An engine includes a cylinder block including a cylinder hole, a crank shaft as an offset crank, and a connecting rod that connects the piston and the crank shaft. An inclined surface is provided on an entire circumference of a crank-shaft-side opening edge of one end of the cylinder hole. When viewed in the axial direction of the crank shaft, a boundary line between the inclined surface and the cylinder hole extends towards the other end of the cylinder hole as it extends toward an offset side on which the crank shaft is offset from the center axis of the cylinder hole. The offset crank engine has the entire circumference of the crank-shaft-side opening edge of the cylinder hole chamfered without any bad influence on the sliding surface and posture of the piston to avoid interference between the crank-shaft-side opening edge of the cylinder hole and the connecting rod.

The invention provides a dental milling tool for milling dental materials in the making of dental prostheses. The dental milling tool is a ball-nose end mill having three helical flutes, each flute being associated with a cutting edge, each cutting edge having chip breakers along the curved edges of the ball. The dental milling tool may be formed from a hard material such as carbide based material, ceramic, cermet, superhard materials including polycrystalline diamond (PCD) and cubic boron nitride (CBN), and diamond composite. Alternatively, the dental milling tool may be coated with a hard coating such as diamond coating, diamond-like-carbon (DLC), nitride based coating such as titanium aluminium nitride (TiAlN), aluminium titanium nitride, (AlTiN), and titanium nitride (TiN), and ceramic coating.

An end mill body comprises: bottom blades formed at ridgelines where gashes and tip flank faces intersect, the gashes are formed at the tips of chip discharge grooves. At least one of the bottom blades serves as a long bottom blade that extends toward an inner peripheral side longer than the remaining bottom blades. The end mill body also has coolant holes formed between the chip discharge grooves. A coolant hole which is located between a chip discharge groove of a gash and a chip discharge groove located behind the chip discharge groove in a rotational direction is open to the tip clearance face of the long bottom blade. A coolant hole which is located between the chip discharge groove of the gash and a chip discharge groove located in front of the chip discharge groove in the rotational direction is open to the gash of the long bottom blade.

A multi-flute ball end mill of the present invention includes: a shank portion configured to rotate about a rotational axis; a cutting edge portion; three or more ball edges formed on the cutting edge portion; gashes formed between the ball edges; peripheral cutting edges continuous with end portions of the ball edges on the shank portion side; and flutes formed between the peripheral cutting edges continuously with the gashes. The degree of curvature of the ball edges is 35% to 55%. Each of the gashes includes four faces of a rake face of each of the ball edges, a gash wall face, a first gash face, and a second gash face. The second gash face is formed such that the closer the second gash face is to the rotation center point, the more inwardly the second gash face enters a second face of each of the ball edges.

Novel endmills are provided. Such endmills have a body with outside diameter (OD), and outer surface, and a longitudinal axis, a plurality of flutes, helical in some embodiments. Flutes include a narrow leading edge land portion with circular segment profile and having flute cutting edge portions along a substantially uniform circumferential location, with an eccentric relief margin rotationally rearward of the narrow leading edge land portions. Face portions are provided with face cutting edge portions, and with a first dish portion adjacent each of the cutting edge portions sloping inwardly and downwardly generally toward a central longitudinal axis at a first dish angle alpha (α). Corner blend portions extend from flute cutting edge portions to the face cutting edge portions. Corner blend portions are provided in a variety of profiles, including an embodiment wherein the profile of the corner blend portions are truncated before the segment of curvature becomes tangential to the face cutting edge portions. In various embodiments, one or more coolant passageways are provided, and in an embodiment, an exit port for coolant is provided at the center of rotation of the end face portion.

The invention provides a dental milling tool for milling dental materials in the making of dental prostheses. The dental milling tool is a ball-nose end mill having three helical flutes, each flute being associated with a cutting edge, each cutting edge having chip breakers along the curved edges of the ball. The dental milling tool may be formed from a hard material such as carbide based material, ceramic, cermet, superhard materials including polycrystalline diamond (PCD) and cubic boron nitride (CBN), and diamond composite. Alternatively, the dental milling tool may be coated with a hard coating such as diamond coating, diamond-like-carbon (DLC), nitride based coating such as titanium aluminium nitride (TiAIN), aluminium titanium nitride, (AITiN), and titanium nitride (TiN), and ceramic coating.

A rotary tool may include a holder and a cutting insert. The cutting insert may include an upper surface including a first upper side, a lower surface including a first lower side, and a lateral surface. The lateral surface may include a first lateral surface, a second lateral surface, and a third lateral surface. The first upper side may include a first end. The first end may be located closer to the third lateral surface than the second lateral surface. The first lower side may include a second end. The second end may be located closer to the second lateral surface than the third lateral surface. In a front view of the upper surface, the first lateral surface may include a tip region surrounded by the first end and the second end, and the tip region may be recessed toward the rear end.

A cutting body rotatable about a tool axis has an insert receiving pocket with a seat surface at an axial forward end thereof. The seat surface has a plurality of abutment elements, including an axial abutment element having an axially forward facing abutment surface and at least one radial abutment element. In a top view of the insert receiving pocket, the axially forward facing abutment surface forms an external acute clamping angle with a radially outward facing pocket wall. A rotary cutting tool includes the cutting body, and a cutting insert removably secured in the insert receiving pocket, having a base surface in contact with the seat surface. The at least one radial abutment element occupies or is occupied by at least one radial abutting element of the base surface, and the axially forward facing abutment surface is in contact with an axial abutting surface of the base surface.

A slotting tool body includes a disc-like cutter portion and a shank portion projecting rearwardly therefrom. The cutter portion includes a resilient clamping portion having a peripherally disposed insert receiving slot. The shank portion includes a peripherally disposed forward shank recess that is axially adjacent the cutter portion. A radially inward portion of the insert receiving slot merges in the rearward direction with the forward shank recess. A cutting insert is releasably and resiliently clamped in the insert receiving slot to form a rotary slot cutting tool. The cutting insert includes two cutting portions that each include a long and short insert lateral extension, the long insert lateral extension being longer than the short insert lateral extension. The longest insert lateral extensions are orated on opposite sides of the cutting insert.

A cutting body rotatable about a tool axis has an insert receiving pocket with a seat surface at an axial forward end thereof. The seat surface has a plurality of abutment elements, including an axial abutment element having an axially forward facing abutment surface and at least one radial abutment element. In a top view of the insert receiving pocket, the axially forward facing abutment surface forms an external acute clamping angle with a radially outward facing pocket wall. A rotary cutting tool includes the cutting body, and a cutting insert removably secured in the insert receiving pocket, having a base surface in contact with the seat surface. The at least one radial abutment element occupies or is occupied by at least one radial abutting element of the base surface, and the axially forward facing abutment surface is in contact with an axial abutting surface of the base surface.