JP2005111642A - End mill for spot facing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an end mill for spot facing capable of performing highly efficient spot facing by suppressing chip plugging. <P>SOLUTION: In the end mill 1, the groove diameter Dg is set in the range of substantially 15% or more and substantially 40% or less of the outer diameter of the outer peripheral cutting edge 4, the torsion angle β of the outer peripheral cutting edge 4 is set in the range of substantially 15° and more and substantially 35° or less, and the rake angle α of a bottom cutting edge 5 is set in the range of substantially 2° or more and substantially 15° or less. Therefore, the discharge force of the chips is made strong, and the chip plugging can be suppressed certainly. Thus, the spot facing can be performed without step processing and hence highly efficient spot facing can be performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an end mill for counterbore processing, and more particularly to an end mill for counterbore processing capable of suppressing chip clogging and performing highly efficient counterbore processing.

  When a sink hole for embedding a bolt head is processed, it may be performed by a drilling process (a thrust process) using an end mill. The seating surface of this sinking hole needs to be machined into a flat surface to improve the seating of the bolt head. Therefore, the countersink machining has a bottom blade clearance angle of approximately 0 °. End mills are used.

  By the way, the end mill is mainly used for groove processing and side surface processing. For example, in side machining, the side opposite to the cutting side is in an open state, so there is almost no need to consider chip discharge, while the cutting side is constrained and cantilevered, resulting in bending force. It is necessary to prevent cutting defects and breakage.

Therefore, the conventional end mill is configured to ensure mechanical rigidity by setting the groove diameter (web thickness) in the range of 50% to 90% of the end mill diameter (Patent Document 1).
Japanese Patent Laid-Open No. 51-47672 (FIG. 4 etc.)

  However, in the above-described end mill, when spot facing is performed by drilling processing (chipping processing), chip pockets for chip discharge are insufficient and chips are clogged regardless of the presence or absence of pilot holes in the work material. There was a problem that it was easy to occur. Therefore, in order to suppress such clogging of chips, it is necessary to perform step processing (repeating forward and backward in the processing direction), resulting in problems that processing time is increased and processing efficiency is deteriorated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a counterbore end mill capable of suppressing chip clogging and performing highly efficient counterbore processing.

  In order to achieve this object, an end mill for counterbore according to claim 1 is formed along a main body, a twist groove recessed by being twisted around an axis of the main body, and the twist groove. An outer peripheral blade and a bottom blade formed at the bottom of the main body, which performs cutting by being moved in the axial direction relative to the workpiece while being driven to rotate about the axial center of the main body The rake angle of the bottom blade is in a range of approximately 2 ° to approximately 15 °, the twist angle of the outer peripheral blade is in a range of approximately 15 ° to approximately 35 °, and the groove of the twist groove The groove diameter, which is the diameter of the circle connecting the bottoms, is in the range of about 15% to about 40% of the outer diameter of the outer peripheral blade.

  According to the end mill for counterbore processing according to claim 1, chips generated by the cutting action of the bottom blade during the counterbore processing are stored in the chip pocket formed by the torsional groove and twisted. It is discharged outside from the hole to be processed through the groove.

  According to the end mill for counterbore processing according to claim 1, since the groove diameter is set to about 40% or less of the outer diameter of the outer peripheral blade, the chip pocket capacity for chip discharge is secured and the cutting is performed. Waste clogging can be suppressed, and as a result, there is an effect that high-efficiency processing is possible without requiring step processing. On the other hand, since the groove diameter is about 15% or more of the outer diameter of the outer peripheral blade, it is possible to secure a sufficient core thickness and suppress the mechanical rigidity from being lowered. There is an effect that defects such as breakage during cutting can be suppressed. In other words, even if the groove diameter is reduced and the mechanical rigidity is lowered, the chip pocket capacity is secured correspondingly and chip clogging is suppressed. As a result, the occurrence of breakage and the like can be suppressed. it can.

  Moreover, since the torsion angle of the outer peripheral blade is approximately 15 ° or more, the chip discharge force can be strengthened and the chip clogging can be reliably suppressed. There is an effect that highly efficient processing becomes possible. On the other hand, since the torsion angle of the outer peripheral blade is set to about 35 ° or less, it is possible to suppress an increase in manufacturing cost due to the helix angle becoming too strong and difficult to form. There is an effect.

  Furthermore, since the rake angle of the bottom blade is approximately 2 ° or more, the cutting resistance can be reduced by improving the sharpness and improving the machinability. Therefore, even if the mechanical rigidity is lowered by reducing the groove diameter, there is an effect that the occurrence of breakage or the like can be suppressed by reducing the cutting resistance, and accordingly, the groove diameter can be further reduced. it can. As a result, the chip pocket capacity is ensured and the chip discharge performance is further improved. As a result, there is an effect that breakage due to chip clogging is suppressed. On the other hand, since the rake angle of the bottom blade is about 15 ° or less, there is an effect that it is possible to suppress the occurrence of chipping and the like due to the reduced rigidity of the blade edge.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a front view of an end mill 1 according to an embodiment of the present invention. 2A is a side view of the end mill 1 viewed from the direction of the arrow IIa in FIG. 1, and FIG. 2B is a back view of the end mill 1 viewed from the direction of the arrow IIb in FIG. First, the overall configuration of the end mill 1 will be described with reference to FIGS. 1 and 2.

  The end mill 1 is a solid-type end mill that mainly includes a main body 2, a twist groove 3 formed in the main body 2, an outer peripheral blade 4, and a bottom blade 5, and holds the shank portion 2 a of the main body 2. This is a tool used mainly for counter boring, in which the rotational force of a processing machine such as a machining center is transmitted through a holder (not shown).

  In the counterbore processing, for example, when two plate members B1 and B2 are fastened with fastening bolts S, cutting for making a sink hole H for embedding the head of the fastening bolt S into the plate material B1 is performed. In order to improve the sitting of the fastening bolt S, the seat surface Ha of the sink hole H is formed in a substantially flat surface shape (see FIG. 6).

  Therefore, as shown in FIG. 1, the end mill 1 has a clearance angle γ of the bottom blade 5 of approximately 0 °, and is rotationally driven about the axis L of the main body 2 while being axially centered with respect to the plate material B1. By moving in the direction (opposite direction of arrow IIa in FIG. 1), the seat surface Ha is cut into a substantially flat surface (spot-off process) while the sink hole H is recessed by the cutting action of the bottom blade 5. .

  The main body 2 is made of a cemented carbide obtained by pressure-sintering tungsten carbide (WC) or the like, and the shank portion 2a is substantially circular on the base side (left side in FIG. 1) as shown in FIG. In addition to being formed in a columnar shape, a torsion groove 3, an outer peripheral blade 4 and a bottom blade 5 are formed on the other end side (right side in FIG. 1) of the shank portion 2a.

  The torsion groove 3 is formed to be twisted around the axis L of the main body 2, and the outer peripheral edge 4 is formed along the ridge line of the torsion groove 3. The groove diameter Dg, which is the diameter of the circle connecting the groove bottoms of the twisted groove 3 (see FIG. 2 (a)), is considered to be outside of the outer peripheral blade 4 in consideration of chip dischargeability and the mechanical rigidity of the end mill 1. It is preferable that the diameter D is in a range of approximately 15% (approximately 0.15D) or more and approximately 40% (approximately 0.4D) or less.

  By setting the groove diameter Dg to be approximately 40% (approximately 04.D) or less of the outer diameter D of the outer peripheral blade 4, a sufficient chip pocket capacity for chip discharge is secured, and chip clogging is suppressed. be able to. As a result, there is no need to perform step machining as in the case of a conventional end mill, so that the machining time can be shortened, and accordingly, highly efficient counter boring can be performed. On the other hand, by setting the groove diameter Dg to be approximately 15% (approximately 0.15D) or more of the outer diameter D of the outer peripheral blade 4, it is possible to secure a sufficient core thickness and suppress a decrease in mechanical rigidity. As a result, problems such as breakage during cutting (counterbore machining) can be suppressed.

  That is, according to the end mill 1 of the present invention, even if the mechanical rigidity is reduced as compared with the conventional end mill by reducing the groove diameter Dg, the capacity of the chip pocket is ensured correspondingly, and chip clogging occurs. As a result, the occurrence of breakage or the like can be suppressed. In this embodiment, the groove diameter Dg is 18% (0.18 D) of the outer diameter D of the outer peripheral blade 4.

  The torsion angle β of the outer peripheral blade 4 is preferably set to a range of approximately 15 ° or more and approximately 35 ° or less in consideration of chip discharge and workability. By setting the twist angle β to approximately 15 ° or more, the chip discharging force can be strengthened and chip clogging can be reliably suppressed. As a result, there is no need to perform step machining as in the case of a conventional end mill, so that the machining time can be shortened, and accordingly, highly efficient counter boring can be performed.

  On the other hand, by setting the twist angle β of the outer peripheral blade 4 to be approximately 35 ° or less, it is possible to suppress the twist angle β from becoming too strong and making its molding (polishing process) difficult. As a result, it is possible to suppress an increase in manufacturing cost due to a complicated polishing process. In this embodiment, the twist angle β is 30 °.

  As described above, the bottom blade 5 is formed with a clearance angle γ of approximately 0 ° at the bottom (right side of FIG. 1) of the main body 2 (see FIG. 1), and FIGS. As shown in FIG. 4, there is a contact of the gash 6 on a part of the axis L side. Note that the gasche angle (not shown) of the gasche 6 is 45 °. The rake angle α of the bottom blade 5 (see FIG. 2B) is preferably about 2 ° or more and about 15 ° or less in consideration of cutting performance and durability.

  By setting the rake angle α of the bottom blade 5 to approximately 2 ° or more, the cutting resistance can be improved and the cutting resistance can be reduced by improving the cutting performance. Therefore, as described above, even if the mechanical rigidity is reduced by reducing the groove diameter Dg, the occurrence of breakage or the like can be suppressed by reducing the cutting resistance, and accordingly, the groove diameter Dg is further reduced. can do. As a result, the capacity of the chip pocket is ensured and the chip discharge performance is further improved. As a result, breakage due to chip clogging is further suppressed.

  On the other hand, by setting the rake angle α of the bottom blade 5 to be approximately 15 ° or less, the cutting edge of the bottom blade 5 becomes too sharp and its rigidity is reduced, which causes chipping or chipping. It can be suppressed in advance. In the present embodiment, the rake angle α of the bottom blade 5 is 8 °. The second angle ζ1 of the bottom blade 5 is 6 °, and the third angle ζ2 of the bottom blade 5 is 16 °.

  Next, a cutting test performed using the end mill 1 configured as described above will be described with reference to FIG. This cutting test is a test for measuring the maximum feed rate at which the counterbore can be countersunk when the counterbored hole H is embedded in the plate material B1 to embed the head of the fastening bolt S (see FIG. 6). It is.

  Detailed specifications of the cutting test are as follows: Work material (plate material B1): JIS-S50C, machine used: vertical machining center, cutting method: drilling (butting), cutting oil: not used (air blow), machining depth (Depth of sink hole H): 14 mm, presence / absence of pilot hole: none, cutting speed: 80 m / min (1820 revolutions / min). In this cutting test, step processing was not performed, and the feed rate was 0.04 mm / rotation every 0.04 mm / rotation in a range from 0.04 mm / rotation to 0.24 mm / rotation (see FIG. 3).

  In the cutting test, the end mill 1 described in the present embodiment, which has various values for the groove diameter Dg, the torsion angle β of the outer peripheral blade 4, and the rake angle α of the bottom blade 5, was used. (See FIG. 3). The outer diameter D of the outer peripheral blade 4 of the end mill 1 is D = 14 mm. The determination of the maximum feed rate was mainly made based on the presence / absence (degree) of tool vibration.

  FIG. 3 is a diagram showing the results of the cutting test. In the figure, the “No.” column indicates the measurement No. It shows that the measurement was performed for 8 types of end mills. Since the “groove diameter Dg, torsion angle β, and bottom edge rake angle α” fields are as described above (see FIGS. 1 and 2), the description thereof is omitted.

  The “groove bottom roundness” column indicates the shape of the groove bottom of the twisted groove 3, that is, the capacity of the chip pocket. That is, as the value of the groove diameter Dg increases (decreases), the roundness of the groove bottom decreases (increases). That is, the capacity of the chip pocket becomes small (large).

  As shown in FIG. 1 and no. 2 end mills generate tool vibration during counterbore at a feed rate of 0.04 mm / rotation, regardless of the rake angle α of the bottom blade 5 (α = 2 ° and 7 °). The cutting test could not be continued. This is because the groove diameter Dg is as large as 50% or 65%, and the roundness of the groove bottom is reduced accordingly, so that the capacity of the chip pocket cannot be secured sufficiently, and further, step processing is not performed. This is probably because chips could not be discharged smoothly and chip clogging occurred.

  On the other hand, the measurement No. in which the groove diameter Dg was set to 35% or less. 3 to No. In the end mill of No. 8, the rake angle α of the bottom blade 5 is α = 3 ° and the measurement No. Although it was smaller than the case of the end mill of 2, as shown in FIG. 3, it was possible to carry out good counterbore processing at least up to a feed rate of 0.12 mm / rotation.

  That is, it was confirmed that by reducing the groove diameter Dg as in this condition, the capacity of the chip pocket is secured, chips can be discharged smoothly, and chip clogging can be reliably suppressed. . As a result, according to the end mill 1 of the present invention, the feed rate can be increased, and step machining can be eliminated, so that highly efficient counter boring can be performed correspondingly.

  When the twist angle β of the outer peripheral blade 4 is set to β = 7 ° (measurement No. 4 and No. 8), as shown in FIG. 3, tool vibration is generated at a feed rate of 0.16 mm / rotation. However, when the torsion angle β is set to β = 20 ° or 30 ° while the cutting test cannot be continued, good counterbore processing can be performed up to a feed rate of 0.24 mm / rotation. It was. This is considered to be because when the twist angle β is set to β = 7 °, the twist angle is weak, and the chip discharging force is not sufficiently exhibited.

  Next, the results of the durability test will be described with reference to FIG. The durability test is a test for measuring the maximum number of holes that can be machined by carrying out counterbore machining of the sinking hole H (see FIG. 6). The detailed specifications of the durability test are the same as those of the cutting test described above except that the feed rate is fixed at 0.16 mm / rotation. In the durability test, the same measurement No. as that used in the cutting test described above was used. 1 to No. An 8 end mill was used.

  FIG. 4 is a diagram showing the results of the durability test. Measurement No. 1 and no. The end mill No. 2 was able to carry out spot facing of the first sunk hole H while generating tool vibration. However, as shown in FIG. Inside, the bottom blade 5 was damaged, and it was impossible to continue the durability test. As in the case of the cutting test described above, this is because the groove diameter Dg is large, the chip pocket capacity cannot be sufficiently secured, and the chips are discharged smoothly because step processing is not performed. It is not possible to do this, and it seems to be due to the occurrence of chip clogging.

  In addition, the measurement No. in which the groove diameter Dg was set to 35% or less. 3 to No. In the case of the end mill of 8 as well, when the twist angle β of the outer peripheral blade 4 is set to β = 7 ° (measurement No. 4 and No. 8), as shown in FIG. During the counterbore processing of the hole H, the tool vibration became large, and it was impossible to continue the durability test. As in the case of the cutting test described above, when the twist angle β is set to β = 7 °, it is considered that the twist angle is weak and the chip discharging force cannot be sufficiently exhibited.

  On the other hand, the measurement No. with the groove diameter Dg set to 35%. In the end mill 3, tool vibration occurred at the time when 30 counterbore holes were counterbored. In addition, the measurement No. in which the groove diameter Dg was set to 25% or 18%. 5 to No. In the end mill of No. 7, abnormalities such as tool vibration and chipping of the cutting edge did not occur even when 40 counterbored holes H were counterbored, and the durability test could be continued as it was. In this way, by reducing the groove diameter Dg to ensure the capacity of the chip pocket and by setting the twist angle β to be larger than a predetermined value, chips are smoothly discharged and chip clogging is reliably suppressed. As a result, it was confirmed that the end mill 1 having excellent durability can be obtained.

  From the above results, the groove diameter Dg is about 40% or less, more preferably about 35% or less in consideration of chip discharge, and about 15% or more, more preferably in consideration of mechanical rigidity. The range of about 18% or more is set, and the torsion angle β of the outer peripheral blade 4 is about 15 ° or more, more preferably about 20 ° or more in consideration of chip discharge, and the manufacturing cost is low. In consideration of the above, it is possible to suppress chip clogging by setting the angle within a range of approximately 35 ° or less, more preferably approximately 30 ° or less. It was confirmed that it was possible to carry out counterbore machining and to obtain high durability.

  Next, the second cutting test will be described with reference to FIG. The second cutting test is obtained by changing the material of the work material to a material having higher hardness and adding the shape condition of the end mill to the cutting test described above. The material of the work material (plate material B1) is JIS-SKD61, and its hardness is 40 HRC. The added end mill has a measurement No. A to No. As shown in FIG. 5, the rake angle α is mainly changed in its shape condition.

  FIG. 5 is a diagram showing the results of the second cutting test. As shown in FIG. 1 to No. The eight types of end mills No. 8 have a lower overall feed rate value that can be countersunk as compared with the case of the cutting test described above (see FIG. 3). This is due to the fact that the work material is changed from JIS-S50C (raw material) to JIS-SKD61 (quenched material) and its hardness is increased, which can be said to be an appropriate result.

  On the other hand, it is an end mill added in the second cutting test, in which the rake angle α of the bottom blade 5 is set to a range of α = 7 ° to 12 °. A, No. B and No. In the end mill of E, as shown in FIG. 5, it was possible to perform spot facing in a good state at least up to a feed rate of 0.20 mm / rotation. This seems to be due to the fact that the cutting resistance is reduced by increasing the rake angle α of the bottom blade 5 and improving the cutting performance and cutting ability.

  However, in the measurement No. 1 in which the rake angle α of the bottom blade 5 is set to α = 16 °. In the end mill of C, as shown in FIG. 5, tool vibration occurred at a feed rate of 0.12 mm / rotation, making it impossible to continue the cutting test. This seems to be caused by the fact that the rake angle α of the bottom blade 5 is excessively increased, the edge of the blade becomes sharp and chipping is likely to occur.

  From the above results, the rake angle α of the bottom blade 5 is about 2 ° or more in consideration of cutting performance, more preferably about 7 ° or more, and about 15 ° or less in consideration of chipping resistance. Preferably, by setting to a range of about 12 ° or less, even if the groove diameter Dg is reduced and the mechanical rigidity is reduced, the occurrence of breakage or the like can be suppressed by reducing the cutting resistance. It was confirmed that the chip diameter can be further reduced to further improve the chip discharge performance.

  As described above, according to the end mill 1 of the present invention, the groove diameter Dg is in the range of about 15% or more and about 40% or less of the outer diameter D of the outer peripheral blade 4, and the twist angle β of the outer peripheral blade 4 is set. Since the rake angle α of the bottom blade 5 is in the range of approximately 2 ° or more and approximately 15 ° or less in the range of about 15 ° to about 35 °, Clogging can be reliably suppressed. Therefore, it is possible to perform spot facing without performing step machining, and as a result, it is possible to perform highly efficient spot facing.

  The present invention has been described based on the embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be easily made without departing from the spirit of the present invention. It can be guessed.

  For example, in each of the above-described embodiments, the case where the end mill 1 is configured with two blades has been described. However, the present invention is not necessarily limited to this configuration. For example, the end mill 1 may be configured with three blades. . By configuring the end mill 1 with two blades, it is easier to ensure the capacity of the chip pocket. On the other hand, when it is configured with three blades, the capacity of the chip pocket is ensured, but the centripetality in counterboring is achieved. There is an effect that the counterbore processing can be performed with higher accuracy.

It is a front view of the end mill in one example of the present invention. (A) is a side view of the end mill seen from the direction of arrow IIa in FIG. 1, and (b) is a back view of the end mill seen from the direction of arrow IIb in FIG. It is the figure which showed the result of the cutting test. It is the figure which showed the result of the endurance test. It is the figure which showed the result of the 2nd cutting test. It is sectional drawing which shows the sink hole formed by counterbore processing.

Explanation of symbols

1 End mill 2 Body 3 Torsion groove 4 Outer peripheral edge 5 Bottom edge α Bottom blade rake angle β Outer edge twist angle γ Bottom edge clearance angle Dg Groove diameter

Claims (1)

A main body, a torsion groove recessed by being twisted around an axis of the main body, an outer peripheral blade formed along the torsion groove, and a bottom blade formed at the bottom of the main body; In an end mill for counterbore machining that performs cutting by being moved in the axial direction relative to the workpiece while being driven to rotate around the axis of
The rake angle of the bottom blade is in a range of about 2 ° to about 15 °,
The twist angle of the outer peripheral blade is in a range of approximately 15 ° to approximately 35 °,
An end mill for counterbore processing, wherein a groove diameter, which is a diameter of a circle connecting the bottoms of the twisted grooves, is in a range of approximately 15% to approximately 40% of the outer diameter of the outer peripheral blade. .

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