M18 Couplings | McMaster-Carr

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How to Identify and Measure Fittings

Pipe size is an industry designation, not the actual size. View information about how to measure threaded and unthreaded pipe and pipe fittings.

About Nuts, Materials, and Finishes

About Hose

Extreme-Pressure Stainless Steel Threaded Pipe Fittings

With the strength to handle extreme pressures, these fittings can be used to connect equipment in hydraulic fluid lines. 316 stainless steel fittings have excellent corrosion resistance. BSPP and metric male threads have either a gasket or a gasket and washer to prevent leaks. UN/UNF (SAE) threads are also known as O-ring boss threads; the male threads have a gasket to prevent leaks.

For technical drawings and 3-D models, click on a part number.

Straight Adapters, Female × Male

Straight Adapter

BSPP and Metric
Male Threads with
Gasket and Washer

BSPP, Metric, and
UN/UNF (SAE) Male
Threads with Gasket

Specifications Met: See table
For Use With: See table

								316 Stainless Steel
Pipe Size (A)	Thread Size (A)	Dash Size (A)	Thread Size (B)	Dash Size (B)	Max. Pressure	For Use With	Specifications Met		Each
NPT Female × Metric Male
3/8	__	06	M18 × 1.5 mm	__	4,500 psi @ 72° F	Hydraulic Fluid, Oil, Water	ASME B1.20.3, DIN 7631, ISO 9974	00000000	000000
1/2	__	08	M18 × 1.5 mm	__	4,000 psi @ 72° F	Hydraulic Fluid, Oil, Water	ASME B1.20.3, DIN 7631, ISO 9974	00000000	00000
UN/UNF (SAE) Female × Metric Male
__	3/4"-16	08	M18 × 1.5 mm	__	3,500 psi @ 72° F	Hydraulic Fluid (Petroleum Base), Oil, Water	__	000000000	00000
Metric Female × UN/UNF (SAE) Male
__	M18 × 1.5 mm	__	3/4"-16	08	6,000 psi @ 72° F	Hydraulic Fluid (Petroleum Base), Oil, Water	__	000000000	00000

Straight Adapters, Male

Front

BSPP and Metric
Male Threads with
Gasket and Washer

For Use With: See table
Specifications Met: See table

						316 Stainless Steel
Pipe Size (A)	Dash Size (A)	Thread Size (B)	Max. Pressure	For Use With	Specifications Met		Each
BSPP Male × Metric Male
1/4	04	M18 × 1.5 mm	5,000 psi @ 72° F	Hydraulic Fluid, Oil, Water	DIN 7631, ISO 1179, ISO 8434-6, ISO 9974	00000000	000000
3/8	06	M18 × 1.5 mm	5,000 psi @ 72° F	Hydraulic Fluid, Oil, Water	DIN 7631, ISO 1179, ISO 8434-6, ISO 9974	00000000	00000
1/2	08	M18 × 1.5 mm	4,500 psi @ 72° F	Hydraulic Fluid, Oil, Water	DIN 7631, ISO 1179, ISO 8434-6, ISO 9974	00000000	00000

Replacement Washers

Temperature Range: -22° to 230° F

			316 Stainless Steel
For Pipe Size	For Thread Size	Gasket Material	Thickness		Each
For BSPP Male
1/4	__	Buna-N Rubber	2.03mm	00000000	00000
3/8	__	Buna-N Rubber	2mm	00000000	0000
1/2	__	Buna-N Rubber	2.5mm	00000000	0000
For Metric Male
__	M18	Buna-N Rubber	1.5mm	00000000	0000

Compact Extreme-Pressure Steel Threaded Pipe Fittings

These fittings are strong enough to handle extreme pressures, yet small enough to fit into cramped spaces. They are galvanized steel, which has fair corrosion resistance. BSPP and metric male threads have either a gasket, or a gasket and washer, to prevent leaks.

For technical drawings and 3-D models, click on a part number.

Straight Connectors, Female

For Use With:
NPTF: Air, Hydraulic Fluid, Water
Metric: Air, Hydraulic Fluid, Oil, Water
Specifications Met:
NPTF: ASTM A108
Metric: DIN 7631, ISO 6149, ISO 9974

Metric Female
Thread Size	Max. Pressure		Each
M18 × 1.5 mm	4,000 psi @ 72° F	00000000	000000

Straight Adapters, Female × Male

BSPP and Metric
Male Threads with
Gasket and Washer

For Use With: See table
Specifications Met: See table

NPT Female × Metric Male
Pipe Size (A)	Thread Size (A)	Dash Size (A)	Pipe Size (B)	Thread Size (B)	Dash Size (B)	Max. Pressure	For Use With	Specifications Met		Each
3/8	__	06	__	M18 × 1.5 mm	__	4,000 psi @ 72° F	Air, Hydraulic Fluid, Oil, Water	ASME B1.20.3, DIN 2353, ISO 8434-1	00000000	00000
1/2	__	08	__	M18 × 1.5 mm	__	3,500 psi @ 72° F	Air, Hydraulic Fluid, Oil, Water	ASME B1.20.3, DIN 2353, ISO 8434-1	00000000	0000
Metric Female × NPT Male
__	M18 × 1.5 mm	__	3/8	__	06	5,500 psi @ 72° F	Air, Hydraulic Fluid, Oil, Water	ASME B1.20.3, DIN 7631, ISO 6149, ISO 9974	00000000	00000
__	M18 × 1.5 mm	__	1/2	__	08	4,500 psi @ 72° F	Air, Hydraulic Fluid, Oil, Water	ASME B1.20.3, DIN 7631, ISO 6149, ISO 9974	00000000	00000

Straight Adapters, Male

BSPP, Metric, and UN/UNF
(SAE) Male Threads with
Gasket and Washer

For Use With: See table
Specifications Met: See table

NPT Male × Metric Male
Pipe Size (A)	Dash Size (A)	Thread Size (B)	Max. Pressure	For Use With	Specifications Met		Each
3/8	06	M18 × 1.5 mm	5,500 psi @ 72° F	Air, Hydraulic Fluid, Oil, Water	ASME B1.20.3, DIN 2353, ISO 8434-1	00000000	000000
BSPP Male × Metric Male
1/2	08	M18 × 1.5 mm	4,500 psi @ 72° F	Air, Diesel Fuel, Gasoline, Hydraulic Fluid, Oil, Water	DIN 7631, ISO 1179, ISO 6149, ISO 8434-6, ISO 9974	00000000	00000

Replacement Washers

Temperature Range: -20° to 230° F

For BSPP Male
For Pipe Size	For Thread Size	Gasket Material	Thickness		Each
1/2	__	Buna-N Rubber	2.5mm	00000000	00000
For Metric Male
__	M18	Buna-N Rubber	1.5mm	00000000	0000

Metal Barbed Hose Fittings for Air and Water

Slide the barbed end into rubber hose and secure with the appropriate clamp or crimp-on hose ferrule.

Brass fittings are softer than other metal fittings, so they’re easier to thread together. Plain brass fittings have good corrosion resistance.Aluminum fittings are lighter in weight than other metal fittings. They have good corrosion resistance.

Stainless steel fittings have very good corrosion resistance. 303 stainless steel fittings won’t rust when exposed to water, making them good for areas that require frequent cleanings. Fittings with a threaded end are also known as hose nipples.

Metric, UN/UNF (SAE), and BSPP male threads with gasket protect against leaks.

For technical drawings and 3-D models, click on a part number.

Straight Adapters, Hose × Metric Male Threaded Pipe

NPT/NPTF, Metric, BSPP,
and UN/UNF (SAE) Male
Threads with Gasket

Maximum Pressure: See table
Maximum Vacuum: 27 in. of Hg @ 72° F
Temperature Range: See table
Attachment Type: See table
Specifications Met: See table

Brass
For Hose ID	Thread Size	Gasket Material	Max. Pressure	Temperature Range, °F	Attachment Type	Pkg. Qty.		Pkg.
1/2"	M18 × 1.5 mm	Buna-N Rubber	300 psi @ 72° F	-30° to 200°	Worm-Drive Clamp, Band-and-Buckle Clamp, Crimp-On Hose Ferrule	1	00000000	000000
3/4"	M18 × 1.5 mm	Buna-N Rubber	300 psi @ 72° F	-30° to 200°	Worm-Drive Clamp, Band-and-Buckle Clamp, Crimp-On Hose Ferrule	1	00000000	00000
Aluminum
1/2"	M18 × 1.5 mm	Buna-N Rubber	125 psi @ 72° F	-30° to 200°	Worm-Drive Clamp, Band-and-Buckle Clamp, Crimp-On Hose Ferrule	1	00000000	00000
303 Stainless Steel
1/2"	M18 × 1.5 mm	Buna-N Rubber	125 psi @ 72° F	-30° to 200°	Worm-Drive Clamp, Band-and-Buckle Clamp, Crimp-On Hose Ferrule	1	00000000	00000
3/4"	M18 × 1.5 mm	Buna-N Rubber	125 psi @ 72° F	-30° to 200°	Worm-Drive Clamp, Band-and-Buckle Clamp, Crimp-On Hose Ferrule	1	00000000	00000
19mm	M18 × 1.5 mm	Buna-N Rubber	125 psi @ 72° F	-30° to 200°	Worm-Drive Clamp, Band-and-Buckle Clamp, Crimp-On Hose Ferrule	1	00000000	00000

International Standard ISO Minimal-Spill
Quick-Disconnect Hose Couplings for Hydraulic Fluid

3/8 Coupling Size

1/2 Coupling Size

Also known as flush-face couplings, the plugs and sockets have a flat face, which allows them to mate close against each other, reducing fluid loss when connecting and disconnecting the line. A complete coupling consists of a plug and a socket (both sold separately) that connect and disconnect quickly. Use them when you need frequent access to a line. All of the International Standard ISO Minimal-Spill quick-disconnect plugs are compatible with any of the International Standard ISO Minimal-Spill quick-disconnect sockets of the same coupling size, regardless of the pipe size. Couplings are compatible with ISO 16028 Parker FEM, ISO 16028 Perfecting HT, and ISO 16028 Snap-Tite 74 couplings. Also known as double shut-off couplings, the plugs and sockets both have a shut-off valve that stops the flow when the coupling is separated. They are zinc-plated steel, which has excellent strength and durability and fair corrosion resistance.

Plugs are also known as nipples.

Sockets are push-to-connect style. To connect, push the plug into the socket until you hear a click. To disconnect, slide the sleeve on the socket forward until the plug ejects.

Note: To ensure a correct fit, make sure that the plug and socket have the same coupling size. Pressure ratings are given for static (constant) pressure conditions.

Warning: Never attempt to connect or disconnect couplings when operating at maximum pressure. Stop the flow before you disconnect the line.

For technical drawings and 3-D models, click on a part number.

Plugs, Metric Male Threaded Pipe

3/8 Coupling Size

1/2 Coupling Size

Maximum Pressure: See table
Temperature Range: -20° to 212° F
Compatible With: ISO 16028 Parker FEM, ISO 16028 Perfecting HT, ISO 16028 Snap-Tite 74
Specifications Met
Specifications Met: ISO 16028

Plugs
	Plug Tip		Thread						Optional Dust Caps
Coupling Size	Lg.	Dia.	Size	Pitch, mm	Dash Size	Max. Pressure		Each		Each
Zinc-Plated Steel
3/8	3/16"	3/4"	M18	1.5	06	5,800 psi @ 72° F	0000000	000000	0000000	00000
1/2	3/8"	15/16"	M18	1.5	08	5,800 psi @ 72° F	0000000	00000	0000000	0000

Push-to-Connect Sockets, Metric Male Threaded Pipe

3/8 Coupling Size

1/2 Coupling Size

Maximum Pressure: See table
Temperature Range: -20° to 212° F
Compatible With: ISO 16028 Parker FEM, ISO 16028 Perfecting HT, ISO 16028 Snap-Tite 74
Specifications Met
Specifications Met: ISO 16028

Sockets
	For Plug Tip		Thread						Optional Dust Plugs
Coupling Size	Lg.	Dia.	Size	Pitch, mm	Dash Size	Max. Pressure		Each		Each
Zinc-Plated Steel
3/8	3/16"	3/4"	M18	1.5	06	5,800 psi @ 72° F	0000000	000000	0000000	00000
1/2	3/8"	15/16"	M18	1.5	08	5,800 psi @ 72° F	0000000	00000	0000000	0000

Push-On Barbed Hose Fittings for Hydraulic Fluid

These fittings have sharp barbs to grip rubber push-on hose with no clamps or ferrules required. The more you pull on the fittings, the tighter the hose will grip. Use them in low-pressure hydraulic applications up to 350 psi. Also known as hose nipples, they adapt a barbed end to a threaded end, so you can connect to pumps, cylinders, and other equipment in your hydraulic system. Fittings are zinc-plated steel, which has excellent strength and durability. Fittings have fair corrosion resistance.

Fittings that swivel until tightened rotate 360° for easy installation.

Note: To ensure proper connection, the barbed end has to be pushed in all the way, with the hose end concealed by the ring.

For technical drawings and 3-D models, click on a part number.

Straight Adapters, Hose × Metric Male Threaded Pipe

Maximum Pressure: 350 psi @ 72° F
Maximum Vacuum: 28 in. of Hg @ 72° F
Temperature Range: -40° to 155° F
For Hose Manufacturer Series: Parker 801

Fittings
		Thread		Ring Stop					10-ft. Hose
For Hose ID	Dash Size	Size	Pitch, mm	Material	Color	Manufacturer Series		Each		Each
Zinc-Plated Steel
3/8"	06	M18	1.5	Plastic	Yellow	Parker 82	00000000	000000	0000000	000000

Straight Adapters (Swivels Until Tightened), Hose × Metric Female Threaded Pipe

Maximum Pressure: See table
Maximum Vacuum: 28 in. of Hg @ 72° F
Temperature Range: -40° to 155° F
For Hose Manufacturer Series: Parker 801

Fittings
		Thread		Ring Stop						10-ft. Hose
For Hose ID	Dash Size	Size	Pitch, mm	Material	Color	Max. Pressure	Manufacturer Series		Each		Each
Zinc-Plated Steel
3/8"	06	M18	1.5	Plastic	Yellow	350 psi @ 72° F	Parker 82	00000000	000000	0000000	000000

Plastic Barbed Tube Fittings for Air and Water

Fittings have barbs that grip onto tubing.

Nylon fittings have excellent impact and abrasion resistance.

For technical drawings and 3-D models, click on a part number.

Straight Adapters, Tube × Male Threaded Pipe

Temperature Range: See table
Tubing: Semi-Clear: Use with firm or soft (Durometer 45A-80A) polyurethane rubber or PVC plastic
Opaque: Use with firm or soft (Durometer 40A-80A) polyurethane rubber or PVC plastic

Metric Threads
For Tube ID	Thread Size	Material	Color	Clarity	Max. Pressure	Temp. Range, °F	Pkg. Qty.		Pkg.
12mm	M18 × 1.5 mm	Nylon Plastic	Gray	Opaque	145 psi @ 72° F	-40° to 190°	10	00000000	000000

90° Elbow Adapters, Tube × Male Threaded Pipe

Temperature Range: See table
Tubing: Semi-Clear: Use with firm or soft (Durometer 45A-80A) polyurethane rubber or PVC plastic
Opaque: Use with firm or soft (Durometer 40A-80A) polyurethane rubber or PVC plastic

Metric Threads
For Tube ID	Thread Size	Material	Color	Clarity	Max. Pressure	Temp. Range, °F	Pkg. Qty.		Pkg.
8mm	M18 × 1.5 mm	Nylon Plastic	Gray	Opaque	145 psi @ 72° F	-40° to 190°	10	00000000	000000
12mm	M18 × 1.5 mm	Nylon Plastic	Gray	Opaque	145 psi @ 72° F	-40° to 190°	10	00000000	00000

Compression Fittings for Copper Tubing

For Use With: Air, Cutting Oil, Fuel Oil, Hydraulic Fluid, Mineral Oil, Water
Temperature Range: See Table
Tubing: Use with copper
Specifications Met: See Table

A single sleeve (ferrule) bites into tubing as you tighten the nut, creating a strong seal. The nut and sleeve are included. Fittings are also known as flareless fittings. They are brass for good corrosion resistance.

For technical drawings and 3-D models, click on a part number.

Straight Adapters, Tube × Male Threaded Pipe

For Tube
OD	Wall Thick.	Thread Size	Thread Pitch, mm	Material	Max. Pressure	Temp. Range, °F		Each
Metric Threads
10mm	1mm	M18	1.5	Brass	1,080 psi @ 72° F	-40° to 250°	00000000	000000

37° Flared Fittings for Steel Tubing

Tubing: Use with seamless steel
Specifications Met: SAE J514

Also known as JIC (Joint Industrial Council) fittings, these provide a tight metal-to-metal seal on tubing that is flared to 37°. They require a nut and a sleeve (ferrule) for each tube end. Nuts and sleeves are sold separately. Fittings are zinc-plated steel for fair corrosion resistance.

To prevent leaks, UN/UNF (SAE) male threads have a gasket. Metric and BSPP male threads have either a gasket or a gasket and washer.

For technical drawings and 3-D models, click on a part number.

Straight Adapters, Male Tube × Male Threaded Pipe

BSPP and Metric
Male Threads with
Gasket and Washer

For Use With: See Table
Temperature Range: See Table

Metric Threads
For Tube OD	Thread Size	Thread Pitch, mm	For Use With	Material	Gasket Material	Washer Material	Max. Pressure	Temp. Range, °F		Each
1/2"	M18	1.5	Air, Fuel Oil, Hydraulic Fluid, Mineral Oil	Zinc-Plated Steel	Buna-N Rubber	__	2,300 psi @ 72° F	-30° to 200°	00000000	000000
1/2"	M18	1.5	Cutting Oil, Fuel Oil, Hydraulic Fluid, Mineral Oil	Zinc-Plated Steel	Buna-N Rubber	Zinc-Plated Steel	4,500 psi @ 72° F	-20° to 212°	00000000	00000
5/8"	M18	1.5	Air, Fuel Oil, Hydraulic Fluid, Mineral Oil	Zinc-Plated Steel	Buna-N Rubber	__	2,300 psi @ 72° F	-30° to 200°	00000000	00000

90° Elbow Adapters, Male Tube × Male Threaded Pipe

For Use With: NPTF, Metric, BSPP with O-Rings, BSPT: Air, Fuel, Oil, Hydraulic Fluid, Mineral Oil
BSPP with Washers: Cutting Oil, Fuel Oil, Hydraulic Fluid, Mineral Oil
Temperature Range: NPTF and BSPT: -60° to 400° F
Metric and BSPP with O-Rings: -30° to 200°F
BSPP with Washers: -20° to 212° F

Metric Threads
For Tube OD	Thread Size	Thread Pitch, mm	Material	Gasket Material	Max. Pressure		Each
1/2"	M18	1.5	Zinc-Plated Steel	Buna-N Rubber	2,300 psi @ 72° F	00000000	000000
5/8"	M18	1.5	Zinc-Plated Steel	Buna-N Rubber	2,300 psi @ 72° F	00000000	00000

Nuts

For Use With: Air, Fuel Oil, Hydraulic Fluid, Mineral Oil
Temperature Range: -60° to 400° F

For Tube OD	Nut Material	Max. Pressure		Each
1/2"	Zinc-Plated Steel	4,000 psi @ 72° F	000000000	00000
5/8"	Zinc-Plated Steel	3,000 psi @ 72° F	000000000	0000

Sleeves

For Use With: Air, Fuel Oil, Hydraulic Fluid, Mineral Oil
Temperature Range: -60° to 400° F

Use these sleeves with a nut and fitting to provide a tight metal-to-metal seal on steel tubing that is flared to 37°. Sleeves are zinc-plated steel for fair corrosion resistance. They are also known as ferrules.

Inch × metric sleeve adapters convert the fitting from inch to metric.

For Tube OD
Inch	Metric, mm	Sleeve Material	Max. Pressure		Each
Inch Sleeves
1/2"	__	Zinc-Plated Steel	4,000 psi @ 72° F	000000000	00000
5/8"	__	Zinc-Plated Steel	3,000 psi @ 72° F	000000000	0000
Inch × Metric Sleeve Adapters
1/2"	12	Zinc-Plated Steel	4,000 psi @ 72° F	000000000	0000
5/8"	14	Zinc-Plated Steel	3,000 psi @ 72° F	000000000	0000
5/8"	15	Zinc-Plated Steel	3,000 psi @ 72° F	000000000	0000
5/8"	16	Zinc-Plated Steel	3,000 psi @ 72° F	000000000	0000

Metric Low-Strength Steel Coupling Nuts

Often referred to as extension nuts, use these to connect and extend threaded rods. They're about half the strength of medium-strength steel coupling nuts for use in light duty fastening applications.

Zinc-plated steel coupling nuts resist corrosion in wet environments.

Black-oxide steel coupling nuts have a dark surface color and are mildly corrosion resistant in dry environments.

For technical drawings and 3-D models, click on a part number.

Thread						Each
Size	Pitch, mm	Lg., mm	Wd., mm	Specifications Met		1-9	10-Up
Zinc-Plated Steel
M18	2.5	54	27	DIN 6334	000000000	000000	000000
Black-Oxide Steel
M18	2.5	54	27	DIN 6334	000000000	00000	00000

Metric Medium-Strength Steel Coupling Nuts—Class 8

Often referred to as extension nuts, use these to connect and extend threaded rods. They're comparable in strength to Class 8.8 bolts.

Zinc-plated steel coupling nuts resist corrosion in wet environments.

Black-oxide steel coupling nuts have a dark surface color and are mildly corrosion resistant in dry environments.

For technical drawings and 3-D models, click on a part number.

Thread						Each
Size	Pitch, mm	Lg., mm	Wd., mm	Specifications Met		1-9	10-Up
Zinc-Plated Steel—Class 8
M18	2.5	54	27	DIN 6334	000000000	000000	000000
Black-Oxide Steel—Class 8
M18	2.5	54	27	DIN 6334	000000000	00000	00000

Metric 18-8 Stainless Steel Coupling Nuts

Stainless Steel

Made from 18-8 stainless steel, these metric coupling nuts have good chemical resistance and may be mildly magnetic. Also known as extension nuts, use them to connect and extend threaded rods.

For technical drawings and 3-D models, click on a part number.

Thread						Each
Size	Pitch, mm	Lg., mm	Wd., mm	Specifications Met		1-9	10-Up
18-8 Stainless Steel
M18	2.5	54	27	DIN 6334	000000000	000000	000000

Metric Super-Corrosion-Resistant 316 Stainless Steel Coupling Nuts

Made from 316 stainless steel, these coupling have excellent resistance to chemicals and salt water. Also known as extension nuts, use them to connect and extend threaded rods. They may be mildly magnetic.

For technical drawings and 3-D models, click on a part number.

Thread						Each
Size	Pitch, mm	Lg., mm	Wd., mm	Specifications Met		1-9	10-Up
316 Stainless Steel
M18	2.5	54	27	DIN 6334	000000000	000000	000000

How to Identify and Measure Fittings

About Nuts, Materials, and Finishes

About Hose

Extreme-Pressure Stainless Steel Threaded Pipe Fittings

Compact Extreme-Pressure Steel Threaded Pipe Fittings

Metal Barbed Hose Fittings for Air and Water

International Standard ISO Minimal-SpillQuick-Disconnect Hose Couplings for Hydraulic Fluid

Push-On Barbed Hose Fittings for Hydraulic Fluid

Plastic Barbed Tube Fittings for Air and Water

Compression Fittings for Copper Tubing

37° Flared Fittings for Steel Tubing

Metric Low-Strength Steel Coupling Nuts

Metric Medium-Strength Steel Coupling Nuts—Class 8

Metric 18-8 Stainless Steel Coupling Nuts

Metric Super-Corrosion-Resistant 316 Stainless Steel Coupling Nuts

International Standard ISO Minimal-Spill
Quick-Disconnect Hose Couplings for Hydraulic Fluid