Do you need a BSPT thread chart? Or would you like to learn more about the detailed parameter values in the BSPT thread chart, as well as what BSPT thread is? Keep reading—FIREMINUS not only explains what BSPT thread is but also provides a comprehensive BSPT thread chart with complete size data.
BSPT Thread Chart - 1/16-6 Inches Dimension
1/2 nominal thread size BSPT thread：
- Threads per Inch：14n
- Major Diameter at Gauge Plane：955mm
- Gauge Length (l₁):7.5 mm
- Effective Thread Length (l₂): 19 mm
- 2 1/2 nominal thread size BSPT thread：
- Threads per Inch：11 n
- Major Diameter at Gauge Plane：184mm
- Gauge Length (l₁):5mm
- Effective Thread Length (l₂): 40 mm
- 6 nominal thread size BSPT thread：
- Threads per Inch：11 n
- Major Diameter at Gauge Plane：83mm
- Gauge Length (l₁):25 mm
- Effective Thread Length (l₂): 69 mm
Nominal Thread Size | Threads per Inch (n) | Pitch (P) mm | Major Diameter at Gauge Plane (d=D) mm | Gauge Length (l₁) mm | Effective Thread Length (l₂) approx. mm | Recommended Tap Drill Size (for Rc Internal Thread) mm |
1/16 | 28 | 0.907 | 7.723 | 4 | 10 | 6.6 |
1/8 | 28 | 0.907 | 9.728 | 4 | 11 | 8.6 |
1/4 | 19 | 1.337 | 13.157 | 5.5 | 14.5 | 11.5 |
3/8 | 19 | 1.337 | 16.662 | 6 | 15.5 | 14.9 |
1/2 | 14 | 1.814 | 20.955 | 7.5 | 19 | 18.6 |
3/4 | 14 | 1.814 | 26.441 | 9 | 22.5 | 24.1 |
1 | 11 | 2.309 | 33.249 | 10.5 | 26 | 30.5 |
1 ¹⁄₄ | 11 | 2.309 | 41.91 | 11 | 28.5 | 39.2 |
1 ¹⁄₂ | 11 | 2.309 | 47.803 | 11.5 | 30 | 45.1 |
2 | 11 | 2.309 | 59.614 | 13 | 35 | 56.6 |
2 ¹⁄₂ | 11 | 2.309 | 75.184 | 14.5 | 40 | 71.8 |
3 | 11 | 2.309 | 87.884 | 16 | 45 | 84.4 |
3 ¹⁄₂ | 11 | 2.309 | 100.33 | 17.5 | 49 | 96.7 |
4 | 11 | 2.309 | 113.03 | 19 | 53 | 109.3 |
4 ¹⁄₂ | 11 | 2.309 | 125.73 | 20.5 | 57 | 121.9 |
5 | 11 | 2.309 | 138.43 | 22 | 61 | 134.5 |
5 ¹⁄₂ | 11 | 2.309 | 151.13 | 23.5 | 65 | 147.1 |
6 | 11 | 2.309 | 163.83 | 25 | 69 | 159.7 |
Note:
- Gauge Plane: A theoretical reference plane; the dimensions of the minor diameter, major diameter, or pitch diameter of a thread must conform to this standard value.
- Gauge Length (l₁): The axial distance from the minor end face of the external thread to the reference plane.
- Effective Thread Length (l₂): Refers to the total length of the complete tapered thread that must be machined, encompassing both l₁ and the “tightening allowance.”
BSPT Thread Chart Function and Its Principle
A standard BSPT thread chart should provides the detailed parameters you require, including thread designation, threads per inch, major diameter, mean diameter, minor diameter, and effective thread length of the nominal diameter.
The BSPT thread chart employs the “base hole system” principle, ensuring effective interference fits between threaded pairs even under extreme dimensional conditions by controlling the minor diameter tolerance of internal threads and the major diameter tolerance of external threads.
What Is BSPT Thread
The History of BSPT Thread and BSP Standards
Beyond the use of NPT thread standards in North America, the BSP series of threads has become the globally prevalent standard for pipes and fittings. The origins of the BSP series trace back to 1905, when the predecessor of the British Standards Institution first published the world’s first pipe thread standard, including the Whitworth thread—a 55° sealing pipe thread. It comprises British Standard Pipe Parallel (straight) threads (BSPP) and British Standard Pipe Taper threads (BSPT).
BSPT Thread - British Standard Pipe Taper
BSPT stands for British Standard Pipe Taper. This thread follows the British Whitworth standard. Its tapered design eliminates the need for seals or gaskets. It achieves pressure-sealed connections solely through the thread engagement. Featuring a distinct pitch and a 55-degree thread degree, it creates an interference fit during rotation and tightening, relying on the elastic deformation of the metal itself to form the seal. Today, the BSPT thread has successfully become the standard thread specification for Commonwealth nations and European countries.
BSPT employs a 55° thread degree with rounded crests and roots. This 55° degree prevents stress concentration in threaded components. The rounded-top, rounded-root design significantly enhances thread strength while eliminating the tendency for micro-cracks at sharp corners, resulting in superior fatigue resistance. On the other hand, BSPT features a 1:16 taper ratio, representing a precisely calculated equilibrium point. A ratio below this value compromises sealing performance, while a higher ratio makes engagement difficult and prone to damage. This taper ratio translates to a diameter change of 1 unit for every 16 units of axial length along the thread axis.
