NPT thread

2025-06-27

Here is a concise summary of the provided text about NPT threads:

NPT (National Pipe Thread) – developed in the US by William Sellers (1864). Now most used in the US and Canada.

Key differences from BSP:

Thread angle: 60° (vs. 55°) – more pronounced edges.
Taper: 1° 47’ (tapered, though parallel versions exist).
Pitch difference example: 1" BSP = 11 TPI; 1" NPT = 11.5 TPI.

Designation: NPT + nominal diameter + threads per inch.
Example: 3/8 - 18 NPT = 3/8" pipe, 18 TPI.

Standard: ANSI B1.20.1 (replaced B2.1 in 1973).

Sealing: Requires sealant (e.g., PTFE tape).

NPTF (Dryseal / Fuel): Same diameter, TPI, and taper as NPT, but roots and crests interfere during tightening to create a seal without sealant.
Designation example: 1/8 - 27 NPTF-1 (class 1).
Standard: ANSI B20.3 (replaced B2.2 in 1973). Gauge specs: ANSI B20.5.

Other North American standards: NPSC, NPTR, NPSM, NPSL.

Note: BADA manufactures taper threads upon request (ISO 7-1 or NPT).

Metric thread

BSP thread