The NO GO plug gauges for G BSPP parallel pipe threads are inspection tools designed to verify the upper acceptance limit of internal parallel threads according to DIN ISO 228 part 1. They are suitable for checking that threaded holes are not oversized, worn, deformed or out of tolerance on fittings, valve bodies, sleeves, adapters, pneumatic components, hydraulic parts, fluid power elements and mechanical components intended for non-pressure-tight threaded joints.

Unlike GO gauges, these plug gauges perform the NO GO function only: they must not screw into the internal thread beyond the specified limit. If the NO GO gauge enters too far, the thread may be too large, worn, deformed or not compliant with the required tolerance. This inspection is essential when it is not enough to verify that the corresponding male fitting or threaded component can screw in correctly, but it is also necessary to exclude excessive clearance, unstable engagement, loss of accuracy or threads unsuitable for final assembly.

G parallel pipe threads, also known as BSPP, use a 55° Whitworth profile and are widely used in fluid systems, pneumatics, hydraulics, industrial piping and technical connections with parallel gas pipe thread standards. According to DIN ISO 228-1, these threads are intended for non-pressure-tight threaded joints: sealing is not normally achieved by thread interference, but by gaskets, washers, flat seats, O-rings or dedicated sealing systems. For this reason, checking the NO GO limit is important to ensure that the internal thread does not have excessive clearance and that the connection maintains correct mechanical function.

It is essential to distinguish these gauges from plug gauges for BSPT taper pipe threads, NPT threads or other inch-based standards, because thread profile, connection function, sealing method and inspection procedure are not interchangeable. For reliable checking, the NO GO plug gauge must be used on clean threads, free from chips, burrs, oxides, dirt, coolant residues or visible deformation. During inspection, correct coaxial alignment with the threaded hole must be maintained and the gauge must never be forced, because the NO GO plug gauge is used to indicate the tolerance limit and must not be used as a thread repair or correction tool.

Misaligned or forced use may damage both the gauge and the inspected component, affecting the accuracy of subsequent checks. These gauges are suitable for quality control, mechanical workshops, CNC departments, fitting manufacturers, industrial maintenance, pneumatics, hydraulics, fluid power and plant engineering where it is necessary to verify simply, quickly and repeatably that internal G BSPP parallel threads do not exceed the admitted dimensional limit.

ACCREDIA certification or a calibration report can be supplied on request; because the item must be sent to the inspection or certification body, this documentation may increase delivery time.