876 Modern Welding Orthographic projection: A method of making a working drawing and projecting the sizes from one view to another. Oscillated: Moved back-and-forth or side-to-side. Oscillating: Moving back-and-forth or side-to-side. Other side: On a drawing of a welded part, the surface opposite from the surface indicated by the arrow. Output slope: The general slope of the volt-ampere curve. Outside corner joint: A fused joint of two pieces that are at an angle (often 90°) to each other. The weld is performed on the side opposite the vertex of the corner. Oven solder: Parts are assembled with preformed and preplaced solder forms in each joint. A precise amount of fl ux is placed on each joint and the parts are then placed in the soldering oven and heated until the solder fl ows. Overhead (4G) welding position: A welding position in which the weld axis is horizontal, but the weld is made from the underside. Overheating: Damaging the properties of a metal by applying too much heat. When original properties cannot be restored, the overheating is known as “burning.” Overlap: Extension of the weld face metal beyond the toe of the weld. Oxidation: Combining of a substance with oxygen. Rapid oxidation is called burning. Oxide: The new material that is formed through the chem- ical combination of a metal and oxygen. Oxidize: To combine with oxygen. A substance burns when it is rapidly oxidized. Oxidizing: The process in which oxygen combines with any other substance. Oxidizing fl ame: The fl ame produced by an excess of oxygen in the torch mixture, which leaves some free oxygen that tends to burn the molten metal. Oxyacetylene: Oxygen and acetylene. Oxyacetylene cutting: An oxyfuel gas cutting process that uses an oxygen and acetylene fl ame for heat and a jet of oxygen to oxidize the molten metal and form a cut. Oxyacetylene torch test: Melting a pool in steel. The appearance on the edge of the pool or hole indicates the weldability of the steel. Oxyacetylene welding (OAW): Method of oxyfuel gas welding in which oxygen and acetylene are combined and burned to provide the heat. Oxyfuel gas cutting: Cutting metal using an oxygen jet and a preheating fl ame that combines oxygen and a fuel gas. Oxyfuel gas welding: Method of welding that combines and burns oxygen and a fuel gas to create the required heat. Oxyfuel gas welding outfi t: The basic equipment needed to weld with oxygen and fuel gas. Oxyfuel gas welding station: The oxyfuel gas welding outfi t, welding table, ventilation, lighting, and other equipment necessary for welding and the welder’s comfort. Oxygen (O 2 ): Gas that makes up 21% of the composition of air. A gas used to support combustion in oxyfuel gas welding and cutting. Oxygen cylinder: A specially built container manufactured according to ICC standards and used to store and ship certain quantities of oxygen. Oxygen hose: A reinforced, multilayered fl exible tube, usually made from rubber, that is used to carry high- pressure gases. Oxygen jet: A stream of compressed oxygen released through the center orifi ce of a cutting tip when the cutting lever of an oxyfuel gas cutting torch is pressed. This jet rapidly oxidizes the heated metal, resulting in a cutting action. Oxygen lance cutting (OLC): An oxyfuel gas cutting process that heats base metal and then blows away the molten metal with a jet of oxygen from an iron pipe. Oxygen line regulator: In a manifold system, device that is used at each welding station to control the oxygen pres- sure to each torch. Oxygen regulator: Valve used to reduce cylinder pressures to torch pressures and to keep the pressures constant. Oxyhydrogen: A mixture of oxygen and hydrogen. Oxyhydrogen fl ame: The chemical combining of oxygen with the fuel gas hydrogen. Oxynatural gas: A mixture of oxygen and natural gas. Oxypropane: A mixture of oxygen and propane, a liquefi ed petroleum gas. P Parallel gap resistance spot welding: A variation of spot welding that allows spot welds to be made from one side only. Pascal: The SI Metric unit for measuring pressure. Pass: See Weld pass. Peak current: The period of high current that is used to melt and weld the base metal. Pearlite: A form of steel that has alternating layers of ferrite and cementite. Pecking: Striking the arc with a straight down-and-up motion of the electrode. Peel test: A destructive test that mechanically separates a resistance welded lap joint by peeling one piece away from the other. Peening: Hitting metal with a hammer or with hard round balls (like ball bearings) propelled by air pressure. Penetrant: Either a liquid or a gas that, when applied to the surface of a metal, enters cracks (discontinuities) to make them visible. Penetration: The extent to which the weld metal combines with the base metal, as measured from the surface of the base metal. Percussion welding (PEW): A type of resistance welding in which the heat comes from an arc produced by an electrical discharge and instantaneous pressure applied during or immediately following the heating. Personal management skills: General skills that enable a worker to be successful at any job. These skills are not specifi c to the worker’s trade. Physical properties: Properties or qualities (other than mechanical properties) that have to do with the physics of a material. Examples are density, ability to conduct elec- tricity, ability to conduct heat, and thermal expansion.