JPH106116A - Core drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a cutting edge of a drill body from suddenly engaging with a cutting object by holding a center drill so that the tip of a center pin is put in a prescribed position projecting forward more than the cutting edge of the drill body. SOLUTION: When cutting by a core drill is started, first of all, since a drill member 40 existing on the tip of a center drill 42 is pressed against a cutting object, a pin 52 is pushed in backward, and cutting of a center opening of the cutting object by the drill member 40 is performed here. The drill member 40 thrusts through the cutting object, and when the center opening is formed, the drill member 40 is pushed in the center opening, and the tip of a center pin 38 is engaged with the cutting object, and a cutting edge 46 of a cylindrical drill body 34 immediately engages with the cutting object, and the occurrence of damage or the like can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core drill suitable for drilling (ie, drilling) a wall or a plate.

[0002]

2. Description of the Related Art FIG. 1 shows a typical example of this type of core drill.

[0003] That is, this core drill comprises a shank 20 mounted on an electric drill body or the like for rotational driving, a cylindrical drill body 24 connected to the shank and having a cutting blade 22 for drilling at a leading edge thereof. A center drill 26 attached to the center of the drill body. In the case of performing a drilling operation using this core drill, first, the tip of the center drill 26 is applied to the center of a portion of the material M to be drilled, and the core drill is driven to rotate to thereby make the center hole formed by the center drill. Perforate the
Next, drilling is performed by the cutting blade 22 of the drill body.

[0004] The center drill 26 is provided with a drill body 24.
The centering and guiding operations in the drilling operation by the cutting blade 22 are performed, and the drilling operation can be performed smoothly.

[0005]

However, this type of core drill has the following disadvantages.

That is, as shown in the figure, when the center drill 26 pierces, the material M
A gap is left between the core drill and the cutting blade 22 of the drill body, and the force for pushing the core drill in the drilling direction (right direction in the illustrated example) due to the drilling by the center drill. , The cutting edge 22 of the drill body is suddenly engaged with the material, and the cutting edge may be damaged.

The applicant of the present application has filed an invention of a novel core drill for solving such a problem on June 12, 1995 (Japanese Patent Application No. 7-14476).

According to the present invention, there is provided a shank member connected to a rotary driving device, a drill body having a cutting blade, a center pin slidably set in a hole of the drill body, and a tip formed at the tip of the center pin. A center drill having a drill member having a diameter smaller than at least the tip, a spring for urging the center drill in the axial direction so that the drill member protrudes forward of the cutting blade, and a center pin. And a center drill press-inhibiting means capable of holding the tip of the drill body protruding more forward than the cutting blade of the drill body and preventing the drill body from being pushed backward in the axial direction. However, the work piece engages with the tip of the center pin and the tip of the center pin is Since it is held in a position protruding forward from the cutting edge of the drill body engagement with the cutting edge of the object to be cut and drill body it would be blocked, the above such problems are overcome. However, in order to perform cutting by the drill body, in order to push the tip of the center pin behind the cutting blade of the drill body, the operator operates the center drill push prevention means so that it does not work. In that respect, the work was complicated.

The present invention has been made in view of the above circumstances, and has as its object to provide a core drill which solves such a problem.

[0010]

That is, a core drill according to the present invention comprises a shank member connected to a rotary driving device, a cylindrical drill body drivingly connected to the shank member and having a cutting blade at a leading edge. A center hole formed along a rotation center axis of the core drill, a center pin slidably set in the center hole, extending from an opening in front of the center hole, and the center pin. A center drill having a drill member formed to project forward from the tip of the drill, and having a diameter smaller than at least the tip, and a center drill having a tip of the center pin projecting forward from a cutting blade of the drill body. And a cam mechanism provided between the center drill and the center hole, wherein the cam mechanism has a center. When the rill is brought into contact with the workpiece and pressed rearward along the axis, the center drill is held so that the center pin is located at a predetermined position protruding forward from the cutting blade of the drill body. State 1 and a second state in which the center drill, which has been released from contact with the workpiece and urged by the spring and pushed forward from the first state, is held at a predetermined position. ,
The third state of holding the center drill in a state where the tip of the center pin is pressed rearward of the cutting blade of the drill body rearward while being in contact with the object to be cut again and urged rearward is sequentially generated. There is a feature.

More specifically, a groove having a contour curve for generating the first to third states is formed on the outer peripheral surface of the center pin, and a pin engaging with the groove is mounted on the inner surface of the center hole. To be able to

Conversely, a groove having a contour curve may be provided on the inner surface of the center hole, and a pin engaging with the groove may be attached to the outer peripheral surface of the center pin.

Further, the cam groove is formed in an annular shape, and the pins are displaced relatively in a predetermined direction along the annular groove so that the first to third states are repeatedly generated. Can be.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to FIGS.
This will be described in detail based on FIG.

As shown, a core drill 30 according to the present invention is shown.
Includes a shank member 32, a cylindrical drill body 34 coupled to the shank member, a center pin 38 slidably mounted in a center hole 36 formed along the center axis of the drill body. Center drill 4 consisting of drill member 40 attached to the tip of center pin
2 and a spring 44 set in the center hole and urging the center drill forward. The drill member of the center drill has a smaller diameter than the center pin. The cylindrical drill body 34 has a cutting blade 46 made of a cemented carbide or the like at its tip. Although the drill body is caulked and fixed to the shank member 32 in the illustrated example, the drill body may be separable by screwing or the like.

A cam groove 50 of a cam mechanism, which will be described in detail below, is formed on the outer peripheral surface of the center pin 38. On the other hand, a pin 52 engaging with the cam groove is formed on the shank member.
Is attached. In the illustrated example, the pin 52 extends radially inward from the outer peripheral surface of the shank member, and is inserted into a pair of radial holes 54 opened to the center hole.
The shank member is prevented from coming off by a ring 56 fitted on the outer peripheral surface thereof.

FIG. 4 is a development view of the cam groove, and shows the relationship between the cam groove 50 and the pin 52. FIG. 3 shows the relative position of the center pin 38 in the axial direction with respect to the core drill shown in FIG. 2 corresponding to the relationship between the cam groove 50 and the pin 52 in FIG.

A center drill 42 shown in FIG.
As shown in FIG. 2, the center drill is
4 shows a case where the core drill is pushed out most forward when the core drill is not used. Pin 5 in this state
Reference numeral 2 denotes one of the positions indicated by 1 or 8 of the cam groove 50.

Now, with the pin in the position indicated by 1,
Assuming that cutting by the core drill is started, first, the drill member 40 at the tip of the center drill 42 is pressed against the work, so that the pin 42
Is pushed backward until it reaches the position shown by (FIG. 3B),
Here, the center opening of the workpiece is cut by the drill member 40.

When the drill member 40 penetrates the workpiece and the center opening is formed, the drill member is pushed into the center opening, and the tip of the center pin 38 is engaged with the workpiece. It is possible to prevent the cutting blade 46 of the cylindrical drill body 34 from immediately engaging with the object to be cut to cause damage or the like.

Then, when the operator pulls the core drill 30 slightly backward, the center drill 42 is pushed out by the action of the spring 44, and the pin passes through the position 3 to the position 4.

When the operator presses the core drill against the workpiece again, the center drill 42 is pushed in until the pin passes through the position 5 and reaches the position 6. In this position, the tip of the center drill 42 is
The cutting blade 46 is located behind the cutting blade 46 at the tip of No. 4 and cutting is performed by the cutting blade (FIG. 3C).

When the core drill 30 is separated from the workpiece after the cutting operation is completed, the center drill 42 is moved forward until the pin reaches the position 8 (FIG. 3A). This position is in the same position as the position 1 in the contour curve of the cam groove 50. Therefore, when cutting is started again using the core drill 30, the pin passes through the position 9-14. The center drill is moved to the first 1 position.

In the above example, the cam groove 50 is provided on the outer peripheral surface of the center drill 42. On the contrary, the cam groove 50 is provided on the inner peripheral surface of the center hole 36 of the shank member 32. A pin that engages with this can be provided on the center drill 42.

[0025]

The core drill 30 according to the present invention has the above-described configuration and operation. By simply pushing and returning the center drill, the parts of the core drill are specially operated as disclosed in Japanese Patent Application Laid-Open No. HEI 10-205702. Without the necessity, the problem that the cutting edge of the drill body suddenly collides with the material and is damaged as in the above-described conventional core drill can be avoided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a conventional typical core drill.

FIG. 2 is a sectional view showing a state in which the core drill according to the present invention is not used.

FIG. 3 is a side view of a center drill in the core drill, and shows an axial position of the center drill in the core drill.

FIG. 4 is a development view of a cam groove provided on an outer peripheral surface of the center drill.

[Explanation of symbols]

 30 --- core drill 32 --- shank member 34 --- drill body 36 --- center hole 38 --- center pin 40 --- drill member 42 --- center drill 44 --- spring 46 --- Cutting blade 50 --- Cam groove 52 --- Pin

Claims (4)

[Claims] 1. A core drill having a shank member connected to a rotary driving device, and a cylindrical drill body drivingly connected to the shank member and having a cutting blade at a leading edge thereof, wherein the core drill extends along a rotation center axis of the core drill. A center pin formed so as to be slidable in the center hole, extending from an opening in front of the center hole, and formed so as to protrude forward from a tip of the center pin, at least the tip A center drill having a drill member having a smaller diameter than the center drill, a spring for urging the center drill forward in the axial direction such that the tip of the center pin projects forward from the cutting blade of the drill body, and a center drill. A cam mechanism provided between the center hole and the center hole. Sometimes the center drill is
A first state in which the tip of the center pin is held at a predetermined position protruding forward of the cutting blade of the drill body; and a first state in which the center pin is released from abutment with the workpiece and urged by the spring, and A second state in which the center drill extruded forward from the first state is held at a predetermined position; and a second state in which the center drill is abutted against the work to be urged rearward, and the tip of the center pin is drilled. 3. A core drill, wherein a third state in which the center drill is pushed rearward of the cutting blade is sequentially generated. 2. A groove having a contour curve for generating the first to third states is formed on an outer peripheral surface of the center pin along a circumferential direction thereof, and a groove is formed on an inner surface of the center hole. The core drill according to claim 1, wherein an engaging pin is attached. 3. A groove having a contour curve for producing the first to third states is provided on an inner surface of the center hole along a circumferential direction thereof, and an outer surface of the center pin is provided with the groove on the inner surface. The core drill according to claim 1, wherein an engaging pin is attached. 4. A groove having the contour curve is formed in an annular shape, and the pins are displaced relatively in a predetermined direction along the annular groove, so that the first to third states are repeatedly generated. The core drill according to claim 2, wherein the core drill is provided.