Compasses of ability direct measurement size

The utility model discloses a compasses of ability direct measurement size comprises slide rule nut (1), cylinder handle (2), cell type leg frame (3), compasses pivot (4), slide rule screw rod (5), compasses right side leg (6), compasses left side leg (7), size marking (8), compasses slide rule (9), compasses needle (10) water -color paintbrush spring (11), water -color paintbrush (12), water -color paintbrush nut (13), water -color paintbrush head (14). Firstly, slide rule screw rod (5) are upward threaded, and will rise thereupon or descend in slide rule screw rod (5) and compasses slide rule (9) when rotating slide rule nut (1). Secondly, compasses right side leg (6) and compasses left side leg (7) superscript are carved with size marking (8), and the scale interval above it has the relation that equals that corresponds with the radius that compasses are drawn. A radius size is accurate that compasses of ability direct measurement size, not with the help of the ruler radial circle of fixed length that just