A simple solution to squaring your machine. Zero the indicators on a flat surface, install the Spindle Square in the milling machine spindle, bring the spindle down to the table, and adjust the head until both indicators read the same. 3/8-inch shank; Fully assembled with indicators mounted and ready to use; No more tramming or split reading, compensating for loose, worn gears or mirrors; Can also be used with a sine bar or protractor to set angle; Constructed of steel with precision-ground contact points for durability and accuracy; Includes fitted case