A drill of simple construction, using commercially available tips or tips obtained by simply modifying them, well balanced in cutting resistance, and capable of drilling small-diameter holes. A main cutting edge (12) of a center-side cutting edge 1 is situated on a base line VP of a circular cone having its vertex on a point V on a tool central axis OO and a half vertical angle .alpha.. An intermediate cutting edge (2) having a length substantially equal to 1/2 of the length of the main cutting edge (12) is arranged on a straight line V'Q', extending parallel to a base line VQ, which is symmetrical to the base line VP with respect to the tool central axis OO and advanced ahead of the base line VQ for a lip height t mm in the axial direction, so that a straight line connecting the respective middle points of the intermediate cutting edge (2) and the main cutting edge (12) intersect the tool central axis (OO) substantially at right angles. Since the intermediate cutting edge (2) is advanced only by the lip height t mm, a workpiece is cut by the intermediate cutting edge (2), and a portion of the main cutting edge (12) which corresponds to the intermediate cutting edge (2) is not used for cutting work, so that the cutting resistance is well balanced. Tips (20) and (21), which constitute the cutting edges individually, have a simple construction, and can be formed of commercially available tips or tips obtained by simply modifying them.
Drilling tool with a drill head with an end face pointing in the feed direction and which has a main bit, which forms a drill point located in the drill axis and the bit is inclined on either side in a substantially roof-shaped manner and the tool has drilling dust grooves. The main bit has a primary cutting edge, which extends radially over at least one side of the main bit, and a secondary cutting edge, which extends radially over substantially the remaining length of the main bit and is axially set back with respect to the primary cutting edge counter to the feed direction by at least the amount of feed in millimeters per revolution.
A self-centering indexable drill having cutting inserts disposed such that cutting forces on the inboard and outboard flutes of the drill body are substantially equal while boring a hole, thereby keeping the drill body substantially centered. The drill includes a drill body and a plurality of cutting inserts. The drill body includes a shank portion configured to be received by the spindle of a machine using the drill, a collar, and a fluted portion. The fluted portion of the drill body defines an inboard flute and an outboard flute. At least one cutting insert is releasably secured to each of the inboard and outboard flutes, with an equal number of cutting inserts carried by each. An insert pocket is defined by the drill for closely receiving each cutting insert such that the leading face of the cutting insert is substantially flush with the face of the flute. The cutting inserts are spaced on the inboard and outboard flutes such that as the drill bores a workpiece, the material removed by the cutting inserts on the inboard flute is equal to that removed by the cutting inserts on the outboard flute. The exposed cutting edge of the innermost inboard cutting insert is disposed at a first angle with respect to a line normal to the axis of rotation. Each remaining cutting insert carried by the inboard flute, and each cutting insert carried by the outboard flute is disposed at a second angle with respect to a line normal to the axis of rotation. A drill guide may be provided for assisting in preventing the drill from drifting off-center, especially when the exit surface of the workpiece is not parallel to the entrance surface of the workpiece.
A metal cutting drill includes a steel drill body, and a carbide insert brazed therein. The drill body includes a front face having a recess formed therein, the recess radially overlapping a longitudinal axis of the drill body. The insert is brazed in the recess and includes a plurality of spaced-apart cutting edges disposed on opposite sides of the axis. The cutting edges radially overlap during a drilling operation. One of the cutting edges projects radially outwardly beyond a side face of the head, and another of the cutting edges terminates radially inwardly of the side face.
The invention relates to a dual-cutting drilling tool. The drilling tool comprises a base body (14) which is rotatable about a drill axis (36) and in which two plate seats (16) are arranged on the front face thereof for receiving identically configured alternating cutting plates (16). The alternative cutting plates are respectively provided on a main cutting edge (28) thereof with an adjacent first face (30), forming a cutting wedge, and a free surface (24). The main cutting edges (28) of the alternating cutting plates (20) complement each other in the region of a central, offset cutting part (28'), forming a cross-cutting edge which is interrupted by a center hole (60). The aim of the Invention is to reduce the risk of breakage in the center area of the alternating cutting plates and to provide better guidance for the tool. According to the invention, slanting guiding inclinations (56) are provided on the free surface of the alternating cutting places (20), extending from an apex line (54) to the center corner (46) of the plates. The free surfaces (24) are positively inclined in a radially outer region in the direction of advancement and are negatively inclined in the region of the guiding inclinations (56) thereof.
