Abstract

Self-piloting tools feature the unique use of two support pads and the surrounding hole as a guide bushing to steer itself along the hole being machined. The piloting hole, in conjunction with the two support pads, provides for the tool balance in the hole transverse cross-section. However, in the axial section plane, the tool alignment with the piloting hole depends on the boring bar to which the tool appears as a solid extension. This study shows that the alterations in the output quality and the support pads' wear pattern can be explained by in-process encountered boring bar bending. This is because even minor inclinations near the tool tip appear significant when considered in the small front-end area of the support pads where burnishing occurs. The study is to explain the inherent feature of the conventional self-piloting tool design to deflect the boring bar in 3D enough to make a difference between the effective area involved in burnishing and the area as designed.

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