Mention has been made in another paragraph of methods of bending copper pipes and small iron or brass pipes.

Two essentials in pipe bending are (1) to keep the pipe from flattening into elliptical shape in the bend, and (2) to avoid wrinkles in the concave part of the bend. These may be accomplished by bending the pipe over a grooved form shown in Fig. 259. The sides of the form may be extended well above the groove to hold the sides of the pipe against bulging along the bend. This form may be used for cold bending of pipes up to about 1 1/2-inch diameter.

A more elaborate form, suited to larger piping, is shown in Fig. 260. Large pipes should be heated red to facilitate bending.

A pipe may be filled with sand and plugged to assist in holding its circular cross section, and, if a bending form is not available, the jaws of a vise may be spread apart just far enough for the pipe to be held between them during bending. This will keep the pipe sides from bulging. The welded seam of a pipe should be in the throat or concave part of the bend.

Fig. 260. - Form for Bending Large Pipes.