What’s a BSP Thread?
BSP, short for British Standard Pipe, is a standard for pipe fittings popular in the UK, Europe, Asia, Australia, New Zealand, and South Africa. This standard is known for its distinctive 55-degree thread angle. Under BSP, there are two main types of threading – BSPP (British Standard Pipe Parallel) and BSPT (British Standard Pipe Taper).
BSPP Thread
BSPP, or British Standard Pipe Parallel, it is a straight/parallel thread meets DIN ISO 228-1 standard.The threads have a 55-degree angle, maintaining a parallel configuration. When connecting BSPP fittings, a bonded seal ring or a 60-degree cone is employed to ensure a tight seal. This seal is created when the bonded ring is compressed between a shoulder on the male fitting and the face of the female fitting.
BSPP Female Thread
The BSPP female thread is not assigned a class-of-fit, and thus has no class-of-fit letter designated.
BSPP Male Thread
The class-of-fit designation is specifically applicable to the BSPP femael thread and, by extension, the associated ring gages. Under the ISO-228 screw thread specification, there are two predefined classes-of-fit available for the male G-series screw thread: Class-A and Class-B.
Similarities:
In the ISO-228 G-series screw thread standard, both Class-A and Class-B have the same basic size, meaning their maximum material size is identical. Consequently, the GO gauge, which checks this size, can be used interchangeably for both classes and may be marked as A, B, A/B, or left unmarked.
Dissimilarities:
The class-of-fit affects the minimum material condition. Class-A has tighter tolerances, making it the Precision Class, while Class-B allows for double the tolerance, suiting commercial applications. Class-A generally incurs higher production costs due to its tighter tolerances but offers savings on gauge purchases since the Class-A NOGO gauge can verify products meeting both Class-A and Class-B standards. Conversely, Class-B can reduce production costs with its wider tolerances, but its NOGO gauges, being less commonly stocked, are typically priced higher and require longer lead times.
Conclusion:
For BSPP thread ring gauges, buy the GO gauge for use with either class. For Class-A requirements, purchase the Class-A NOGO gauge. For Class-B requirements, if production is limited, the Class-A NOGO gauge suffices; for larger runs, opt for the Class-B NOGO gauge. Consider purchasing both types if needed to meet varying production demands.
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