CN113795347A - Cutting tool - Google Patents

Abstract

The invention provides a cutting tool, which comprises an end mill with a bottom cutting edge formed on the front end surface of a tool body. An end mill (1) comprising: a plurality of outer peripheral blades (6) formed spirally on the outer periphery of the tool body (2); a chip groove (5) formed on the front side of the peripheral blade (6) in the direction of rotation; and a plurality of end blades formed on the front end surface (4) of the tool body (2) and connected to the outer peripheral blade (6). The bottom blade is provided with: a first cutting edge (10) extending from the central axis (O) of the front end surface (4) or the vicinity thereof toward the outer peripheral edge; and a second cutting edge (12) formed on the outer peripheral side. The first cutting edge (10) is retreated toward the base end side of the tool body (2) relative to the second cutting edge (12), and damage to the end edge can be suppressed without causing chip clogging during machining.

Description

Cutting tool

Technical Field

The present invention relates to a cutting tool including an end mill having a bottom cutting edge formed on a distal end surface of a tool body.

The application takes the application with the application date of 2019, 3 and 29, and the application number of special application 2019-.

Background

In general, in the field of machining, for example, square end mills are used for cutting dies, parts, and the like. Such a square end mill is used as a cutting tool for cutting and machining a difficult-to-cut material such as stainless steel, titanium alloy, heat-resistant alloy, and the like. As one of the efficient cutting methods of the end mill, the end mill is fed in the direction of the central axis while rotating at a high speed, and a notch is cut into a workpiece to perform drilling. At this time, since the chips are continuously generated and travel in the chip groove, the chips easily get clogged by rubbing against the surface of the chip groove, and damage to the end edge, the tool body, and the like easily occur.

As an end mill having improved chip discharge performance in drilling, for example, patent document 1 proposes a configuration. In this end mill, a non-cutting portion is formed by cutting out a portion of the plurality of end cutting edges formed on the distal end surface of the tool body on the outer peripheral side thereof, and a cutting portion extending from the non-cutting portion to the tool center side via a stepped portion is provided. The other end cutting edge extends from the outer peripheral edge of the tool body beyond the non-cutting portion of a part of the end cutting edge to the tool center side overlapping the cutting portion.

Therefore, when the end mill drills a workpiece, the non-cutting portion of some of the end blades overlaps with the rotation locus of the other end blade, and the amount of chips is reduced while ensuring the cutting amount, so that the chip clogging can be prevented.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4870498

Disclosure of Invention

(problems to be solved by the invention)

However, in the end mill described above, since the other end cutting edge extends from the tool center side of the tool body across the outer peripheral edge, the width and volume of chips are large, and scratches generated by chips traveling in the chip discharge groove remain, and flow is difficult. Therefore, there is a problem that chip clogging is likely to occur in the chip discharge groove. Further, since the non-cutting portion is provided by forming a notch on the outer peripheral side of the partial end cutting edge, the corner portion of the cutting portion rising from the notch of the non-cutting portion is easily broken at the time of cutting, and there is a problem that the tool life is short.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a cutting tool capable of suppressing damage to a bottom edge without causing chip clogging at the time of drilling.

(means for solving the problems)

The cutting tool of the present invention comprises: a plurality of outer peripheral blades spirally formed at predetermined intervals on a distal-side outer peripheral surface of a tool body that is rotatable about a central axis; a chip groove formed on the front side of the peripheral blade in the rotation direction; and a plurality of end cutting edges formed on a distal end surface of the tool body and connected to the outer peripheral cutting edge, the end cutting edge including: a first cutting edge formed to extend from a central axis of the front end surface or a vicinity thereof toward the outer peripheral edge; and a second cutting edge formed on the outer peripheral side of the tip end surface, the first cutting edge being set so as to recede toward the base end side of the tool body from the second cutting edge.

According to the present invention, when the cutting tool is fed in the center axis direction to perform drilling, the outer peripheral region is first machined by the second cutting edge, and the first cutting edge is later machined in the region on the center axis side that does not overlap with the second cutting edge. In particular, chips originally generated by cutting with the first cutting edge tend to be clogged on the tool center side, and in this aspect, clogging of chips does not occur due to the small width and volume.

Further, assuming that the outer diameter of the end edge of the tip end surface is D, the first cutting edge is set back toward the base end side with respect to the second cutting edge in the range of 0.005D to 0.020D, preferably in the range of 0.01D to 0.015D.

Since the recessed amount of the first cutting edge with respect to the second cutting edge is within the above range, there is no fear that the first cutting edge is cut so as to overlap the second cutting edge when the recessed amount is too small, chips having a large width and volume are generated and clogged in the chip discharge groove, and it is possible to prevent the second cutting edge from being excessively loaded when the recessed amount is too large.

Preferably, the first groove portion formed in the first cutting edge extends and connects to the chip groove from a position on the opposite side beyond the central axis.

Even if the first cutting edge performs cutting on the center side of the tool body, since the first flute portion of the first cutting edge is formed to extend to a position on the opposite side beyond the center axis, chips generated by the first cutting edge are rounded in the first flute portion and smoothly fed out, the chips travel in the chip discharge groove, and chip clogging does not occur on the center side.

Preferably, the radial length of the second cutting edge on the tip surface is set in a range of 0.23D to 0.30D, where D is the outer diameter of the bottom edge of the tip surface.

Since the second cutting edge and the first cutting edge have the same cutting width, the balance during cutting is good, the width of chips is also easily discharged to the substantially same extent, and the vibration of the cutting edge can be suppressed.

Further, it is preferable to include: a first groove portion formed in front of the first cutting edge in the rotation direction; and a second groove portion formed forward of the second cutting edge in the rotation direction, wherein a depth of an intersection of the first groove portion and the second groove portion from the tool tip of the second cutting edge is set within a range of 0.05D to 0.15D.

Since the intersection of the first groove and the second groove is within a range of 0.05D to 0.15D from the groove depth of the second cutting edge, chips generated by the first cutting edge and the second cutting edge are smoothly discharged without impairing the tool rigidity.

Preferably, the outer diameter of the end edge of the end face is D, and the edge width in the central axis direction from the end corner of the second cutting edge to the boundary between the groove portion formed forward in the rotation direction of the second cutting edge and the flute in the longitudinal direction of the outer peripheral edge is set within a range of 0.01D to 0.05D, and the end corner of the first cutting edge is located within the range of the edge width.

When the cutting tool is fed in the traverse direction, the first cutting edge is retracted by a predetermined amount rearward in the center axis direction with respect to the second cutting edge, and the amount of retraction is within the range of the allowable error during the traverse processing, that is, within the edge width.

Further, the bottom edges may be four edges which are not equally divided, or the peripheral edges may be set to unequal leads.

In the cutting tool of the present invention, the bottom cutting edges are four unequal cutting edges, or the outer peripheral cutting edges are set to have unequal leads, and therefore, vibration during cutting can be suppressed.

Preferably, the first groove portion formed forward in the rotational direction of the first cutting edge and the second groove portion formed forward in the rotational direction of the second cutting edge have arc-shaped cross sections orthogonal to each other in the longitudinal direction.

Since the cross-sectional shape of the deepest portions of the first groove portion and the second groove portion is formed in an arc shape, the flow of chips is improved, and tool breakage due to chip retention can be suppressed.

(effect of the invention)

According to the cutting tool of the present invention, in the drilling process, the outer peripheral side is cut by the second cutting edge and the center side is cut by the first cutting edge, and therefore, chips are generated separately on the outer peripheral side and the tool center side. Therefore, in the drilling process, the width and volume of the chips are small, and the chips can be smoothly discharged without being blocked by the chip discharge groove. Further, since the first cutting edge is formed to extend in the direction of the outer peripheral edge from the center axis side and the second cutting edge is formed on the outer peripheral side rotating at high speed, the bottom edge is less likely to be damaged.

Drawings

Fig. 1 is a side view illustrating a cutting edge part of an end mill according to a first embodiment of the present invention.

Fig. 2 is a front end view of the end mill shown in fig. 1.

Fig. 3 is a side view showing a short edge formed on the front end surface of the end mill.

Fig. 4 is a side view showing a long edge formed on a front end surface of an end mill.

Fig. 5 is a view showing the depth of the intersection of the nick of the major edge and the nick of the minor edge.

Fig. 6 is a front end view of an end mill according to a first modification.

Fig. 7 is a side view of a drill bit according to a second embodiment.

Fig. 8 is a front end view of the drill bit shown in fig. 7.

Description of the reference numerals

1. 25: end mill

2: tool body

3: blade part

5: chip groove

6: peripheral edge

10: long edge

10 a: cutting edge part

12: short edge

14. 14A, 14B: cutting groove

31. 31A, 31B: grinding part

O: a central axis.

Detailed Description

Hereinafter, an end mill according to an embodiment of the present invention is explained based on the drawings.

Fig. 1 to 4 show an end mill 1 as a cutting tool of a first embodiment of the present invention. The end mill 1 is, for example, a four-edged square end mill. In fig. 1, an end mill 1 according to the embodiment is formed in a substantially cylindrical shape, and includes a tool body 2 that rotates about a central axis O, and a blade portion 3 formed at a distal end portion of the tool body 2. In the present specification, the blade 3 side along the central axis O is referred to as a tip side, and the opposite side connected to the main shaft is referred to as a base side and a rear side.

The end mill 1 is, for example, a square end mill in which the maximum outer diameter D of the end cutting edge on the tip end surface 4 of the cutting edge portion 3 is formed in the range of, for example, 1mm to 12mm, and is used for cutting a machine tool part, a die, or the like. The end mill 1 is suitable for cutting of difficult-to-cut materials such as stainless steel, titanium alloy, and heat-resistant alloy.

A plurality of, for example, four chip grooves 5 twisted at a predetermined angle around the central axis O from the distal end side toward the proximal end side are spirally formed at predetermined intervals in the circumferential direction on the outer peripheral surface of the blade portion 3. In each chip groove 5 formed in the side surface of the blade portion 3, an outer peripheral blade 6 is formed at a crossing ridge line portion between a wall surface facing the rotational direction and an outer peripheral surface continuing to the rear side in the rotational direction. A wall surface facing the direction of rotation of the chip groove 5 is referred to as an outer peripheral rake surface (outer peripheral すくい surface) 7 of the outer peripheral edge 6, and an outer peripheral surface facing rearward in the direction of rotation via the outer peripheral edge 6 is referred to as an outer peripheral relief surface (outer peripheral slip-on surface) 8.

The peripheral relief surface 8 of the peripheral edge 6 is formed into a convex curved surface along the rotational locus of the peripheral edge 6, and a positive edge bevel is formed without rubbing the machined surface, thereby ensuring the edge tip strength of the peripheral edge 6. Alternatively, the peripheral relief surface 8 may have a positive edge bevel in a flat surface shape. During the rotary cutting of the outer peripheral edge 6, the outer peripheral relief surface 8 does not rub against the machined surface of the workpiece.

A pair of long blades 10 extending, for example, linearly from a pair of opposed outer peripheral blades 6 toward a central axis O is formed on a tip end surface 4 of the blade portion 3 shown in fig. 2 so as to be rotationally symmetrical with respect to the central axis O forming a rotation center thereof. A core raised portion 11 having a predetermined thickness is formed on the center side of the pair of long blades 10 extending opposite to each other, sandwiching the center axis O. The ridge line formed in the core raised portion of each long blade 10 extends to the opposite side through the vicinity of the central axis O. Alternatively, the long edge 10 may pass through the central axis O.

In fig. 4, the long cutting edge 10 is inclined from the outer peripheral end, which is the connection portion with the outer peripheral edge 6, toward the base end side toward the central axis O side with respect to an imaginary line orthogonal to the central axis O on the tip end side of the cutting edge portion 3 as a reference line L, and an inclination angle (clearance angle) θ 1 thereof is set in a range of, for example, 2 ° to 5 °. Further, the distal end side of the long blade 10 is formed linearly in side view, but may be curved to form a convex curve.

A pair of short blades 12 are formed at a predetermined angle, for example, in a range of 97 ° to 102 °, in front of each long blade 10 in the rotation direction on the distal end surface 4. The short cutting edge 12 also extends continuously with the outer peripheral cutting edge 6 of the outer peripheral surface toward the radial center side, for example, linearly. Each of the minor cutting edges 12 is formed from the outer peripheral end connected to the outer peripheral cutting edge 6 to a length of, for example, about 1/2 from the radius (0.5D) of the front end surface 4. Therefore, the short edge 12 does not reach the vicinity of the central axis O and is interrupted halfway.

In fig. 3, the minor cutting edge 12 is inclined from the outer peripheral edge, which is the connection with the outer peripheral cutting edge 6, toward the base end side toward the central axis O side, and the inclination angle θ 2 thereof is set, for example, within the range of 2 ° to 5 °. The tip end of the short blade 12 may be formed in a straight line shape or a slightly curved convex curve shape in a side view. Two long edges 10 and two short edges 12, which are formed on the tip end surface 4 so as to face each other and be rotationally symmetrical, are referred to as end edges. The long blade 10 and the short blade 12 are formed in the core raised portion, and may be formed in the core depressed portion. The two long edges 10 and the two short edges 12 are alternately and unequally arranged in the circumferential direction. Therefore, vibration can be suppressed during cutting. Further, instead of the structure in which the bottom cutting edges are arranged in unequal intervals, the outer peripheral cutting edges 6 may be arranged with unequal leads.

Four cutting grooves 14 are formed at predetermined intervals on the front side in the rotation direction of the end blade around the center axis O on the front end surface 4, and are concavely cut toward the proximal end side. Here, the notch 14 formed forward in the rotational direction of the long blade 10 is denoted by reference numeral 14A, and the notch 14B formed forward in the rotational direction of the short blade 12 is denoted by reference numeral 14B.

In the front end surface 4, the intersecting ridge line portion between each cutting groove 14A and the second clearance surface 15 formed on the rear side in the rotational direction thereof is the major cutting edge 10. A third relief surface 16 is formed on the rotationally rear side of the second relief surface 15. A rake face 14A is formed in a notch 14A formed on the front side in the rotation direction of the major blade 10. The second relief surface 15 of the long blade 10 is formed in, for example, a convex curved surface or a flat surface, and a positive edge bevel is set so that the rotation locus thereof recedes toward the base end side without rubbing the machining surface of the long blade 10. The rear end side of the cutting groove 14A of each major blade 10 extends along the chip groove 5 and continues to extend toward the base end side, and the tip end side of the cutting groove 14A extends along the core raised portion 11 beyond the center axis O toward the opposite side.

In the front end surface 4, the short cutting edge 12 is a ridge intersecting portion between each notch 14B and the second clearance surface 18 formed on the rear side in the rotational direction. A third relief surface 19 is formed on the rotationally rear side of the second relief surface 18. A rake face 14B is formed in a notch 14B formed on the front side in the rotation direction of the minor blade 12. The second relief surface 18 of the short blade 12 is formed in a convex curved surface shape or a flat surface shape, for example, and a positive edge bevel that recedes toward the base end side is set so that the rotation locus thereof does not scrape the machined surface of the short blade 12. The cutting groove 14B of each minor cutting edge 12 extends toward the base end side so that the rear end side thereof is connected to the chip groove 5, and the front end side of the cutting groove 14B extends toward the center axis O side of the minor cutting edge 12 to the vicinity of the center axis O.

In the tip surface 4, the deepest portions in the longitudinal direction of the grooves of the cutting groove 14A of the long blade 10 and the cutting groove 14B of the short blade 12, that is, in the direction orthogonal to the machining direction of the grindstone, are formed in an arc shape in cross section, so that the flow of chips is improved, and the breakage of the tool due to the retention of chips can be suppressed. The depth F of the groove 17 formed by the intersection of the notch 14A and the notch 14B from the tip of the short blade 12 is set to be in the range of 0.05D to 0.15D, and more preferably in the range of 0.07D to 0.12D (see fig. 5). Therefore, the chips can be smoothly discharged without damaging the tool rigidity. When the depth F of the groove 17 is less than 0.05D, the chip discharge performance is deteriorated, and when it exceeds 0.15D, the tool rigidity is reduced.

In the end cutting edge, the long cutting edge 10 is recessed toward the base end side than the short cutting edge 12. Therefore, when drilling is performed in which the end mill 1 is rotated and fed in the direction of the central axis O with respect to the workpiece, that is, when drilling is performed, the outer peripheral region is first cut by the short cutting edge 12, and the central region (the central axis O side) where the short cutting edge 12 is not provided is later cut by the long cutting edge 10. Therefore, the long blade 10 is subjected to cutting processing only in a portion of the center side region that does not overlap with the rotationally cut short blade 12, and this portion is defined as the cutting edge portion 10 a.

The length of the short blade 12 is preferably set in the range of 0.23D to 0.30D. Accordingly, since the cutting loads of the cutting edge portion 10a of the long blade 10 and the short blade 12 can be set to substantially the same level, the vibration of the cutting edge portion 10a of the long blade 10 and the short blade 12 can be suppressed. The length of the short edge 12 is more preferably set in the range of 0.25D to 0.28D.

The amount of retreat (amount of recess) of the long blade 10 with respect to the short blade 12 in the direction of the central axis O is set, for example, within a range of 0.005D to 0.020D. The amount of retreat is a distance in the direction of the center axis O between the tip of the short blade 12 and the tip of the long blade 10. When the amount of retreat of the long blade 10 is within this range, chips generated by cutting with the short blade 12 and the long blade 10 are divided into the same degree, and the chips can be smoothly discharged without excessive rubbing or load when traveling in the chip groove 5. On the other hand, if the amount of retreat is less than 0.005D, the time difference between cutting by the short blade 12 and the long blade 10 is small, and the cutting of the workpiece may be performed over almost the entire length of the long blade 10, and therefore, the effect of reducing the chip volume cannot be obtained. When the amount of retreat is larger than 0.020D, the cutting load applied to the short edge 12 becomes large and the breakage becomes easy.

In fig. 3, the distance in the direction of the center axis O from the corner of the tip intersecting the short edge 12 on the ridge line of the outer peripheral edge 6 to the intersection of the cutting groove 14B of the short edge 12 and the flute 5 with the outer peripheral edge 6 is referred to as the edge width P. In the plunge cutting, machining errors, variations, height differences, and the like of the short blade 12 and the long blade 10 with respect to the workpiece within the range of the blade width P are set within the allowable error range. In the present embodiment, the blade width P is set to a length of 0.01D to 0.05D, and the distal end corner of the long blade 10 is disposed in the range of 1/2 of 0.01D to 0.05D from the distal end corner of the short blade 12 at the center of the blade width P.

Therefore, when the end mill 1 is fed laterally after drilling, the distal end corner portions of the rotating short blade 12 and the long blade 10 are sequentially cut, so that an excessive load is not applied to the distal end corner portion of the short blade 12. Therefore, the cutting edge strength of the corner portion of the tip of the short blade 12 is not impaired, and breakage can be suppressed. Moreover, the corner portions of the short cutting edge 12 and the long cutting edge 10 are positioned on the outer peripheral cutting edge 6, so that machining errors such as height differences do not occur.

In the case where the peripheral cutting edge 6 is formed so as to be curved so as to converge toward the central axis O in the tip corner where the short cutting edge 12 and the peripheral cutting edge 6 intersect, even in the case where cutting remains are generated on the machining surface of the short cutting edge 12 during the traverse, since the cutting work is performed on the tip corner where the long cutting edge 10 and the peripheral cutting edge 6 intersect after the short cutting edge 12, it is possible to prevent a height difference from remaining on the machining surface of the workpiece.

In addition, even if a machining error such as a height difference occurs in the machining surface due to a deviation between the machining point of the distal end corner of the short blade 12 and the machining point of the distal end corner of the long blade 10 in the direction of the center axis O when the side surface of the workpiece is cut by the plunge, the machining error can be within the allowable error range because the machining error is within the range of the blade width P.

Since the end mill 1 of the present embodiment has the above-described configuration, when the end mill 1 is used to cut a workpiece, for example, a drilling process of feeding in the direction of the center axis O is first performed, and then, a shoulder cutting process is performed by feeding in the lateral direction.

When the end mill 1 is fed in the direction of the central axis O while rotating at high speed about the central axis O to perform drilling, cutting is first performed by a pair of short blades 12 arranged on the outer peripheral side of the distal end surface 4 of the blade portion 3. The workpiece is cut into a ring shape by cutting the outer peripheral region with the short cutting edge 12. The chips generated by the short edge 12 have a width and volume of about half of the total length of the long edge 10. Therefore, the chips smoothly travel from the cut groove 14B into the chip groove 5 and are discharged.

Next, the long blade 10 retreated from the short blade 12 performs cutting processing on the central side region of the workpiece left after cutting with the central side cutting edge portion 10a not overlapping with the short blade 12. The chips generated by the long edges 10 have substantially the same width and volume as the chips generated by the short edges 12. Therefore, the chips are also smoothly discharged from the cut groove 14A into the chip discharge groove 5.

In this way, the chips generated by the cutting process of the short blade 12 and the long blade 10 are each cut into a width and a volume of about half of the width and volume of the chip when the cutting process is performed over the entire length of the long blade 10. Therefore, the chips are smoothly discharged from the cut grooves 14A and 14B into the chip discharge groove 5.

In particular, the rotation speed is low on the center side of the distal end surface 4 of the tool body 2, the generated chips are easily clogged, and the chips generated by the cutting edge portion 10a on the center side of the long blade 10 are small in width and volume, so that clogging of the chips in the cutting groove 14A or the chip discharge groove 5 can be reliably prevented. Further, since the cutting groove 14A of the major cutting edge 10 extends beyond the central axis O to the opposite side, the chips generated by the cutting edge portion 10a can be smoothly guided out from the cutting groove 14A to the chip discharge groove 5. Further, since the long cutting edge 10 extends radially from the center axis O side to the outer peripheral cutting edge 6 and the short cutting edge 12 is formed on the outer peripheral side of the high-speed rotation, it is difficult to break the cutting edge.

After the drilling process is completed, the end mill 1 is fed laterally to cut the shoulder of the processed surface of the workpiece.

As described above, according to the end mill 1 of the present embodiment, even in the drilling process, since the material to be cut is cut by the cutting edge portions 10a of the short cutting edge 12 and the long cutting edge 10 having the short cutting edge, the generated chip has a width and volume of about 1/2 as compared with the chip in the case of cutting through the entire length of the long cutting edge 10. Therefore, the chips can be smoothly discharged without clogging the cutting grooves 14A, 14B and the chip discharge groove 5. In particular, since the center-side rotational speed is low and the chips are easily clogged, and the width and volume of the chips generated by the cutting edge portion 10a on the center side of the long blade 10 are small, the chips can be reliably prevented from clogging in the cutting groove 14A and the chip discharge groove 5.

Further, since the tip of the long blade 10 is set back in the direction of the central axis O in the range of 0.005D to 0.02D with respect to the tip of the short blade 12, the chip biting can be suppressed and the cutting balance between the short blade 12 and the long blade 10 can be maintained. Further, since the edge width P is set to a length of 0.01D to 0.05D in the direction of the outer peripheral edge 6 from the distal end corner of the minor cutting edge 12 and the distal end corner of the major cutting edge 10 is disposed in the vicinity of the center thereof, it is possible to suppress breakage while securing the cutting strength of the distal end corner of the minor cutting edge 12 and to avoid a level difference from being generated on the machined surface during the plunge cutting.

Further, the pair of long blades 10 and the pair of short blades 12 facing each other are disposed at a predetermined interval in the end blade of the distal end surface 4, and the cutting edge portion 10a of the long blade 10 on the cutting center side and the short blade 12 on the cutting outer peripheral side are alternately arranged at the same length, so that the cutting balance is good.

Further, since the end cutting edge is formed to protrude by a predetermined length on the outer peripheral side and is rotated at high speed, the end cutting edge is less likely to be broken even at the corner of the end cutting edge 12. On the other hand, the long blade 10 is cut at a relatively low speed with the central portion as the cutting edge portion 10a, and the outer peripheral portion other than the cutting edge portion 10a also extends linearly to the outer peripheral blade 6 continuously to the cutting edge portion 10a, so that there is no corner portion or notch, and no damage or the like occurs.

The end mill 1 of the present embodiment has been described above, but the present invention is not limited to the above-described embodiment, and various different forms and embodiments can be adopted without departing from the scope of the present invention. These forms and embodiments are included in the scope of the present invention.

The following describes modifications of the present invention, and the same or similar parts or components as those of the above-described embodiments will be described with the same reference numerals.

An end mill according to a modification of the present invention will be described below.

The end mill 25 shown in fig. 6 shows a first modification.

The end mill 25 of the first modification includes three end cutting edges on the distal end surface 4. That is, one long cutting edge 10 connected to the outer peripheral cutting edge 6 through the central axis O or its vicinity and two short cutting edges 12 formed on the outer peripheral side of the tip end surface 4 are arranged at a predetermined interval. As in the above embodiment, the long blade 10 is formed so as to recede toward the base end side within a range of 0.005D to 0.02D from the short blade 12. The long blade 10 can be cut only by the inner peripheral cutting edge portion 10a that does not overlap with the rotation locus of the short blade 12 during drilling.

A notch 14A connected to the chip groove 5 is formed forward in the rotational direction of the long blade 10, and a notch 14B connected to the chip groove 5 is formed forward in the rotational direction of the short blade 12.

Further, instead of the configuration of the first modification, the three-edged end mill 25 may be configured by two long edges 10 and one short edge 12.

Next, a drill 30 as a cutting tool according to a second embodiment of the present invention will be described with reference to fig. 7 and 8.

The drill 30 according to the second embodiment of the present invention includes four end cutting edges on the distal end surface 4, as in the end mill 1 according to the first embodiment. In the drill 30, two long cutting edges 10 connected to the outer peripheral cutting edge 6 through the central axis O or the vicinity thereof and two short cutting edges 12 formed on the outer peripheral side of the tip end surface 4 are alternately arranged at a predetermined interval. As in the first embodiment, each long blade 10 is formed so as to recede toward the base end side within a range of 0.005D to 0.02D from the short blade 12. The long cutting edge 10 can be cut only by the inner cutting edge portion 10a that does not overlap with the rotation locus of the outer short cutting edge 12 during drilling.

In the drill 30 of the present embodiment, a groove-shaped thinning portion 31 is formed in the front end surface 4 in the rotational direction of the long blade 10 and the short blade 12, instead of the cutting groove 14. The thinning portion 31 provided forward in the rotation direction of the long blade 10 is denoted by reference numeral 31A and a rake face 31A, and the thinning portion 31 provided forward in the rotation direction of the short blade 12 is denoted by reference numeral 31B and a rake face 31B.

Each of the minor cutting edges 12 is formed from the outer peripheral end to a length of, for example, about 1/2 of the radius (0.5D) of the front end surface 4. The short blade 12 has a thinning portion 31B formed on an inner peripheral side portion on a forward side in a rotation direction thereof, and a chip discharge groove 5 formed on an outer peripheral side portion. The outer peripheral side portion of the short blade 12 intersects the chip groove 5 and is bent toward the base end side. The length of the short blade 12 is preferably set in the range of 0.23D to 0.30D, preferably 0.25D to 0.28D.

In the drill 30 of the present embodiment, the long blades 10 and the short blades 12 may be arranged at equal intervals, for example, at 90 ° intervals, or may be arranged at unequal intervals, in order to equalize the cutting load during drilling and suppress vibration. A thinning portion 31A connected to the chip groove 5 is formed on the front side in the rotation direction of each long blade 10.

In the second embodiment, when the drill 30 is fed in the direction of the central axis O while rotating at high speed around the central axis O to perform drilling, cutting is performed by the pair of short blades 12 arranged on the outer peripheral side of the tip surface 4 of the blade portion 3 first. The workpiece is drilled into a ring shape by cutting the outer peripheral region with the short cutting edge 12. The chips generated by the short blade 12 have a width and volume of approximately half of the total length of the long blade 10, and therefore, the chips are smoothly discharged from the thinning portion 31B into the chip discharge groove 5.

Next, with the long blade 10 retreated from the short blade 12, a hole is formed in the center side region left by cutting the workpiece with the center side cutting edge portion 10a that does not overlap with the short blade 12. The chips generated by the long edges 10 have substantially the same width and volume as the chips generated by the short edges 12. Therefore, the chips are also smoothly advanced and discharged from the thinning portion 31A in the chip discharge groove 5.

In this way, the chips generated by the cutting process of the short blade 12 and the long blade 10 are each cut into a width and a volume of about half of the width and volume of the chip when the cutting process is performed over the entire length of the long blade 10. Therefore, the chips are smoothly discharged from the thinning portions 31A and 31B into the chip discharge groove 5. Therefore, when drilling, it is possible to prevent the occurrence of chips or damage to the tool body due to clogging with chips.

In the first embodiment and the modification described above, the square end mill is explained as the end mill 1, and the present invention is applicable to a radial end mill, a ball end mill, and the like, instead of the square end mill. In the second embodiment, drilling can be performed as the drill 30. As a modification of the drill 30 of the second embodiment, three end blades can be used. In this case, one of the end cutting edges may be the long cutting edge 10 or the short cutting edge 12, and the other two end cutting edges may be the short cutting edge 12 or the long cutting edge 10.

In the above embodiments and modifications, the end mill 1 and the drill 30 having four end cutting edges and three end cutting edges have been described, but two or more than five end cutting edges may be provided. In this case, the long blades 10 and the short blades 12 are preferably arranged alternately in the circumferential direction of the distal end surface 4. The number of rows of the long blades 10 and the short blades 12 can be set as appropriate.

In each of the above embodiments, the end cutting edges arranged on the distal end surface 4 are configured such that the long cutting edges 10 and the short cutting edges 12 are alternately arranged, and the arrangement intervals are alternately set to a range of 97 ° to 102 °, a range of 78 ° to 83 °, 90 °, and the like, and the arrangement intervals of the end cutting edges can be appropriately set. For example, the long edges 10 and the short edges 12 may be alternately arranged at appropriate equal intervals or unequal intervals.

Further, by setting the edge bevel of the third relief surface 16 of the long blade 10 to be 3 to 5 ° larger than the edge bevel of the third relief surface 19 of the short blade 12, the chip discharge performance of the short blade 12 can be improved, and the limit value of the feed speed of the end mill 1 can be improved.

In the end cutting edges of the embodiments, the modifications, and the like, the long cutting edge 10 is included in the first cutting edge, and the short cutting edge 12 is included in the second cutting edge. The notch 14A and the thinning portion 31A of the long blade 10 are included in the first groove portion, and the notch 14B and the thinning portion 31B of the short blade 12 are included in the second groove portion.

The preferred embodiments and modifications of the present invention have been described above, and the present invention is not limited to the above-described embodiments and modifications. Additions, omissions, substitutions, and other modifications can be made to the structure without departing from the spirit of the invention. The present invention is not limited by the foregoing description, but is only limited by the scope of the claims.

Industrial applicability

The present invention relates to a cutting tool including an end mill having a bottom cutting edge formed on a distal end surface of a tool body. The cutting tool of the present invention is a cutting tool including: a plurality of outer peripheral blades spirally formed at predetermined intervals on an outer peripheral surface of a tip side of the tool body, the tool body being rotatable around a central axis; a chip groove formed on the front side of the rotation direction of the peripheral blade; and a plurality of bottom blades formed on the front end surface of the tool body and connected with the peripheral blades. The end blade is characterized in that: a first cutting edge formed to extend from the central axis of the front end surface or the vicinity thereof toward the outer peripheral edge; and a second cutting edge formed on the outer peripheral side of the distal end surface, wherein the first cutting edge is set to be set back toward the base end side of the tool body from the second cutting edge.

According to the cutting tool of the present invention, during drilling, the outer peripheral side is cut by the second cutting edge slightly later than the second cutting edge and the center side is cut by the first cutting edge, and therefore, chips are generated separately on the outer peripheral side and the tool center side of the tool. Therefore, in the drilling process, the width and volume of the chips are small, and the chips can be smoothly discharged without being blocked by the chip discharge groove. Since the first cutting edge is formed to extend in the direction from the center axis side to the outer peripheral edge and the second cutting edge is formed on the outer peripheral side rotating at high speed, the bottom edge is less likely to be damaged.

Claims (7)

1. A cutting tool comprising: a plurality of outer peripheral blades spirally formed at predetermined intervals on a distal-side outer peripheral surface of a tool body that is rotatable about a central axis; a chip groove formed on the front side of the peripheral blade in the rotation direction; and a plurality of end blades formed on a front end surface of the tool body and connected to the outer peripheral blade, the cutting tool being characterized in that,

the bottom blade includes:

a first cutting edge formed to extend from the central axis or the vicinity of the central axis of the tip end surface toward an outer peripheral edge; and

a second cutting edge formed on an outer peripheral side of the tip end surface,

the first cutting edge is provided so as to recede toward the base end side of the tool body from the second cutting edge.

2. The cutting tool according to claim 1, wherein an outer diameter of the bottom edge of the distal end surface is D, and the first cutting edge is set back to a proximal end side with respect to the second cutting edge within a range of 0.005D to 0.020D.

3. The cutting tool of claim 1, wherein a first flute portion formed in the first cutting edge extends from a position beyond an opposite side of the central axis to connect to the flute.

4. The cutting tool according to claim 1, wherein an outer diameter of the bottom edge of the tip surface is D, and a length of the second cutting edge in a radial direction on the tip surface is set within a range of 0.23D to 0.30D.

5. The cutting tool of claim 1, comprising: a first groove portion formed in front of the first cutting edge in a rotation direction; and a second groove portion formed in front of the second cutting edge in the rotation direction, wherein the groove portion at the intersection of the first groove portion and the second groove portion is set to have a depth within a range of 0.05D to 0.15D from the second cutting edge.

6. The cutting tool of claim 1,

the outer diameter of the end edge of the end face is D, and a cutting edge width in the central axis direction from a distal end corner of the second cutting edge to a boundary between a second groove formed forward of the second cutting edge in the rotation direction and the flute is set within a range of 0.01D to 0.05D in the longitudinal direction of the outer peripheral edge, and the distal end corner of the first cutting edge is located within the range of the cutting edge width.

7. The cutting tool according to claim 1, wherein the bottom edge is an unequal four-edged edge, or the peripheral edge is set to an unequal lead.

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