The NO GO ring gauges for G BSPP parallel pipe threads are inspection tools designed to verify the upper acceptance limit of external parallel threads according to DIN ISO 228 part 1. They are used to check male fittings, nipples, adapters, threaded bodies, valve connections, pneumatic components, hydraulic parts, fluid power elements and mechanical components intended for non-pressure-tight threaded joints, where it is necessary to confirm that the external thread is not undersized, worn, deformed or out of tolerance.

These ring gauges perform the NO GO function: they must not screw onto the external thread beyond the specified limit. If the NO GO gauge enters too far, the thread may be non-compliant, with incorrect diameters, worn profile, deformation or excessive clearance for the required mating condition. This inspection is essential when it is not enough to verify that the component screws in with a GO gauge, but it is also necessary to exclude out-of-limit external threads, unstable engagement, loss of accuracy and non-conforming assemblies.

G parallel pipe threads, also known as BSPP, use a 55° Whitworth profile and are employed in non-pressure-tight threaded connections. In these joints, sealing is generally not achieved by thread interference, but by gaskets, washers, flat seats, O-rings or other dedicated sealing systems. For this reason, checking the external thread with a NO GO ring gauge is important to ensure that the male component maintains correct dimensional compatibility with the female thread and does not show clearance or defects that could compromise assembly, alignment and connection reliability.

The correct gauge must be selected according to the nominal G size, the pitch defined by ISO 228-1 and the inspection function required by the technical drawing or inspection cycle. It is essential to distinguish these ring gauges from those for BSPT taper pipe threads, NPT, metric or other inch-based standards, because profile, mating function, tolerance and inspection method are not interchangeable. Upon request, the gauge can be supplied with Accredia certification or, alternatively, with a calibration report. This documentation requires additional delivery time, as the item must be sent to the inspection body or appointed calibration/certification laboratory before final shipment to the customer.

For reliable inspection, the NO GO ring gauge must be used on clean external threads, free from chips, burrs, oxides, dirt, machining residues or visible deformation. During checking, the gauge must be screwed on without forcing and with correct alignment to the thread axis, because misaligned or excessive use may affect the inspection result and damage both the gauge and the checked component. The NO GO gauge must not be used as a thread repair or correction tool, but only as an instrument for checking the dimensional limit. These ring gauges are suitable for mechanical workshops, fitting manufacturers, CNC departments, quality control, industrial maintenance, pneumatics, hydraulics, fluid power and plant engineering where external G BSPP parallel threads must be checked simply, quickly and repeatably against the permitted limits.