JPH08168912A - Boring tool - Google Patents

Abstract

PURPOSE: To provide a boring tool where oil is supplied well to the drill edge at the tip of a drill shank and by which the boring can be performed stably, when performing the preliminary boring, finishing processing, and chamfering of the hole at the same time. CONSTITUTION: In a boring tool, where a drill edge 12 is provided at the tip of a drill shank 10 and a margin 14 having a reamer edge 14a through a groove from the peripheral margin 12a of this drill edge is provided, chamfering edges 18 are made continuously only on the extension of either the peripheral margin of the drill edge or the margin having the reamer edge when providing the chamfering edges 18 whose diameters have become larger, inclining outward in radial direction at the rear side a specified interval apart from the tip of the drill shank. And it is arranged so that the radial height of the other not provided with a chamfering edge may be lower than the one provided with a chamfering edge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drilling tool for cutting an object to be holed, and particularly to a hole finishing process such as a pre-hole process and a reaming process for an object to be cut such as metal. And chamfering of holes can be done efficiently at the same time,
The present invention relates to a drilling tool in which oil is stably supplied to a drill blade provided at the tip of a drill shaft and the drill blade is not chipped or the drill shaft is not broken during this processing.

[0002]

2. Description of the Related Art Conventionally, when cutting an object to be cut such as metal to make a hole, generally, a hole is prepared by a drill and then finished by a reamer. The above-mentioned holes are chamfered.

However, it is very troublesome to separately perform the prepared hole processing, the hole finishing processing, and the hole chamfering processing, and there is a problem that working efficiency is deteriorated.

Therefore, in recent years, the actual Kaihei 3-4
As shown in Japanese Patent Publication No. 0013, etc., a drill blade is provided at the tip of the drill shaft, and a margin or a guide pad having a reamer blade for reaming is provided on the outer peripheral portion of the drill shaft to prepare a hole at the same time as drilling. As shown in Japanese Patent Laid-Open No. 5-301109, a drilling tool for finishing is formed so as to be continuous with the outer peripheral edge of the drill blade and the reamer blade, and each of them is inclined radially outward and has a diameter. We have developed a large stepped part, and a chamfering blade that chamfers the stepped part located on the front side of the drill shaft among these stepped parts and chamfers the hole with this chamfering blade. Was done.

However, in any of the above-described drilling tools, when the object to be cut is cut with a drill blade or the like, the chips of the object to be cut are grooves for discharging the chips provided on the drill shaft. Oil may not be able to be properly supplied to the drill blade at the tip of the drill shaft through this groove, and it may not be possible to cut the work piece with the drill blade,
The drill blade is gradually overheated, and the chips of the cut workpiece are welded and hardened in the vicinity of the drill blade, which further reduces the cutting of the workpiece by the drill blade, and the drill blade may be chipped. There has been a problem that a large load is applied to the rotation of the drill shaft and the drill shaft is broken.

[0006]

DISCLOSURE OF THE INVENTION The present invention relates to the above-described drilling tool for simultaneously performing pre-drilling, hole finishing such as reaming, and chamfering of a hole in a workpiece such as metal. The problem is to solve such problems.

That is, in the drilling tool of the present invention, when simultaneously performing the pilot hole processing, the hole finishing processing and the hole chamfering processing on the object to be cut, the object to be cut is cut by a drill blade or the like. There is no possibility that chips will clog up in the chip discharge groove provided on the drill shaft and oil such as cutting oil will not be supplied to the drill blade at the tip of the drill shaft. It is stably supplied to the drill blade at the tip of the shaft, and like the conventional drilling tools, the chips of the cut workpiece are welded and hardened in the vicinity of the drill blade, which makes it easier to cut the workpiece. It does not become impossible to perform, the drill blade is chipped, and the rotation of the drill shaft does not break and the drill shaft breaks. It is an object of the invention to the chamfering and at the same time stable performed so.

[0008]

In order to solve the above problems, in the first drilling tool according to the present invention, a drill blade is provided at the tip of the drill shaft, and the outer peripheral edge and the groove of the drill blade are provided. There is a margin with a reaming blade that performs reaming via a hole, and a chamfering blade with a large diameter that is inclined radially outward on the rear side with a required distance from the tip of the drill shaft. In the tool, the chamfering blade is formed continuously only on an extension line of either one of the outer peripheral edge of the drill blade and the margin having the reamer blade, and the chamfering blade is not provided with a chamfering blade whose height in the radial direction is the other. Is lower than the one provided.

Further, in the second drilling tool according to the present invention, a drill blade is provided at the tip of the drill shaft,
An outer peripheral edge of the drill blade, a margin having a reaming blade for reaming, and a guide pad are provided through the grooves, respectively, and radially outward from the tip of the drill shaft to the rear side with a required interval. In a drilling tool in which a chamfering blade having an inclined and large diameter is formed, the chamfering blade is continuously provided only on an extension line of the outer periphery of the drill blade, the margin having the reamer blade, and the guide pad. It was formed so that the other two radial heights without chamfer blades are lower than those with chamfer blades.

Here, in the above-mentioned first and second drilling tools, the contact surface in the groove on the front side in the rotation direction of the drill blade against which the chips of the object cut by the drill blade hit, and the reamer blade Along the groove having a contact surface with the oil passage space portion by notching between the end portion on the rear side in the rotation direction of the margin having, or the end portion on the rear side in the rotation direction of the guide pad. It is preferable to form continuously.

In the above-described first and second drilling tools, each groove between the outer peripheral edge of the drill blade, the margin provided with the reamer blade for reaming, and the guide pad is the drill shaft. It may extend linearly in the axial direction, or may be formed by spirally twisting in the axial direction of the drill shaft.

Further, in forming the oil passage space as described above, a sufficient amount of oil can be provided by a notch such that the size of the space simply forms a flank. Since it cannot be guided to the drill blade in, the size of this space is preferably 10% or more of the size of the groove having the contact surface.

[0013]

In the first drilling tool according to the present invention, the drill shaft is rotated, the object to be drilled is drilled by the drill blade at the tip of the drill shaft, and a hole is drilled around the hole thus drilled. Slightly scrape the wall surface with a reamer blade and finish with burnishing with a margin.
Further, in the second drilling tool, after the burnishing is performed by the margin as described above, the burnishing is further finished by the burnishing by the guide pad, and the thus finished hole is chamfered by the chamfering blade. .

Here, in providing a chamfering blade having a large diameter by inclining outward in the radial direction on the rear side with a required distance from the tip of the drill shaft, in the first drilling tool according to the present invention, the chamfering is performed. The blade is continuously formed only on one extension line of the outer peripheral edge of the drill blade and the margin having the reaming blade, and in the second drilling tool, the outer peripheral edge of the drill blade and the margin and the guide having the reaming blade are provided. Formed continuously only on any one extension line with the pad,
Since the height in the radial direction of the other part where the chamfering blade is not provided is lower than that of the part where the chamfering blade is provided, oil such as cutting oil is supplied to the drill shaft to the drill blade at its tip. At the time of feeding, this oil is smoothly guided to each groove of the drill shaft through the portion where the chamfering blade is not provided, and the oil is sufficiently supplied to the drill blade at the tip of the drill shaft through which the oil is cut. Like

For this reason, this oil smoothly cuts the object to be cut by the drill blade, cools the drill blade, and suppresses overheating of the drill blade during cutting,
The chips of the work piece will not be welded to the vicinity of the drill blade.

Further, in the above-described first and second drilling tools, the contact surface in the groove on the front side in the rotation direction of the drill blade against which the chips of the material cut by the drill blade hits, and the reamer blade are provided. A notch is formed between the margin and the rear end in the rotation direction, or between the end and the rear end of the guide pad in the rotation direction, and a space for oil passage is continuously formed along the groove having a contact surface. Formed,
The chips of the work to be cut by the drill blade hit the contact surface and are regulated, the chips rarely enter the space, and oil such as cutting oil cuts through this space. It is supplied to the drill blade at the tip, and the work to be cut by the drill blade is performed more smoothly, and the drill blade is cooled to prevent overheating of the drill blade during cutting and to be cut near the drill blade. The chips of the object will not be welded.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A drilling tool according to an embodiment of the present invention will be specifically described below with reference to the accompanying drawings.

(Embodiment 1) In the drilling tool of this embodiment, as shown in FIGS. 1A and 1B, a pair of large linear grooves along the axial direction of the drill shaft 10 are provided. 11a are provided so as to face each other, and the pair of grooves 11a
A drill blade 12 having a predetermined tip angle is provided at the tip of the drill shaft 10 behind each of the drill shafts 10 in the rotation direction. Each flank 13a and a thinned portion 13b are formed.

Further, a reamer blade for reaming is formed at a position rearward of the outer peripheral edge 12a of each drill blade 12 in the rotational direction of the drill shaft 10 via a linear groove 11b along the axial direction of the drill shaft 10. Margin 14 with 14a
Is provided so as to project slightly outward in the radial direction from the outer peripheral edge 12a of the drill blade 12.

Then, at a position on the rear side with respect to the tip of the drill shaft 10 with a required space therebetween, on the extension line of each of the margins 14 having the reamer blades 14a, the diameter is inclined radially outward from the reamer blades 14a. Enlarged chamfering blade 1
8 is provided, the outer peripheral edge 12a of the drill blade 12 is extended in the axial direction as it is, so that the radial height of the outer peripheral edge 18a of the chamfering blade 18 is considerably higher than the outer peripheral edge 12a of the drill blade 12. I have to. It is also possible to further reduce the radial height of the outer peripheral edge 12 of the drill blade 12 in the portion corresponding to the outer peripheral edge 18a of the chamfering blade 18.

Further, in the drilling tool of this embodiment, as described above, each margin 14 and each chamfering blade 18 continuously formed on each margin 14 and the next drill blade 12 are formed.
In the groove 11a between the contact surface 16 and the contact surface 16 against which the chips of the workpiece cut by the next drill blade 12 hit, and the margin 14 and the outer peripheral edge 18a of the chamfering blade 18 in the rotation direction rear side. The space 17 for oil passage is continuously formed in the axial direction of the drill shaft 10 along the groove 11a by making a large notch between the end and the end.

In the drilling tool of this embodiment, when performing drilling, finishing and chamfering of a workpiece, the drill shaft 10 is rotated and an oil such as cutting oil is used. Is supplied to the drill shaft 10 to send this oil to the drill blade 12 at the tip of the drill shaft 10, and the drill blade 12 at the tip of the drill shaft 10 is supplied.
The cutting object is cut by using the reamer and the pilot hole is drilled, and the wall surface around the pilot hole drilled by the reamer blade 14a having a rotation radius larger than the outer peripheral edge 12a of the drill blade 12 is slightly cut. The wall surface of the hole cut by the blade 14a is burnished by the margin 14 to finish the hole, and the chamfering blade 18 continuously formed on the margin 14 chamfers the hole. There is.

Here, when oil such as cutting oil is supplied to the drill shaft 10 as described above, the chamfering blade 18 causes the margin 1 to move.
4 is provided only on the extension line, and since the space in the portion where the chamfering blade 18 rotates becomes large, the drill shaft 10
The oil supplied to is fully supplied to the grooves 11a and 11b extending in the axial direction of the drill shaft 10 through this space, and the oil is supplied to the drill blade 12 at the tip of the drill shaft 10 through the grooves 11a and 11b. It will be fully supplied.

Further, in this embodiment, the oil passage space 17 is provided along the groove 11a having the contact surface 16 with which the chips of the material cut by the drill blade 12 hit. Since it is continuously formed in the axial direction of, the chips of the cutting object cut by the drill blade 12 hit the contact surface 16 in the groove 11a,
It becomes round in the groove 11a between the drill blade 12 and the abutment surface 16, the chips are less likely to enter the space 17 and are discharged through the groove 11a.

Therefore, as described above, the oil such as the cutting oil supplied through the space in the portion where the chamfering blade 18 rotates is guided to the drill blade 12 through the space 17 without being disturbed by the chips. Further, the margin 14 having the outer peripheral edge 12a of the drill blade 12 and the reamer blade 14a as a whole along the axial direction of the drill shaft 10
Since it is lower, the wall surface of the hole burned by the reamer blade 14a and the outer peripheral edge 1 of the drill blade 12
A gap is formed between the drill blade 2a and 2a, and the oil is guided to the drill blade 12 at the tip of the drill shaft 10 through this gap.

When the oil such as the cutting oil is sufficiently guided to the drill blade 12 in this manner, the oil causes the drill blade 1 to move.
2 makes it possible to smoothly cut the object to be cut, cools the drill blade 12 and suppresses overheating of the drill blade 12 during cutting, and chips of the object to be cut are welded to the vicinity of the drill blade 12. There is nothing to do.

As a result, when the drilling tool of this embodiment is used, the object to be cut is smoothly cut by the drill blade 12, the drill blade 12 is chipped, and a large load is applied to the rotation of the drill shaft 10. As a result, the drill shaft 10 is not broken, and the prepared hole processing, the hole finishing processing, and the hole chamfering processing can be performed efficiently and stably at the same time.

In this embodiment, the chamfering blade 18 is provided on the extension line of each margin 14 having the reamer blade 14a. Instead of each margin 14, the outer peripheral edge 12a of each drill blade 12 is replaced. It may be provided on the extension line, and similar results were obtained even in this case.

(Embodiment 2) Also in the drilling tool in this embodiment, as shown in FIGS. 2 (A) and 2 (B), a pair of linear large grooves are formed along the axial direction of the drill shaft 10. 11a are provided so as to face each other, and the pair of grooves 11a
A drill blade 12 is provided at the tip of the drill shaft 10 behind the drill shaft 10 in the rotation direction.
The thinning portion 13 is thinned to each flank 13a on the tip end surface of the drill shaft 10 on the rear side in the rotation direction from 2
and b.

In the drilling tool of this embodiment, the drill shaft 10 is located at the position rearward of the outer peripheral edge 12a of each drill blade 12 in the rotational direction of the drill shaft 10.
A margin 14 having a reaming blade 14a for reaming is provided through a linear groove 11b extending along the axial direction of the drill shaft 10 from each of the margins 14.
A guide pad 15 for performing burnishing is provided at a position on the rear side in the rotation direction of the drill via a linear groove 11c along the axial direction of the drill shaft 10.

Here, in the drilling tool of this embodiment, the turning radius of the margin 14 provided with the reamer blade 14a and the guide pad 15 is set to the outer peripheral edge 12a of the drill blade 12.
The radius of gyration is slightly larger than the radius of rotation so that the outer peripheral edge 12a of the drill blade 12 is lower than the margin 14 and the guide pad 15 as a whole along the axial direction of the drill shaft 10.

Then, at the position on the rear side from the tip of the drill shaft 10 with a required space therebetween, on the extension line of each guide pad 15, the diameter becomes larger by inclining radially outward from the guide pad 15. While the chamfering blade 18 is provided, the outer peripheral edge 12a of the drill blade 12 and the margin 14 provided with the reamer blade 14a are extended in the axial direction as they are, and the radial height at the outer peripheral edge 18a of the chamfering blade 18 is the drill blade. The outer peripheral edge 12a of 12 and the reamer blade 14a are set to be considerably higher than the margin 14. Also in this case, as in the case of the first embodiment,
In the portion corresponding to the outer peripheral edge 18a of the chamfering blade 18,
It is possible to further reduce the radial height of the margin 14 provided with the outer peripheral edge 12 of the drill blade 12 and the reamer blade 14a.

Also in the drilling tool of this embodiment, the guide pads 15 and the guide pads 15 described above are also provided.
Chamfering blades 18 continuously formed on the
In the groove 11a between the two, the contact surface 16 against which the chips of the cutting object cut by the next drill blade 12 hit, and the rotation direction of the outer peripheral edge 18a of the guide pad 15 and the chamfering blade 18 A space 17 for oil passage is cut out between the groove 11 and the rear end.
It is formed continuously in the axial direction of the drill shaft 10 along a.

When performing drilling, finishing and chamfering of an object with the drilling tool of this embodiment, the drill shaft 10 is rotated and oil such as cutting oil is added. By supplying this oil to the drill shaft 10 and sending this oil to the drill blade 12 at the tip of the drill shaft 10, the drill blade 12 provided at the tip of the rotating drill shaft 10 cuts the object to be cut and prepares a prepared hole. And the wall surface around the prepared hole drilled by the reamer blade 14a having a rotation radius larger than the outer peripheral edge 12a of the drill blade 12 is slightly cut, and thus the wall surface of the hole cut by the reamer blade 14a is cut. After the burnishing is performed by the margin 14 and further the burnishing is performed by the guide pad 15 to finish the hole, the guide pad 15 is formed.
The hole is chamfered by the chamfering blade 18 formed continuously.

Here, when oil such as cutting oil is supplied to the drill shaft 10 as described above, the chamfering blade 18 is provided only on the extension line of each guide pad 15, and the space in the portion where the chamfering blade 18 rotates. Therefore, the oil supplied to the drill shaft 10 is sufficiently supplied to the grooves 11a, 11b, 11c extending in the axial direction of the drill shaft 10 through this space, and the oil is supplied through the grooves 11a, 11b, 11c. Are sufficiently supplied to the drill blade 12 at the tip of the drill shaft 10.

Also in this embodiment, the oil passage space 17 is provided with the drill shaft 10 along the groove 11a having the contact surface 16 against which the chips of the material cut by the drill blade 12 hit. Since it is continuously formed in the axial direction of, the chips of the work piece cut by the drill blade 12 hit the contact surface 16 of the groove 11a, and in the groove 11a between the drill blade 12 and the contact surface 16. The chips are rounded, the chips are less likely to enter the space 17, and are discharged through the groove 11a.

Therefore, the oil such as the cutting oil supplied through the space in the portion where the chamfering blade 18 rotates as described above is guided to the drill blade 12 through the space 17 without being disturbed by the chips. Further, the margin 1 having the outer peripheral edge 12a of the drill blade 12 and the reamer blade 14a as a whole along the axial direction of the drill shaft 10 is formed.
4 and the guide pad 15 so that a gap is created between the wall surface of the burnished hole and the outer peripheral edge 12a of the drill blade 12, and oil is guided to the drill blade 12 at the tip of the drill shaft 10 through this gap. You will be able to be.

When the oil such as the cutting oil is sufficiently guided to the drill blade 12 in this manner, the oil causes the drill blade 1 to move.
2 makes it possible to smoothly cut the object to be cut, cools the drill blade 12 and suppresses overheating of the drill blade 12 during cutting, so that chips of the object to be cut are welded in the vicinity of the drill blade 12. There is nothing to do.

As a result, even when the drilling tool of this embodiment is used, the object to be cut is smoothly cut by the drill blade 12, the drill blade 12 is chipped, and a large load is applied to the rotation of the drill shaft 10. The drill shaft 10 is not broken due to the addition, and the prepared hole processing, the hole finishing processing, and the hole chamfering processing can be performed efficiently and stably at the same time.

In this embodiment, the chamfering blade 18 is provided on the extension line of each guide pad 15, but instead of each guide pad 15, the chamfering blade 18 is replaced by the outer peripheral edge 12a of each drill blade 12. Or reamer blade 14
It may be provided on the extension line of each margin 14 having a, and similar results were obtained even in such a case.

Here, in the first and second embodiments, the radial height of the margin 14 having the outer peripheral edge 12a of the drill blade 12 and the reamer blade 14a and the guide pad 15 is larger than that of the portion provided with the chamfering blade 18. Except for the explanation of the drilling tool that is uniform along the drill axis 10, the outer peripheral edge 12a of the drill blade 12, the margin 14 having the reamer blade 14a, and the guide for forming a stepped hole in the workpiece. It is also possible to change the radial height of the pad 15 midway.

For example, as in the drilling tool shown in FIGS. 3A and 3B, the outer peripheral edge 12a of the drill blade 12 is located at an appropriate position on the rear side from the tip of the drill shaft 10 with a required gap. Steps 19 in which the radial height of the margin 14 having the reamer blade 14a and the guide pad 15 is increased
a, 19b, 19c are provided, and the steps 19a, 19b,
At an appropriate position on the rear side of 19c, a chamfering blade 18 having a larger diameter is formed on the extension line of the step portion 19a at the outer peripheral edge 12a of the drill blade 12 inclining radially outward from the step portion 19a. While provided, reamer blade 14
The margins 14 having a and the step portions 19b and 19c in the guide pad 15 are extended in the axial direction as they are,
It is also possible that the height of the chamfering blade 18 in the outer peripheral edge 18a in the radial direction is considerably higher than those of the step portions 19b and 19c. The position where the chamfering blade 18 is provided is a step 19a on the outer peripheral edge 12a of the drill blade 12.
Not limited to the position 1 and the margin 1 having the reamer blade 14a
4 may be provided on either the step portion 19b or the guide pad 15 or the step portion 19c.

Further, in the drilling tool of each of the above embodiments, each groove 11a, 11b, 11 in the drill shaft 10 is formed.
Although c is formed linearly in the axial direction of the drill shaft 10, it is also possible to form these grooves 11a, 11b, 11c in the drill shaft 10 in a spiral shape. Even in this case, the same effect can be obtained. can get.

[0044]

As described above in detail, in the drilling tool according to the present invention, a chamfering blade having a large diameter is formed so as to be inclined radially outward toward the rear side with a required distance from the tip of the drill shaft. When installing, the chamfering blade is formed continuously only on the extension line of any one of the outer peripheral edge of the drill blade, the margin having the reamer blade, and the guide pad, and the radial height in the portion where the chamfering blade is not provided is set. Since the chamfering blade is lower than the one with the chamfered edge, when supplying oil such as cutting oil to the drill shaft and sending it to the drill blade at the tip, this oil is drilled through the part without the chamfered edge. The oil was smoothly guided to each groove of the shaft, and oil was sufficiently supplied to the drill blade at the tip of the drill shaft through which the oil was cut.

As a result, in the drilling tool according to the present invention, oil such as cutting oil is sufficiently supplied to the drill blade, the object to be cut is smoothly cut by the drill blade, and the drill blade is cooled. The overheating of the drill blade during cutting is suppressed, the chips of the work piece are not welded near the drill blade, the drill blade is chipped like a conventional drilling tool, and a large load is required to rotate the drill shaft. There is no chance that the drill shaft will break due to
It is now possible to efficiently and stably perform prepared hole processing, hole finishing processing, and hole chamfering processing on a workpiece.

Further, in the drilling tool according to the present invention, the contact surface portion in the groove, which is in contact with the chips of the object to be cut by the drill blade, is notched so that the oil passage space portion has the contact surface. When continuously formed along the groove, the chips of the object to be cut, which are cut by a drill blade, are regulated by hitting the contact surface, the chips are less likely to enter the space, and the oil such as cutting oil is It is supplied stably by the drill blade at the tip of the drill shaft that cuts through the space, making it possible to efficiently and more stably perform prepared hole processing, hole finishing processing and hole chamfering processing on the workpiece. I was able to do it.

[Brief description of drawings]

FIG. 1 is a side view and a schematic front view of a tip end portion of a drilling tool according to a first embodiment of the present invention.

FIG. 2 is a side view and a schematic front view of a tip end portion of a drilling tool according to a second embodiment of the present invention.

3A and 3B are a side view and a schematic front view of a tip end portion of a drilling tool of another embodiment in which a step portion is provided on an outer peripheral edge of a drill blade, a margin having a reamer blade, and a guide pad.

[Explanation of symbols]

 10 Drill Shafts 11a, 11b, 11c Grooves 12 Drill Blades 12a Outer Edges of Drill Blades 14 Margins 14a Reamer Blades 15 Guide Pads 16 Contact Surfaces 17 Spaces 18 Chamfering Blades

Claims (4)

[Claims] 1. A drill blade is provided at a tip portion of a drill shaft, a margin having a reamer blade for reaming is provided through an outer peripheral edge of the drill blade and a groove, and a required distance is provided from a tip of the drill shaft. In a drilling tool provided with a chamfering blade that is inclined outward in the radial direction and has a large diameter on the rear side, the chamfering blade is on the extension line of either the outer peripheral edge of the drill blade or the margin having a reamer blade. And a chamfering blade not provided with a chamfering blade, the other radial height of which is lower than that of the chamfering blade provided. 2. The drilling tool according to claim 1,
Between the contact surface in the groove on the front side in the rotation direction of the drill blade against which the chips of the object to be cut hit by the drill blade and the end portion on the rear side in the rotation direction of the margin, the notched oil passage A drilling tool, wherein a space for use is formed continuously along the groove having a contact surface. 3. A drill blade is provided at a tip end portion of a drill shaft, and an outer peripheral edge of the drill blade, a margin having a reamer blade for reaming, and a guide pad are respectively provided through grooves, and the drill is provided. In a drilling tool in which a chamfering blade with a large diameter is formed on the rear side with a required distance from the tip of the shaft, and is inclined outward in the radial direction,
The chamfering blade is continuously formed only on an extension line of the outer periphery of the drill blade, the margin having the reamer blade, and the guide pad, and the chamfering blade is not provided.
Drilling tool characterized in that the radial heights of the two are lower than those provided with chamfering blades. 4. The drilling tool according to claim 3,
Between the contact surface in the groove on the front side in the rotational direction of the drill blade against which the chips of the object to be cut hit by the drill blade and the end portion on the rear side in the rotational direction of the guide pad are cut off, A drilling tool, wherein a space for passage is formed continuously along the groove having a contact surface.