Thread Pitch Reference Table
Comprehensive thread dimensions and pitch values for BSW, Metric ISO, UNC, and UNF threading standards.
Thread pitch defines the distance between adjacent thread crests. Different standards are used across industries and regions. BSW (British Standard Whitworth) is common in India and the UK, while Metric ISO is the global standard. UNC and UNF are used primarily in North American applications.
BSW (British Standard Whitworth)
| Size | TPI (Threads Per Inch) | Major Dia (mm) | Pitch (mm) |
|---|---|---|---|
| 1/4" | 20 | 6.35 | 1.270 |
| 5/16" | 18 | 7.94 | 1.411 |
| 3/8" | 16 | 9.53 | 1.588 |
| 7/16" | 14 | 11.11 | 1.814 |
| 1/2" | 12 | 12.70 | 2.117 |
| 5/8" | 11 | 15.88 | 2.309 |
| 3/4" | 10 | 19.05 | 2.540 |
| 7/8" | 9 | 22.23 | 2.822 |
| 1" | 8 | 25.40 | 3.175 |
Metric ISO (Coarse Thread)
| Size | Pitch (mm) | Major Dia (mm) |
|---|---|---|
| M3 | 0.5 | 3.00 |
| M4 | 0.7 | 4.00 |
| M5 | 0.8 | 5.00 |
| M6 | 1.0 | 6.00 |
| M8 | 1.25 | 8.00 |
| M10 | 1.5 | 10.00 |
| M12 | 1.75 | 12.00 |
| M14 | 2.0 | 14.00 |
| M16 | 2.0 | 16.00 |
| M18 | 2.5 | 18.00 |
| M20 | 2.5 | 20.00 |
| M22 | 2.5 | 22.00 |
| M24 | 3.0 | 24.00 |
| M27 | 3.0 | 27.00 |
| M30 | 3.5 | 30.00 |
UNC (Unified National Coarse)
| Size | TPI (Threads Per Inch) | Major Dia (mm) |
|---|---|---|
| 1/4"-20 | 20 | 6.35 |
| 5/16"-18 | 18 | 7.94 |
| 3/8"-16 | 16 | 9.53 |
| 7/16"-14 | 14 | 11.11 |
| 1/2"-13 | 13 | 12.70 |
| 5/8"-11 | 11 | 15.88 |
| 3/4"-10 | 10 | 19.05 |
| 7/8"-9 | 9 | 22.23 |
| 1"-8 | 8 | 25.40 |
Thread Standard Notes
- —BSW threads have a 55-degree thread angle; UNC/UNF use 60-degree
- —Metric coarse pitch is the default; fine pitch is available but must be specified
- —BSW and IS (Indian Standard) threads are interchangeable for common sizes
- —Pankaj Fasteners manufactures in both BSW/IS and Metric standards
Disclaimer: Values provided in this reference are approximate and intended for general guidance only. Actual specifications may vary based on manufacturing tolerances, surface conditions, and environmental factors. Always consult relevant IS/ISO/ASTM standards and project engineering specifications for critical applications. Pankaj Fasteners Pvt. Ltd. assumes no liability for the use of these reference values in design or construction.
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