1/4" BSP parallel (G1/4 / BSPP) (G1/4)
Where G1/4 is used, its real dimensions, and how to connect it to other standards.
G1/4Thread standard
DesignationG1/4
Major diameter13.157 mm
Threads per inch / pitch19
Thread formparallel, 55 degree
Seals onflat washer or bonded seal on the face
Used on: compressor and air-line fittings, gauge ports, small pumps.
G1/4 at 19 TPI is the standard air-tool and gauge thread. It is parallel, so on air work it is usually paired with a bonded seal or PTFE tape on a tapered mating part.
Quick-connect click fittings from Hozelock, Gardena and Karcher are proprietary and do not interchange. They all sit on top of a standard thread underneath, so the reliable way to move between brands is to adapt at the threaded tap or hose-end fitting, then use each brand's own connector above it.
Connect this thread
Connect to Industrial / Milton M-style air couplerneeds an adapterConnect 1/4" NPT (National Pipe Taper) to 1/4" BSP parallel (G1/4 / BSPP)needs an adapter1/8" BSP parallel (G1/8 / BSPP)related standard (G1/8)3/8" BSP parallel (G3/8 / BSPP)related standard (G3/8)1/2" BSP parallel (G1/2 / BSPP)related standard (G1/2)3/4" BSP parallel (G3/4 / BSPP)related standard (G3/4)1" BSP parallel (G1 / BSPP)related standard (G1)1-1/4" BSP parallel (G1-1/4 / BSPP)related standard (G1-1/4)1-1/2" BSP parallel (G1-1/2 / BSPP)related standard (G1-1/2)1/4" BSP tapered (R1/4 / BSPT)related standard (R1/4)
Sources: ISO 228-1 (G / BSPP parallel pipe threads) · BSP thread dimensions chart (ISO 228 / ISO 7), AmesWeb