Abstract: A machine vise protractor which can be installed onto and removed from the base of a machine vise while the vise is mounted on a table, to permit rotating the vise about a known center point to a desired angle. The protractor assembly is easy to make, can be adapted to a wide number of machine vises, and can be removed once the vise is properly located to keep the table uncluttered while the vise is clamped in place. The protractor can also be used with a plurality of vises for setting up several machine tools, or with several vises on the same machine tool without incurring the expense of separate protractors for each vise.