The National Machine Tool Builders Association (now called the Association for Manufacturing Technology) defined a steep taper that is commonly used on milling machines. The taper is variously referred to as NMTB, NMT or NT. The taper is 3.500 inches per foot and is also referred to as "7 in 24" or 7/24; the computed angle is 16.5943 degrees. All NMTB tooling has this taper but the tooling comes in different sizes: NMTB-10, 15, 20, 25, 30, 35, 40, 45, 50 and 60. These tapers were apparently also specified in ASA (now ANSI) B5.10-1943.