Drawing instrument for symmetrical drawings - has lugs and locking eccentric, securing interchangeable scale plate to baseplate

摘要

The drawing instrument is for symmetrical drawings, and comprises a baseplate, on which and on the paper underneath there bears a scale plate with markings round a circular opening. The latter accommodates a circular disc with cut-out portions of different shapes, and markings corresponding to these portions round its periphery. The scale plate is detachably secured to the baseplate by holding lugs and a locking eccentric. The design allows easy changing of the scale plate, while holding this firmly on the baseplate.(DS).