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BA |
BSC |
BSF |
BSP |
BSTP |
BSW |
CEI |
UNC |
UNF |
ME |
BSB
BSC - British Standard Cycle
Diameter
(Inches) |
Threads
per inch |
Pitch
(Inch) |
Core
Diameter
(Inch) |
Tapping
Drill Size |
0.125
(1/8th) inch |
40 Tpi |
0.025
|
0.0984
ins |
Number
Drill 39
0.1004 inch
2.5mm |
0.1563
5/32 inch |
32 Tpi |
0.0312
|
0.1231
ins |
Number
Drill 30
0.126 inch
3.25mm |
0.1875
(3/16) inch |
32 Tpi |
0.0312
|
0.1542
ins |
Number
Drill 23
0.1562 inch
3.97mm |
0.250
(1/4) inch |
26 Tpi |
0.0385
|
0.2091
ins |
Number
Drill 3
0.2188 inch
5.56mm |
0.281
(9/32) inch |
26 Tpi |
0.0385
|
0.2403
ins |
Letter
Drill D
0.2441 inch
6.2 mm |
0.3125
(5/16) inch |
26 Tpi |
0.0385
|
0.2715
ins |
Letter
Drill J
0.2756 inch
7 mm |
0.375
(3/8) inch |
26 Tpi |
0.0385
|
0.334
ins |
Letter
Drill R
0.3368 inch
8.65 mm |
0.4375
(7/16) inch |
26 Tpi |
0.0385
|
0.3965
ins |
Letter
Drill X
0.3976 inch
10.1 mm |
0.5
(1/2) inch |
26 Tpi |
0.0385
|
0.4590
ins |
0.4606
inch
11.7 mm |
0.5625
(9/16) inch |
26 Tpi |
0.0385
|
0.5215
ins |
0.5156
(33/64) inch
13.1 mm |
0.625
(5/8) inch |
26 Tpi |
0.0385
|
0.5840
ins |
0.5906
inch
15 mm |
0.6875
(11/16) inch |
26 Tpi |
0.0385
|
0.6465
ins |
0.6496
inch
16.5 mm |
| 1 inch |
26 Tpi |
0.0385
|
0.959
ins |
0.9688
(31/32) inch
24.61.1 mm |
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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[by whom?] 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:
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 × 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:
Bottom Bracket cups diameter with a 24 tpi ISO standard or a 26 tpi Raleigh (now obsolete) standard.
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