Position lock for folding rule for setting angles

摘要

One end (1) of a section of the rule is provided with a circular recess. The bottom of the recess has a bevel gear profile of heights (2) and valleys (3). The end (4) of the next section has a matching raised bevel gear profile. When the two ends are riveted together they form a friction coupling which locks the rule sections together at angles determined by the angular pitch of the bevel profile. The angles are not 90 deg .