BSF (British Standard Fine) Thread Data
Since 1908 this thread, in conjunction with BSW (British Standard Whitworth) has been the mainstay of British Engineering, and was used when finer pitches were required.
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Angle of thread = 55
o
degrees
Diameter
Inches
T P I
Pitch
inches
Core
Diameter
Tapping Drill Size
3/16
32
0.0313
0.1475
5/32 inch
(3.97 mm)
7/32
28
0.0357
0.173
Number drill 15
(4.6 mm)
1/4
26
0.0385
0.2008
Number drill 6
(5.3 mm)
5/16
22
0.0455
0.2543
17/64 inch
(6.75 mm)
3/8
20
0.05
0.311
Letter drill P
(8.2 mm)
7/16
18
0.0556
0.3663
9.7 mm
(0.3819 inch)
1/2
16
0.0625
0.42
7/16 inch
(11.11 mm)
9/16
16
0.0625
0.4825
1/2 inch
(12.7 mm)
5/8
14
0.0714
0.5336
14mm
(0.5512 inch)
11/16
14
0.0714
0.5961
15.5 mm
(0.6102 inch)
3/4
12
0.0833
0.6432
16.75 mm
(0.6594 inch)
7/8
11
0.0909
0.7586
25/32 inch
(19.84 mm)
1 inch
10
0.1
0.872
22.75 mm
(0.8957 inch)
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