the box. The opening permits the wrench to first slip over tubing and then slide onto a flare nut. Each end of the flare-nut wrench has a different- sized opening. 2.2.6 Adjustable Wrenches An adjustable wrench has a movable lower jaw, Figure 2-6. Like an open-end wrench, this wrench tends to slip. When using an adjustable wrench, make sure it is tightly adjusted to the nut. Pull only in the direction that will put force on the fixed side of the jaw. See Figure 2-7. 2.2.7 Allen Wrenches An Allen wrench, also known as a hex key, is a hardened steel shaft with a special hexagonal (6-sided) shape. It is used most often to turn setscrews. Allen wrench sets are available in “jackknife” style, as long individual wrenches, or with T-handles for applying increased torque. See Figure 2-8. Long wrenches allow easy access to setscrews used to anchor fan blades and pulleys to a shaft. To prevent damage to the wrench, be sure it is fully inserted in the screw before turning. Goodheart-Willcox Publisher Figure 2-5. The opening in the box end of the flare- nut wrench allows it to slip over tubing and fit on a flare nut tightly. Goodheart-Willcox Publisher Figure 2-6. An adjustable wrench tends to slip, unless the movable jaw is tightened firmly on the nut or bolt head. Movable jaw Fixed jaw John Walker Figure 2-7. When using an adjustable wrench, pull only in the direction shown, so that force is exerted on the fixed jaw. A B C Klein Tools, Inc. Goodheart-Willcox Publisher Figure 2-8. Allen wrenches, or hex wrenches, fit hex- agonal recesses in setscrews and other fasteners. A—“Jackknife”-style key set. B—Individual wrenches. C—T-handle wrenches. Chapter 2 Hand Tools 19 Copyright Goodheart-Willcox Co., Inc.