British Standard Pipe Parallel (BSPP) :

This connection has a male half with a 300 seat, and a female half with a rotating tapered nose, that forms the seal.

NOTE: The male connector may appear to look like the male American National Pipe Straight Mechanical, or NPSM; however, their thread pitches are not the same, and are not compatible.

British Standard Pipe Tapered (BSPT) :

These are connectors where the seal is made between a tapered male and female thread.

NOTE: Although the BSPT male connector appears to look like the National Pipe Tapered Fuel, or NPTF; their thread size and form are not the same and therefore they are not compatible.

Flat Face Port with British Standard Pipe Parallel Threads (ISO 1179-1) :

DIN 3852, Part 2

These connectors form their seal between the male half and the smooth surface of the female half, using a combination of rings or washers between their parallel threads.

Flat Face Port with Metric Threads (ISO 9974-1) :

DIN 3852, Part 1

These connectors form their seal between the male half and the smooth surface of the female half, using a combination of rings or washers between their parallel threads.

ISO 261 Metric threads

ISO 6149 Metric Port and Stud Ends :

ISO 261 threads & O-ring seal

Connection with both male and female halves having straight threads. The female half has a smooth surface and a chamfer, and the male half has an O-ring. That O-ring compresses against the female chamfer to form the seal. . The male and female threads mesh to form a solid connection.

NOTE: Except for the metric threads on the ISO 6149, it connects in the same way as the SAE J1926-1O-ring Boss.

Metric 60° Cone :

DIN 7631

These connectors commonly found in hydraulic systems. The female connector has a globeseal seat, while the male has a 60° recessed cone (which forms the seal against the female's tapered nose). Both male and female have straight threads, that mesh to form a solid connection.

Metric Compression Fittings (DIN 2353 24° Cone) :

Both male and female connectors have straight threads, with the male having a 240 cone, and the three female connectors a sealing surface. The 240 cone (male) and the sealing surfaces (females) form the seal.

There are two types of connectors - the DIN 2353 L light class, and the DIN 2353 S heavy class. The chart below lists tube sizes and thread dimensions for each class:

Japanese Industrial Standard JIS 300 Flare :

Both male and female connectors have straight threads, however the female has a 300 seat, and the male a 30° seat. (Although the 30° seat and BSPP-like thread dimensions differ from the American 37° Flare, the connections are very much alike.)

Komatsu 30° Flare (JIS Metric) :

These connectors are commonly used on Komatsu equipment. With a 30° seat and parallel metric threads, it's not unlike the JIS 300 flare (the difference being the metric threads vs. the BSPP-like thread dimensions on the JIS 300).

National Pipe Straight Mechanical (NPSM) :

A connection where the male thread (with a 300 internal chamfer), and female thread (with an inverted 300 seat), are both straight. When the two are threaded together, the tapered seat forms a leak-resistant connection. These connections are used widely across fluid power systems.

NOTE: A NPSM female and a chamfered NPTF male can form a seal together.

JIC 37° Flare (SAE J514) :

This connection is widely used in hydraulic systems, and both the male and female connectors have straight threads and a 37º flare seat. The straight threads of each half hold the connection together, sealing the flared seats.

NOTE: Most SAE J514 threads are exactly the same as the SAE 45º flare threads, however their seating angles differ.

SAE 45° Flare (SAE J512) :

Typically used with low pressure systems like refrigerant lines, fuel lines, and automotive applications, the SAE male and female connectors similarly have a 45° flare seat which forms the seal. The threads of both halves mesh together for a strong mechanical connection. The SAE 45° Flare connectors are exactly the same as the JIC 37° Flare connectors, however their seating angles differ.

SAE Straight Thread O-ring (O-Ring Boss) :

SAE J1926-1 and ISO 11296-1

A connection commonly found in high pressure hydraulic systems. While both halves have straight threads, the female has a sealing face and chamfer, and the male has an O-ring which when compressed into the opposing chamfer, forms the seal. The male and female threads mesh to form a solid connection.

Compression Tube Fittings (SAE J514) :

The female connector includes a compression sleeve, a female nut, and a tube. The male connector has a 240 seat, which makes the seal with the female compression sleeve (the seal forms on the female side between the tubing and the compression sleeve). With non-flared tube fittings with straight threads, the male and female threads mesh to form a solid connection.

O-Ring Face Seal (SAE J1453) :

These fittings join to form a highly leak resistive connection, in applications up to 6000 psi. Both halves have a straight thread, with the female having a flat surface and the male connector containing an O-ring. The seal is made when the O-ring on the male compresses against the flat surface of the female. The outside nut on the female connector holds the connection together.

SAE Inverted Flare (SAE J512) :

These connectors are widely used in the automotive industry. With the flared male tubing having a 450 seat, and the machined connector a 420 seat, the sealing surface is formed with the 420 seat on the end of the flare of the female connector. The male and female threads mesh to form a solid connection.

Four-Bolt Flange (SAE J518 and ISO 6162) :

These commonly used in fluid power systems, and suitable for joining 1/2" - 3" hose or tube. The seal forms between the flat surface of the female port and the O-ring of the male (seated in the ring groove). A split clamp, using 4 bolts, hold the male/female together.

Note that there are two types of SAE J518 flanges available: standard pressure (code 61), and high pressure (code 62).

O-Ring Pilot Threads :

These connections are typically seen in automotive and commercial air conditioning applications. Both halves of the connection have a pilot, making the seal by compressing the O-ring. The male and female threads mesh to form a solid connection.