A drill has a shank with a central axis of rotation and at least one insert on one end of the shank. The insert has at least two cutting edges. The first and second cutting edges cooperate to form a hole when rotated about the central axis. One of the top and bottom faces acts as a seating face and the other acts as a cutting face. Cutting edges are formed on opposite sides of the cutting face. One end of each of the first cutting edges terminates in a juncture with a second cutting edge that extends from the cutting face toward the seating face. The first and second cutting edges cooperate to form a radiused hole when rotated about a central axis. The bottom of said hole is cut continuously across its entire area.

A drill having at least two indexable radially spaced inserts arranged with axially projecting cutting points to machine overlapping concentric grooves, the outermost insert machining a groove having an outside diameter equal to the diameter of the hole and the innermost insert machining a groove overlapping the center of the hole, and radial components of the cutting thrust on said inserts being in opposition and balancing each other. The cutting thrust may be balanced by the number, shape and/or the rake of the cutting edges.

A drill body for drilling solid metal and for finish boring having, at the working end, two or more replaceable, indexable, hard metal inserts dimensioned and spaced radially to cut equal volumes of metal. The inserts are retained in pockets by a headed screw with a through passage for a wrench. The outside insert is also shaped and positioned so the drill body may be shifted radially from the drilling axis and used as a boring bar.

To reduce the requirement for stocking different types of holder plates for cutting chips 9, at least the chip holder plate 16 carrying the radially outermost chip, and the next adjacent chip holder plate 6 carrying the radially more inwardly positioned chip, have mutually engaged common abutment surfaces 19, 27. The tool body 1 is formed with a recess 5 in which the radially outermost chip holder plate and the next adjacent plate are commonly secured, for example by clamping bolts or screws extending inwardly into the tool body at an angle with respect to the tool body axis 26. All of the radially inwardly positioned chip holder plates 6 are of equal size and shape. The boring or drilling diameter of the tool is defined by the width of the radially outermost chip holder plate and the chip positioned thereon. The radially outermost chip holder plate, preferably, is provided with surface deformations in a zone 20 adjacent the abutment surface 27 thereof so that the size of the radially outermost chip holder plate 16 can be reduced, for example by grinding, to thereby permit adjustment of the cutting diameter of the tool. It is then only necessary to stock two chip holder plates, namely of the radially inwardly positioned type 6, and the radially outwardly positioned type 16, the latter of maximum size for reduction, as required.

Tool for drilling holes, such as cylinder head drill, woodworking drill, and the like, which includes a carrier member having at least one endwise arranged end face cutter, or first cutting means, and at least one precutter, or second cutting means, extending in endwise direction, and circumferentially beyond the carrier member, the precutter defining the diameter of the hole to be produced with the tool and including at least one cutting edge. At least the part adjacent the cutting edge of the precutter is approximately parallel to the pertaining circumferential portion of the carrier member. The outer side of the precutter includes at least one guide surface parallel to the outer circumferential portion of the carrier member. The end face cutter and the precutter are removably securable with at least one clamping element to the carrier member and can be in the form of reversible cutting elements.