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British Threads - Cycle Engineering Institute

 

CEI (Cycle Engineers Institute) Thread Data

This thread series was superseded by BSC (British Standard Cycle) thread. The Thread Profiles were kept, but some of the less popular sizes were dropped

No Thread Profile Drawing Available

Angle of thread = 60°.

Cycle Engineers' Institute (CEI) or British Standard Cycle (BSC)

These are different names commonly used for the same threads. 60 degree thread angle, rather than the 55 degree of BSW and BSF. For sizes from 1/4" through 1/2" by far the most common are 26 tpi, although 24 tpi appear as well. Most, but by no means all, fasteners on post-War BSA's (through the late '60's, when it got more complicated) were CEI. Although the thread form and pitch is different, the head sizes on CBI-threaded fasteners use the same wrenches as BSW/BSF.

Size (inches)Wire GaugeThreads per inchPitchCore DiameterUsual ApplicationsTapping Drill Size
0.056
inch
17 WG62 Tpi0.0161 ins0.0388 insSpokesNumber drill 61
1mm 0.0394 inch
0.064
inch
16 WG62 Tpi0.0161 ins0.0468 insSpokes0.0469 inch (3/64)
0.072
inch
15 WG62 Tpi0.0161 ins0.0598 insSpokesNumber Drill 54
0.0551 inch
1.4mm
0.080
inch
14 WG62 Tpi0.0161 ins0.0628 insSpokesNumber Drill 52
0.0635 inch
1.6 mm
0.092
inch
13 WG56 Tpi0.0178 ins0.0729 insSpokesNumber Drill 49
0.0728 inch
1.85mm
0.104
inch
12 WG44 Tpi0.0227 ins0.0798 insSpokesNumber Drill 46
0.0807 inch
2.05mm
0.125
(1/8th) inch
_40 Tpi0.025 ins0.0984 insSmall Fixing
Screws
Number Drill 39
0.1004 inch
2.5mm
0.154
inch
_40 Tpi0.025 ins0.1274 insChain CouplingsNumber Drill 30
0.126 inch
3.25mm
0.175
inch
_32 Tpi0.0312 ins0.1417 insGeneral UseNumber Drill 27
0.126 inch
3.25mm
0.1875
(3/16) inch
_32 Tpi0.0312 ins0.1542 insMisc ScrewsNumber Drill 23
0.1562 inch
3.97mm
0.250
(1/4) inch
_26 Tpi0.0385 ins0.2091 insCrank CottersNumber Drill 3
0.2188 inch
5.56mm
0.266
inch
_26 Tpi0.0385 ins0.2280 insGeneral UseNumber Drill 1
0.2283 inch
5.8 mm
0.281
inch
_26 Tpi0.0385 ins_ ins_Letter Drill D
0.2441 inch
6.2 mm
0.3125
(5/16) inch
_26 Tpi0.0385 ins0.2715 insFront Wheel SpindlesLetter Drill J
0.2756 inch
7 mm
0.5625
(9/16) inch
_20 Tpi0.05 ins0.498 insPedal Pins in
RH and LH Thread
0.5156 (33/64) inch
13.1 mm
0.9675
(9/16) inch
_30 Tpi0.033 ins0.954 insSteering Stems_
1 inch_26 Tpi0.0385 ins0.959 insSteering Stems0.9688 (31/32) inch
24.61.1 mm