Abstract: Formations on a workpiece (1) are machined along an arcuate path (5) having a center (4) in eccentrically spaced relation to a rotational axis (3) about which the workpiece is indexed by a holder (2). A tool (7) is controllably displaced through its carrier (12) in such a manner as to establish radial alignment of the tool relative to the indexing axis and the path center during operational strokes to enable machining of identical formations spaced along the path. The radius of curvature of the path is greater than the maximum distance (4-14) to which said operational strokes are limited.