DIN vs BSP Hydraulic Fittings: Metric vs British Thread Systems
DIN fittings use metric threads per ISO 8434 with a 24-degree cone seal. BSP fittings use Whitworth thread form per ISO 228 with either a tapered seal (BSPT) or bonded washer seal (BSPP). Both are common in European and international equipment but they are not interchangeable.
Key Differences
Thread Form: Metric (M threads, 60-degree angle) vs Whitworth (55-degree angle).
Seal Method: 24-degree cone or flat washer vs BSPT: tapered thread seal, BSPP: bonded washer.
Standard: ISO 8434, DIN 2353 vs ISO 228, BS 21.
Primary Region: Germany, Central Europe, Asia (metric equipment) vs UK, Commonwealth, international.
Thread Measurement: Measured in millimeters (M12x1.5, M18x1.5) vs Measured in pipe size fractions (1/4, 3/8, 1/2).
Tube Connection: Compression or bite-type (cutting ring) vs Various adapter styles.
When to Choose DIN 2353 / ISO 8434-1
DIN when the equipment uses metric ports (German, Asian, and most modern European machinery)
Also preferred for new system design where metric standardization is the goal.
When to Choose BSP (BSPP/BSPT)
BSP when the equipment has Whitworth-thread ports (UK-origin, Commonwealth, marine, and many internationally sourced machines)
Required for maintenance and replacement on existing BSP systems.
Practical Notes
Equipment from German manufacturers (Rexroth, Hawe, Hydac) typically uses DIN fittings. Equipment from UK or broader international sources often uses BSP. Adapters between DIN and BSP are readily available because both are common in the same markets. Always verify thread pitch with a thread gauge since some DIN and BSP sizes have similar diameters but different pitches.
Common Mistake
Assuming DIN and BSP threads are interchangeable because they appear similar in size. The thread angle (60 degrees for DIN vs 55 degrees for BSP) and pitch differences mean cross-threading is possible and creates a leak path.