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 Whilst it is being superseded by the ISO Metric system, the thread form is still widely used and Trojan Special Fasteners can manufacture these in normal and left handed form. This is a coarse pitch thread form, so it is prone to vibrational loosening.
| 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 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 |
