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 shank for a tool bit employing an offset arrangement is provided, the shank being able to respond to various types of machining through replacement of heads and having a structure to save time and steps necessary for such replacement of the heads. A cutting tool having such shank is also provided.

A shank 53 of a head-replaceable cutting tool has at least one head attaching part 53A, 53B that is arranged off-center relative to an axis 53X of the shank 53. The axis 53X of the shank 53 corresponds to an axis extending in a longitudinal direction of the shank 53, and the head attaching part 53A, 53B may be arranged so as to be off-center in a direction perpendicular to the axis 53X.

A controller of a machine tool acquires coordinates of a first machining start point of an eccentric shape in a reference phase of a workpiece around a spindle axis, a second machining start point in an anti-phase, a first machining end point in the reference phase, and a second machining end point in the anti-phase. The controller decides a moving path of the tool in association with rotation of the workpiece at least according to the coordinates of the first start point, the second start point, the first end point, and the second end point to form the eccentric shape around an eccentric axis passing a start point origin between the first start point and the second start point and an end point origin between the first end point and the second end point and thereby controls movement of the tool in association with rotation of the workpiece.

To make it possible for bores (16) that are in line with one another to be efficiently worked by means of a boring bar (2), the boring bar has a main body (10) with an axis of rotation (R) and a number of cutting elements (12, 12A) at intervals from one another in the axial direction (4) and also guiding elements (14) for guiding the main body (10) in a guiding bore (16A). The guiding elements (14) are kept at a distance from the axis of rotation (R) equivalent to a guide radius (r1). The main body (10) is divided into a functional region (19) and an eccentric region (10), wherein the cutting elements (12, 12A) and the guiding elements (14) are arranged such that they are distributed around the main body (10) over an angular range (a) of less than 180°. Furthermore, the circumferential side (22) of the main body (10) can be passed eccentrically through a respective bore (16, 16A) of which the unworked tube radius (r2) is less than the guide radius (r1).

A boring-bar arrangement includes a boring bar, a securing device, and a clamping bolt. The securing device has a reduction sleeve, which is secured in a tool chuck, which has a front end that faces away from the tool chuck and a protruding hollow section which receives the boring bar. The hollow section has a hollow-section interior, a hollow-section outer wall, and a hollow-section wall which is arranged therebetween. The hollow-section wall has a first thickness in a side region where the cutting tool protrudes from the boring bar which is less than a second thickness in a rest of the hollow-section wall. The boring bar is releasably secured as a replaceable head, via its back end, at a front end of the protruding hollow section. A front end of the clamping bolt has a male thread which sits in the female thread of the boring bar.

A boring bar has a generally cylindrical elongate tool body has a proximal end for mounting to drive unit and a distal end for attachment to a tool head. A passageway extends longitudinally along the central axis of the elongate tool body. A plurality of longitudinally extending cavities are disposed annularly about the tool body. A compressive material is disposed in each of the cavities. An adjustable compression fitting is disposed in at least one end of each of the cavities, where each of the compression fitting can be adjusted to change compression of the material disposed in a respective cavity.

A pipe spinning power drill accessory a stem, shaft, first knurled assembly, second knurled assembly, first state, and second state. The first knurled assembly and the second knurled assembly are each cylindrically shaped. The first knurled assembly is centrally affixed to the stem. The shaft is centrally affixed to the first knurled assembly opposite the stem. The second knurled assembly is centrally affixed to the shaft opposite the first knurled assembly. The first knurled assembly and the second knurled assembly each selectively expand laterally. In the first state, the first knurled assembly and the second knurled assembly are each not laterally expanded. In the second state, at least one of the first knurled assembly and the second knurled assembly are laterally expanded. The stem is configured to be inserted into a chuck of a power drill. The stem is cross-sectionally hexagonally shaped and includes a region of decreased diameter.

A pipe spinning power drill accessory a stem, shaft, first knurled assembly, second knurled assembly, first state, and second state. The first knurled assembly and the second knurled assembly are each cylindrically shaped. The first knurled assembly is centrally affixed to the stem. The shaft is centrally affixed to the first knurled assembly opposite the stem. The second knurled assembly is centrally affixed to the shaft opposite the first knurled assembly. The first knurled assembly and the second knurled assembly each selectively expand laterally. In the first state, the first knurled assembly and the second knurled assembly are each not laterally expanded. In the second state, at least one of the first knurled assembly and the second knurled assembly are laterally expanded. The stem is configured to be inserted into a chuck of a power drill. The stem is cross-sectionally hexagonally shaped and includes a region of decreased diameter.

The present technology presents system of a guide for widening a drilled hole. In various embodiments the system comprises a hub including a circular central member and a plurality of slots for shims around a circumference of the circular central member. Embodiments include a plurality of shims with the plurality of shims being fit into the plurality of slots around the circumference of the circular central member. Furthermore, the plurality of shims each include a narrow end and a wide end with the narrow end of each of the plurality of shims being in a same direction and the wide end of each of the plurality of shims being in an opposite direction to the narrow end allowing for the guide to fit securely into the existing hole before drilling the new hole.

A device for the precise angular positioning of tool-holders includes a front part, a rear part, and a plug cooperating with a pair of pins arranged orthogonally relative to the plug. A first portion of the plug is inserted in a blind hole formed in the front part and a second portion of the plug is inserted in a corresponding blind hole formed in a front area defining a plate on the rear part of the tool-holder. The plate of the rear part has an upper surface in which a pair of bored holes is formed having equal diameters and depths. The bored holes extend vertically in the plate and orthogonally relative to the plug. A pin is rotatably inserted in each of the pair of bored holes to selectively rotate the plug in a clockwise or counter-clockwise direction to orientate the front part relative to the rear part.