The tube bender, shown in figure 6-11, is issued as a kit. The kit contains the equipment necessary for bending tubing from 1/4 inch to 3/4 inch in diameter. This tube bender is designed for use with aircraft grade, high-strength, stainless-steel tubing, as well as all other metal tubing. It is designed to be fastened to a bench or tripod, and the base is formed to provide a secure grip in a vise.

Figure 6-11.Mechanical operated tube bender.

The simple hand bender shown in figure 6-10 uses two handles as levers to provide the mechanical advantage necessary to bend the tubing, while the mechanical operated tube bender employs a hand crank and gears. The forming die is keyed to the drive gear and secured by a screw (fig. 6-11).

The forming die on the mechanical tube bender is calibrated in degrees similar to the radius block of the hand-type bender. A length of replacement tubing may be bent to a specified number of degrees or it may be bent to duplicate the bend in the damaged tube or pattern. Duplicating the bend of a damaged tube or pattern is accomplished by laying the pattern on top of the tube being bent and slowly bending the new tube to the required bend.

NOTE: Certain types of tubing are more elastic than others. It may be necessary to bend the tube past the required bend to allow for springback. 

Before bending aluminum alloy tubing, it should be packed with fusible alloy Federal Specification QQ-F-838. In an emergency, when aluminum alloy QQ-F-838 is not available, aluminum alloy tubing may be packed with shot or sand and both ends closed with protective closures before bending. Where sand or fusible alloy is used, wash or blow out all particles after the tubing has been bent. Particles of aluminum alloy or sand can cause serious damage to component parts.

The two major tube joints are the flared fittings and flareless fittings. Preparation for these tube joints differ.