Compression fittings are machined with a 37-degree flare seating surface and parallel threads. They are commonly manufactured in which materials?

• A. Aluminum
• B. Nickel alloys, brass, carbon & stainless steel
• C. Rubber
• D. Glass

Answer: (B)

Compression fittings with a 37-degree flare seating surface create a metal-to-metal seal when the flared tubing end presses into the seat as the nut is tightened. This type of seal, typical of JIC-style connections, requires materials that combine high strength, good machinability, and resistance to corrosion from hydraulic fluids. Nickel alloys provide strong, corrosion-resistant performance in demanding environments, making them suitable for high-pressure and high-temperature applications. Brass is easy to machine, economical, and offers decent corrosion resistance, which is why it’s commonly used for fittings. Carbon steel and stainless steel cover a wide range of strength and corrosion resistance needs, with stainless offering excellent durability in corrosive or fluid-oxidizing environments. Aluminum, while lighter, is not as strong or durable for demanding hydraulic pressures, and rubber or glass are unsuitable for rigid metal compression fittings. That combination explains why these metals are the typical choices for these fittings.