End mill

Abstract

To suppress a decrease in transparency of a processed surface.SOLUTION: An end mill includes a blade part. The blade part includes an outer peripheral blade 25 and a bottom blade 22. The bottom blade 22 includes a rake cutting blade 23 continuous to the outer peripheral blade 25, and a connection blade 24 continuous to the rake cutting blade 23 and extending toward a radially inside of the end mill. A dimension of the rake cutting blade 23 is 5% of a diameter of the blade part.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to end mills. [Background technology]

[0002] The end mill disclosed in Patent Document 1 includes a cutting edge portion and a stopper portion that comes into contact with the workpiece when the cutting edge portion cuts the workpiece. When the workpiece is made of resin, the end mill disclosed in Patent Document 1 can prevent cutting marks that follow the shape of the cutting edge portion from being left on the workpiece. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-12532 Summary of the Invention [Problem to be solved by the invention]

[0004] When processing transparent resin with an end mill, the transparency of the processed surface may decrease, which may result in a loss of design appeal for the resin. [Means for solving the problem]

[0005] The end mill that solves the above problem is an end mill equipped with a cutting portion having an outer cutting edge and a bottom cutting edge, wherein the bottom cutting edge has a scraping edge that is continuous with the outer cutting edge and a connecting edge that is continuous with the scraping edge and extends radially inward of the end mill, and the dimension of the scraping edge is 5% of the diameter of the cutting edge.

[0006] By providing a scraping blade, it is possible to prevent a decrease in the transparency of the processed surface processed by the bottom blade when processing transparent resin with an end mill. In the end mill, the end cutting edge and the peripheral cutting edge may be one.

[0007] In the end mill, the helix angle of the spiral flutes provided adjacent to the peripheral cutting edge may be 15°, and the rake angle of the cutting edge may be 20°. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress a decrease in the transparency of the processed surface. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of the end mill. [Figure 2] FIG. 2 is an enlarged side view of the blade portion. [Figure 3] FIG. 3 is a view of the cutting edge as seen from the axial direction. [Figure 4] FIG. 4 is an enlarged view of the bottom cutting edge. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the end mill will now be described. As shown in FIG. 1, the end mill 10 includes a cylindrical shank 11, a cutting portion 12, and a helical flute 13. The end mill 10 is manufactured by machining a single cylindrical member. The cutting portion 12 is provided at one axial end of the shank 11. The direction along the central axis C of the end mill 10 is defined as the axial direction. The diameter of the cutting portion 12 is defined as the tip diameter D, the length of the cutting portion 12 in the axial direction as the cutting length L1, and the length of the helical flute 13 in the axial direction as the flute length L2. In this embodiment, the flute length L2 is three times or less the tip diameter D.

[0011] As shown in Figures 2 and 3, the cutting edge 12 includes a cutting edge 21, a first flank 31, and a second flank 32. The cutting edge 21 includes a bottom cutting edge 22 and a peripheral cutting edge 25 that is continuous with the bottom cutting edge 22. In this embodiment, the bottom cutting edge 22 and the peripheral cutting edge 25 are one. Therefore, the end mill 10 of this embodiment has a single blade. The helical flute 13 is provided adjacent to the peripheral cutting edge 25. The helical flute 13 extends in the axial direction while twisting in the radial direction of the end mill 10.

[0012] <Bottom blade> FIG. 4 is an enlarged view of the area indicated by the symbol A in FIG. 1. As shown in FIG. 4, the bottom cutting edge 22 is provided at the tip of the end mill 10. The bottom cutting edge 22 is a blade that extends radially of the cutting portion 12 at the tip of the end mill 10. The bottom cutting edge 22 includes a scraping edge 23 and a connecting edge 24. The scraping edge 23 is a blade that extends perpendicular to the central axis C. The scraping edge 23 is continuous with the peripheral cutting edge 25. Therefore, the scraping edge 23 is a blade that is located on the outer periphery of the bottom cutting edge 22.

[0013] The dimension of the scraper blade 23 is 5% of the diameter of the cutting portion 12. Note that the 5% mentioned here is a design value, and in reality, the dimension of the scraper blade 23 varies within the tolerance range. Therefore, the dimension of the scraper blade 23 allows for a tolerance. For example, suppose the diameter of the cutting portion 12 is 6 mm and the tolerance is ±0.1 mm. In this case, the dimension of the scraper blade 23 is 0.3 ±0.1 mm.

[0014] The connecting edge 24 is located radially inward of the flattening edge 23 on the bottom cutting edge 22. The connecting edge 24 is continuous with the flattening edge 23 and extends radially inward of the end mill 10. Specifically, the connecting edge 24 connects the top 14 of the cutting portion 12, which is positioned offset from the central axis C, to the flattening edge 23. The connecting edge 24 is inclined from the top 14 toward the flattening edge 23 in a direction away from the shank 11. In other words, the bottom cutting edge 22 protrudes axially in the opposite direction from the shank 11 beyond the top 14. The connecting edge 24 is inclined at a predetermined inclination angle θ1 with respect to an imaginary line segment perpendicular to the central axis C. The inclination angle θ1 is, for example, 5°. Note that the 5° referred to here is a design value; in reality, the inclination angle θ1 varies within the tolerance range. Therefore, the inclination angle θ1 allows for tolerance. For example, if the tolerance is ±1°, the tilt angle θ1 is 5±1°.

[0015] 3, the cutting edge 12 is provided so as to be center-down. In this embodiment, center-down means that the bottom cutting edge 22 is positioned in the opposite direction to the rotation direction with respect to an imaginary line segment that is perpendicular to the central axis C and parallel to the bottom cutting edge 22.

[0016] <Peripheral blade> As shown in FIG. 1, the peripheral cutting edge 25 extends in the axial direction of the end mill 10. The peripheral cutting edge 25 extends spirally along the spiral flute 13. The helix angle θ2 of the spiral flute 13 is 15°. The helix angle θ2 is the angle of the spiral flute 13 with respect to the central axis C. Note that the 15° mentioned here is the design value, and in reality, the helix angle θ2 varies within the tolerance range. Therefore, the helix angle θ2 allows for the tolerance. For example, if the tolerance is ±1°, the helix angle θ2 is 15±1°.

[0017] As shown in FIG. 3, the first flank 31 is a plane extending from the peripheral cutting edge 25 in the circumferential direction of the cutting portion 12. The second flank 32 is a plane extending from the first flank 31 in the circumferential direction of the cutting portion 12. The rake angle (second angle) θ3 of the cutting portion 12 is 20°. The rake angle θ3 is the angle of the first flank 31. More specifically, the rake angle θ3 is the angle between the workpiece and the first flank 31 when the peripheral cutting edge 25 contacts the workpiece. Note that the 20° mentioned here is the design value, and in reality, the rake angle θ3 varies within the tolerance range. Therefore, the rake angle θ3 allows for a tolerance. For example, if the tolerance is ±1°, the helix angle θ2 is 15±1°.

[0018] [Operation of this embodiment] The end mill 10 of this embodiment is used to process transparent resin as the workpiece. When processing transparent resin using the end mill 10, the bottom surface is processed by the bottom cutting edge 22. The side surface is processed by the peripheral cutting edge 25. The surface processed by the bottom cutting edge 22 is the bottom surface, and the surface processed by the peripheral cutting edge 25 is the side surface. "Transparent" means that at least a portion of visible light is transmitted. The resin is, for example, acrylic resin or polycarbonate.

[0019] The bottom cutting edge 22 is equipped with a scraping edge 23. By providing the scraping edge 23, it is possible to prevent a decrease in the transparency of the machined surface processed by the bottom cutting edge 22 when processing transparent resin with the end mill 10. This is presumably because the machined surface is polished as it is scraped by the scraping edge 23. Therefore, by processing transparent resin using the end mill 10 of this embodiment, it is possible to prevent a decrease in transparency due to cloudiness of the machined surface.

[0020] [Effects of this embodiment] (1) By providing the flattening blade 23, it is possible to prevent the transparency of the machined surface machined by the bottom cutting edge 22 from decreasing when a transparent resin is machined with the end mill 10.

[0021] Furthermore, as a result of experiments conducted by the inventors using the end mill 10, it was found that the decrease in transparency of the bottom surface, which becomes the machined surface, can be minimized by setting the dimension of the scraping blade 23 to 5% of the diameter of the cutting portion 12. By setting the dimension of the scraping blade 23 to 5% of the diameter of the cutting portion 12, it is possible to further minimize the decrease in transparency due to turbidity of the machined surface.

[0022] (2) The end mill 10 has a single blade. A single-blade end mill 10 does not have a lip height, so it is less likely to damage the machined surface when machining the side. In particular, if the end mill 10 has multiple peripheral blades, the machined surface machined by one peripheral blade may be damaged by a peripheral blade of a different height. This may result in a decrease in the transparency of the machined surface. When the end mill 10 has a single blade, the machined surface is less likely to be damaged by the peripheral blade 25, so a decrease in the transparency of the machined surface can be suppressed.

[0023] (3) The helix angle θ2 of the helical flute 13 is 15°, and the rake angle θ3 of the cutting edge 12 is 20°. As a result of experiments conducted by the inventors using a single-flute end mill 10, it was discovered that by setting the helix angle θ2 and the rake angle θ3 in this way, the decrease in transparency of the side surface that becomes the machined surface can be minimized. By setting the helix angle θ2 and the rake angle θ3 in this way, the decrease in transparency of the machined surface can be further minimized.

[0024] [Example of change] The embodiment can be modified as follows: The embodiment and the following modifications can be combined with each other to the extent that they are not technically inconsistent.

[0025] The cutting portion 12 may have two or more blades 21. For example, if the flute length L2 is greater than three times the tip diameter D, the cutting portion 12 may have two or more blades 21. In this case, it is preferable to set the helix angle θ2 and the rake angle θ3 according to the number of blades 21.

[0026] The helix angle θ2 and the rake angle θ3 may be changed as appropriate. [Explanation of symbols]

[0027] 10...end mill, 12...cutting edge, 22...end cutting edge, 23...scraping edge, 24...connecting edge, 25...peripheral cutting edge.

Claims

1. An end mill having a cutting portion with a peripheral cutting edge and a bottom cutting edge, The end cutting edge is a scraping blade continuous with the peripheral cutting edge; A connecting blade that is continuous with the scraping blade and extends toward the radially inner side of the end mill, An end mill, wherein the dimension of the scraper blade is 5% of the diameter of the cutting edge.

2. The end mill according to claim 1 , wherein the bottom cutting edge and the peripheral cutting edge are one.

3. The helix angle of the spiral flutes provided adjacent to the peripheral cutting edge is 15°, The end mill according to claim 2 , wherein the cutting edge has a rake angle of 20°.

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