The invention relates to a method for forming an elongate cut-out (2), which has a varying transverse dimension in the longitudinal direction, in a workpiece (1), which is preferably composed of wood, wood materials, plastic, or the like at least in some segments, wherein the method comprises plunging a machining device into the workpiece (I), which machining device has an adjustable machining diameter; moving the machining device and the workpiece in relation to each other (II); adjusting the machining diameter of the machining device (III); and removing the machining device from the workpiece (IV).

A method of cutting (e.g. micro-milling) brittle materials where a protective ductile layer is present on the brittle material during the cutting step. The method offers an improved edge quality of the machined profile relative to previous cutting (e.g. micro-milling) techniques. A machined product obtained by or obtainable by this method is disclosed.

The present invention is to eliminate formation of a shape that induces reduction of fatigue strength, without forming a step part, in a shape portion formed by machining. This processing apparatus includes end mills having bottom blades formed in a curved convex shape, and arcuately formed radial blades provided in corner areas; a drive section for driving the end mills; and a control unit for controlling the drive unit. The control unit includes a planar-shape-formation unit that controls the drive unit so as to form, in a workpiece, only a planar-shape portion adjacent to a fillet shape portion in such a manner that a portion of the shape to be processed corresponding to the fillet shape portion is left unprocessed; and a fillet formation unit that controls the drive unit so as to form the fillet shape portion in the workpiece in a single pass using the radial blades.