Thread forms

Trojan Special Fasteners Ltd have the tooling and expertise to cut and roll multiple thread forms. Trojan can manufacture in the following diameters:

1. Inch series 2BA to 2.1/4 Inches

2. Metric series M4 to M52

In the following thread forms: Whitworth Thread Forms The three forms that come under this banner are: BSW (British Standard Whitworth), BSF (British Standard Fine) BSC or CEI (British Standard Cycle) (60 degree angle)

BSW (British Standard Whitworth)

This thread was the world's first national screw thread and was standardised in 1841 by British Engineer Sir Joseph Whitworth (1803-87). Whilst it is being superseded by the ISO Metric system, the thread form is still widely used and Trojan Special Fasteners can manufacture these in normal and left handed form.

Angle of Thread 55 degrees
Thread Pitch p = 1/TPI
Height of fundamental triangle H = p/(2 tan Θ) = 0.96049106p
Thread Depth h = p/(3 tan Θ)= 0.64032738p
Peaks rounded with 2×(90°−Θ) = 180°−55° = 125° circular arc
Arc height e = H sin Θ/12 = 0.073917569p
Straight Flank Depth h−2e = 0.49249224p
Radius r = e/(1−sin Θ) = 0.13732908p

BSF (British Standard Fine)

This is a coarse pitch thread form, so it is prone to vibrational loosening. In which case it is better to use a BSF thread form: This thread form is a fine pitch alternative to the BSW thread and was introduced by the British Engineering Standards Association in 1908. It was co developed by R E B Crompton and George Field. As this thread form was less prone to loosening (unlike BSW) it was commonly used on motorcycles, cars and other machinery.

Angle of Thread 000
Angle of Thread 55 degrees Thread Pitch 000
Height of fundamental triangle 000
Thread Depth 000
Peaks rounded with 000
Arc height 000
Straight Flank Depth 000
Radius 000

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