TABLE OF CONTENTS Fixed gages embody the direct or reverse physical replica of the object dimension to be measured. The gage may represent the part dimension either in its nominal condition the master gages or in one of its limit conditions resulting from the specified tolerances of the dimension the limit gages.
The master gages, which constitute a direct replica, are primarily used as setting gages for setting up comparator type measuring instruments or as reference standards for calibrating measuring tools that require periodic readjustment. Master gages are dimensioned to represent the dimension to be gaged either in its basic size or the median size of the designed tolerance zone.
The limit gages are made to contain the reverse replica of the dimension to be checked, and are intended for the purpose of inspection gages. Because manufactured parts are made, as a rule, to specific tolerances, the acceptable size of the part is determined by its limit dimensions. Accordingly, for the inspection by fixed gages of any critical dimension on a manufactured part, two gages are usually required that are made to constitute the design limits of that dimension.
The gaging portion of the fixed gage is manufactured to consistently retain a specific size. This goal is usually accomplished by means of rigid gage elements, although gages with adjustable members are also used as fixed gages, particularly in limit gage applications. For the purpose of gage classification, however, the functional service of the gage should be considered...
