CL. Drill. Major Diameter. TAPPING. Effective Diameter. NUT DATA. No. OD. TPI. CLEARING. NUT DATA. DRILL. BA THREAD CHART. % A/F. DIA. ThickB. Minor Diameter. Thread Size. Minor Diameter: D Min: DMin: Max: DMin: MaxBA#BA#BA#BA The basic sizes of the major diameter, in millimetres, have been calculated from the formula 6P 6/The form of the B.A. thread is specified as having the crests and roots rounded with equal radii, such that the basic depth of thread istimes the pitch (see Clauseand Figure 1