NPT Threads - Taps and Drill Sizes
The NPT - National Pipe Taper Threads - is based on the Briggs Standard Pipe Thread.
Drill sizes for Briggs Standard Pipe taps for direct tapping without reaming are indicated below:
| Size Taps (inches) | TPI | Size Drill (inches) |
|---|---|---|
| 1/8 | 27 | 21/64 |
| 1/4 | 18 | 27/64 |
| 3/8 | 18 | 9/16 |
| 1/2 | 14 | 11/16 |
| 3/4 | 14 | 29/32 |
| 1 | 11.5 | 1 1/8 |
| 1 1/4 | 11.5 | 1 15/32 |
| 1 1/2 | 11.5 | 1 23/32 |
| 2 | 11.5 | 2 3/16 |
| 2 1/2 | 8 | 2 9/16 |
| 3 | 8 | 3 3/16 |
| 3 1/2 | 8 | 3 11/16 |
| 4 | 8 | 4 3/16 |
- TPI = threads per inch
- 1 inch = 25.4 mm
Related Topics
• Dimensions of Pipes and Tubes
Pipe, tube and fittings sizes and dimensions. Inside and outside diameters, weights and more.
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Related Documents
ANSI B1.20.1 - NPS - American National Standard Straight Pipe Threads
NPS pressure tight straight pipe threads with lubricant or sealer.
ANSI B1.20.1 - NPT - American National Standard Taper Pipe Threads
NPT and NPTF pipe threads - dimensions according ANSI/ASME B1.20.1/3.
ISO 7 - Pipe Threads where Pressure-tight Joints are made on the Threads
Pressure-tight joints made on the pipe threads.
ISO 724 - Metric Threads
Dimensions of metric threads according ISO 724.
Metric Threads - Clearance Holes and Tapping Drill Sizes
Recommended clearance holes and drill tap sizes.
Piping Thread Standards
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Threads commonly used in Piping
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Withworth Threads - Taps and Drill Sizes
Taps and drill sizes used for Whitworth - ISO 7 and ISO 228 threads.