British Standard Cycle (BSC or BSCy) is a British Imperial screw thread standard. Unlike other major British imperial thread standards (

British Standard Whitworth British Standard Whitworth (BSW) is an imperial-unit-based screw thread standard, devised and specified by Joseph Whitworth in 1841 and later adopted as a British Standard. It was the world's first national screw thread standard, and is the basi ...

and British Standard Fine) the thread runs at a 60 degrees rather than a 55 degrees

angle In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the ''vertex'' of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles ...

. All sizes inch and larger use 26

threads per inch A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a ...

(tpi), making them similar to 1 mm ISO threads, which are 25.4 per inch and also run at a 60 degrees angle. It was originally used with both

bicycle A bicycle, also called a pedal cycle, bike or cycle, is a human-powered or motor-powered assisted, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A is called a cyclist, or bicyclist. B ...

s and

motorcycle A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle Steering, steered by a Motorcycle handlebar, handlebar. Motorcycle design varies greatly to suit a range of different purposes: Long-distance ...

s. However it is now believed 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, which are derived from pre-WWII British roadsters. Cycle thread in and inch sizes also come in 20 tpi and 24 tpi options. Traditionally the parts it would be found on are: * Front axle and seat pin clamp bolt diameter, 24 or 26 tpi threading * Rear axle diameter, 26 tpi * GB Stems using diameter, 26 tpi for the handlebar clamp Note that M8 × 1.00 metric threaded parts can interchange with diameter × 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 threads include: * Bottom Bracket cups diameter with a 24 tpi ISO standard or a 26 tpi

Raleigh Raleigh (; ) is the capital city of the state of North Carolina and the seat of Wake County in the United States. It is the second-most populous city in North Carolina, after Charlotte. Raleigh is the tenth-most populous city in the Southeas ...

(now obsolete) standard

History

The thread was defined to meet a requirement for a thread form for

s and

s, originally specified by the

Cycle Engineering Institute The Institution of Mechanical Engineers (IMechE) is an independent professional association and learned society headquartered in London, United Kingdom, that represents mechanical engineers and the engineering profession. With over 120,000 membe ...

. Before being adopted as a British Standard it was known as the CEI thread.

References

Thread standards Screws British Standards {{standard-stub

History

See also

References