A method and suitable honing tools for honing conical bores are proposed.

A honing method for machining the inner surface of a bore in a workpiece via at least one honing operation using an expandable honing tool with an annular cutting group. The method includes coupling of the honing tool to a working spindle of a machine tool, and; inserting the honing tool into an inlet of the bore with the cutting material elements retracted, until it is in a final insertion position, in which the cutting group is located in an end region of the bore.

Then the honing tool is turned and the annular cutting group is simultaneously expanded to create a cylindrical widening of the bore, followed by withdrawal of the honing tool from the bore with simultaneous turning of the honing tool in such a way that the bore is successively further widened in the direction of the inlet side.

A honing tool has a tool body and shells disposed on the tool body. Honing stone sets each provided with two or more honing stones are provided. The shells each support one of the honing stone sets. Guide bars of the honing tool are placed against the bore and a portion of the bore is conically honed with decreasing stroke of the honing tool, wherein a lower reversing point of the honing tool remains substantially unchanged. Honing is terminated as soon as an upper reversing point has reached a predetermined terminal value. Alternatively, a portion of the bore is conically honed with a constant stroke of the honing tool, wherein reversing points of the stroke of the honing tool remain substantially unchanged and a feeding force pressing the honing stones against the bore is controlled as a function of a position of the honing tool in the bore.

A method of milling an engine bore is disclosed. The method may include inserting a milling tool having a plurality of cutting edges along a longitudinal axis into an engine bore, rotating the milling tool about the longitudinal axis and moving the milling tool around a perimeter of the engine bore to remove material from the engine bore, and rough honing the bore. The milling may generate a tapered bore (e.g., frustoconical). The rough honing process may increase a minimum diameter of the tapered bore by at least 60 m. A total time of the milling and honing process may be less than 60 seconds. In one embodiment, the honing step may include using a grit size of at least 200 m and/or using a honing force of at least 200 kgf. The method may reduce the cycle time and tooling requirements of forming engine bores.