BSP vs JIS Fittings: Thread Standards, Regional Use & Identification
The key difference: BSP has a 55-degree Whitworth thread form. Full breakdown below.
BSP uses Whitworth thread form (55-degree thread angle) in parallel (BSPP) or tapered (BSPT) configurations. JIS B 2351 uses metric threads with a 30-degree flare seat. BSP is the international standard outside North America; JIS is specific to Japanese-manufactured equipment.
Key Differences
BSP has a 55-degree Whitworth thread form.
JIS has a standard 60-degree metric thread form with a 30-degree flare seal.
BSPP seals with a bonded washer; BSPT seals on tapered threads.
JIS seals metal-to-metal at the 30-degree flare cone.
BSP uses nominal pipe bore sizing.
JIS uses metric tube OD sizing.
BSP thread pitches follow the Whitworth series.
JIS thread pitches follow standard metric (ISO) conventions.
When to Choose BSP (BSPP/BSPT)
Equipment built to British, European, or international standards
General industrial applications outside North America and Japan
Systems where BSPP or BSPT is the established port standard.
When to Choose JIS B 2351
Japanese-built hydraulic equipment
Replacement fittings for Komatsu, Hitachi, Kobelco, Kubota, or other Japanese OEM systems
When the equipment manual specifies JIS B 2351.
Practical Notes
BSP and JIS appear together most often on Japanese equipment exported to countries that use BSP as their local standard (UK, Australia, much of Asia and Africa). The machine may have JIS ports on OEM components and BSP on locally sourced hose assemblies. Adapters are needed at these junction points.
Common Mistake
Confusing BSPT (tapered BSP) with JIS because both can have metric-appearing threads. BSPT is tapered with Whitworth form; JIS is straight with standard metric form and a 30-degree flare. Thread gauges are essential for correct identification.
Reference data only. Verify thread dimensions with a thread identification gauge before making connections. Working with pressurized hydraulic systems involves serious injury risks including high-pressure injection, burns, and crushing hazards. This site does not replace manufacturer specifications, proper training, or employer safety procedures. See full terms of use.