Benders allow the maintenance technician to make precise angled bends .The objective in tube bending is to obtain a smooth bend without flattening the tube. Tube bending is usually done with either a hand tube bender or a mechanically operated bender. These tools include spring tube, hand tube, mechanically operated tube, and electrical conduit hand benders. In this chapter, you will learn about different types of benders and their uses. You will also learn how to select the right bender for the job, use various types of benders, and provide the proper care of the benders to keep them in good working condition.
When you have completed this chapter, you will be able to do the following:
Two types of spring tube benders are available: external and internal. The spring tube bender (Figure 1) permits the bending of small-diameter soft copper and aluminum tubing by hand without collapsing the tubing. Spring tube benders are available in 1/4-, 5/16-, 3/8-, 7/16-, 1/2-, 5/8-, 3/4-, and 7/8-inch diameter sizes.
Figure 1 — Spring tube bender.
External benders are used to bend straight sections of tubing that have at least one end that has not been flared. The external benders should slip over the tubing and be positioned in the middle of the proposed bend.
Internal benders are used for bending straight sections of tubing that have both ends flared. The internal benders should fit inside the tubing and be positioned in the middle of the proposed bend. Attach a string to the internal spring bender for easy removal after making the bend.
The hand tube bender (Figure 2) consists of a handle, a radius block, a clip, and a slide bar. The handle and slide bar are used as levers to provide the mechanical advantage necessary to bend tubing. The radius block is marked on degrees of bend ranging from 0 to 180 degrees. The slide bar has a mark that is lined up with the zero mark on the radius block. The hand tube bender is available in 3/16-, 1/4-, 5/16-, 3/8-, and 1/2-inch diameter sizes. The hand tube bender is used to bend copper, brass, or aluminum tubing to specific angles.
Figure 2 — Hand tube bender.
The mechanical tube bender (Figure 3) is issued as a kit. The kit contains the equipment necessary for bending tubing from 1/4 to 3/4 inch in diameter. This tube bender is designed for bending 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 3 — Mechanical tube bender.
The simple hand bender, shown in Figure 2, uses two handles as levers to provide the mechanical advantage necessary to bend the tubing, while the mechanically operated tube bender employs a hand crank and gears. The forming die is keyed to the drive gear and secured by a screw (Figure 3). 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. To duplicate the bend of a damaged tube or pattern, lay the pattern on top of the tube being bent and slowly bend the new tube to the required bend.
The electrical conduit hand bender has precise grooves to ensure a smooth bend. It has a concave base, a foot rest, and a retaining hook to keep conduit from slipping as it is being bent. The bender has a threaded opening for attaching a threaded piece of pipe to be used as a handle. The electrical conduit hand bender is available in 1 /2-, 3/4-, 1-, 1 1/4-, 1 1/2-, and 2-inch diameter sizes.
Two types of manual benders are used to bend rigid conduit and electrical metallic tubing (EMT). They are the rigid bender, called the one-shot bender (Figure 4), and a hickey (Figure 5). The one-shot bender is normally made for EMT, but some are made for both EMT and rigid tubing. The one-shot bender was given its name because it can make a full 90- degree bend with a single motion. With manual benders, you can bend conduit sizes up to 1-inch rigid tubing or 1 1/4-inch EMT without much trouble. To bend larger sizes, use mechanical or hydraulic benders.
Figure 4 — One-shot bender.
Figure 5 — Hickey bender.
The hickey bender does not usually have degree markings on it. This feature makes the bending procedures slightly different. For instance, to make a 90-degree bend in 1/2-inch rigid metal conduit, you should make small bites on the bend to reduce the possibility of crimping or kinking the conduit.
Figure 6 — Using a tubing bender.
The following steps describe how to use a tubing bender properly (Figure 6):
The following steps describe how to use an electrical conduit hand bender properly:
Figure 7 — Align the bender arrow and mark for bend.
DO NOT jerk the handle. Jerking will create internal cracks and ridges in the conduit, which will cut the wires.
Figure 8 — Right-angle bend obtained.
Use the following guidelines when working with benders:
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14-1. How many types of spring tube benders are available?
14-2. Which of the following tools is used to bend a straight section of tubing that has both ends flared?
14-3. The handles on a hand tube bender provide what type of advantage necessary to bend tubing?
14-4. What bender is issued as a kit?
14-5. To duplicate the bend of a damaged tube, you should place the pattern in what location?
14-6. For what reason was the one-shot bender given its name?
14-7. The manual electrical conduit hand bender can bend rigid conduit of what maximum size, in inches?
14-8. You should stop bending the tubing when the zero mark on the slide bar matches what mark on the block?
14-9. When using an electrical conduit hand bender, where should you position your feet?
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