Thread type: BSC - British Standard Cycle Thread

British bicycle thread

The BSC thread from the table is a British thread that is specially designed for use on bicycles. BSC stands for British Standard Cycle or British bicycle thread. It was originally developed as a thread for both bicycles and motorcycles, but is now used almost exclusively in the bicycle sector. The BSC thread has a flank angle of 60°, which distinguishes it from most other British thread types, which usually have a flank angle of 55°. In addition, according to the BSC thread table, the thread has a fine pitch, which is directly related to the application of the thread. It leads to good self-locking, which makes all thread sizes in the BSC thread table particularly resistant to vibrations. This ensures that screws cannot loosen by themselves, even on long journeys over uneven ground.

As you can see from the BSC thread table, the pitch is a particularly interesting aspect of this thread. As with most inch threads, the pitch in the BSC thread table is given in threads per inch. This value is 40 or 32 threads per inch for the first three thread sizes, but remains constant at 26 threads per inch for all other sizes. For this reason, the BSC thread often gives the impression that it is a thread with a fixed pitch. However, the BSC thread table clearly shows that this is not the case and that the pitch differs for at least some sizes.

The thread designation in the BSC thread table is made up of the abbreviation BSC and the outside diameter in inches. In the BSC thread table, we have listed this outside diameter again, including a practical conversion to mm. Also listed in the BSC thread table are the core hole diameter and the pitch. As is usual for inch threads, we have listed the number of threads per inch. In addition, we have also added a conversion to the pitch in mm to our BSC thread table. This means you have all the required values to hand, even if you prefer to work in metric.

   outside-Ø in Inchoutside-Ø in mmcore hole-Ø in mmThreads per InchPitch P in mm
BSC 1/8"1/83,1752,50400,635
BSC 5/32"5/323,9693,13320,794
BSC 3/18"3/184,2333,92320,794
BSC 7/32"7/325,5564,52260,977
BSC 1/4"1/46,3505,31260,977
BSC 9/32"9/327,1446,10260,977
BSC 5/16"5/167,9386,90260,977
BSC 3/8"3/89,5258,49260,977
BSC 7/16"7/1611,11310,07260,977
BSC 1/2"1/212,70011,66260,977
BSC 9/16"9/1614,28813,25260,977
BSC 5/8"5/815,87514,84260,977
BSC 11/16"11/1617,46316,42260,977
BSC 3/4"3/419,05018,00260,977
Cross section of a BSC thread