What is the outside diameter range for tubing that can be flared with a double flare?

• A. 1/8 to 1/4 inch
• B. 1/4 to 1/2 inch
• C. 3/8 to 1/2 inch
• D. 1/8 to 3/8 inch

Answer: (D)

Double flare tooling is designed to form two precise flare angles on a tube end, and the tube must fit the tool’s dies exactly to produce a safe, leak-free seal. The outer diameter of the tubing determines whether the flare can be formed cleanly: if the tube is too small, the flare won’t take shape properly; if it’s too large, the tool can’t form the flare without deforming or weakening the tubing. In typical aviation practice, a double flare can be reliably formed on tubing with an outside diameter from about 1/8 inch up to 3/8 inch. So the valid range is 1/8 to 3/8 inch. Always check the specific flaring tool’s specifications to confirm the exact range it supports.