JP2000024814A - Composite drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a drilling speed and reduce a thrust load by forming a composite drill with a central drill and a peripheral drill concentrically surrounding the central drill both of which can be independently rotated and have cutting edges at the tip. SOLUTION: A central drill drive motor 26 provided on a casing 22 rotates a central drill 1 held by a central drill chuck 16. A peripheral drill drive motor 27 provided on the casing 22 rotates a peripheral drill 3 through a peripheral drill shank section 6 via a peripheral drill drive shaft 21, a pinion 23, a gear 10 and a key 18. The revolving speeds of the central drill 1 and the peripheral drill 3 are independently controlled by dedicated motors 26, 27 respectively to cope with changes of various drilling conditions. The diameter of the head section of the central drill 1 is made larger than the diameter of the barrel section, a step is provided between them, and a thrust load is shared by the peripheral drill 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill capable of improving an axial drilling speed, reducing a thrust load, reducing a reaction torque of a workpiece, and the like.

[0002]

2. Description of the Related Art A conventional drill is a single piece having a cutting edge at a tip and a chip discharge groove at an outer periphery. It is common to discharge through a hole through a hole. As special ones, those with a drill with a smaller diameter than the target hole diameter at the tip and those with a chamfer or counterbore cutting blade attached in the middle of the drill length direction are known, Each of them is used integrally or in combination and rotated as one. Therefore, the peripheral speed near the axis of the tip cutting edge is naturally lower than the peripheral speed of the outer peripheral portion.

[0003]

The maximum drilling speed of a conventional drill is determined by the speed at which the flesh of the workpiece is removed in front of the axis of the cutting edge. When the rotational speed of the cutting edge is increased, the outer peripheral portion of the tip cutting edge exceeds the permissible peripheral speed of cutting, causing heat softening, seizure, etc.In addition, if the thrust load is increased to increase the drilling speed, the torsional stress of the drill increases It may cause breakage. From this, the maximum drilling speed of the drill is in accordance with the maximum permissible rotation speed (the maximum permissible cutting speed that does not cause heat softening or seizure of the outer peripheral portion of the tip cutting edge) as long as the drill does not break.

[0004] When the thrust load of the drill increases, the thrust load on the workpiece and the reaction torque also increase.
It is necessary to firmly fix the workpiece and the like. An object of the present invention is to provide a drill that can achieve, alone or in combination, increasing a drilling speed, reducing a thrust load, and reducing a thrust load and a reaction torque of a workpiece.

[0005]

The above object can be attained by constructing a drill with a plurality of elements of an axial portion and an outer peripheral portion, and making the directions and speeds of rotation thereof different. That is, the present invention is a composite drill comprising a center drill, each of which is independently rotatable and has a cutting edge at its tip, and an outer peripheral drill which concentrically surrounds the center drill.

In the composite drill of the present invention, one or more intermediate drills may be arranged between the center drill and the outer peripheral drill. Then, each drill has a rotational speed adapted to each, that is, the central side drill has a higher rotational speed than the outer peripheral side drill, so that the axial portion of the conventional integrated drill is excessively low. There is no need to compensate for the cutting speed with an excessive thrust load, and it is possible to set an appropriate thrust load.Thus, the thrust load and reaction torque applied to the workpiece are reduced, and the axial center of the composite drill is reduced. The speed of removing the meat of the front workpiece and thus the speed of drilling can be improved.

[0007] Further, when the center drill and the outer peripheral drill are rotated in reverse, the reaction torque becomes a difference and further decreases. In the composite drill of the present invention, by setting each drill to a different rotation speed, even in the case of cutting conditions in which cutting chips are continuous, there is an effect of cutting the cutting chips and facilitating discharge.

In the present invention, the center drill and the intermediate drill may have a chip discharge groove at an outer peripheral portion of a length portion which overlaps an inner peripheral portion of the drill at the outer peripheral portion thereof. In particular, if a general-purpose twist drill currently available on the market in large quantities is used as the center drill, an inexpensive composite drill can be obtained. Further, if the center drill has no groove in the outer peripheral portion, the torsion strength is increased, breakage due to torsion stress can be prevented, and a more powerful and efficient drilling operation can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of using a composite drill according to the present invention will now be described with reference to the drawings of the embodiment. FIG. 1 is a diagram showing a structural example of a composite drill of the present invention and a drilling machine on which the drill is mounted. In FIG. 1, a casing 22 is fastened to a vertically movable table provided on a stand (not shown), and a center drill drive motor 26 provided on an upper portion of the casing 22 holds a center drill 1 gripped by a center drill chuck 16. Rotate.

At the upper part of the casing 22, there is provided an outer peripheral drill drive motor 27 provided separately from the above-mentioned center drill drive motor. The outer drill drive motor 27 is composed of an outer peripheral drill drive shaft 21, a pinion 23 directly connected to the shaft, and a gear 10. The outer peripheral drill 3 is rotated via the outer peripheral drill shank part 6 via the key 18. The center drill drive motor 26 and the outer periphery drill drive motor 27 are each independently controlled to an appropriate rotation speed by a rotation speed variable control device (not shown).
Drilling work can be performed by lowering a table (not shown) to which the casing 22 having the above-described device is fastened. In the present embodiment, the cutting chips of the workpiece cut by the tip cutting edge 2 of the center drill 1 together with the cutting chips cut by the tip cutting edge 4 of the outer peripheral drill, together with the chip discharge groove 5 provided on the outer periphery of the outer peripheral drill Through the hole to the outside. However, the chips generated by the tip cutting edge 2 of the center drill are provided with a chip discharge groove on the outer periphery as a center drill.
The gas may be discharged through the groove.

In this embodiment, a lubricating oil to which an appropriate pressure is applied is sent from an oil pipe 12 provided at an upper portion of a casing 22, passes through an oil hole 13, passes through a gap between an outer peripheral drill shank 7 and a lid 20, and passes through a center drill. Through the gap between the outer peripheral part of the drill 1 and the inner peripheral part of the outer peripheral drill 3, it is supplied to the cutting blade at the tip of the drill. For this reason, it becomes possible to improve the cutting conditions of each drill. The outer peripheral portion, the inner peripheral portion of the lid 20, and the gap between the casing 22 and the outer peripheral drill shank 7 prevent leakage of the lubricating oil pressurized by the oil seal.

The composite drill T of the present embodiment has a center drill 1
The outer drill 3 is a two-drill type, and the structure is simple. The center drill 1 and the outer drill 3 can be independently controlled in rotational speed by dedicated motors 26 and 27, respectively. Can be changed. In addition, the center drill 1 has a head with a diameter larger than that of the trunk, and a step is provided between the two parts so that a thrust load can be applied to the outer drill. In order to reduce the reaction torque applied to the workpiece, the long center drill achieved high strength and a simplified shape with a cylindrical shaft.
Etc.

However, the present invention is not limited to these, and 3
Drill type, multiple motors are driven to rotate by one motor, and the center drill and intermediate drill have a chip discharge groove on the outer circumference of the part that overlaps the inner circumference of the drill immediately on the outer circumference side And the drills may be driven to rotate in the same direction.

[0014]

As described above, the composite drill according to the present invention is capable of independently rotating and has a cutting edge at its tip.
Each of the drills, including the intermediate drill, is driven to rotate at a rotational speed matching the diameter of the center drill, and the outer drill is concentrically surrounding the center drill. There is no seizure, overheating, etc. due to a low drilling speed due to a low cutting speed and an excessively high cutting speed in the outer peripheral portion, and elimination of a chip discharge obstacle by these can be achieved alone or in combination.

[Brief description of the drawings]

FIG. 1 is an assembled sectional view showing one embodiment of the present invention.

[Explanation of symbols]

T compound drill, 1 center drill, 2 center drill tip cutting edge, 3 outer circumference drill, 4 outer circumference drill tip cutting edge,
5 Chip discharge groove, 6 Peripheral drill taper shank,
Reference Signs List 10 gear, 12 oil piping, 13 oil hole, 16 center drill chuck, 18 keys, 20 lid, 21 outer peripheral drill drive shaft, 22 casing, 23 pinion, 26
Center drill drive motor, 27 peripheral drill drive motor

Claims (2)

[Claims] 1. A composite drill comprising a center drill, each of which is independently rotatable and has a cutting edge at a tip, and an outer peripheral drill which concentrically surrounds the center drill. 2. In the case where an intermediate drill is provided between the center drill and the outer peripheral drill, the intermediate drill or the central drill is provided at an outer peripheral portion of a length portion which overlaps an inner peripheral portion of the outer peripheral drill. The composite drill according to claim 1, wherein the composite drill has a chip discharge groove.