| 摘要 |
Pistons and cylinders are manufactured to an oval shape, which is defined as being an oval where the ratio of the major axis to the major axis is between 1.1:1 and 3:1. Pistons and cylinders are generally finish machined by relative rotation between the tool and the workpiece and movement of the tool in a defined path to produce a finished profile. In general, however, conventional machine tools cannot machine such oval profiles at commercial production rates because of the excessively high tool accelerations which this would involve and of which the conventional machine tools are not capable. Disclosed are a machine tool for matching such oval pistons in which an oval piston blank is rotated in a path such that, when each part of the piston surface reaches the tool, it is at a constant datum position. Thus the tool considers that it is machining a surface of constant radius and normal tool movements can be performed. There is also a boring machine for machining such oval cylinders where the tool is moved in a required oval path. A mechanism is disclosed which can be used either for turning pistons or boring cylinders to ensure that they are complementary with one another.
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