BSW (British Standard Whitworth)

A coarse thread devised and standardised at Manchester in 1841
by British Engineer Sir Joseph Whitworth (1803 - 87). It is used in many types of engineering throughout the world,
although in Britain its use is now being superseded by the ISO metric system.

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Angle of Thread = 55o Degrees
Sizes range from 1/16inch to 21/2inches.

Diameter
Inches		 T P I Pitch
inches		 Core
Diameter		 Tapping Drill Size
1/16 60 0.0167 0.0411 Number Drill 56
(1.2 mm)
3/32 48 0.0208 0.0672 Number Drill 49
(1.85 mm)
1/8 40 0.025 0.093 Number Drill 39
(2.55 mm)
5/32 32 0.0313 0.1162 Number Drill 30
(3.2 mm)
3/16 24 0.0417 0.1341 Number Drill 26
(3.7 mm)
7/32 24 0.0417 0.1654 Number Drill 16
(4.5 mm)
1/4 20 0.05 0.186 Number Drill 9
(5.1 mm)
5/16 18 0.0556 0.2413 Letter Drill F
(6.5 mm)
3/8 16 0.0625 0.295 5/16 inch
(7.94 mm)
7/16 14 0.0714 0.3461 Letter Drill U
(9.3 mm)
1/2 12 0.0833 0.3932 Letter Drill Z
(10.5 mm)
9/16 12 0.0833 0.4557 12.1 mm
(0.4764 inch)
5/8 11 0.0909 0.5086 13.5 mm
(0.5315 inch)
11/16 11 0.0909 0.5711 15 mm
(0.5906 inch)
3/4 10 0.1 0.622 41/64 inch
(16.27 mm)
13/16 10 0.1 0.6845 18 mm
(0.7087 inch)
7/8 9 0.1111 0.7328 19.25 mm
(0.7579 inch)
15/16 9 0.1111 0.7953 20.75 mm
(0.8169 inch)
1 inch 8 0.125 0.84 22 mm
(0.8661 inch)

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