| 摘要 |
<p>A multi-purpose drawing instrument comprising a set square (1) with a measured graduations on its sides, an aperture (13) formed in said set square (1), a flat disc (5) supported for rotation within said aperture, said disc (5) being formed with a multiplicity of openings (7) for receiving a marking instrument, the openings (7) being spaced at predetermined radii from the centre of the disc to enable circles of radii corresponding to said openings to be drawn by rotating the disc by means of the marking instrument engaging one of said openings (7), a retaining ring (9) overlying the edge of said disc to retain said disc in said aperture (13), said retaining ring having gradations (10) divided into 360° to enable a desired angle to be drawn by rotating the disc (5) through a predetermined arc from any set point, additionally the set square (1) has template type openings (11) for drawing smaller diameter circles and other shapes such as benzene rings (12).</p> |
