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.

A method includes inserting a machining tool through a hole of at least one workpiece that includes a first surface and a second surface opposite the first surface and extends from the first surface to the second surface. The hole forms an inner wall. The machining tool includes a shaft and a cutting tip proximate to one end of the shaft. The cutting tip includes a cutting portion. The method includes positioning the cutting portion of the cutting tip to abut an edge of the hole. The edge is located at a junction of the second surface of the one of the at least one workpiece and the inner wall. The method includes forming a surface modification at the edge with the cutting tip. The method includes removing the machining tool from the hole. The method includes installing a fastener within the hole. The fastener engages the surface modification.

In a method for creating a through-thread, thread creation means is moved in a screw-in movement in an axial forward direction (VR) through a workpiece from a first workpiece side to a second workpiece side opposite the first workpiece side such that the end face projects out of the workpiece, wherein the thread creation means is moved through the workpiece, in particular along a first line which is a helical line, wherein then, to create at least one countersink, the thread creation means is moved in a countersinking movement, in particular along a second line that differs from the first line, and wherein, for subsequent withdrawal, the thread creation means is moved back through the workpiece in a screw-out movement in the axial backward direction (RR), in particular at least substantially along the first line.

The present disclosure belongs to the technical field of hole machining equipment, and provides a hole chamfering device including blades in bilateral symmetry and a blade posture adjusting assembly. The hole chamfering device not only can be fed from the front face of a hole to complete chamfering work on the front face of the hole, but also can solve the problem of chamfering the back face of the hole under the condition that a chamfering tool cannot be directly fed from the back face of the hole. The hole chamfering device can be fed from the front face of the hole to complete chamfering work on the front face and the back face of the hole, and meanwhile, can remove burrs in the hole, thereby meeting the machining requirement of conventional chamfering of the hole.

A first plate includes: a first hole penetrating a first front surface and a first back surface; an opening edge constituting the first hole, a front-side first opening edge being provided in the first front surface; a back-side first opening edge constituting the first hole, the back-side first opening edge being provided in the first back surface; and a first chamfered portion provided on at least one of the front-side first opening edge and the back-side first opening edge, a second plate includes: a second hole including a back-side second opening edge provided in at least a second back surface; and a back-side second chamfered portion provided at the back-side second opening edge, an axis of the first hole and an axis of the second hole are coaxial, and the at least one of the first chamfered portion and the back-side second chamfered portion have a cutting mark.

A deburring tool includes a shank attached at a first end to a chuck and a working portion at a second end of the shank. The working portion includes a first end portion closest to and joining the second end of the shank at a first end of the first end portion, a second end portion furthest from the shank, and an intermediate portion disposed between the first end portion and the second end portion, a first end of the intermediate portion joining a second end of the first end portion and a second end of the intermediate portion joining a first end of the second end portion. The intermediate portion tapers continuously from a largest diameter at the first end of the intermediate portion to a smallest diameter at the second end of the intermediate portion, and deburring cutter members provided on the second end portion adjacent the second end of the intermediate portion.

A method includes inserting a machining tool through a hole of at least one workpiece that includes a first surface and a second surface opposite the first surface and extends from the first surface to the second surface. The hole forms an inner wall. The machining tool includes a shaft and a cutting tip proximate to one end of the shaft. The cutting tip includes a cutting portion. The method includes positioning the cutting portion of the cutting tip to abut an edge of the hole. The edge is located at a junction of the second surface of the one of the at least one workpiece and the inner wall. The method includes forming a surface modification at the edge with the cutting tip. The method includes removing the machining tool from the hole. The method includes installing a fastener within the hole. The fastener engages the surface modification.

A back spotfacing system having a machining apparatus with a through-hole cutter tool. The tool has an elongate member movable to coaxially extend through a hole in a workpiece from a first side of the workpiece, the workpiece coupled to the apparatus. The tool has a cutter element pivotal between a stowed position on the elongate member, a contact position with an inner surface of the hole, and an extended position extending radially from the elongate member. In the extended position, the cutter element extends to machine and back spotface a surface on a second side of the workpiece opposite the first side. The system has a power system for powering the apparatus and tool, and a measurement system coupled to the apparatus for measuring one or more hole exit positions of the cutter element and one or more surface contact positions of the cutter element on the surface.

The present disclosure belongs to the field of machining of chamfers of holes. The hole chamfering device includes blades in bilateral symmetry and a blade distance adjusting, through the blade distance adjusting, the distance between the blades on the left side and the right side can be adjusted, thus, after the blades on the left side and the right side of the hole chamfering device process chamfers on the front face of a hole, the distance between the blades is reduced to enable the blades to pass through the hole to process chamfers on the back face of the hole, after processing of the chamfers on the back face of the hole is completed, the distance between the blades is reduced, the hole chamfering device not only can chamfer the front face of the hole, but also can chamfer the back face of the hole.

The present disclosure belongs to the technical field of hole machining equipment, and provides a hole chamfering device including blades in bilateral symmetry and a blade posture adjusting assembly. The hole chamfering device not only can be fed from the front face of a hole to complete chamfering work on the front face of the hole, but also can solve the problem of chamfering the back face of the hole under the condition that a chamfering tool cannot be directly fed from the back face of the hole. The hole chamfering device can be fed from the front face of the hole to complete chamfering work on the front face and the back face of the hole, and meanwhile, can remove burrs in the hole, thereby meeting the machining requirement of conventional chamfering of the hole.