Metric Hydraulic Fittings

What Are Metric Hydraulic Fittings?

Metric hydraulic fittings are threaded connectors dimensioned in millimeters and made to European metric standards, rather than to inch-based American or British pipe threads. Two metric systems dominate hydraulic hose assemblies:

• 24° cone fittings (ISO 8434-1 / DIN 2353): a metric male stud with a 24° cone seat that seals metal-to-metal against the matching cone of a female port or adapter. This is the classic European system, available in light series (L) and heavy series (S).
• Metric O-ring port fittings (ISO 6149, SAE J2244): a metric straight thread with an O-ring compressed against a flat spotface, giving a positive face seal for high-pressure and zero-leak service.

Both systems use metric thread designations such as M22 x 1.5, where the first number is the nominal diameter in millimeters and the second is the thread pitch. Because metric and inch threads are never interchangeable, identifying the thread correctly is the first step of every order.

Core value: confirm the metric system, the thread, and the series — and the connection holds pressure without leakage; guess, and threads gall or ports crack.

Three customer paths:

• For OEM manufacturers — standardize 24° cone or ISO 6149 ports across your machine range and lock in repeatable assembly quality.
• For end users and maintenance teams — identify whether the failed line is 24° cone, ISO 6149, or a look-alike inch thread, then order the correct replacement the first time.
• For distributors — consolidate metric and inch connection families in one catalog, with mixed-size sample kits and private labeling.

Key Specifications

Connection-Side: Metric Thread and Port Table

The table below lists the metric male threads and cone profiles we supply, per the 10411-RW technical drawings and ISO 8434-1. Thread E is the metric male thread; the 24° cone seat profile follows ISO 8434-1 (DIN 2353 equivalent).

Companion ISO 6149 metric O-ring port studs are available with O-ring face seals in the commonly used sizes from M12 x 1.5 to M60 x 2; confirm your port marking and we supply the matching stud, O-ring, and backup ring.

Hose-Side: Matching Ferrule Series

The hose end of each metric fitting is matched to a hose family and its ferrule series. The table below lists the full crimp-side range, dash 03 to 32 (DN 4 to 50).

The 24° cone hose fittings shown above are the light series for braided hoses (1SN and 2SN); for spiral hoses, use the companion heavy-duty series per the specification. Assembly working pressure follows the hose family: 1SN to 250 bar, 2SN to 400 bar, 4SP to 450 bar in the smallest sizes, R12 at 4,000 psi (276 bar) constant, and PTFE to about 207 bar (3,000 psi) in small bores. Confirm the final value against your hose data sheet.

Material and Surface Finish

Material choice is a key decision when selecting metric hydraulic fittings for corrosive or hygienic service.

Key Features

• 24° cone seat per ISO 8434-1 (DIN 2353), light series; heavy series on request
• ISO 6149 metric O-ring port ends (SAE J2244 equivalent) for zero-leak face seals
• Metric threads from M12 x 1.5 to M52 x 2, hex (S1) wrench design
• Configurations: straight, 45° and 90° elbows, tees, bulkhead, reducers
• Matched hose-tail and ferrule sets for leak-free crimped assemblies

Crimping and Installation

The hose end of every metric fitting is crimped with standard hydraulic crimping machines and common die sets. We provide reference crimp data and die selection for your machine model with every order.

Crimp-side steps:

1. Cut the hose square with a sharp hose cutter.
2. Prepare the hose end per the hose maker’s instructions (skive where required, e.g. 4SH and R12).
3. Insert the stem fully into the hose bore.
4. Slide the ferrule over the hose end and seat it against the stem shoulder.
5. Crimp with a hydraulic hose crimping machine to the target crimp diameter from the hose maker’s chart.
6. Verify the crimp O.D. with a caliper and record the value.

Metric connection-side rules:

• Clean and inspect the 24° cone seat before every assembly; a scratched cone leaks.
• For 24° cone connections, align the stud square with the port, hand-tighten, then torque on the hex to the value for the size.
• For ISO 6149 ports, fit the O-ring and backup ring, and do not exceed the tightening torque — the seal is the O-ring, not the threads.
• Never mix metric threads with inch threads: M22 x 1.5 and 7/8-14 UNF look alike at a glance but are not interchangeable.
• Never apply thread sealant to ISO 6149 O-ring connections; it contaminates the circuit.

Nomenclature: How Metric Sizes Are Designated

Metric part numbers state the thread in millimeters, and every metric thread designation carries a pitch. Learn these rules and you can read any metric fitting description:

A typical description reads: M22 x 1.5 24° cone male x 1/2 in hose, straight. The first field states the metric thread and cone system, the second states the hose size, and the third states the configuration. We assign the exact part number for your configuration on request — send us the thread, hose family, and dash size, and our engineers confirm the code before you order.

Matching and Identification

The most common error is confusing metric threads with inch threads of similar size. Use this table before ordering metric hydraulic fittings:

Metric and inch threads are not interchangeable. When in doubt, measure the thread O.D. in millimeters, check the pitch with a thread gauge, and count the threads per inch if it could be inch-based — or send us a photo and we identify the connection for you free of charge.

Applications and Industries

Metric hydraulic fittings dominate European and Asian equipment and appear wherever metric ports are specified:

• Machine tools and injection molding machines
• Agricultural machinery: tractors and implements
• Construction and mobile equipment
• Hydraulic power units and industrial hydraulics
• Forestry, mining, and material handling
• Marine and offshore hydraulics
• Food and beverage processing: stainless steel variants

Operating range follows the hose and fluid: rubber assemblies typically run from -40 °C to +100 °C (R12 to +121 °C), and PTFE assemblies from -70 °C to +260 °C at the core.

Ordering and Packaging

• Unit of measure: sold per piece (EA), packed in boxes per size
• MOQ: one box per size; mixed-size sample kits available
• Customization: light or heavy series, ISO 6149 studs, material, surface finish, private labeling, special packaging
• Export packing: corrugated cartons with moisture barrier for sea freight

Metric Hydraulic Fittings FAQ

Can metric fittings be connected to NPT or BSP ports? No. Metric threads are sized in millimeters with a 60° ISO thread profile; NPT is a 60° American tapered pipe thread sized in inches, and BSP is a 55° British thread. They are not interchangeable, and forcing them together causes galling, leaks, or thread damage.

How do I confirm a metric fitting matches my hose? Three checks: confirm the metric thread (e.g. M22 x 1.5) and cone system on the port, match the hose I.D. to the dash size, and confirm the hose construction against the ferrule series table. Send us both measurements and we verify the full part number.

Brass or stainless steel — which do I need? Brass suits low-pressure air, water, and general service. Stainless steel suits corrosive chemicals, food, pharmaceuticals, and marine environments. Our range is supplied in zinc-plated carbon steel or stainless steel.

What is the difference between ISO 8434-1 and DIN 2353? They describe the same 24° cone connection system. DIN 2353 is the original German standard; ISO 8434-1 is the international standard that supersedes it. Most suppliers and drawings still use the DIN 2353 name.

Light series or heavy series — which do I choose? Light series (L) fittings have a lighter body and match the pressure range of braided hoses. Heavy series (S) fittings have thicker bodies for heavier duty and are specified with spiral hoses. Tell us your hose construction and we supply the correct series.

How do I read a metric thread like M22 x 1.5? M means metric thread, 22 is the nominal outside diameter in millimeters, and 1.5 is the pitch in millimeters. The pitch matters: M22 x 1.5 and M22 x 1.0 are different threads that will not mate correctly.

When should I use a 24° cone fitting instead of an ISO 6149 O-ring fitting? Use 24° cone fittings where the port has a 24° cone seat and metal-to-metal sealing is accepted. Use ISO 6149 O-ring studs where the port has a flat spotface with O-ring groove, typically for zero-leak, high-pressure, or high-vibration service.