JIS for pipe threads

Technical information and Q&A applicable to all years and models of Goldwings
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Motorcycle: 81 GL1100 (Widowmaker not in service), 83GL1100, CB350f x 6, CB400f x2, CB550f sold, CL350 (seized engine), plus enough donors to take me through retirement.

JIS for pipe threads

Postby eklimek » Sun Aug 07, 2016 1:20 pm

I have previously written about the JIS for screws; essentially a cross head resembling Phillips with a metric thread. ( viewtopic.php?t=15547 )

In attempting to install a oil pressure gauge on my 1972 cb350f I fell down another rabbit hole and found another JIS, this time for pipe thread.

In brief, pipe can be parallel or tapered. Tapered seals by thread closure and uses sealants. Parallel thread seals on the landing face or with an "O" ring. Sometimes one finds pipe in water applications such as a dish washer attachment using teflon tape on the thread to improve seal. Teflon tape is not recommended for other applications because the bits of tape can and do become dislodged.

JIS for pipe thread adopted BSPT (British Standard Pipe Tapered). This has also been renamed as ISO 7/1.

BSPT closely resembles NPT, but isn't. Those inclined to read the original standard will find it published under Japanese Industrial Standard JIS B 0203 (1966) in English translation. It is copyrighted.

https://law.resource.org/pub/jp/ibr/jis ... e.1982.pdf

NPT (also known as ASME B1.20.1)
■ Truncation of roots and crests are flat
■ 60° thread angle
■ Pitch is measured in threads 27 per inch

BSPT or ISO 7/1 (also known as EN 10226‑1 and JIS B0203)
■ Truncation of roots and crests are rounded
■ 55° thread angle
■ Pitch is measured in threads 28 per inch

BSPT or JIS or ISO 7/1
BSPT or JIS or ISO 7/1

Although the pipe thread are similar in that both are tapered (1 degree 47 minutes), they differ in pitch (27 vs 28 per inch) and morphology ( 55 vs 60 degree thread angle and truncation). Pitch changes with size.

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