British Standard Cycle (BSC)

screw thread series

Sometimes the symbol “BSCy” is used. This series replaced the Cycle Engineers' Institute (CEI) thread. Though the two series are somewhat different, in the early 21st century the BSC series was still sometimes being called the CEI series. For an even earlier thread, see the bottom of the BSW page.

Symmetrical 60° thread angle, with rounded roots and crests having a radius of 0.166 times the pitch. Actual depth, 0.5327 times the pitch. The smaller sizes are for spokes.

Imperial
Wire Gauge
Diameter
inches
Threads
per inch
Tap Drill Size
17 0.056 62 61
16 0.064 62 56
15 0.072 62 54
14 0.080 62 1/16 inch
13 0.920 56 49
12 0.104 44 47
0.125 40 2.5 mm
0.154 40 30
0.175 32 27
0.1875 32 23
0.250 26 4
0.266 26 1
0.281 26 C
0.3125 26 J
0.375 26 8.5 mm
0.5625 20 13 mm
1.000 26 24.5 mm
1.290 24 1¼ inch
1.370 24 1 21/64 inch
1.4375 24 35.5 mm
1.500 24 37 mm

British Standard 811-1938. British Standard Cycle (B.S.C.) Threads.

Resources

Fasteners with these threads can be obtained from:

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