Abstract: A boring tool for working a small diameter bore in a workpiece having a shaft of circular cross-section comprising a clamping portion for supporting the tool and a neck portion extending forwardly therefrom. The forward end of the neck portion carries a cutting plate. The cutting plate is located entirely within the circular cross-section of the neck portion, except for a cutting point on such cutting plate which extends somewhat laterally beyond the circular cross-section of the neck portion. The neck portion has a channel of semicircular cross-section which spirals from the front end thereof toward the clamping portion of the shaft, the spiral being in the directions of rotation and of feed of the workpiece with respect to the tool. In a modification, a cuttings breaker is mounted to overlie the cutting plate, extends close to the cutting point and has an axially extending cuttings breaking channel running the length thereof parallel to the axis of the neck portion and opening toward the cutting plate.