torch has certain advantages over the low-pressure type because the flame can be more readily adjusted, and since equal pressures are used for each gas, the torch is less susceptible to flashbacks. The welding tips are made of hard, drawn, electrolytic copper or 95-percent copper and 5-percent tellurium. They are made in various styles and types, some having a one-piece tip either with a single orifice or a number of orifices, and others with two or more tips attached to one mixing head. The diameters of the tip orifices differ to control the quantit y of heat and the type of flame. These tip sizes are designated by numbers that are arranged according to the individual manufacturer’s system. In general, the smaller the number, the smaller the tip orifice. No matter what type or size tip you select, the tip must be kept clean. Quite often the orifice becomes clogged with slag. When this happens, the flame will not burn properly. Inspect the tip before you use it. If the passage is obstructed, you can clear it with wire tip cleaners of the proper diameter, or with soft copper wire. Tips should not be cleaned with machinists drills or other sharp instruments. These devices may enlarge or scratch the tip opening and greatly reduce the efficiency of the torch tip. HOSE.—The hose used to make the connection between the torch and the regulators is strong, nonporous, light, and flexible to make the torch movements easy. It is made to withstand high internal pressures, and the rubber used in its manufacture is chemically treated to remove sulfur to avoid the danger of spontaneous combustion. The oxygen hose is GREEN, and the acetylene hose is RED. The hose is a rubber tube with braided or wrapped cotton or rayon reinforcements and a rubber covering. The hoses have connections at each end so they can be connected to their respective regulator outlet and torch inlet connections. To prevent a dangerous interchange of acetylene and oxygen hoses, all threaded fittings used for the acetylene hookup are left-handed threads, and all threaded fittings for oxygen hookup are right-handed threads. The hoses are obtainable as a single hose for each gas or with the hoses bonded together along their length under a common outer rubber jacket. This type prevents the hose from kinking or becoming entangled during the welding operation. LIGHTERS.—A flint lighter is provided for igniting the torch. The lighter consist of a file-shaped piece of steel, usually recessed in a cuplike device, and a piece of flint that can be drawn across the steel, which produces the sparks required to light the torch. WARNING Matches should never be used to ignite a torch; their length requires bringing the hand too close to the tip to ignite the gas. Accumulated gas may envelope the hand and, when ignited, cause a severe burn. GOGGLES.—Welding goggles are fitted with colored lenses to keep out heat and light rays and to protect the eyes from sparks and molten metal. Regardless of the shade of lens used, goggles should be protected by a clear cover glass. The welding operator should select the shade or density of color that is best suited for his/her particular work. The desired lens is the darkest shade that will show a clear definition of the work without eyestrain. Goggles should fit closely around the eyes, and should be worn at all times during welding and cutting operations. Special goggles, using standard lenses, are available for use with spectacles. WELDING (FILLER) RODS.—The use of the proper type of filler rod is very important in oxyacetylene welding operations. This material not only adds reinforcement to the weld area, but also adds desired properties to the finished weld. By selecting the proper type of rod, either tensile strength or ductility can be secured in a weld. Similarly, rods can be selected that will help retain the desired amount of corrosion resistance. In some cases, a suitable rod with a lower melting point will eliminate possible cracks from expansion and contraction. Welding rods are classified as ferrous and nonferrous. The ferrous rods include carbon and alloy steel rods as well as cast iron rods. Nonferrous rods include brazing and bronze rods, aluminum and aluminum alloy rods, magnesium and magnesium alloy rods, copper rods, and silver rods. The diameter of the rod used is governed by the thickness of the metals being joined. If the rod is to small, it will not conduct heat away from the puddle rapidly enough, and a burned weld will result. A rod that is to large will chill the puddle. As in selecting the proper size welding torch tip, experience will enable the welder to select the proper diameter welding rod. Welding Flames The welding flame is classified as neutral, carburizing, or oxidizing. Each type of flame has its own special function The operator can adjust the torch to produce the type of flame best suited for the job at hand. 15-22