Standardized bushings are shown in Fig, J4-1 and the six basic types are shown in Fig. 14-2. They comprise press-fit and renewable bushings. Press-fit bushings are either liner bushings or press-fit wearing bushings, however, for the same diameter, liner bushings are shorter. Liner bushings are provided with and without heads and are permanently installed in a jig to receive the renewable wearing bushings. They are sometimes called "master bushings." Press-fit wearing bushings to guide the tool are for installation directly in the jig without the use of a liner and are employed principally where the bushings are used for short production runs and will not
require replacement. They are also intended for use where the closeness of the center distance of holes will not permit the installation of liners and renewable bushings. Press-fit wearing
bushings are made in two types, with heads and without