Which process allows joining two soft copper tubes of the same size without fittings?

• A. Soldering
• B. Welding
• C. Brazing
• D. Swaging

Answer: (D)

Swaging is a mechanical forming process that creates a seamless joint by deforming the end of one tube to fit over the other and then forming the two tubes together as a single piece. This is ideal when you have two soft copper tubes of the same outside diameter because you can expand or taper one end enough to slip over the other, then swage the assembly so the bore remains essentially continuous and the joint is tight without any added fittings or filler metal. This keeps the interior bore unobstructed and avoids introducing solder, braze, or weld material that would alter the flow or require additional finishing. Soldering, brazing, and welding rely on heat and filler material and typically involve a seam or bond rather than a true, seamless mechanical join, which is why swaging is the best choice for joining equal-diameter copper tubes without fittings.