Patent ID: 8574031

Claim:
A method of machining a crankshaft having two cylindrical crankshaft surfaces centered on respective parallel axes and each flanked by a pair of arcuately rounded and annular corners also centered on the respective axes, the corners flanking one of the cylindrical crankshaft surfaces having a small radius of curvature and the corners flanking the other of the cylindrical crankshaft surfaces having a large radius of curvature greater than the small radius, the apparatus comprising: means for holding and rotating the crankshaft about a main axis parallel to the axis of one of the crankshaft surfaces; a pair of grinders having wheels generally diametrally flanking the crankshaft, each of the wheels being rotatable about a respective wheel axis parallel to the main axis and having a central cylindrical outer wheel surface centered on the respective wheel axis and a pair of arcuately rounded edge surfaces also centered on the respective wheel axis, both of the edge surfaces of one of the wheels having the large radius of curvature and both of the edge surfaces of the other of the wheels having the small radius of curvature; and guide means for moving the grinders parallel to the axes such that the small-radius edge surfaces are pressed axially into the small-radius corners and the large-radius edge surfaces are pressed into the large-radius corners while simultaneously pressing both of the cylindrical outer wheel surfaces diametrally oppositely against the cylindrical crankshaft surfaces.