Abstract: A method of providing tubes of the type intended primarily for use in boilers with a variably rifled interior surface. The function of the latter surface is to create turbulence within the tube operative to break up the laminar flow of the water or steam flowing therethrough so as to thereby promote more efficient heat transfer during steam generation and so as to minimize the susceptibility of the tube to overheat due to the effects of nucleate boiling.

Abstract: A method of providing tubes, of the type intended primarily for use in boilers, with a variably rifled interior surface. The function of the latter surface is to create a turbulence within the tube operative to break up laminar flow of the water or steam flowing therethrough so as to thereby promote more efficient heat transfer during steam generation and so as to prevent overheating of the tube. The subject method includes the steps of providing a suitably dimensioned, smooth surface, hardened mandrel; wrapping a wire-like member on the hardened mandrel so as to form thereon a reverse image of the desired, variably patterned tube rifling; inserting the hardened mandrel into a tube; with the hardened mandrel so positioned in the tube producing a reduction in the tube diameter so as to cause the wire-like member to become embedded in the inner wall of the tube; and thereafter withdrawing the hardened mandrel from the tube while leaving the wire-like member embedded in the tube inner wall.

Abstract: A method and apparatus for upsetting a tube end using a one-piece upset die. The tube is heated at the end to be upset and secured in a gripper clamp so as to remain stationary during the upset operation. The upset die is hydrualically forced over the tube end and a mandrel is hydraulically positioned into the tube end. A longitudinal compressive force is then hydraulically applied to upset the tube end. The upset die is hydraulically pulled off the upset tube and thereby accomplishing removal of the tube from the one-piece die without damage to the tube or the die.

Abstract: An apparatus for reducing the radius of the bend in a U-shaped tube comprises two squeeze dies and a back die. The back die is hollowed to form a chamber that accommodates the bent section of the tube and supports the entire circumference of the tube at the center of the bent section. Mating slide surfaces on the back die and the squeeze dies cooperate to extend the back die during squeezing in such a manner as to accommodate the longitudinal extension of the tube legs that results from the squeezing; i.e., there is no relative longitudinal movement between the squeeze dies and the tube legs. This arrangement enables relatively thin-walled tubes to be squeezed without undue deformation of the tube.

Abstract: Nipples are extruded on metal parts around holes therethrough by providing an initial hole having a wide portion and a narrower portion, the wide portion having the diameter desired in the finished hole. A tapered mandrel is forced through the initial hole, extruding a nipple and resulting in a hole of the desired diameter.