JP3985713B2 - Drill - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drill used for drilling for forming a machining hole in a work material.
[0002]
[Prior art]
As an example of such a drill, a pair of chip discharge grooves extending toward the rear end side are formed by twisting around the axis on the outer periphery of the cutting edge portion which is the tip side portion of the drill body rotated around the axis, Some cutting edges are formed at the intersection ridge line between the rake face formed on the inner peripheral surface of the chip discharge groove and the tip flank surface of the cutting edge, and conventionally, the entire surface of the cutting edge of such a drill ( Various techniques for improving wear resistance by coating a hard coating on the entire surface of the cutting edge portion such as the tip flank, the land portion, and the inner peripheral surface of the chip discharge groove of the cutting edge portion have been studied. (For example, refer to Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-326107
[Problems to be solved by the invention]
By the way, in such a drill, the tip side of the portion facing the front side of the drill rotation direction on the inner peripheral surface of the chip discharge groove is the rake face of the cutting edge, and the chips generated by the cutting edge are removed from the rake face. It is sent to the rear end side while being slidably contacted with the inner peripheral surface of the chip discharge groove and discharged, but as described above, the inner peripheral surface of the chip discharge groove is covered with a hard film having a relatively large surface roughness. If this is done, there is a problem that chip discharge resistance increases and chip clogging is likely to occur, and in severe cases, there is a risk of breakage of the cutting edge.
[0005]
In addition, a margin part adjacent to the rear side in the drill rotation direction of the chip discharge groove is formed in the land part of the cutting edge part, and this margin part comes into contact with the inner wall surface of the machining hole formed by drilling. It plays the role of guiding the cutting edge, but as described above, it is covered with a hard film having a relatively large surface roughness up to the surface of the margin portion that comes into contact with the inner wall surface of the formed hole. And there is a problem that the inner wall surface roughness of the machined hole is deteriorated, especially at the initial stage of cutting in which the phenomenon that the surface roughness of the margin portion is reduced by friction with the inner wall surface of the machined hole has not occurred. The deterioration of the inner wall surface roughness of the processed hole was remarkable.
[0006]
The present invention has been made in view of the above problems, and even if the drill has a hard coating on the surface of the cutting edge to improve wear resistance, chip discharge resistance is reduced and chip clogging occurs. An object of the present invention is to provide a drill capable of preventing the above-described problem and reducing the roughness of the inner wall surface of the formed hole.
[0007]
[Means for Solving the Problems]
Therefore, as a result of intensive studies, the present inventors have applied a hard coating on the surface of the blade edge part with the aim of improving wear resistance, and then at least the inner peripheral surface of the chip discharge groove and the surface of the margin part. On the other hand, it has been found that the problems of increased chip discharge resistance and worsening of the inner wall surface roughness of the processed hole can be solved by polishing the surface and setting the surface roughness small.
[0008]
Such polishing is applied to at least the inner peripheral surface of the chip discharge groove and the surface of the margin portion in consideration of the purpose of reducing chip discharge resistance and reducing the inner wall roughness of the processing hole. In other words, it may be applied to the entire surface of the blade edge portion coated with the hard film, but the surface of the blade edge portion is polished and polished to the surface. It is not preferable to set the roughness small.
[0009]
This is because when the cutting edge bites into the work material, the first contact area with the work material is the tip flank of the cutting edge, so the surface roughness of the tip flank is set small. This is because the cutting edge portion at the time of biting is shaken as the drill body rotates.
That is, if the cutting edge portion is shaken and stable biting cannot be performed, the thrust force when pushing the cutting edge portion toward the tip end side in the axial direction increases, and a large force is exerted on the cutting edge portion. Despite attempts to reduce the service life by applying a load and improving the inner wall surface roughness of the hole by polishing the margin area, On the contrary, there was a problem that the wall roughness was worsened.
[0010]
In the present invention thus made, a chip discharge groove extending toward the rear end side is formed on the outer periphery of the cutting edge portion which is the tip side portion of the drill body rotated about the axis, and the inner periphery of the chip discharge groove In a drill in which a cutting edge is formed at an intersecting ridge line portion between a rake face formed on a surface and a tip flank surface of the cutting edge portion, a surface of the cutting edge portion is coated with a hard film, and at least the chip discharge groove inner for the formed margin of the surface the land section of the circumferential surface and the blade edge have polished processing is given, and subjected to polishing process for the tip flank of at least the cutting edge of the It is characterized in that the hard coating is only covered .
[0011]
According to the present invention, it is possible to obtain the effect of improving the wear resistance by coating the surface of the blade edge portion with the hard coating, but the inside of the chip discharge groove in which the generated chips are in sliding contact. Polishing the peripheral surface to make it smooth with low surface roughness reduces the chip discharge resistance, prevents chip clogging, and makes contact with the inner wall of the formed hole By making the surface of the part smooth with a small surface roughness by polishing, the inner wall surface roughness of the processed hole can be kept small and good.
Furthermore, the tip flank of the cutting edge is not polished, and the surface roughness remains relatively large so that the cutting edge does not shake when biting on the work material. Since it is possible to stabilize the biting, the thrust force when pushing the blade edge part toward the tip end in the axial direction can be suppressed to a small level, and the inner wall surface roughness near the entrance to the machining hole can be reduced. There will be no inadvertent deterioration.
[0012]
At this time, the surface roughness Ra of the polished portion, that is, at least the surface roughness Ra on the inner peripheral surface of the chip discharge groove and the surface of the margin portion is the effect of preventing increase in chip discharge resistance and the processing hole. Considering the effect of preventing the deterioration of the inner wall surface roughness and the time and effort required for polishing, it is preferably set in the range of 0.1 μm to 0.4 μm.
Further, the surface roughness Ra of the portion that has not been polished, that is, the surface roughness Ra of at least the tip flank of the cutting edge portion is an effect of preventing the vibration of the cutting edge portion when the cutting edge bites the work material. Is taken into consideration, it is preferable that the thickness is set to 0.5 μm or more.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIG. 1, the drill body 10 of the drill according to the present embodiment is formed in a substantially cylindrical shape centering on the axis O with a hard material such as cemented carbide, and the rear end side portion is a rotation of the machine tool. The shank portion 11 is held by the shaft, and the tip side portion is the cutting edge portion 12.
[0014]
On the outer periphery of the cutting edge portion 12, a pair of chips discharged that twist to the rear side in the drill rotation direction T with a constant twist angle from the tip flank 13 located at the tip of the cutting edge portion 12 toward the rear end side in the axis O direction. The grooves 14 and 14 are formed symmetrically with respect to the axis O.
The tip side of the inner peripheral surfaces 15, 15 of the chip discharge grooves 14, 14 facing the front side of the drill rotation direction T is a rake face 16, 16, and the rake face 16, 16 intersects the tip flank 13. Cutting edges 17 and 17 are formed at the ridge lines, respectively.
[0015]
As shown in FIG. 2, the tip flank 13 of the blade tip 12 is a first flank formed by cutting edges 17, 17 at the ridge line on the front side in the drill rotation direction T when the rake surfaces 16, 16 intersect. 13A, 13A and the second flank surfaces 13B, 13B connected to the rear side of the drill rotation direction T of these first flank surfaces 13A, 13A are formed in a multi-stage surface shape, A relief that increases in a multi-step manner is provided as it goes to the rear side in the drill rotation direction T including thinning surfaces 18 and 18 to be described later.
Further, the tip flank 13 is inclined toward the rear end side of the blade edge portion 12 as it goes from the inner peripheral side to the outer peripheral side, so that a predetermined tip angle is given to the cutting blades 17 and 17. It has become.
[0016]
Note that the second flank surfaces 13B and 13B of the tip flank 13 have an axis O in the drill body 10 in the same manner as the chip discharge grooves 14 and 14 from the shank portion 11 toward the tip in the axis O direction. A pair of coolant holes 10A and 10A extending while twisting around are opened, and the coolant is supplied from the coolant holes 10A and 10A to the cutting site during cutting.
[0017]
Further, on the tip end side of the inner peripheral surface 15 of the chip discharge groove 14, the rear side of the drill rotation direction T from the inner peripheral side region of the rake face 16, which is a portion facing the front side of the drill rotation direction T in the inner peripheral surface 15. The crossing ridge line part with the tip flank 13 (first flank 13A and second flank 13B) up to the entire area of the facing part is directed to the inside of the chip discharge groove 14 toward the rear end side of the blade edge part 12. Thus, a thinning surface 18 is formed so as to reach the land portion 19.
As a result, the inner peripheral end side of the cutting edge 17 is formed at the intersecting ridge line portion of the thinning surface 18 and the first flank 13A, and the axis located at the center of the tip flank 13 as it goes toward the inner peripheral side. The thinning cutting edge portion 17A extends toward O.
[0018]
Here, the outer peripheral surface excluding the pair of chip discharge grooves 14, 14 in the blade edge portion 12, that is, the land portion 19 in the blade edge portion 12 is a portion of the inner peripheral surface 15 of the chip discharge groove 14 facing the front side in the drill rotation direction T. A margin part 20 that intersects with the outer peripheral side ridge line part and forms a substantially arc-shaped cross section centered on the axis O, and is connected to the rear side of the drill part T in the drill rotation direction T. It is comprised from the 2nd picking surface 21 which makes the cross-section substantially circular arc shape centering on the axis line O which has an outer diameter one step smaller.
[0019]
Further, like the chip discharge groove 14, the margin portion 20 and the second picking surface 21 are twisted toward the rear side in the drill rotation direction T from the portion intersecting the tip flank 13 toward the rear end side in the axis O direction. In this way, the blade edge portion 12 is formed over substantially the entire length in the direction of the axis O.
The margin portion 20 and the second picking surface 21 may be provided with a back taper.
[0020]
And in this embodiment, the whole surface of the blade edge | tip part 12 in the drill main body 10, ie, the surface of the land part 19 (margin part 20 and the 2nd picking surface 21) which is the outer peripheral surface of the blade edge | tip part 12, the chip discharge groove | channel 14. One or more kinds of hard coatings such as TiC, TiN, TiCN, and TiAlN are coated on the entire surface of the cutting edge portion 12 such as the inner peripheral surface 15, the thinning surface 18, and the tip clearance surface 13.
Further, on the surface of the blade edge portion 12 coated with the hard film, hard particles such as diamond particles are applied to the surface of the margin portion 20 in the land portion 19, the inner peripheral surface 15 of the chip discharge groove 14, and the thinning surface 18. Polishing is performed by applying and polishing the contained paste on a brush (the portion subjected to polishing is indicated by hatching in the figure).
[0021]
Therefore, the surface roughness Ra of the surface of the margin portion 20, the inner peripheral surface 15 of the chip discharge groove 14 and the thinning surface 18 is set in a range of Ra = 0.1 μm to 0.4 μm (polishing is performed). In the previous state, Ra = 0.5 μm to 1.0 μm), and the surface of these polished parts is smooth.
On the other hand, the surface roughness Ra of the tip flank 13 of the cutting edge portion 12 that has not been polished and the second face 21 of the land portion 19 is set in a range of Ra = 0.5 μm to 1.0 μm, respectively. ing.
In addition, surface roughness Ra [micrometer] used by this embodiment has shown the arithmetic mean roughness prescribed | regulated to JISB0601-1994.
[0022]
Although the drill of this embodiment configured as described above is partially polished by the fact that the entire surface of the blade edge portion 12 is covered with the hard coating, Due to its presence, it has an excellent wear resistance as before.
[0023]
Further, after the hard coating is applied to the entire surface of the blade edge portion 12, the inner peripheral surface 15 and the thinning surface 18 of the chip discharge groove 14 whose surface roughness tends to be relatively increased by the hard coating are polished. Since the inner peripheral surface 15 and the thinning surface 18 of the chip discharge groove 14 are smooth with a small surface roughness (Ra = 0.1 μm to 0.4 μm), the thinning cutting is performed. Friction resistance when chips generated by the cutting blade 17 including the blade portion 17A are sent out from the thinning surface 18 and the rake face 16 to the rear end side while sliding on the inner peripheral surface 15 of the chip discharge groove 14 is reduced. Have been able to.
In this way, since the chip discharge resistance can be reduced, it is possible to prevent the occurrence of chip clogging and to smoothly discharge the chips from the machining hole, and the cutting edge 12 is broken due to chip clogging. Thus, a reliable and stable drilling process can be continued.
[0024]
Further, the surface of the margin portion 20 in the land portion 19 that tends to have a relatively large surface roughness due to the hard film is also polished so that the margin portion 20 has a small surface roughness (Ra = 0.1 μm to 0.4 μm) Even when the cutting edge 12 is guided by contacting the inner wall surface of the processed hole to be formed, the inner wall surface of the processed hole is roughened. There is no.
Therefore, the inner wall surface roughness of the processed hole can be kept small and favorable even in the initial stage of cutting where the phenomenon that the surface roughness of the margin portion 20 is reduced due to friction with the inner wall surface of the processed hole.
[0025]
Here, a portion subjected to polishing after being coated with the hard film (at least the inner peripheral surface 15 of the chip discharge groove 14 and the surface of the margin portion 20, in this embodiment, the inner peripheral surface 15 of the chip discharge groove 14, The surface roughness Ra of the surface of the margin portion 20 and the thinning surface 18) is set in the range of 0.1 μm to 0.4 μm. This is because polishing is performed when the surface roughness Ra is set smaller than 0.1 μm. However, if the surface roughness Ra is set to be larger than 0.4 μm, the chip discharge resistance is reduced or the inner wall surface roughness of the processed hole is improved. This is because there is a possibility that it cannot be performed.
In order to surely eliminate such a fear, it is preferable that the surface roughness Ra of the portion subjected to the polishing process is set in the range of 0.2 μm to 0.3 μm.
[0026]
The tip flank 13 of the blade edge portion 12 is not polished and is only covered with a hard film, and has a relatively large surface roughness (Ra = 0.5 to 1.0 μm). Therefore, when the cutting edge portion 12 bites into the work material, the cutting edge portion 12 is not shaken with the rotation of the drill body 10 rotated around the axis O, and the biting can be stabilized. It has become.
Therefore, the thrust force when pushing the blade edge portion 12 toward the tip end side in the axis O direction can be suppressed to a small level without increasing, and the inner wall surface roughness near the entrance to the formed hole is unnecessarily deteriorated. There is no such thing as letting you.
[0027]
Here, the surface roughness Ra of the portion (at least the tip flank 13, in this embodiment, the tip flank 13 and the second catching surface 21) that is not polished after being coated with the hard coating is 0.5 μm or more. Although it is set, if the surface roughness Ra is set to be smaller than 0.5 μm, there is a risk that the effect of preventing the deflection of the cutting edge portion 12 when the cutting edge portion 12 bites the work material may not be obtained. Because there is.
[0028]
【Example】
Hereinafter, an embodiment of the present invention (after coating the entire surface of the blade edge portion with a hard film, the inner peripheral surface of the chip discharge groove and the surface of the margin portion are polished, and the tip flank Are drills that have not been polished), conventional examples (drills that only have a hard coating on the entire surface of the cutting edge), and comparative examples (the cutting edge after applying a hard coating to the entire surface of the cutting edge) The drilling test was conducted using a drill that was polished on the entire surface of the surface, and the net cutting power, torque, and thrust were measured. The result is shown in FIG.
The cutting conditions and the like are: work material: carbon steel test piece (S50C), cutting speed: 120 mm / min, feed: 0.25 mm / rev, coolant: emulsion (concentration: 10%).
[0029]
As shown in FIG. 3, in the conventional example, when the cutting edge part bites the work material, the thrust force can be reduced without causing the vibration of the cutting edge part (sign A in FIG. 3). The chip discharge resistance increased and chip clogging occurred (symbols B and C in FIG. 3).
Further, in the comparative example, chip discharge resistance could be reduced and chip clogging did not occur (symbols D and E in FIG. 3), but when the blade tip bites on the work material, the blade tip was shaken. As a result, the thrust force was increased (symbol F in FIG. 3).
Compared to these conventional examples and comparative examples, the embodiment which is an example of the present invention can reduce the chip discharge resistance, does not cause chip clogging (signs G and H in FIG. 3), and the cutting edge portion. It can also be seen that the thrust force can be reduced (symbol I in FIG. 3) without causing the vibration of the cutting edge when the workpiece bites into the work material.
[0030]
【The invention's effect】
According to the present invention, the surface of the cutting edge portion is coated with a hard coating, and the inner peripheral surface of the chip discharge groove to which the generated chips slide is polished while obtaining the effect of improving the wear resistance. By making the surface smooth with a small surface roughness, the chip discharge resistance is reduced to prevent the occurrence of chip clogging, and the surface of the margin part that comes into contact with the inner wall surface of the formed hole is also the same. By making the surface smooth with a small surface roughness by polishing, the inner wall surface roughness of the processed hole can be kept small and good.
In addition, the tip flank of the blade edge part is not polished, and is kept relatively large in surface roughness, so that the blade edge part does not shake when biting on the work material, Since the biting can be stabilized, the thrust force when the blade edge is pushed toward the tip end in the axial direction can be suppressed to a small level, and the inner wall surface roughness near the entrance to the machining hole can be reduced. There will be no worsening of preparation.
[Brief description of the drawings]
FIG. 1 is a side view showing a drill according to an embodiment of the present invention.
FIG. 2 is a front view showing a drill according to an embodiment of the present invention.
FIG. 3 is a graph showing the results of a drilling test for demonstrating the effect of the drill of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Drill main body 12 Cutting edge part 13 Tip flank 14 Chip discharge groove 15 Inner peripheral surface 16 Rake face 17 Cutting edge 18 Thinning surface 19 Land part 20 Margin part 21 Second picking surface

Claims (3)

A chip discharge groove extending toward the rear end side is formed on the outer periphery of the cutting edge portion, which is the tip side portion of the drill body rotated about the axis, and the rake surface formed on the inner peripheral surface of the chip discharge groove and the cutting edge In the drill in which the cutting edge is formed at the intersecting ridge line part with the tip flank of the part,
While the surface of the blade edge is coated with a hard film,
Polishing is applied to at least the inner peripheral surface of the chip discharge groove and the surface of the margin portion formed in the land portion of the cutting edge portion,
In addition, the drill is characterized in that at least the tip flank of the cutting edge is not polished and is only covered with the hard coating . The drill according to claim 1,
The drill having the surface roughness Ra of the portion subjected to the polishing process set in a range of 0.1 μm to 0.4 μm. The drill according to claim 1 or 2,
The drill having the surface roughness Ra of the portion not subjected to the polishing process set to 0.5 μm or more.

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