DCOLO Cobalt, Long Length 1/4-28 Threaded Shank Adapter Drills, Size: #D, NAS965-D. Widely used in the aircraft industry, threaded shank adapter drills facilitate access to space-restricted areas unsuited for standard chuck-type drills. They can be used with a host of angle-drills and offset drills. All threaded shank adapter drills feature 135° split points.