Compass (drafting)

A pair of compasses, also known simply as a compass, is a technical drawing instrument that can be used for inscribing circles or arcs. As dividers, they can also be used as tools to measure distances, in particular on maps. Compasses can be used for mathematics, drafting, navigation and other purposes.

Compasses are usually made of metal or plastic, and consist of two parts connected by a hinge which can be adjusted to allow the changing of the radius of the circle drawn. Typically one part has a spike at its end, and the other part a pencil, or sometimes a pen.

Prior to computerization, compasses and other tools for manual drafting were often packaged as a "bow set" with interchangeable parts. Today these facilities are more often provided by computer-aided design programs, so the physical tools serve mainly a didactic purpose in teaching geometry, technical drawing, etc.

Compasses are usually made of metal or plastic, and consist of two parts connected by a hinge which can be adjusted to allow the changing of the radius of the circle drawn. Typically one part has a spike at its end, and the other part a pencil, or sometimes a pen.

The handle is usually about half an inch long. Users can grip it between their pointer finger and thumb.

There are two types of legs in a pair of compasses: the straight or the steady leg and the adjustable one. Each has a separate purpose; the steady leg serves as the basis or support for the needle point, while the adjustable leg can be altered in order to draw different sizes of circles.

The screw on your hinge holds the two legs in its position; the hinge can be adjusted depending on desired stiffness. The tighter the screw the better the compass’ performance.

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Wikipedia