A combination tool including a tool holder that extends along a tool rotational axis that defines an axial extension, an inner cutting tool for machining a first, central hole region and an outer, sleeve-shaped cutting tool for machining a second hole region radially outwards relative to the first hole region.

A cutting tool assembly includes a first tool part and a second tool part. The first tool part has a forward end portion including a cutting edge and a rearward end portion having a conical section and an engagement section. The second tool part includes a conical recess and a clamping device rearwards the conical recess. The clamping device is provided in a transversal cavity of the second tool part and has a first clamp block, a second clamp block and a differential screw engaging the first and second clamp blocks. The first and second clamp blocks engage the engagement section of the first tool part to pull the first tool part into the conical recess when the first and second clamp blocks are moved towards each other by the differential screw protruding rearwards from the first and second clamp blocks.

A combination tool including a tool holder that extends along a tool rotational axis that defines an axial extension, an inner cutting tool for machining a first, central hole region and an outer, sleeve-shaped cutting tool for machining a second hole region radially outwards relative to the first hole region.

A manufacturing method for an engine includes: preparing, as a preparing step, a cylinder head having a surface on which a ceiling surface of a combustion chamber is formed; forming, as a film formation step, a thermal insulation film on the ceiling surface; measuring, as a measurement step, a volume of the thermal insulation film; and selecting, as a selection step, a rank for an engine valve to be used in combination with the ceiling surface so as to correspond to an amount of difference of a measured volume of the thermal insulation film from a designed value of a volume of the thermal insulation film, the rank being selected from a plurality of ranks set in correspondence with thicknesses of umbrella portions of engine valves.

A manufacturing method for an engine includes: preparing, as a preparing step, a cylinder head having a surface on which a ceiling surface of a combustion chamber is formed; forming, as a film formation step, a thermal insulation film on the ceiling surface; measuring, as a measurement step, a volume of the thermal insulation film; and selecting, as a selection step, a rank for an engine valve to be used in combination with the ceiling surface so as to correspond to an amount of difference of a measured volume of the thermal insulation film from a designed value of a volume of the thermal insulation film, the rank being selected from a plurality of ranks set in correspondence with thicknesses of umbrella portions of engine valves.

Cutting insert with a cuboid body has a substantially square top face and bottom face, said top face and bottom face connected by four peripheral adjoining side surfaces. At least two cutting edges are formed at the transition of the top face to at least two side surfaces, that cutting edges defining a plane of the top face. To provide a cutting insert and a corresponding tool suited to produce valve seat surfaces with high precision but still having a rather simple construction and being precisely mountable with ease and less efforts of adjustment, the plane defined by the top face cutting edges of the cutting insert has maximum dimensions of 7 mm7 mm, where the bottom face has a supporting surface formed exactly parallel to the plane defined by the top face cutting edges by means of grinding within a tolerance of less than 5 angular minutes.