Catalogue · Standards
A standard answers one question: what has to match between two parts so that the joint holds pressure. The thread is only half of the answer; the other half is the seat — the surface that actually seals. Below is what each standard in our catalogue covers and what to look at when selecting.
Where to start
A connection has three parts, each covered by its own standard: the thread that provides the clamping force, the seat that seals, and the port in the machine body that decides what can be fitted at all.
Hence the main rule: a matching thread does not mean a matching connection. A G1/2 male thread is used on a 60° cone, on a flat O-ring face seal and on a bulkhead end. All of them will screw together; only the right pair will seal.
The second common argument is the cone angle. The same seat is quoted two ways: 37° is measured from the axis, 74° is the included angle. The same applies to DIN: 24° from the axis, 48° included.
Threads
The thread provides the clamping force. It seals by itself in one case only — when it is tapered.
ISO 228-1Parallel pipe thread G, also called BSPP
Whitworth profile, 55°, pitch given in threads per inch. The designation is not the diameter: G1/2 measures 20.96 mm across the male thread.
It does not seal by itself — sealing comes from a cone, a cutting ring, an O-ring or a bonded washer.
ISO 7-1Taper pipe thread R and Rc, also called BSPT
Taper 1:16, same 55° profile. It seals on the thread flanks, with or without sealant.
Engagement depth is not fixed, so the outlet of an elbow ends up roughly where the torque leaves it. If you need an exact orientation, use a parallel thread with a separate seal.
ISO 261, ISO 965Metric thread M
Hydraulics almost always uses the fine pitch: M14×1.5, M18×1.5, M22×1.5. First number is the outside diameter in millimetres, second is the pitch.
ASME B1.20.1NPT and NPTF taper threads
American taper thread: 60° profile, taper 1:16, seals on the flanks.
Not interchangeable with BSPT — different profile and, in most sizes, a different number of threads per inch.
SAE J514UN/UNF inch threads used for JIC and ORFS
One 60° profile. The designation reads as diameter in inches and threads per inch: 7/16-20, 9/16-18, 1 1/16-12.
The same thread serves both the 37° flare and the O-ring face seal, so the thread alone will not tell the two apart — look at the end face.
Seats: the ISO 8434 series
This series defines how a tube connection seals. The parts are not interchangeable with each other, even where the thread is the same.
ISO 8434-124° cone with a cutting ring (DIN 2353)
The ring bites into the tube and is pressed against the 24° cone. The tube is not flared.
Two series: light (L) and heavy (S). For the same tube they use different threads and hex sizes, and roughly double the working pressure.
ISO 8434-237° flare, known as JIC (SAE J514)
The tube is flared to 37° from the axis. Metal-to-metal seal, no elastomer, so it tolerates high temperature and any fluid.
Catalogues often print this cone as 74° — that is the included angle for the same seat.
ISO 8434-3O-ring face seal, ORFS (SAE J1453)
The O-ring sits in a groove on the end face and is squeezed by the flat face of the mating part. The thread only clamps.
Of the common systems this one handles vibration best, because sealing does not depend on cone accuracy or on tightening torque.
ISO 8434-424° cone with an O-ring
Same 24° geometry with an elastomeric ring in the cone.
ISO 8434-660° cone, with or without an O-ring
A 60° female cone against the male cone of the mating part. Combined with the G pipe thread this is the most widespread connection in Asia.
Japanese 60° connections share the cone geometry but use a different thread.
Ports in the machine body
A port is a threaded hole in a block, a pump or a cylinder. Its standard fixes not only the thread but the shape of the seating face, the depth and the chamfer. If the part goes into a machine, check the port against its own standard, not against the part you unscrewed from it.
ISO 1179Ports and stud ends with G threads
Part 1 covers the port itself; parts 2, 3 and 4 cover the stud ends — elastomeric sealing, metal-to-metal sealing and adjustable ends.
ISO 6149Metric ports with O-ring sealing
Metric thread, the ring is squeezed in the chamfer of the port. The default port on new European machinery.
ISO 9974Metric ports with elastomeric or metal-to-metal sealing
Older and simpler than ISO 6149 and easy to mistake for it: thread sizes overlap, depth and chamfer do not.
Flanges
ISO 6162-1 and ISO 6162-2Flange connections, SAE J518 Code 61 and Code 62
Part 1 is standard pressure (Code 61), part 2 is high pressure (Code 62). For the same bore they use a different bolt circle, flange thickness and bolts.
Check the bolt spacing, not the bore.
Hose connections
ISO 12151Hose fittings, one part per end type
Part 1 — ORFS, part 2 — 24° cone with an O-ring, part 3 — ISO 6162 flanges, part 4 — ISO 6149 metric stud ends, part 5 — 37° flare, part 6 — 60° cone.
SAE J516 and SAE J517Hose fittings and hoses
J517 defines the hose types — the 100R1, 100R2, 100R12 designations used to select a hose by pressure and bend radius. J516 covers the fittings.
The European equivalents for hoses are EN 853 and EN 856 (ISO 1436).
Testing and plating
ISO 19879Test methods for connections
Burst, leakage, impulse and vibration tests. When a supplier says "tested to ISO 19879", ask which test and how many cycles.
ISO 9227Neutral salt spray test
The hours quoted are hours to red rust, that is, to corrosion of the base metal. White deposits are zinc corrosion products; they appear earlier and are not a defect.
For zinc-plated hydraulic connections 96 hours to red rust is the usual requirement; zinc flake coatings are rated in hundreds of hours.
ISO 4042 and ISO 10683Coatings
ISO 4042 covers electroplated coatings on fasteners; ISO 10683 covers non-electrolytically applied zinc flake coatings.
Commonly confused
- M22×1.5 and G1/2: close diameters, only the pitch tells them apart.
- BSP 60° and Japanese 60°: same cone, different thread.
- JIC 37° and BSP 60°: adjacent diameters, different angles. It assembles and then leaks at the cone.
- NPT and BSPT: both taper, 60° against 55° profile.
- Code 61 and Code 62 flanges: same bore, different bolt circle.
- DIN 2353 light and heavy series: same tube, different threads.
How to use this when selecting
- Identify the thread — outside diameter and pitch.
- Identify the seat — cone, face with an O-ring, flat with a washer, cutting ring.
- The pair of thread and seat is the system used to find the part in the catalogue.
- Check the pressure rating: light and heavy series differ for the same seat.
- If the part goes into a machine, verify the port against its own standard, not against the part you removed from it.
Smart search
Not sure which system you have?
Send a photo of the part and the hex size — we will tell you what the connection is and give you the part number.