This part of IS0 228 specifies the verification, by means of limit gauges, of cylindrical threads, the dimensions and tolerances of which are given in IS0 228-l. Symbol Explanation b3 Width of clearance groove at the major and minor diameter respectively of the thread profile with truncated flanks For industrial applications (see for example IS0 1179), it may be necessary to carry out additional checks. I d= D 1 Basic major diameter of the thread I - 1,280 654 P : Basic minor diameter of the 1 d’ = D1 1 iredad 1 d2 = D2 1 thread - d - 0,646 327 P : Basic pitch diameter of the Since this 55O profile has different elements to be verified, it is necessary to provide for several GO and several NOT GO gauges : m Distance between the middle of the tolerance zones TR of the threaded ring gauge and TcP of the GO check plug a) the threaded GO gauges (see clauses 6 and 7) shall ensure that the profile of the machined piece does not exceed the maximum of material provided for by the tolerances applied to the dimensions of the profile defined by IS0 228-l; I n I Nominal value of b3 I I P I Pitch I Displacement of the clearance groove with trun- 1 ’ ( cated flanks I b) the threaded NOT GO gauges for the threads of the pieces (see clauses 6 and 7) fix the minimum material limit on the flanks of the thread.