摘要 |
Three solid round bars are prepared as auger members, respectively as a main body member, an upper shaft member, and a lower shaft member. End surfaces of the members are coaxially joined together by friction welding. Turning machining is then performed by using a lathe, forming a helical blade, a spline, and the like. In addition, burnishing is performed on a corner portion that includes an outer circumferential edge of a joining surface where friction welding is performed, and another corner portion that includes an outer circumferential edge of another joining surface where friction welding is performed. The burnishing is performed by pressing a roller, which is freely rotatable about a roller support shaft center of a Superoll, toward the corner portions of the rotating auger. Roller burnishing may also be performed two times on the same location, with a predetermined time interval therebetween.
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