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Engineering ToolBox > Thread Standards - Piping

Piping thread standards

Thread Standards

Most piping threads are produced to national or industry group standards describing threads form - threads angle, pitch and diameter. Common standards are

• ANSI/ASME B1.1-1989, Unified Inch Screw Threads (UN and UNR Thread Forms)
• ANSI/ASME B1.20.1-1983 (R1992), Pipe Threads, General Purpose (Inch)
• DIN 2999, Pipe threads for tubes and fittings - parallel internal thread and taper external thread
• ISO 261, ISO general-purpose metric screw threads

Pitch

In general pitch refers to threads per inch for fractional screw threads and pipe threads. For metric screw threads pitch refers to the distance between threads.

Piping Threads

Common piping thread standards in the United States are

• NPT - American Standard Pipe Taper Thread (also known as ANSI/ASME B1.20.1)
• NPSC - American Standard Straight Coupling Pipe Thread
• NPTR - American Standard Taper Railing Pipe Thread
• NPSM - American Standard Straight Mechanical Pipe Thread
• NPSL - American Standard Straight Locknut Pipe Thread

Other common piping thread standards

• ISO 7/1 Tapered Pipe Threads - also known as DIN 2999, BSP 21, JIS B0203
• ISO 228/1 Parallel Pipe Threads - equivalent to DIN ISO 228/1, BSP PL, JIS B0202, G 1/8 and G 1/4 etc.
• BSP British standard pipe thread - British standard BS 21

Tapered threads are for joining and sealing and straight threads are only for joining.

More about piping thread standards.