Scaled Compass / Compass

Compass is one of the necessary tools for drawing circle and arch in engineering drawing. Usually, the radius or diameter should be measured and marked at first. And then, the compass is used to draw shape according to the mark. This is not convenient, accompanying with extra error. The Scaled Compass integrates the traditional compass with the ruler, which has a ring scale at the top of the legs. The scale between the two red lines indicates the exact distance between the ends of two legs. The user could select radius by turning legs slightly, and draw the shape easily.