BOX WRENCHES

The non-adjustable union nut wrench (fig. 1-29) is used to assemble and disassemble launch valve piping union nuts. These special open-end wrenches are designed to pass over the piping and then slide onto the union nut to fully engage five of the six flats, thus reducing the probability of damaging the nuts. NOTE These non-adjustable union nut wrenches are the preferred type for launch valve piping. Under no circumstances should any other type of adjustable or open-end wrench be used on launch valve piping fittings. BOX WRENCHES Box wrenches (fig. 1-30) are safer than open-end wrenches since there is less likelihood they will slip off the work. They completely surround, or box, a nut or bolt head. The most frequently used box wrench has 12 points or notches arranged in a circle in the head and can be used with a minimum swing angle of 30 degrees. Six- and eight-point wrenches are used for heavy duty; twelve-point for medium, and sixteen for light-duty only. One advantage of the 12-point construction is the thin wall. It is more suitable for turning nuts that are hard to get at with an open-end wrench. Another advantage is that the wrench will operate between obstructions where the space for handle swing is limited. A very short swing of the handle will turn the nut far enough to allow the wrench to be lifted and the next set of points fitted to the corners of the nut. One disadvantage of the box-end wrench is the time loss that occurs whenever a craftsman has to lift the wrench off and place it back on the nut in another position when there is insufficient clearance to spin the wrench in a full circle. COMBINATION WRENCH After a tight nut is broken loose, it can be unscrewed much more quickly with an open-end wrench than with a box-wrench. A combination box-open end wrench (fig. 1-31) comes in handy in a situation of the type. You can use the box-end for breaking nuts loose or for snuggling them down, and the open-end for faster turning. The box-end portion of the wrench can be designed with an offset in the handle. Notice in figure 1-31 how the 15-degree offset allows clearance over nearby parts. The correct use of open-end and box-end wrenches can be summed up in a few simple rules, most important of which is to be sure that the wrench properly fits the nut or bolt head. When you have to pull hard on the wrench, as in loosening a tight nut, make sure the wrench is seated squarely on the flats of the nut. Pull on the wrench—DO NOT PUSH. Pushing a wrench is a good way to skin your knuckles if the wrench slips or the nut breaks loose unexpectedly. If it is impossible to pull the wrench and you must push, do it with the palm of your hand and hold your palm open. Only actual practice will tell you if you are using the right amount of force on the wrench. The best way to tighten a nut is to turn it until the wrench has a firm, solid "feel." This will turn the nut to proper tightness without stripping the threads or twisting off the bolt. This "feel" is developed by experience alone. Practice until you have mastered the "feel." 1-21 ABEf0106 Figure 1-29.—Nonadjustable union nut wrench. Figure 1-30.—12-point box-end wrench. Figure 1-31.—Offset combination wrench.