A ROTARY SCALE

摘要

A rotary ring for use in scale reading apparatus, comprises a flexible ring (10) which has scale markings (14) provided on a surface thereof. The rotary ring is mounted onto a machine part (22) by providing the machine part with a region of increased diameter (26) and stretching or shrinking the flexible rotary scale (10) over said region of increased diameter. The manufacturing tolerance of the rotary scale or differential e.g. thermal expansion is thus taken up by stretching or shrinking it into place. The region of increased diameter may comprise an annular protrusion or an O-ring, for example.