Countermeasures against polygonal deformation of borehole in reaming process

Abstract

Reaming is a processing method for widening pilot holes such as drill holes and press holes to obtain a highly accurate finish. However, in machining using a regular-pitch reamer, polygonal deformation of the borehole occurs. This deformation is also called a spiral mark because the polygonal shape twists in the feed direction. Although several papers have dealt with vibration phenomena during reaming, countermeasures to date have not been sufficient. In previous studies, the authors considered polygonal deformation of a machined hole during reaming as a self-excited vibration caused by a time delay and clarified its mechanism. In the present study, we theoretically and experimentally investigated the suppression of polygonal deformation by optimizing the angular arrangement of the cutting edges of irregular-pitch reamers for an 8-flute reamer. In addition, we suggested a new evaluation standard to reduce the calculation load and to evaluate the optimum angular arrangement of the irregular-pitch cutting edges of reamers with other numbers of flutes.