JPH0630330Y2 - Gun drill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an improved structure of a gun drill mainly used for drilling deep holes.

[Prior Art] Conventionally, when drilling with a gun drill, a large amount of runout occurs due to the large resistance applied to the cutting edge of the drill tip, which causes variations in the dimensional accuracy of the drilled holes, and the required dimensions or roundness / straightness The problem remains that the stability of the cutting edge cannot be obtained, and burrs are generated on the cutting surface due to chattering due to runout, which reduces the roughness of the finished surface of the hole. It was noticeable in the drill.

Therefore, in order to reduce the resistance applied to the cutting edge of the drill at the time of drilling, for example, in the "gun drill" described in Japanese Utility Model Laid-Open No. 51-151179, the outer peripheral end of the cutting edge is provided with a flank to form a flank. Aim to absorb and attenuate resistance.

[Problems to be solved by the invention] However, such flanks are merely auxiliary ones for damping action only by the flanks of the outer peripheral end of the cutting blade when the cutting blade rotates, and the cutting edge of the core is inclined. Only a single angle is provided and a notch for forming the cutting edge is provided on the surface of the intermediate portion, and in the end, the resistance applied to the cutting edge cannot be remarkably reduced.

[Means for Solving the Problems] Therefore, in the present invention, a pair of chip discharge grooves having a V-shaped cross section are provided linearly along the longitudinal direction at symmetrical positions on the outer peripheral surface of a cylindrical body, and the tip end surface is substantially conical. In the gun drill formed in (1), the outer peripheral ends of the pair of cutting blades are linearly cut at an angle slightly smaller than the tip angle formed by the cutting blades to form a cutting portion, thereby providing the cutting blades with different angles. An inclined surface is formed, and a flank having a substantially triangular shape is formed so as to be in contact with the cut portion and gradually expand toward the outer peripheral direction.

[Operation] Since the cutting portions are formed at the outer peripheral ends of the pair of cutting blades so that the inclination angles are different from each other, the cutting blades with a large inclination angle are gradually inclined so that the resistance is small during cutting. The sliding surface of the work piece moves to the cutting edge with a small angle.

[Embodiment] In the drawings, 1 is a cylindrical cylinder of a gun drill, and a pair of chip discharge grooves 2 and 2 having a V-shaped cross section are formed at symmetrical positions on the outer peripheral surface in a straight line along the longitudinal direction of the cylindrical cylinder 1. Is forming. The tip portion, that is, the tip end surface 3 of the cylindrical body 1 is formed in a substantially conical shape with a flank, and the cutting edges 4 and 4 are symmetrical with the line of intersection between the tip end surface 3 and the chip discharge grooves 2 and 2. It is located and provided. The tip angles of the cutting blades 4 and 4 are set to 130 ° in this embodiment.

Thus, 5 and 5 are the outer peripheral ends of the cutting blades 4 and 4, respectively.
It is a cutout portion that is cut linearly at an angle slightly smaller than the tip angle formed by. As a result, the cutting blades 4 and 4 are formed to have different inclination angles, and the resistance can be attenuated by the two-step stance. Further, the distal end surface 3 is provided with flanks 6 and 6 of a substantially triangular shape which are in contact with the cutouts 5 and 5 and gradually expand toward the outer peripheral direction.

Next, to explain the operation of the gun drill of the present invention, the gun drill has a shank provided on the upper portion of a cylindrical body 1 (not shown) supported and fixed to a machine tool such as a drilling machine, and slidably contacts a work piece by a predetermined feed. Then, the cutting blades 4 and 4 are used for cutting. At this time, the outer peripheral ends of the cutting blades 4 and 4 provided at the tips are configured to be cut along a straight line at an angle slightly smaller than the tip angle formed by the cutting blades 4 and 4 to provide the cutting portions 5 and 5. Therefore, the cutouts 5, 5 become sharper than the cutting blades 4, 4 and the resistance in the traveling direction of the drill is reduced, and the flanks 6, 6 are provided in contact with the cutouts 5, 5, The resistance to the direction of rotation will also be reduced. As a result, runout of the gun drill is almost eliminated, the drill can be fed smoothly, and the accuracy of the hole size to be drilled and the roundness / straightness are improved, and variations in these dimensions can be eliminated.
Further, it is possible to improve the finished surface roughness of the inner peripheral surface of the hole.

In this embodiment, the angle formed by the cutting portions 5, 5 is 120 ° (second angle) for the gun drill having the tip angle of 130 ° (second angle 15 ° -16 °) formed by the cutting blades 4, 4 as described above. 5 ° to 6 °), but the present invention is not limited to this drill, but for a drill having a tip angle of 118 °, 120 °, etc., if the outer peripheral end of the cutting edge is appropriately cut off, the effect of the present invention can be sufficiently achieved. You can

[Advantages of the Invention] As described above, the gun drill of the present invention is provided with a cutting portion that is linearly cut at the outer peripheral end of the cutting blade at an angle slightly smaller than the tip angle formed by the cutting blade. It is possible to reduce the resistance of the drill, which allows the feed to be performed smoothly with almost no runout of the drill, to perform stable hole drilling, and to improve the accuracy of hole dimensions as well as the roundness and straightness. The inner peripheral surface of the hole is mirror-finished so that it is almost unnecessary to ream it and the finished surface accuracy is good, and eventually, the wear of the cutting edge is reduced and the life of the drill can be extended. It is a thing.

[Brief description of drawings]

1 is a side view of a tip of a gun drill, FIG. 2 is a front view of the same, and FIG. 3 is a view for explaining angles of a cutting edge and a cutting portion of the tip. It is a side view. 1 ... Cylindrical cylinder, 2, 2 ... Chip discharging groove, 3 ... Tip surface, 4, 4 ... Cutting edge, 5, 5 ... Cutting portion, 6, 6 ... Flank surface.

Claims (1)

[Scope of utility model registration request] 1. A pair of cross sections V at symmetrical positions on the outer peripheral surface of a cylindrical body.
In a gun drill with a chip discharge groove formed in a straight line along its longitudinal direction and the tip surface formed in a substantially conical shape,
By providing a cutting portion by linearly cutting the outer peripheral ends of the pair of cutting blades at an angle slightly smaller than the tip angle formed by the cutting blades, an inclined surface having different angles is formed on the end surfaces of the cutting blades, Further, the gun drill is provided with a substantially triangular flank which is in contact with the cut portion and gradually expands toward the outer peripheral direction.