UNC Thread Form P = Pitch = 1/Number of threads per inch (tpi) H = Angular Depth = 0.866025 x P H/8 = Shortening of major dia = 0.108253 x P H/4 = Shortening of minor dia = 0.216506 x P d = Actual Depth = 0.541266 x P r = Radius at the Root = 0.1443 x P Hn = Basic height of Internal Thread = 0.54127 x P Hs = Basic height of External Thread = 0.61344 x P BSW Thread Form P = Pitch = 1/Number of threads per inch (tpi) h = Angular Depth = 0.960491 x P D = Depth of Rounding = 0.073917 x P h/6 = Shortening = 0.160083 x P d = Actual Depth = 0.640327 x P r = Radius at the Crest & Root = 0.137329 x P C = Core diameter = Major Diameter - 1.280654 x P Effective or Pitch Diameter = Major Diameter - .640327 x P BSF Thread Form P = Pitch = 1/Number of threads per inch (tpi) h = Angular Depth = 0.960491 x P D = Depth of Rounding = 0.073917 x P h/6 = Shortening = 0.160083 x P d = Actual Depth = 0.640327 x P r = Radius at the Crest & Root = 0.137329 x P C = Core diameter = Major Diameter - 1.280654 x P Effective or Pitch Diameter = Major Diameter - .640327 x P BA Thread Form P = Pitch = 1/Number of threads per inch (tpi) h = Triangular height = 1.1363365 x P d = Actual Depth = 0.60000 x P t = Shortening = 0.2681688 x P r = Radius at the Crest & Root = 0.1808346 x P Effective or Pitch Diameter = Major Diameter - 0.6000 x P (d) C = Core diameter = Major Diameter - 1.2000 x P (2d) Nuts and Bolts across flats is nominally 1.75 x Major Diameter