5/8"-18 Couplings | McMaster-Carr

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118 Products

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.

Metal Barbed Hose Fittings for Air and Water

Metal hose fittings have better durability than plastic barbed hose fittings.

Metal Push-On Barbed Hose
Fittings for Air and Water

Fittings are metal for better durability than plastic barbed hose fittings. They have sharper barbs than standard barbed hose fittings to grip push-on hose without the need for clamps or ferrules. The more you pull on the fittings, the tighter the hose will grip.

Threaded Hose Fittings for Compressed Gas

Use these CGA fittings to connect welding hose to pressure regulators and torches.

Nuts for Barbed Hose Fittings for Compressed Gas

Also known as CGA nuts, these are designed for low-pressure welding applications downstream of your pressure regulator. Attach them to barbed hose fittings for compressed gas to make a threaded connection to torches or pressure regulators.

Nuts for High-Pressure Nipples for Compressed Gas

These nuts attach to high-pressure nipples for compressed gas so you can connect your tank to the inlet of a pressure regulator.

Tubing and Tube Fittings

45° Flared Fittings for Copper and Brass Tubing

No sleeve is required to assemble these fittings, which makes for a faster, more convenient installation compared to 37° flared fittings. They are also known as refrigeration and SAE fittings.

Nuts for 45° Flared Fittings
for Copper and Brass Tubing

Supported 45° Flared Fittings
for Copper and Brass Tubing

The flared end of the fitting nests inside the fitting body, providing extra support to the tubing. Fittings are also known as inverted 45° flared fittings.