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【正文】 ture will shorten the length of the internal bustion engine, pact and widely used in highpower lootives used tanks and Vshaped internal bustion engine. Boring In machining, boring is the process of enlarging a hole that has already been drilled (or cast), by means of a singlepoint cutting tool (or of a boring head containing several such tools), for example as in boring a cannon barrel. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. The term boring is also sometimes used for drilling a hole. Machine Boring The boring process can be carried out on a lathe for smaller operations, but for larger production pieces a special boring mill (work piece rotation around a vertical axis) or a horizontal boring machine (rotation around horizontal axis) are used. A tapered hole can also be made by swiveling the head. The boring machines (similar to the milling machines such as the classic Van Norman) e in a large variety of sizes and styles. Work piece diameters are monly 14m (312 ft) but can be as large as 20m (60ft). Power requirements can be as much as 200 hp. The control systems can be puterbased, allowing for automation and increased consistency. Because boring is meant to decrease the product tolerances on preexisting holes, several design considerations must be made. First, large lengthtoborediameters are not preferred due to cutting tool deflection. Next, through holes are preferred over blind holes (holes that do not traverse the thickness of the work piece). Interrupted internal working surfaces— where the cutting tool and surface have discontinuous contact— should be avoided. The boring bar is the protruding arm of the machine that holds cutting tool(s), and must be very rigid. Forging Forging is the term for shaping metal by using localized pressive forces. Cold forging is done at room temperature or near room temperature. Hot forging is done at a high temperature, which makes metal easier to shape and less likely to fracture. Warm forging is done at intermediate temperature between room temperature and hot forging temperatures. Forged parts can range in weight from less than a kilogram to 170 metric parts usually require further processing to achieve a finished part. 。 it can result from fatigue near a physical defect in the rod, lubrication failure in a bearing due to faulty maintenance, or from failure of the rod bolts from a defect, improper tightening, or reuse of already used (stressed) bolts where not remended. Despite their frequent occurrence on televised petitive automobile events, such failures are quite rare on production cars during normal daily driving. This is because production auto parts have a much larger factor of safety, and often more systematic quality control. When building a high performance engine, great attention is paid to the con rods, eliminating stress risers by such techniques as grinding
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