Abstract: A heat exchange unit for a heat exchanger which includes a first tube with an outer surface and extended surface members located axially along the outer surface. Each member has a tube engagement surface and are axially Positioned. There is also taught a heat exchange fin block having a heat exchange unit with a second tube interconnected to the first tube by the extended surface members, wherein the extended surface members being tube fins at predetermined axial spacings. A tube finning machine is disclosed which includes a base with clamping means mounted thereon, carrier means movable relative to the base, and drive means for moving the carrier means. The clamping means clamps a portion of the first tube, and the carrier means transports at least one fin to an axially predetermined position adjacent the portion.