According to one implementation, a drill has at least one cutting edge. A projected shape of a passing area of a ridgeline of the at least one cutting edge when the at least one cutting edge is rotated around a tool axis becomes a line-symmetric and discontinuous line along a parabola, two parabolas, an ellipse or two ellipses. The projected shape is drawn on a projection plane parallel to the tool axis.

A pocket hole jig system is formed of a plurality of jig segments, wherein each jig segment includes a main body having a drill guide and a lock feature that protrudes outward on a first side of the main body and a recess that protrudes inward on a second side of the main body. The system also includes one or more spacers that have a main body of varying width and a lock feature that protrudes outward on a first side of the main body and a recess that protrudes inward on a second side of the main body. Jig segments and spacers may be connected together by inserting the lock feature of a jig segment or spacer into the recess of an adjacent jig segment or spacer. In one arrangement opposing jig segments and/or spacers lock together with a combination of rotational movement as well as sliding movement.

The outer peripheral surface is provided with a first margin contiguous to each of the cutting edge and the flank face, and a second margin that is located on the rear side with respect to the first margin in a rotation direction and that is separated from each of the flank face and the thinning face. An outer peripheral portion of the first margin and an outer peripheral portion of the second margin have respective back tapers having the same angle. In a direction parallel to the axial line, a distance between a front end of the first margin and a front end of the second margin is more than or equal to 3 mm and less than or equal to 5 mm.

An adjustment unit (1) for a guide bar (4) on a machining tool (0), comprising an actuation part (5) and the guide bar (4), wherein the actuation part (5) is connected to the machining tool (0) and directly or indirectly interacts with the guide bar (4) in order to move the guide bar (4) continuously in a radial direction R-R of the machining tool (0) by actuation of the actuation part (5).

Tools and methods for creating a plurality of aligned holes from a plurality of near full-sized holes. The tool includes a cutting member having a first diameter and a pilot member connected to and coaxial with the cutting member. A first section of the pilot member includes a centering member and is positioned between the cutting member and the second section having a second diameter. The centering member may include a cutting surface. The second diameter corresponds to a positional tolerance of misalignment of a plurality of near full-sized holes of the same diameter and a full-size hole diameter. The centering member may have a third diameter between the first and second diameters. The centering member may be tapered. The pilot member may be inserted into a plurality of near-full sized holes and the cutting member may cut through the holes to form a plurality of aligned full sized holes.

In a surface-coated cutting tool in which a hard coating layer having a total layer thickness of 0.5 to 10 μm is deposited on a surface of a tool body made of WC-based cemented carbide or TiCN-based cermet, the hard coating layer has an alternately laminated structure of A layers and B layers, in a case where the A layer is: (Al.sub.aTi.sub.1-a)N (here, a is in atomic ratio), the A layer satisfies 0.50≦a<0.75, in a case where the B layer is: (Al.sub.bTi.sub.1-b)N (here, b is in atomic ratio), the B layer satisfies 0.75≦b≦0.95, and when a layer thickness per layer of the A layers is represented by x (nm) and a layer thickness per layer of the B layers is represented by y (nm), 5y≧x≧3y and 250 (nm)≧x+y≧100 (nm) are satisfied.

In a surface-coated cutting tool in which a hard coating layer having a total layer thickness of 0.5 to 10 μm is deposited on a surface of a tool body made of WC-based cemented carbide or TiCN-based cermet, the hard coating layer has an alternately laminated structure of A layers and B layers, in a case where the A layer is: (Al.sub.aTi.sub.1-a)N (here, a is in atomic ratio), the A layer satisfies 0.50≦a<0.75, in a case where the B layer is: (Al.sub.bTi.sub.1-b)N (here, b is in atomic ratio), the B layer satisfies 0.75≦b≦0.95, and when a layer thickness per layer of the A layers is represented by x (nm) and a layer thickness per layer of the B layers is represented by y (nm), 5y≧x≧3y and 250 (nm)≧x+y≧100 (nm) are satisfied.

A multi-blade type woodworking bit includes a driving section for coupling with an external tool and a working section in front of the driving section. The working section includes a first cutting section and a second cutting section behind the first cutting section. The first cutting section is conic and has a front pointed end. The first cutting section further includes at least two angularly spaced first dust discharge grooves. The second cutting section includes a shank portion axially connected to a rear end of the first cutting section. At least two angularly spaced blades extend radially from the shank portion. Each blade includes a front cutting end. A rear end of each first dust discharge groove is located between a pair of blades. A second dust discharge groove is formed between each pair of blades and has a width lager than a width of each first dust discharge groove.

The drill head (2) extends along a rotational axis (24) in the axial direction (22) and has a central area (6) on the front with first main cutting edges (26), an intermediate area (8) connecting thereto, and an outer area (10) in turn connecting thereto with second main cutting edges (30). The intermediate area (8) in this case expands in the axial direction (22) toward the outer area (10) and in particular forms an expanding conical shell. A centering effect is hereby achieved via the intermediate area (8).

A boring device includes: a rotatable body, which has a workpiece holder, a valve seat receiver and a debris passage portion; a laser emitter; a pump and a control unit. The workpiece holder can hold a nozzle body. The valve seat receiver contacts a valve seat of the nozzle body that is held by the workpiece holder. The laser emitter emits a laser beam to an outer wall of the nozzle body to bore injection holes at the nozzle body. The debris passage portion includes a debris passage that is placed on a radially inner side of the valve seat receiver and guides debris formed at the time of boring the injection holes with the laser beam. The pump vacuums the debris through the debris passage. The control unit controls a laser output power of the laser emitter and a suction force of the pump.