Locating Datum of Cast Iron V-block

Cast iron V-block is a special positioning element. Although it is a separate positioning element, but the structural elements of its location base surface is not single. Positioning reference of most positioning elements are positioning the base surface itself or formed therefrom point, surface, line. According to this reasoning, positioning reference of cast iron V-block should have two, one is the intersected line of two positioning plane, another is the plane of symmetry of the two planes, intersected line as vertical positioning reference; the plane of symmetry as horizontal positioning reference.

Because cast iron V-block integrated positioning by two planes, it can not use positioning reference method that analyze single surface of the positioning element.