Alpha HSS Tap Set UNF-5/16x24 UNFHS516INTERMEDIATE taps have a lead of four threads and are used in most general purpose applications. Alpha Intermediate taps can be identified by the two rings on the shaft near the driving square. BOTTOMING taps have a lead of two threads and are used when tapping blind holes. Usually preceded by a taper or intermediate tap. Alpha bottoming taps can be identified by their plain shaft, they have no rings on the shaft near the driving square. Diameter: 5