| 摘要 |
<p>The draughtsmans arc template has one or more sets of concentric arc-shaped cut out portions extending to one or both sides of a common radial line and pref. symmetrical in relation to it. It has one or more datum edges (12) inclined to the radial line (2) or to a first datum edge (9) to the side of the arc centre and at right angles to this radial line. Its angle of inclination corresponds to the arc lengths of the cut out ports (3-7) from the radial line to their ends or to datum marks before the ends. There can be a second datum edge inclined at the same angle, but in the opposite direction, and a second set of arc-shaped cut out portions (14, 15) coaxial to the first and to which the radial line is common. Their length is different from that of the first set, a separate datum edge (16) being provided for them.</p> |
