SAFETY PRECAUTIONS Hammers are dangerous tools when used carelessly and without consideration. Practice will help you learn to use a hammer properly. Some important things to remember when using a hammer or mallet follow: Do not use a hammer handle for bumping parts in assembly, and never use it as a pry bar. Such abuses will cause the handle to split, and a split handle can produce bad cuts or pinches. When a handle splits or cracks, do not try to repair it by binding with string, wire, or tape. Replace it. Make sure the handle fits tightly on the head. Do not strike a hardened steel surface with a steel hammer. Small pieces of steel may break off and injure someone in the eye or damage the work. However, it is permissible to strike a punch or chisel directly with a ball-peen hammer, because the steel in the heads of punches and chisels is slightly softer than that of the hammerhead. WRENCHES A wrench is a basic tool that is used to exert a twisting force on bolt heads, nuts, studs, and pipes. The special wrenches designed to do certain jobs are, in most cases, variations of the basic wrenches that are described in this section. The best wrenches are made of chrome vanadium steel. Wrenches made of this material are lightweight Figure 1-3.-Open-end wrenches. and almost unbreakable. This is an expensive material, however, so the most common wrenches found in the Navy are made of forged carbon steel or molybdenum steel. These latter materials make good wrenches, but they are generally built a little heavier and bulkier to achieve the same degree of strength as chrome vanadium steel. The size of any wrench used on bolt heads or nuts is determined by the size of the opening between the jaws of the wrench. The opening of a wrench is manufactured slightly larger than the bolt head or nut that it is designed to fit. Hex-nuts (six-sided) and other types of nut or bolt heads are measured across opposite flats (fig. 1-3). A wrench that is designed to fit a 3/8-inch nut or bolt usually has a clearance of from 5 to 8 thousandths of an inch. This clearance allows the wrench to slide on and off the nut or bolt with a minimum of “play.” If the wrench is too large, the points of the nut or bolt head will be rounded and destroyed. There are many types of wrenches. Each type is designed for a specific use. Let’s discuss some of them. OPEN-END WRENCHES Solid, nonadjustable wrenches with openings in one or both ends are called open-end wrenches. (See fig. 1-3.) Usually they come in sets of from 6 to 10 wrenches, with sizes ranging from 5/16 to 1 inch. Wrenches with small openings are usually shorter than wrenches with large openings. This proportions the lever advantage of the wrench to the bolt or stud and helps prevent wrench breakage or damage to the bolt or stud. One exception exists. Hydraulic piping installations for catapult and arresting gear are often in close spaces. During certain phases of hydraulic maintenance it may be impossible to swing an ordinary wrench because of its length. Ordinary wrenches that are normally available increase in length as their size increases. Thus, when a large-size wrench is needed, the length of the wrench sometimes prevents its use, due to the space available to swing the wrench. The Bonney wrench, shown in figure 1-4, is an open-end wrench that may be used to great advantage because of its thickness and short length. This wrench is normally procured in the larger sizes, although it is available in a range of sizes to fit most hydraulic fittings. 1-4