WO2017145699A1

WO2017145699A1 - Drilling method and drilling apparatus

Info

Publication number: WO2017145699A1
Application number: PCT/JP2017/003907
Authority: WO
Inventors: 兼司山本; 裕瑛二井
Original assignee: 株式会社神戸製鋼所
Priority date: 2016-02-24
Filing date: 2017-02-03
Publication date: 2017-08-31
Also published as: JP2017148894A

Abstract

A drilling method for drilling a hole in a work material (10) using a drill bit (2), on the side surface of which a margin section is provided. Said drilling method is provided with a step for preparing the work material (10) and a drilling step for forming a hole (10A) in the work material (10) by advancing the drill bit (2), which is rotating around the axis, toward the work material (10) in the axial direction and cutting the work material (10). In the drilling step, the hole (10A) is formed in the work material (10) while maintaining a positive value for the feed rate of the drill bit (2) in the forward direction D1 and continuously or intermittently changing the rate.

Description

Drilling method and punching apparatus

The present invention relates to a drilling method and a drilling apparatus. The present invention particularly relates to a drilling method and a drilling apparatus using a drill bit.

Conventionally, many cutting tools such as drill bits, end mills, turning inserts or milling inserts have been improved to extend tool life by coating hard films such as TiN and TiAlN to improve wear resistance. ing. In these cutting tools, characteristic wear occurs in each tool on the sliding surface with the work material, such as flank wear which is easy to wear.

In the drill bits disclosed in Patent Documents 1 to 3 below, wear called feed marks occurs at the side margins. This feed mark is a linear wear mark formed in the margin portion, and is generated perpendicular to the feed direction of the drill bit and along the width direction of the margin portion. However, the cause of the generation of the feed mark is not necessarily clarified.

In the following

Patent Documents

1 and 2, it is proposed to suppress wear of the margin part by covering the margin part with a hard film. Further, in Patent Document 3 below, the feed rate is once set to 0 or a negative value by vibrating the drill bit during cutting. In this way, it has been proposed to fragment the chips and cool the drill bit by making the time not to cut.

In the following

Patent Documents

1 and 2, the wear of the margin portion can be suppressed to some extent by the coating of the hard film, but the depth of the feed mark exceeds the thickness of the hard film during cutting and reaches the base material of the drill bit. May end up. In this case, since it is necessary to increase the length of re-polishing the drill bit during maintenance, the number of times the drill bit can be used repeatedly is reduced. As a result, the tool life of the drill bit is shortened. Therefore, in order to improve the tool life of the drill bit, it is necessary to make the depth of the feed mark formed in the margin portion smaller.

JP-A-62-84911 JP-A-8-174341 JP 2012-187656 A

An object of the present invention is to provide a drilling method and a drilling device capable of further reducing the depth of a feed mark formed in a margin portion in drilling a work material using a drill bit.

The drilling method according to one aspect of the present invention is a method of drilling a work material using a drill bit having a side portion provided with a margin portion. The drilling method includes the steps of preparing the work material, and cutting the work material by advancing the drill bit rotating about an axis in the axial direction toward the work material. A perforating step for forming a hole in the material. In the drilling step, a hole is formed in the work material while maintaining the feed rate of the drill bit in the advancing direction at a positive value and continuously or intermittently changing it.

A drilling apparatus according to another aspect of the present invention is an apparatus for drilling a work material using a drill bit. The drilling device includes a drill bit provided with a margin on a side surface and configured to be rotatable around an axis, and a control unit that advances the drill bit toward the work material while rotating the drill bit around the axis. And. The controller advances the drill bit so that the feed rate in the traveling direction is maintained at a positive value and continuously or intermittently changes.

It is a figure which shows the structure of the punching apparatus which concerns on embodiment of this invention. It is the figure which expanded the front-end | tip part of a drill bit. It is a figure which shows the cross-section of a drill bit. It is a figure which shows the change pattern of the feed rate of a drill bit. It is a figure which shows the protrusion formed in the hole inner surface during cutting by a drill bit. It is a figure which shows the cross-section of the drill bit in a comparative example.

<Outline of Embodiment of the Present Invention>
First, an outline of a drilling method and a drilling apparatus according to an embodiment of the present invention will be described.

The drilling method according to the present embodiment is a method of drilling a work material using a drill bit having a side portion provided with a margin portion. The drilling method includes the steps of preparing the work material, and cutting the work material by causing the drill bit rotating about an axis to advance in the axial direction toward the work material. A perforating step for forming a hole in the material. In the drilling step, a hole is formed in the work material while maintaining the feed rate of the drill bit in the advancing direction at a positive value and continuously or intermittently changing it.

In order to reduce the depth of the feed mark (wear mark) formed at the side margin in the drilling process using a drill bit, the present inventor first conducted intensive studies on the mechanism by which the feed mark is formed. As a result, at the time of drilling with a drill bit, a plurality of hard projections are formed at equal intervals in the feed direction of the drill on the hole inner surface of the work material in the vicinity of the cutting edge, and the margin portion slides with respect to the projections. It has been found that a feed mark is formed by wear. Then, the inventor considers such a formation mechanism, and when the feed rate of the drill bit at the time of cutting is constant, the same portion in the margin portion always slides with respect to the plurality of protrusions, By paying attention to the fact that the depth of the feed mark is thereby increased, the present invention has been conceived.

In the above drilling method, when the hole is formed by cutting the work material with the drill bit, the feed rate in the traveling direction of the drill bit is maintained at a positive value (that is, the feed rate of the drill bit is being drilled). The drill bit feed rate changes continuously or intermittently. Thereby, it can prevent that several protrusion formed in the hole inner surface always slides with respect to the same location in a margin part. That is, by continuously changing the feed rate of the drill bit during cutting, it is possible to avoid a portion that slides with respect to one protrusion from sliding with respect to the next protrusion. Thereby, it is possible to prevent the feed marks from being concentratedly formed at the same portion of the margin portion, and as a result, the depth of the feed marks can be further reduced.

Here, “the feed rate changes continuously” means that the feed rate constantly changes during the drilling step. “The feed rate changes intermittently” means that the feed rate continuously changes while including the time during which the feed rate is constant during the drilling step. It is small enough for the whole time. In addition, “the feed speed of the drill bit in the advancing direction is maintained at a positive value” means that the drill bit does not move or stop in a direction away from the work material during the drilling step, but approaches the work material. Means always moving in the direction.

In the drilling method, in the drilling step, the feed rate may change within a range of ± 50% of the average feed rate.

When the feed rate falls below -50% of the average feed rate, the cutting speed is lowered and the drilling efficiency is lowered. On the other hand, if the feed rate exceeds the value of + 50% of the average feed rate, the chips become too thick, and problems such as winding around the drill bit occur. For this reason, the feed speed is preferably changed within a range of ± 50% of the average feed speed, and more preferably changed within a range of ± 25%.

In the drilling method, in the drilling step, the feed rate may change by one period while one hole is formed in the work material. Thereby, mechanical control which changes the feed rate of a drill bit can be performed easily.

In the drilling method, the drill bit in which the margin portion is covered with a hard film may be used in the drilling step.

Thereby, the wear of the margin portion can be effectively suppressed by the coating of the hard film. Further, as described above, by changing the feed rate of the drill bit to make the feed mark shallower, it is possible to suppress the depth of the feed mark from exceeding the thickness of the hard film and reaching the base material.

The drilling device according to the present embodiment is a device that performs drilling on a work material using a drill bit. The drilling device includes a drill bit provided with a margin on a side surface and configured to be rotatable around an axis, and a control unit that advances the drill bit toward the work material while rotating the drill bit around the axis. And. The controller advances the drill bit so that the feed rate in the traveling direction is maintained at a positive value and continuously or intermittently changes.

In the above-described drilling device, when the workpiece is cut by the drill bit to form a hole, the feed rate of the drill bit can be changed continuously or intermittently by the control unit. Thereby, it can prevent that the some protrusion formed in the hole inner surface of a cut material always cuts with respect to the same location in a margin part during cutting. In other words, by continuously changing the feed rate of the drill bit during cutting, it is possible to prevent feed marks from being concentrated and formed at the same location in the margin portion, and as a result, the depth of the feed mark can be reduced. It can be made smaller.

In the drilling device, the control unit may advance the drill bit so that the feed rate changes within a range of ± 50% of the average feed rate.

When the feed rate falls below -50% of the average feed rate, the cutting speed is lowered and the drilling efficiency is lowered. On the other hand, if the feed rate exceeds the value of + 50% of the average feed rate, the chips become too thick, and problems such as winding around the drill bit occur. For this reason, the control unit preferably changes the feed rate of the drill bit within a range of ± 50% of the average feed rate, and more preferably changes within a range of ± 25%.

<Details of Embodiment of the Present Invention>
Hereinafter, a drilling method and a drilling apparatus according to an embodiment of the present invention will be described in detail based on the drawings.

(Punching device)
First, the configuration of a perforating apparatus 1 according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 schematically shows the overall configuration of the perforation apparatus 1. FIG. 2 is an enlarged view of the distal end portion 21 of the drill bit 2 provided in the drilling device 1. FIG. 3 shows a cross-sectional structure of the drill bit 2 in the region III of FIG. As shown in FIG. 1, the drilling device 1 is a device that drills a workpiece 10 using a drill bit 2. The drilling device 1 includes a drill bit 2, a rotary shaft 5 to which the drill bit 2 is attached and a drive unit that drives the drill bit 2, a stage 4 on which a work material 10 is installed, and a drive of the rotary shaft 5. And a control unit 3 that controls the drive of the stage 4.

2, the drill bit 2 is a round bar-shaped cutting tool having an axial direction P. The rotating shaft 5 is configured to rotate the drill bit 2 around the axis by the control unit 3. The drill bit 2 is of a twist type, and a cutting edge 22 is formed at a conical pointed tip portion 21. In the drill bit 2, a second picking surface 34 for reducing friction with the hole inner surface of the work material 10 is formed in the land portion 35, and a portion remaining in the land portion 35 becomes a margin portion 23. ing. The drill bit 2 forms a hole 10A in the work material 10 as shown in FIG. 1 by cutting the work material 10 with the cutting edge 22 while rotating around the axis. Then, the chips generated at the time of cutting are discharged by a groove portion 24 formed in a spiral shape along the axial direction P of the drill bit 2 as shown in FIG.

The drill bit in the present invention is not limited to the structure shown in FIG. 2, and various structures can be adopted. For example, the drill bit is not limited to the right-twist type drill bit shown in FIG. 2, but may be a left-twist type drill bit or a straight-blade type drill bit in which the groove is not twisted. The body (part including the tip 21) and the shank (part attached to the rotating shaft 5) may be a solid type drill bit made of an integral material, or a part having a predetermined length from the tip 21 may be separated. A tip type drill bit made of the above-mentioned material may be used, or an attached blade type drill bit in which a tip serving as a cutting edge is attached to the tip 21 may be used. Further, a single margin type drill bit in which one margin portion is provided in the land portion 35 or a double margin type drill bit in which two margin portions are provided may be used. Also, the overall length of the drill bit, the lengths of the body and shank, the tip angle, etc. are not particularly limited.

FIG. 3 shows a cross-sectional structure of the drill bit 2 in a portion including the margin portion 23. As shown in FIG. 3, the drill bit 2 has a bit body 25 that is a base material, and a hard film 26 that is formed so as to cover the surface of the bit body 25. The feed mark S2 can be formed at the time of drilling with a drill bit 2 described later, and is shown in FIG. 3 for convenience of explanation.

The bit body 25 is made of a hard material such as various tool steels, cemented carbide, cermet, ceramic, CBN, or diamond. Examples of the tool steel include carbon tool steel, alloy tool steel, and high speed tool steel. Examples of the cermet include TiC and NbC. Examples of the ceramic include SiN and Al ₂ O ₃ .

The hard film 26 is made of a hard ceramic material such as TiN or TiAlN, and is coated as a wear-resistant layer for suppressing wear of the bit body 25. The hard film 26 can be formed by a physical vapor deposition (PVD) method such as an arc ion plating method or a chemical vapor deposition (CVD) method, for example. Thus, the drill bit 2 has the hard film 26 formed on the bit body 25 in the margin portion 23, so that the wear of the margin portion 23 during cutting is suppressed.

As shown in FIG. 1, the stage 4 has a horizontal installation surface 4A on which the work material 10 is installed. The stage 4 is an XY stage, and is configured to move in a horizontal plane by the control unit 3. Thus, by horizontally moving the stage 4 in a state where the work material 10 is installed, as shown in FIG. 1, the portion where the hole 10 A is formed can be positioned directly below the distal end portion 21 of the drill bit 2. it can.

The control unit 3 is a controller that controls driving of the rotating shaft 5 and driving of the stage 4. The control unit 3 includes a drive control unit 31 that is a function of the CPU for controlling the drive unit of the rotary shaft 5 and the drive of the stage 4. The drive controller 31 rotates the rotary shaft 5 so that the drill bit 2 rotates around the axis at a predetermined rotation speed (rpm) and descends toward the work material 10 at a predetermined feed speed (mm / rotation). Control the drive. Further, the drive control unit 31 performs control for moving the stage 4 in the horizontal plane.

Here, the control unit 3 maintains the feed speed in the traveling direction D1 of the drill bit 2 (the direction in which the drill bit 2 descends toward the work material 10) at a positive value, and changes continuously or intermittently. Thus, control for lowering the drill bit 2 toward the work material 10 is performed. Here, “the feed speed in the traveling direction D1 is maintained at a positive value” means that the feed speed of the drill bit 2 is always maintained at a value exceeding 0 during drilling. In other words, it means that the drill bit 2 does not rise or stop so as to be separated from the work material 10 but always descends toward the work material 10.

The graph of FIG. 4 shows the change pattern of the feed rate programmed in the storage unit 33 of the control unit 3. In the graph of FIG. 4, the horizontal axis indicates time, and the vertical axis indicates the feed rate of the drill bit 2. In the storage unit 33, a pattern in which the feed rate continuously changes in a sine wave shape (FIG. 4 (1)), a pattern in which the feed rate continuously changes in a triangular wave shape (FIG. 4 (2)), and the feed rate is stepped (step 1 type or a plurality of types of patterns are programmed among the patterns (FIG. 4 (3)) that change intermittently. The user can appropriately select these change patterns on the operation unit 32 of the control unit 3.

As shown in FIG. 4, all the change patterns (1) to (3) are programmed to start from the average feed speed and change within a range between the upper limit feed speed and the lower limit feed speed. More specifically, the feed rate increases from the average feed rate toward the upper limit feed rate, returns from the upper limit feed rate to the average feed rate, decreases from the average feed rate toward the lower limit feed rate, and decreases from the lower limit feed rate. Return to average feed rate. In other words, each change pattern includes a region where the feed rate is increased and a region where the feed rate is increased, and is programmed to decrease after increasing the feed rate. It is also possible to increase the average feed speed after decreasing the feed speed. This cycle is one cycle of the change in feed speed. The time T (minute) for making a hole having a depth L (mm) with a drill bit is expressed by the following equation when the feed rate is f (mm / rotation) and the rotation speed R (rpm).

The upper limit feed speed is set larger than the average feed speed and not more than the value of + 50% (preferably + 25%) of the average feed speed. Further, the lower limit feed speed is set to be smaller than the average feed speed and equal to or more than −50% (preferably −25%) of the average feed speed. That is, the control unit 3 lowers the drill bit 2 so that the feed rate changes within a range of ± 50% (preferably ± 25%) of the average feed rate. Note that, as in this embodiment, the difference between the upper limit feed rate and the average feed rate and the difference between the lower limit feed rate and the average feed rate are the same, and each change pattern may be symmetric about the average feed rate. However, the present invention is not limited to this. For example, the difference between the upper limit feed speed and the average feed speed may be different from the difference between the lower limit feed speed and the average feed speed, and each change pattern may be asymmetric around the average feed speed.

(Drilling method)
Next, a drilling method according to the present embodiment performed using the punching apparatus 1 will be described. In the drilling method according to the present embodiment, drilling is performed on the work material 10 using the drill bit 2 provided with the margin portion 23 on the side surface.

First, a step of preparing the work material 10 is performed. In this step, a work material 10 made of a steel material and processed into a predetermined shape and size is prepared. The work material 10 is made of chromium-molybdenum steel, cold tool steel, hot tool steel, carbon steel, or the like. Examples of chromium-molybdenum steel include JIS standards SCM430 and SCM435. Examples of the cold tool steel include JIS standard SKD11. JIS standard SKD61 etc. are mentioned as hot tool steel. Examples of carbon steel include JIS standards S50C and S55C. The prepared work material 10 is set on an installation surface 4A of the stage 4 as shown in FIG.

Next, a drilling step of cutting the workpiece 10 with the drill bit 2 to open the hole 10A is performed. In this step, first, the stage 4 is moved by the control unit 3 (drive control unit 31), so that the portion where the hole 10A is to be formed is positioned directly below the distal end portion 21 of the drill bit 2. Adjust the position.

Next, the user selects one of the feed rate change patterns (1) to (3) shown in FIG. 4 in the control unit 3 (operation unit 32). Thereafter, the user inputs various cutting conditions such as an average feed speed (mm / rotation), a rotation speed (rpm), and a hole depth (mm). Then, when the user presses the start switch, the drill bit 2 descends toward the work material 10 while rotating around the axis at the set number of rotations, and the work is cut by the cutting edge 22 provided at the tip 21. The material 10 is cut. Thereby, the drilling of the workpiece 10 by the drill bit 2 is started. At this time, the direction in which the drill bit 2 descends toward the work material 10 is the traveling direction D1. Further, an arbitrary lubricant may be supplied onto the work material 10 during cutting.

During the drilling process, the feed speed in the traveling direction D1 of the drill bit 2 is maintained at a positive value. That is, the drill bit 2 does not rise or stop so as to be separated from the work material 10, and always continues to descend toward the work material 10. Further, the feed rate continuously changes in a sine wave shape or a triangular wave shape or changes intermittently in a staircase wave shape according to a change pattern (FIGS. 4 (1) to (3)) selected in advance. At this time, the feed rate changes within a range of ± 50% (preferably within a range of ± 25%) of the average feed rate input in advance. Then, while the feed speed changes for one cycle shown in FIG. 4, that is, while the feed speed returns from the average feed speed to the average feed speed through the upper limit feed speed, and then returns to the average feed speed again through the lower limit feed speed. One hole 10 A is formed in the cutting material 10. When determining the average feed speed, the depth of the hole 10A is also taken into consideration.

In this way, only one hole 10A may be formed in the work material 10, but the second and subsequent holes may be further formed. In this case, after the formation of the first hole 10A is completed, the drill bit 2 is once lifted by the control unit 3, and the stage 4 of the stage 4 is positioned so that the portion where the next hole is formed is located directly below the drill bit 2. The position is adjusted. Then, the next hole is formed by the procedure as described above. When forming the second and subsequent holes, the change pattern of the feed rate of the drill bit 2 (FIGS. 4 (1) to (3)) may be selected again, the average feed rate, the number of rotations, and the hole depth. The cutting conditions such as may be input again. Also, in the second and subsequent holes, the feed rate of the drill bit 2 may be changed by one cycle similarly to the first hole, but the present invention is not limited to this, and may be changed by two cycles or more.

FIG. 5 shows a state in which the hole 10A is formed in the work material 10 by the drill bit 2 in the drilling method. As described above, the cutting edge 22 is formed at the distal end portion 21 of the drill bit 2, but there is no cutting edge at the side surface portion. For this reason, as shown in FIG. 5, protrusions 10 B that remain without the work material 10 being completely cut are formed at equal intervals in the traveling direction of the drill bit 2 on the inner surface of the hole 10 A.

Here, since the work material 10 is made of a steel material having a certain carbon concentration or more as described above, the protrusion 10B has a very high hardness. For this reason, when the projection 10B slides with respect to the margin portion 23 of the drill bit 2 during cutting, the hard film 26 covering the margin portion 23 is worn. As a result, as shown in FIG. 3, a feed mark S 2 that is a wear mark having a predetermined depth D 2 and a width W 2 is formed in the margin portion 23.

Here, unlike the drilling method of the present embodiment, when the drill bit 2 is lowered at a constant feed rate, the same in the margin portion 23 with respect to the plurality of protrusions 10B formed at equal intervals in the drill feed direction. The part always slides. For this reason, wear progresses locally at the same location in the margin portion 23. As a result, as shown in FIG. 6, a feed mark S1 having a small width W1 but a large depth D1 is formed, and the bit body 25 (base material) is easily exposed.

On the other hand, in the drilling method according to the present embodiment, the feed rate of the drill bit 2 changes continuously or intermittently during cutting as shown in the change pattern of FIG. Thereby, it is possible to avoid a portion that slides with respect to one protrusion 10B in the margin portion 23 from sliding with respect to the protrusion 10B below it. For this reason, it is possible to prevent the feed marks from being concentrated on the same portion in the margin portion 23. As a result, the width becomes larger than the feed mark S1 shown in FIG. 6 (W2> W1), but the depth of the feed mark S2 can be made smaller (D2 <D1).

(Function and effect)
Next, features of the perforation method and perforation apparatus 1 according to the present embodiment and the effects thereof will be described.

The above drilling method is a method of drilling the work material 10 using the drill bit 2 provided with the margin portion 23 on the side surface. The drilling method includes a step of preparing the work material 10, and cutting the work material 10 by causing the drill bit 2 rotating around the axis to advance in the axial direction P toward the work material 10. A drilling step of making a hole 10A in the material 10. In the drilling step, the hole 10A is formed in the work material 10 while maintaining the feed rate of the drill bit 2 in the traveling direction D1 at a positive value and continuously or intermittently changing it.

The drilling device 1 is a device for drilling a workpiece 10 using a drill bit 2. The drilling device 1 is provided with a margin portion 23 on the side surface, and a drill bit 2 configured to be rotatable about an axis, and in the axial direction P toward the work material 10 while rotating the drill bit 2 about the axis. And a control unit 3 to be advanced. The control unit 3 advances the drill bit 2 so that the feed speed in the traveling direction D1 is maintained at a positive value and continuously or intermittently changes.

In the drilling method and drilling device 1 described above, when the workpiece 10 is cut by the drill bit 2 to form the hole 10A, the feed rate of the drill bit 2 can be changed continuously or intermittently. Accordingly, it is possible to prevent the plurality of protrusions 10B formed on the inner surface of the hole 10A from always sliding with respect to the same portion of the margin portion 23 during cutting. That is, by continuously changing the feed speed of the drill bit 2 during cutting, it is possible to prevent the feed marks S2 from being concentrated on the same portion of the margin portion 23. As a result, the depth D2 of the feed mark S2 can be further reduced. For this reason, it becomes possible to lengthen the time until the bit body 25 which is the base material is exposed, and it is possible to further increase the time until the drill bit 2 needs to be re-polished.

In the above drilling method, the feed rate varies within a range of ± 50% of the average feed rate in the drilling step. In the drilling device 1, the control unit 3 advances the drill bit 2 so that the feed rate changes within a range of ± 50% of the average feed rate.

When the feed rate falls below -50% of the average feed rate, the cutting speed is lowered and the drilling efficiency is lowered. On the other hand, if the feed rate exceeds a value of + 50% of the average feed rate, the chips become too thick, causing problems such as winding around the drill bit 2. For this reason, the feed speed is preferably changed within a range of ± 50% of the average feed speed, and more preferably changed within a range of ± 25%.

In the above drilling method, the feed rate is changed by one period while one hole 10A is formed in the work material 10 in the drilling step. Thereby, the mechanical control which changes the feed rate of the drill bit 2 in the control part 3 can be performed more easily.

In the drilling method, the drill bit 2 in which the margin portion 23 is covered with the hard film 26 is used in the drilling step. Thereby, the wear of the margin part 23 can be more effectively suppressed by the coating of the hard film 26. Further, as described above, the feed mark S2 is formed shallow by changing the feed speed of the drill bit 2 during cutting, so that the depth D2 of the feed mark S2 exceeds the thickness of the hard film 26 and reaches the base material. Can be suppressed.

(Other embodiments)
Next, other embodiments of the present invention will be described.

In the above-described drilling method and drilling device 1, the feed rate may vary within a range exceeding ± 50% of the average feed rate.

In the above drilling method, it is not limited to the case where the feed rate changes for one cycle while forming one hole 10A, but may change for a half cycle or may change for two cycles or more. Moreover, when forming a some hole, the period which changes a feed rate may differ in formation of each hole, respectively. The feed speed is not limited to the case of starting from the average feed speed, and may be started from a speed higher than the average feed speed or may be started from a speed lower than the average feed speed. Further, this period is not necessarily an integer.

In the drilling method and the drilling apparatus 1, a drill bit in which the hard film 26 is not formed on the surface of the bit body 25 may be used.

An experiment was conducted to confirm the effect of the present invention for reducing the depth of the feed mark formed in the margin part of the drill bit.

First, a work material made of carbon steel (JIS standard S55C) was prepared, and a drilling test was performed under the following cutting conditions using a cemented carbide drill bit (two blades). As the drill bit, a TiAlN film (thickness: 5 μm) whose base material surface was covered was used. Then, investigate the occurrence of feed marks in the margin when the drill bit feed rate (mm / time) is constant during cutting and when the feed rate is changed as shown in the change pattern shown in FIG. did.

<Cutting conditions>
Tool: Cemented carbide drill bit (with oil hole), diameter 8.5mm
Work material: JIS standard S55C (Brinell hardness HB: 200)
Cutting speed: 100 m / min (rotation speed: 3745 rpm)
Hole depth: 20mm
Feed rate (when constant): 0.2 mm / rotation (749 mm / min)
Feeding speed (when changing): 0.2 ± 0.1 mm / revolution, 0.2 ± 0.05 mm / revolution Change in cycle: 1.6 seconds to process one hole Lubrication: Water-soluble emulsion lubrication < Evaluation method>
In the 500th hole and the 1000th hole, the depth of the feed mark formed in the margin portion was measured using a stylus type surface roughness meter. The results are shown in Table 1 below.

<Discussion>
As shown in Table 1, when the feed rate of the drill bit is changed during cutting (No. 2 to 4), the depth of the feed mark is smaller than when the feed rate is constant (No. 1). It decreased significantly. From this result, it was found that changing the feed rate of the drill bit during cutting is effective in reducing the depth of the feed mark in the margin portion. No. As shown in FIGS. 4 and 5, when the rate of change in feed exceeds ± 50%, the drill bit breaks, and it has been found that it is preferable to change the feed rate within the range of ± 50%.

Claims

A drilling method for drilling a work material using a drill bit provided with a margin part on a side surface,
Preparing the work material;
A drilling step of forming a hole in the work material by cutting the work material by causing the drill bit rotating about an axis to advance in the axial direction toward the work material, and
In the drilling step, a hole is formed in the work material while maintaining the feed rate of the drill bit in the traveling direction at a positive value and continuously or intermittently changing the drill bit.
2. The drilling method according to claim 1, wherein in the drilling step, the feed rate changes within a range of ± 50% of an average feed rate.
3. The drilling method according to claim 1, wherein, in the drilling step, the feed speed is changed by one period or more while one hole is formed in the work material.
The drilling method according to claim 1 or 2, wherein the drill bit in which the margin part is covered with a hard film is used in the drilling step.
The drilling method according to claim 3, wherein the drill bit in which the margin portion is covered with a hard film is used in the drilling step.
A drilling device for drilling a work material using a drill bit,
A drill bit provided with a margin portion on the side surface and configured to be rotatable around an axis;
A controller that advances the axial direction of the drill bit while rotating the drill bit around the axis; and
The said control part advances the said drill bit so that the feed rate of the advancing direction is maintained at a positive value, and changes continuously or intermittently, The drilling apparatus characterized by the above-mentioned.
The drilling device according to claim 6, wherein the control unit advances the drill bit so that the feed rate changes within a range of ± 50% of an average feed rate.