British Standard Cycle (BSC) or (BSCy) is a British Imperial screw thread standard. Unlike other major British imperial thread standards (British Standard Whitworth and British Standard Fine) the thread runs at a 60 degrees rather than a 55 degrees angle. It generally comes as 26 threads per inch (tpi) and is similar to 1 mm ISO threads which are equivalent of 25.4 threads per inch and also run at a 60 degrees angle. It was originally used with both bicycles and motorcycles.[1] However it is now believed to be obsolete in motorcycle manufacture. In the bicycle industry it is still found on wheel axles of low-end models manufactured in China.
Traditionally the parts it would be found on are:
Note that M8 × 1.00 metric threaded parts can interchange with 5/16th × 26 tpi parts with a "Class B fit", meaning you should not go back and forth between threadings. British Bicycle standards for other parts which are not strictly BSC but come in similar fine fines include: