This International Standard specifies the thread profile and limits and tolerances for the screw threads used to assemble bottom bracket cups to bottom brackets on bicycles (adjustable cups with right-hand thread, fixed cups with lefthand thread). It is based on a) the use of the ISO basic thread profile given in ISO 68; b) satisfactory interchangeability with the corresponding British Standard Cycle (B.S.C.) thread; this has required the use of an inch pitch (t.p.i.); c) the use of screw thread tolerance grades and tolerance positions given in ISO 965-1 ; d) the use of gauges made to ISO 1502.