HGW Resources
Thread Charts & Connection Types
Identify common hydraulic fitting thread and connection standards, including American, British, Metric, DIN, JIS, ORFS, JIC, NPT, NPSM, BSPP, and BSPT connections. Click any connection below to jump to its detailed section.
Thread & Connection Identification Guide
NPT
National Pipe Thread Tapered — ANSI/ASME B1.20.1
NPT is the most widely used American tapered pipe thread. Threads cut into a 1.7866° taper engage on metal-to-metal contact, with sealant (PTFE tape or anaerobic) carrying the final seal.
- Thread form: 60° thread angle, tapered.
- Seal: thread engagement plus sealant; not a pressure-tight seal on its own.
- Common use: low- to medium-pressure hydraulic plumbing, pneumatic systems, port adapters, plug-and-cap applications.
- Identification: visible taper along the thread length, no O-ring or seat surface, male thread narrows toward the tip.
- Related HGW products: NPT pipe adapters and NPT × JIC / NPT × BSPP / NPT × ORB conversion fittings.
NPSM
National Pipe Straight Mechanical — ANSI/ASME B1.20.1
NPSM uses the same nominal pipe diameter as NPT but with parallel (straight) threads. The seal is made by a swivel against an internal 30° seat, or by an O-ring, rather than by the thread itself.
- Thread form: 60° thread angle, straight (parallel).
- Seal: mechanical — 30° seat or O-ring; no thread sealant required.
- Common use: hydraulic swivel adapters, gauge connections, port-to-pipe assemblies where re-orientation is needed.
- Identification: straight male thread paired with a female swivel nut, often with an internal cone or O-ring visible.
- Related HGW products: NPSM swivel adapters in the Pipe Fittings and NPSM Pipe Swivel Adapters category.
JIC / SAE 37°
Joint Industry Council 37° Flare — SAE J514
The most common American hydraulic flare connection. A 37° cone on the male nose seats against a matching 37° flare on the female, sealed by metal-to-metal contact with straight UN/UNF threads holding the joint.
- Thread form: straight UN/UNF, 60° thread angle.
- Seal: 37° cone seat — metal-to-metal, no O-ring.
- Common use: hydraulic system assembly across mobile, industrial, and OEM equipment.
- Identification: 37° cone on the male nose; straight thread; no taper, no O-ring.
- Related HGW products: the 37° JIC Fittings category (0318, 0319, 2404, 7000 and related series).
SAE O-Ring Boss
SAE J1926 — also referred to as ORB
Straight UN/UNF male thread with an O-ring captured against a chamfer on the boss face. Used for port connections into pumps, motors, valves, and manifolds where leak-free, repeatable sealing is required.
- Thread form: straight UN/UNF, 60° thread angle.
- Seal: O-ring seated against a 12° chamfer on the port face.
- Common use: pump, motor, and manifold port connections; SAE J1926-1 / -2 / -3 male, J1926-1 female.
- Identification: straight thread with an O-ring on the shoulder near the base of the thread.
- Related HGW products: ORB plugs, ORB adapters, ORB conversion fittings (6408 series and related).
ORFS
O-Ring Face Seal — SAE J1453
ORFS connections seal on a flat face with an O-ring captured in a recessed groove. Designed for high-vibration hydraulic systems where face-seal performance outperforms cone-seat or thread-seal designs.
- Thread form: straight UN/UNF.
- Seal: flat face with an elastomeric O-ring in a groove on the male nose.
- Common use: high-vibration mobile equipment, agricultural, and construction hydraulics.
- Identification: flat-face male with a visible O-ring groove; no flare, no taper.
- Related HGW products: O-Ring Face Seal (ORFS) Fittings category.
BSPP
British Standard Pipe Parallel — ISO 228
Parallel (straight) thread used widely in European, UK, and Asia-Pacific hydraulic systems. Sealing is achieved separately from the thread — typically with a bonded seal washer on the male side, an O-ring on an ED seal, or a 60° cone seat for swivel adapters.
- Thread form: 55° thread angle, straight (parallel).
- Seal: bonded washer, O-ring, or 60° cone seat — not the thread.
- Common use: European, UK, Asia-Pacific hydraulic systems; port connections, adapter assembly.
- Identification: straight thread, 55° angle (different visual pitch from 60° American threads), often paired with a bonded seal washer or O-ring.
- Related HGW products: British Standard Fittings category, BSP Conversion sub-categories.
BSPT
British Standard Pipe Tapered — ISO 7
Tapered British pipe thread. Like NPT, BSPT seals on thread engagement, usually with a sealant. Different thread angle and pitch from NPT — the two are not interchangeable.
- Thread form: 55° thread angle, tapered (1.7866°).
- Seal: thread engagement plus sealant.
- Common use: European pipe-thread plumbing and hydraulic adaptation.
- Identification: visible taper; 55° angle distinguishes it from NPT under careful inspection.
- Related HGW products: BSPT fittings in the British Standard Fittings category, BSPT × NPT and BSPT × JIC conversion adapters.
DIN 2353
German DIN 2353 / ISO 8434-1 — 24° cone tube fitting
DIN 2353 is the standard European tube fitting system. A 24° cone seat receives either a cutting ring (bite-type) or a soft-seal ferrule, paired with metric threads. Available in Light (L), Heavy (S), and very-heavy series for different pressure classes.
- Thread form: metric straight thread.
- Seal: 24° cone seat with ferrule, with or without an additional O-ring (DKO).
- Common use: European tube hydraulics, mobile and stationary equipment built to DIN/ISO specs.
- Identification: 24° internal cone in the female port; metric thread; ferrule on the tube.
- Related HGW products: DIN 2353 Metric Tube Fittings category.
Metric Bite Type
Bite-type fittings with metric thread
Bite-type tube fittings use a hardened ferrule that cuts into the tube OD when the nut is tightened, creating a leak-tight metal-to-metal seal. The metric-thread variant follows DIN 2353 / ISO 8434 dimensions.
- Thread form: metric straight.
- Seal: ferrule bites into tube OD, ferrule front face seats against the 24° cone.
- Common use: high-pressure instrumentation lines, mobile hydraulics, European OEM equipment.
- Identification: ferrule visible on assembled tube; 24° cone in the body.
- Related HGW products: Flareless Bite Type Tube Fittings category, DIN 2353 series.
DIN Tube
DIN-standard tube end connections
DIN tube refers to the metric tube-end connections defined in DIN 2353 and related standards — covering tube OD, wall thickness, and ferrule geometry. HGW supplies tube nuts, sleeves, and matching adapter bodies in the metric tube system.
- Thread form: metric straight thread on the nut.
- Seal: 24° cone with ferrule, matched to tube OD.
- Common use: DIN-spec tube assemblies, European hydraulic equipment.
- Identification: metric tube OD (6, 8, 10, 12, 15, 18, 22, 25, 28, 30, 35, 38, 42 mm) paired with metric thread.
- Related HGW products: tube nuts and sleeves under the DIN 2353 Metric Tube Fittings category.
JIS 30°
Japanese Industrial Standard — JIS B 8363 / B 2351
JIS hydraulic connections use a 30° internal flare seat with BSP-form threads (parallel or tapered, depending on series). Common across Japanese mobile equipment, machine tools, and construction hydraulics.
- Thread form: 55° BSP-form threads (parallel or tapered).
- Seal: 30° flare seat on the female, 30° cone on the male.
- Common use: Japanese hydraulic equipment, excavators, agricultural machines.
- Identification: 30° flare seat (vs 37° for JIC); BSP-style 55° thread.
- Related HGW products: JIS-compatible fittings within the British Standard / metric conversion product lines (cross-reference recommended for exact matching).
ISO 6149
ISO 6149 metric port — metric equivalent of SAE ORB
ISO 6149 defines straight metric threads with an O-ring on the male shoulder, sealing against a chamfer in the port. It is the metric equivalent of the SAE O-Ring Boss system and is commonly used in European mobile and industrial hydraulics.
- Thread form: ISO metric straight (M).
- Seal: O-ring seated against a chamfer on the port face.
- Common use: metric port connections in European pumps, motors, valves.
- Identification: metric straight thread + O-ring on the shoulder.
- Related HGW products: request HGW cross-reference for ISO 6149 port adapters.
Metric Thread
ISO metric thread (M-series)
Generic term for ISO metric thread used across hydraulic and pneumatic fittings. Straight metric thread is paired with O-ring or 24° cone seat for sealing; tapered metric thread is rarely used in hydraulics.
- Thread form: ISO metric (M).
- Seal: separate — O-ring, bonded washer, or 24° cone.
- Common use: European and Asian hydraulic systems, instrumentation, port adaptation.
- Identification: nominal diameter quoted in millimeters (e.g., M14, M18, M22); thread pitch quoted separately (e.g., M22×1.5).
- Related HGW products: DIN 2353 Metric Tube Fittings, BSP/Metric conversion adapters.
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