What is the main purpose of using a 45-degree flare angle in copper tube connections?

• A. To reduce corrosion
• B. To ensure a tight seal with the matching flare nut
• C. To increase flow
• D. To resist bending

Answer: (B)

A 45-degree flare creates a conical sealing surface on the end of the tube that matches the seat inside the flare fitting. When you tighten the flare nut, the flare is pressed against that seat and the copper slightly deforms to fill any tiny gaps. The result is a metal-to-metal seal that can hold high pressure and resist leaks, and it’s also easily serviceable because the joint can be disassembled and reassembled. This is why the main purpose is to ensure a tight seal with the matching flare nut. It doesn’t primarily reduce corrosion, increase flow, or resist bending—the seal is the key function of the flare.