British Standard Cycle
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. However it is now believed[by whom?] to be obsolete in motorcycle manufacture. In the bicycle industry it is still found on virtually all bottom bracket threads and the wheel axles of low-end models manufactured in China.
Traditionally the parts it would be found on are:
- Front axle and seat pin 5/16th inch diameter (7.94 mm), 24 or 26 tpi threading
- Rear axle 3/8th inch diameter (9.53 mm), 26 tpi
- GB Stems using 5/16th inch diameter (7.94 mm), 26 tpi for the handlebar clamp
Note that M8 × 1.00 metric threaded parts can interchange with 5/16th × 24 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:
- Bottom Bracket cups diameter with a 24 tpi ISO standard or a 26 tpi Raleigh (now obsolete) standard
- Morgan, Brian. "BSC (British Standard Cycle) Thread Data". Retrieved 2009-06-05.
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