven by turning. The threads prevent the screw from pulling out.

The head of the screw has a recessed area that accepts a tool, such as a drill or screwdriver, which turns the screw into place. Various shapes are used depending on the type of materials being fastened, the intended appearance, and the type of driving device.

The threads are the helical ridges along the screw, which provide the friction that keeps the two materials together..

The pitch is the distance between threads. Coarse-threaded screws have a larger pitch, i.e. the threads are farther apart.

Screw Types

Wood Screw Generally coarse-threaded, threaded point that creates its own mated threads in wood.		Drywall Screw Bugle head, thin shank, specifically designed to fasten drywall to studs, often used as a multi-purpose screw.
Sheetmetal Screw Short, coarse-threaded, typically a round head. Used to fasten sheetmetal or other thin materials.		Cap Screw Threaded screw, no point, used to fasten machine parts with pre-threaded holes. Driven with a bolt driver rather than a screwdriver.
Machine Screw Narrow shank, fine-threaded, used with a nut or driven into a pre-threaded hole.		Set Screw No head, the shank is slotted.

Screw Head Shapes

Screws have various head shapes that are used for different materials or final appearances.

Flat Head		Pan Head		Round Head		Truss Head
Oval Head		Fillister Head		Bugle Head

Screw Head Types

Screws have different slots in the head to accept the different types of driving tools.

Slotted Head

Phillips Head

Allen Head

Square Head

Security Head