Curvature knife for the determination of the curvature is concave and convex circular arcs or solid circles in the trades

摘要

When the aim in handicrafts is subsequently to determine the centre normal or centrepoint on a circular part or a circular arc, in the absence of such a measuring instrument this can be done only graphically or using templates. This measuring instrument would therefore represent a useful simplification. The three application points on the measuring instrument are adapted to the existing radius. Via a mechanical transmission (e.g. toothed wheel shaft) the part with the drawing edge is swivelled in or out by 1/2 the number of degrees by which the right-hand outer runner is set (see drawing). This mode of operation follows from the logic that the three application points, which must be at the same distance from one another, always form two equilateral triangles together with the centrepoint of the circle to be measured. The drawing edge must lead onto the axis of the application point located therebelow. The measuring instrument could additionally be fitted with an automatic radius scale. The measuring instrument can be used in the case of outer and inner circular arcs. It can be used on both sides, and therefore is also functional in the region where a circular arc is cut off. IMAGE