Cycle Engineers' Institute (CEI)
screw thread

Replaced by the British Standard Cycle thread series.

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
13 0.092 62 49
12 0.104 44 47
1/8 40 2.5 mm
0.154 40 30
5/32 32  
0.175 32 27
3/16 32  23
7/32 26  
¼ 26 4
17/64 26  
9/32 26  
5/16 26  1
3/8 26 8.5 mm
7/16 26  
0.4724
(12 mm)
26  
½ 26  
0.5512
(14 mm)
 26  
9/16  26 +20? 13 mm
5/8    
0.9675 30  
1 26 24.5 mm
1.29 24LH
1.37 24 1 21/64
1 7/16 24LH 35.5 mm
24 37 mm

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