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British Threads - British Standard Cycle

 

BSC (British Standard Cycle) Thread Data

This fine thread profile was formulated for, and is well suited to cycle and motorcycle applications. Its fine pitch, allows high torque settings, and resists the tendancy to loosen under vibration, the larger core diameter also gives greater shear strength. Most people think that all cycle threads are 26 tpi pitch. Whilst this is true of all the most popular sizes from 1/4" to 3/4" diameter, other pitches were also used as shown in the tables seen in the CEI section

We have numerous taps and dies in BSC with 20 tpi threads.

Angle of thread = 60°

BSC Thread Profile

Diameter
(Inches)
Threads
per inch
Pitch
(Inch)
Core
Diameter
(Inch)
Tapping Drill Size
0.125
(1/8th) inch
40 Tpi0.0250.0984 insNumber Drill 39
0.1004 inch
2.5mm
0.1563
5/32 inch
32 Tpi0.03120.1231 insNumber Drill 30
0.126 inch
3.25mm
0.1875
(3/16) inch
32 Tpi0.03120.1542 insNumber Drill 23
0.1562 inch
3.97mm
0.250
(1/4) inch
26 Tpi0.03850.2091 insNumber Drill 3
0.2188 inch
5.56mm
0.281
(9/32) inch
26 Tpi0.03850.2403 insLetter Drill D
0.2441 inch
6.2 mm
0.3125
(5/16) inch
26 Tpi0.03850.2715 insLetter Drill J
0.2756 inch
7 mm
0.375
(3/8) inch
26 Tpi0.03850.334 insLetter Drill R
0.3368 inch
8.65 mm
0.4375
(7/16) inch
26 Tpi0.03850.3965 insLetter Drill X
0.3976 inch
10.1 mm
0.5
(1/2) inch
26 Tpi0.03850.4590 ins0.4606 inch
11.7 mm
0.5625
(9/16) inch
26 Tpi0.03850.5215 ins0.5156 (33/64) inch
13.1 mm
0.625
(5/8) inch
26 Tpi0.03850.5840 ins0.5906 inch
15 mm
0.6875
(11/16) inch
26 Tpi0.03850.6465 ins0.6496 inch
16.5 mm
1 inch26 Tpi0.03850.959 ins0.9688 (31/32) inch
24.61.1 mm