Adjustment for draughtsman's ink compasses - writing point held by rocker arm against block mounted on vertical stem

摘要

Draughtsman's compasses for drawing very small circles in ink, have a vertical stem by which they are gripped, with a point (3) at the bottom, and an arm (16) held at an angle to the stem, with the writing point (17) nearby, in the form of an ink delivery tube, both interconnected by a block (6) which fits around the stem, having a tongue (8) extending below it, with a hole into which fits the arm. The tongue is connected to the block by a spring (14) and can rock against it about a pivot (7) under the action of an adjusting screw (15) through the block by menas of which the angle of the arm can be varied, thus determining the size of the circle drawn by the writing point. Other designs of tilting blocks are shown.