EP2703138A1

EP2703138A1 - Cutting blade and rotary cutting tool

Info

Publication number: EP2703138A1
Application number: EP12776292.0A
Authority: EP
Inventors: Satoru Nishio; Hideto Kozawa; Eisuke Muto
Original assignee: Kanefusa KK; Kanefusa Corp
Current assignee: Kanefusa KK; Kanefusa Corp
Priority date: 2011-04-27
Filing date: 2012-04-04
Publication date: 2014-03-05
Also published as: EP2703138A4; TW201244901A; WO2012147282A1; JP2012228842A

Abstract

The invention provides a cutting blade reduced in thickness and accordingly produced with less blade materials wherein the flexural rigidity of the whole blade is improved. A base material used in the blade is a steel material, a cemented carbide, or a steel material with a cemented carbide used in an edge part of the blade alone. The blade is a long and thin plate having a nearly rectangular shape and elastically deformable. The blade is approximately 0.5 mm in thickness. In the blade, the use of any costly blade materials is minimized. As a result, the blade is made available at low prices. A flank face of the blade has a clearance angle that equals 0°. In the blade, a predefined area of a rake face including a cutting edge is coated with a chromium nitride hard film. The blade is bent in a direction opposite to a direction of rotation and then fitted in a fitting groove of the tool body. The twist angles on end-surface sides of the blade are positive and negative angles. Therefore, the depth of the blade is circumferentially large enough, and the blade thereby has a higher flexural rigidity than its original flexural rigidity before bending.

Description

TECHNICAL FIELD

The present invention relates to a plate-shaped cutting blade to be fitted in a cutting tools, for example, a planar head, a milling cutter with a shaft, a fixed knife planer, and a cutter head for molder. The invention further relates to rotary cutting tools using such cutting blades.

BACKGROUND ART

A known example of such cutting blades is disclosed in the Patent Document 1; straight knives that are fitted in blade grooves formed in the outer peripheral surface of a cutter head body in parallel with the axial direction thereof. When the straight knives are used, however, a cutting resistance generated while a work material is being cut is applied to all of the blades at the same time, and the blades, if having a small flexural rigidity, are easily buckled in parts near the cutting edges thereof. To avoid the problem, it is necessary that the blades should be increased in thickness to ensure a flexural rigidity. This, however, requires a large volume of expensive blade materials, unnecessarily increasing the cost of the blades. Another problem with the straight knives is loud noises during the cutting operation that may worsen the work environment.
In the cutting device for woodworking disclosed in the Patent Document 2, for example, blades are spirally twisted and fitted in fitting grooves spirally formed in the outer peripheral surface of its cutter head. When the blades are used, the cutting resistance generated while the work material is being cut is applied to the blades along the spirals, and noises during the cutting operation are thereby effectively reduced. However, the blades of this cutting device also have a relatively small flexural rigidity, though it may not be as small as that of the straight knives. Hence, the problem of buckling is still very likely to occur in these blades near the cutting edges, and the occurrence of buckling is unavoidable with thin blades. This conventional blade has other problems described below. Because the cutting edge of the blade is inclined in a direction relative to the shaft line, an outward force in the direction is applied to the work material on one end side of the blade, which easily causes burr and/or chipping at an either side edge of the work material. In the cutting device, the outward force unidirectionally exercised by the twisted blade is imposed on the work material and the work material is thereby laterally moved. This destabilizes the cutting operation.

CITATION LIST

Patent Document

Patent Document 1: Japanese Patent No. 3474503
Patent Document 2: Japanese Patent Application Laid-Open No. 50-54974 A

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

The invention was accomplished to solve these problems. The invention provides a cutting blade reduced in thickness that can be accordingly produced with less cutting materials and that can still increase the flexural rigidity of the whole blade. The invention further provides a rotary cutting tool where the cutting blade is used.

MEANS FOR SOLVING PROBLEMS

In order to achieve the above subjects, the invention provides a cutting blade to be fitted in a tool body characterized as follows. The blade has a cutting edge whose rake face is coated with a harder material than a base material used in the blade, and the blade has a thickness from 0.2 mm to 0.8 mm. The thickness of the blade may be from 0.2 to 0.8 mm, and preferably from 0.3 to 0.6 mm. Any thicknesses of the blade larger than 0.8 mm undermine a life improvement effect to be achieved in the blade. The blade having any thicknesses smaller than 0.2 mm is reduced in strength and hence practically useless.
By thus reducing the blade in thickness, the invention succeeds in large cost reduction of the blade materials, thereby making the blade available at lower prices. The invention reduces the blade thickness, thereby reducing the length of the flank face along a rotational direction. As a result, a wear width of the flank face can be controlled to an extent of [blade thickness ÷ cos (rake angle)] . In the cutting blade, the length of the flank face along the rotational direction is reduced as compared to any conventional blades larger in thickness. This allows the blade to be still usable even after the cutting edge of the blade is used over a longer period of time than the cutting edges of such thick blades conventionally used. This means that the blade has a service life a few times as long as that of any conventional blade. According to the invention, the rake face is coated with a hard film, and thus excessive abrasion on the rake-face side of the cutting edge is prevented. This increases the durability of the blade. According to the invention, the rake face is coated with a hard film, and thus the flank face of the blade is selectively abraded more aggressively than the rake face. This helps to maintain the sharpness of the cutting edge and prevents any heavy contact between the flank face and the work material, thereby reducing the cutting resistance of the blade.
Preferably, the blade according to the invention is fitted in the tool body in a protruding manner in a direction opposite to a direction where the work material is cut, and twist angles of both end side portions are positive and negative angles. A definition is given to an angle of inclination of the blade from the shaft line perpendicular to the cutting direction on the outer peripheral surface of the tool body that is the twist angle of the cutting edge relative to the shaft line. Viewing the cutting edge from the work-material side, the twist angle is a positive angle when the cutting edge is inclined in a clockwise direction relative to the shaft line, and the twist angle is a negative angle when the cutting edge is inclined in a counterclockwise direction relative to the shaft line. According to the invention, the blade is bent in a manner that protrudes in the direction opposite to the cutting direction. Thereby, a large depth of the blade is three-dimensionally secured in the cutting direction, and the blade thereby has a higher flexural rigidity than its original flexural rigidity before bending. This prevents the cutting edge of any thin blade from buckling. According to the invention, an inward force from the cutting edge of the blade is applied to the work material at both side edges of the work material during the cutting operation. This effectively prevents the occurrence of burr and/or chipping at the both side edges of the work material. According to the invention, the blade is bent in a manner that protrudes in the direction opposite to the cutting direction of the work material, and the coating hard film formed on the rake face is thereby compressed. This increases the rigidity of the hard film.
According to the invention, the blade is fitted in the tool body in a protruding manner in the cutting direction of the work material, and the twist angles of the both end side portions of the cutting edge in the blade are respectively positive and negative angles. Although the blade according to the invention is bent in a protruding manner in the cutting direction, a large depth of the blade is three-dimensionally secured in the cutting direction, and the blade thereby has a higher flexural rigidity than its original flexural rigidity before bending. This prevents the cutting edge of any thin blade from buckling. According to the invention, an outward force is applied to the work material by the blade at the both side edges of the work material during the cutting operation. Thereby, chips generated while the work material is being cut can be discharged from the center toward outer ends on both sides of the work material. With this technical feature, the invention facilitates the discharge of the chips.
Preferably, a base material used in the blade according to the invention is a steel material, a cemented carbide, or a steel material with a cemented carbide used in an edge part of the blade alone. Examples of the steel material include tool steels, high speed tool steels, and stainless steels. When any of these base materials is used, a part of the blade near the cutting edge thereof is slightly elastically deformed by the cutting resistance imposed on the blade, and the flank face thereby moves away from the work material toward the opposite side to the cutting direction. With this technical feature, the invention reduces the cutting resistance imposed on the blade, thereby enabling the cutting operation to be smoothly performed.
According to the invention, when the cutting blades described so far are fitted in the tool body and subjected to jointing, a rotary cutting tool can be provided. In the rotary cutting tool, any possible error in the cutting radius of each blade edge can be reduced to a minimum by jointing similarly to the conventional blades. Because the blades are reduced in thickness, the jointing may be performed to the whole thicknesses of the blades, in which case the edges of the respective blades can be easily controlled to stay in the range of predefined cutting radii.

EFFECT OF THE INVENTION

By thus reducing the blade in thickness, the invention succeeds in large cost reduction of the blade materials, thereby making the blade available at lower prices. According to the invention, the length of the flank face along the rotational direction can be reduced. As a result, a wear width of the flank face can be controlled to at most an extent of [blade thickness ÷ cos (rake angle)]. According to the invention, the rake face is coated with the hard film, and thus excessive abrasion on the rake-face side of the cutting edge is prevented. This increases the durability of the blade. Further, the flank face of the blade is selectively abraded more aggressively than the rake face. This helps to maintain the sharpness of the cutting edge and prevents any heavy contact between the flank face and the work material, thereby reducing the cutting resistance of the blade.
According to the invention, the blade is bent so as to protrude in the direction opposite to the cutting direction or bent so as to protrude in the cutting direction. Thereby, a large depth of the blade is three-dimensionally secured in the cutting direction, and the blade thereby has a higher flexural rigidity than its original flexural rigidity before bending. As a result, a high flexural rigidity can be imparted even to thin blades. According to the invention, the blade is bent in the direction opposite to the cutting direction or in the cutting direction. Not only that, the twist angles of the both end side portions are arranged to be respectively positive and negative angles. Hence, the occurrence of burr and/or chipping is prevented in the work material on the both end sides of the blade or the discharge of the chips is facilitated depending on whether the blade is bent so as to protrude in the direction opposite to the cutting direction or bent so as to protrude in the cutting direction. According to the invention, the base material of the blade is a steel material, a cemented carbide, or a steel material with a cemented carbide used in an edge part of the blade alone. When any of these base materials is used, a part of the blade near the cutting edge thereof is slightly elastically deformed by the cutting resistance, and the flank face thereby moves away from the work material toward the opposite side to the cutting direction. As a result, the cutting resistance imposed on the blade is reduced, and the cutting operation can be thereby smoothly performed. The invention is further advantageous in that the jointing is facilitated in the rotary cutting tool mounted with a plurality of the cutting blades.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a front view of a cutter head according to an example 1 of the invention.
Fig. 2 is a right side view of the cutter head.
Fig. 3 is a cross-sectional view of the illustration of Fig. 1 along the direction of a line III-III.
Fig. 4 is a cross-sectional view of the illustration of Fig. 1 along the direction of a line IV-IV.
Fig. 5A is a front view of a blade in a curved state.
Fig. 5B is a bottom view of the curved blade.
Fig. 5C is a right side view of the curved blade.
Fig. 5D is a partial cross-sectional view of the curved blade (a conventional blade is also illustrated).
Fig. 6A is a front view of a wedge bar.
Fig. 6B is a bottom view of the wedge bar.
Fig. 6C is a right side view of the wedge bar.
Fig. 7 is an illustration of a twist angle in a cutting edge.
Fig. 8 illustrates a shape of the blade fitted in the cutter head according to a modified example 1 of the invention.
Fig. 9 illustrates a shape of the blade fitted in the cutter head according to a modified example 2 of the invention.
Fig. 10 illustrates a shape of the blade fitted in the cutter head according to a modified example 3 of the invention.
Fig. 11 illustrates a shape of the blade fitted in the cutter head according to a modified example 4 of the invention.
Fig. 12 illustrates a shape of the blade fitted in the cutter head according to a modified example 5 of the invention.
Fig. 13 illustrates a shape of the blade fitted in the cutter head according to a modified example 6 of the invention.
Fig. 14 illustrates a shape of the blade fitted in the cutter head according to a modified example 7 of the invention.
Fig. 15 illustrates a shape of the blade fitted in the cutter head according to a modified example 8 of the invention.
Fig. 16 is a front view of a cutter head according to an example 2 of the invention.
Fig. 17 is a right side view of the cutter head.
Fig. 18A is a front view of a blade in a curved state.
Fig. 18B is a bottom view of the curved blade.
Fig. 18C is a right side view of the curved blade.
Fig. 19 illustrates a shape of the blade fitted in the cutter head according to a modified example 9 of the invention.
Fig. 20 illustrates a shape of the blade fitted in the cutter head according to a modified example 10 of the invention.
Fig. 21 illustrates a shape of the blade fitted in the cutter head according to a modified example 11 of the invention.
Fig. 22 illustrates a shape of the blade fitted in the cutter head according to a modified example 12 of the invention.
Fig. 23 illustrates a shape of the blade fitted in the cutter head according to a modified example 13 of the invention.
Fig. 24 illustrates a shape of the blade fitted in the cutter head according to a modified example 14 of the invention.
Fig. 25 illustrates a shape of the blade fitted in the cutter head according to a modified example 15 of the invention.
Fig. 26 illustrates a shape of the blade fitted in the cutter head according to a modified example 16 of the invention.
Fig. 27 is a plan view of a router bit according to an example 3 of the invention.
Fig. 28 is a front view of the router bit.
Fig. 29 is a right side view of the router bit.
Fig. 30 is a cross-sectional view of the illustration of Fig. 28 along the direction of a line A-A.
Fig. 31A is a front view of a blade.
Fig. 31B is a bottom view of the blade.
Fig. 32A is a front view of a blade according to a modified example 17 of the invention.
Fig. 32B is a bottom view of the blade according to the modified example 17.
Fig. 33 is a front view of a cutter head mounted with blades according to an example 4 of the invention.
Fig. 34 is a right side view of the cutter head.
Fig. 35 is a plan view of the cutter head.

MODE FOR CARRYING OUT THE INVENTION

An embodiment of the invention is hereinafter described referring to the accompanied drawings. Figs. 1, 2, 3, and 4 are respectively a front view, a right side view, a cross-sectional view along the direction of a line III-III, and a cross-sectional view along the direction of a line IV-IV of a cutter head for woodworking according to an example 1 of the invention. The cutter head is mounted with cutting blades fitted in fitting grooves formed in the cutter head. This cutter head is illustrated as an example of the rotary cutting tool according to the invention, for instance, cutter head and planar head.
A cutter head for woodworking 10 has four fitting grooves 13 formed in a body 11 made of a metal. The body 11 has an elongated cylindrical shape with a shaft hole 12 formed at the center thereof. The fitting grooves 13 are formed in an identical shape at four positions circumferentially spaced at equal intervals on the outer peripheral side of the body 11. The fitting grooves 13 are dented in substantially radial directions of the body 11 and penetrating through between end surfaces 11a and 11b along the axial direction of the body 11. The fitting grooves 13 each has a nearly rectangular shape in cross section when viewed from the side surface illustrated in Fig. 2. According to this example, a vicinity of the end surface 11a on the inner side thereof is a reference position at which a gauge member for guiding and transporting a work material (not illustrated in the drawings) is positionally adjusted.
The fitting groove 13 is curved in an arc shape in a direction opposite to a direction of rotation R of the body 11. The fitting groove 13 is formed so that both sides thereof in the axial direction relative to the axial center of the body 11 are symmetrical. The fitting groove 13 is inclined so that a rake angle δ is a positive angle. A front wall surface 14 and a rear wall surface 15 of the fitting groove 13 are respectively located on the forward side and the backward side in the direction of rotation. These front and rear wall surfaces are equally spaced from each other along the entire length of the fitting groove 13. A bottom wall surface 16 of the fitting groove 13 is a flat surface perpendicular to the front and rear wall surfaces 14 and 15 and extending in parallel with the axial direction. With a blade 21, which will be described later, already fitted in the fitting groove 13, an angle of inclination of the rear wall surface 15 from the radial direction represents a rake angle δ that equals 15° on the end surfaces 11a and 11b of the body 11. The angle of inclination increases along the curve of the fitting groove 13 and reaches the largest rake angle 25° at the center of the body 11 in the longitudinal direction thereof. As described, the fitting groove 13 is curved in an arc shape, and the bottom wall surface 16 of the fitting groove 13 is in parallel with the shaft. Hence, upper edges of the front and rear wall surfaces 14 and 15 are each recessed in a curved arc shape relative to the bottom wall surface 16 when viewed from the forward side in the direction of rotation.
The body 11 has dented notches 17 opening in the direction of rotation R at positions near the upper edges of the front wall surfaces 14. The dented notches 17 are curved and dented in small measure from the outer peripheral surface of the body 11 and extending between the both ends of the body 11 in the axial direction thereof. The body 11 further has fitting holes 18. The fitting holes 18 are formed more forward in the direction of rotation R than the dented notches 17 at five positions; a middle position and positions near the right-hand and left-hand ends in the axial direction, and intermediate positions therebetween. The fitting holes 18 are through holes extending substantially in parallel with one another. The fitting holes 18 are each extending through to the fitting groove 13 along a direction perpendicular to the shaft of the body 11 and a direction of inclination of the dented notch 17. The fitting holes 18 each has an entry part 18a cylindrically dented and exposed from the surface of the body 11, and a threaded part 18b constituting a thread groove at the tip of the entry part 18a. In the fitting hole 18, a bolt 19 is inserted from the side of the entry part 18a and screwed into the threaded part 18b so that a tip side of the bolt 19 protrudes into the fitting groove 13.
The fitting grooves 13 are each mounted with a blade 21 and a wedge bar 24. As illustrated in Figs. 5A to 5D, a base material used in the blade 21 is a steel material, a cemented carbide, or a steel material with a cemented carbide used in an edge part of the blade alone. The blade 21 is a long and thin plate having a nearly rectangular shape and elastically deformable. The blade 21 is approximately 0.3 to 0.6 mm in thickness. The thickness of the blade 21 differs depending on the base material used therein and the length of protrusion from the body 11, which will be described later. The blade 21 is easily formed by punching the base metal plate. The blade 21 curved as illustrated in the drawings has a length almost equal to that of the fitting groove 13. A bottom surface 21a of the blade 21 on the lower edge side is straight, and a flank face 21b of the blade 21 on the upper edge side including a cutting edge 21c is recessed in small measure inward in an arc shape centered on the center of the blade 21 in the longitudinal direction thereof. Having been subjected to the jointing, the flank face 21b of the blade 21 has a clearance angle γ that equals 0° as illustrated in Fig. 5D.
In the blade 21, a predefined area of a rake face 21d including the cutting edge 21c on one side thereof is coated with a hard film 22. The hard film 22 is a chromium nitride film containing CrN, Cr₂N or a mixture of CrN and Cr₂N. The thickness of the hard film 22 is approximately 0.5 to 10 µm. The material of the hard film 22 is suitably selected depending on a material to be cut and working conditions. Describing a coating method, a plurality of the blades 21 are stacked on one another except the predefined areas on the side of the rake faces 21d thereof to be coated with the hard film 22. Then, the blades 21 can be efficiently coated with the hard film 22 at once. This achieves large cost reduction in the formation of the hard film. There are other options; the whole rake face 21d may be coated with the film, the flank face 21b may also be coated with the film, and the film coating may be applied to the both faces of the blade 21 so that the two surfaces of the blade can be both used as the rake face.
As illustrated in Figs. 6A to 6C, the wedge bar 24 has an elongated square bar shape that is curved in an arc shape that corresponds to the shape of the fitting groove 13. In the wedge bar 24, a front side surface 24a on the forward side in the direction of rotation and a rear side surface 24b on the backward side in the direction of rotation have an equal overall length, and a bottom surface 24c is a flat surface extending perpendicular to the front side surface 24a and the rear side surface 24b. Describing the curved shape of the wedge bar 24, the front side surface 24a is recessed and the rear side surface 24b is bulging. An upper surface 24d of the wedge bar 24 is a curved surface recessed inward in an arc shape between the front and rear side surfaces 24a and 24b. In the front side surface 24a, securing holes 25 are formed at five positions near the upper surface 24d; a middle position and positions near the right-hand left-hand ends in the longitudinal direction, and intermediate positions therebetween. With the wedge bar 24 already inserted and fitted in the fitting groove 13, the securing hole 25 is located coaxial with the fitting hole 18 of the body 11 in a manner that corresponds to a position where the fitting hole 18 is opening in the fitting groove 13.
Below is described how to fit the blade 21 and the wedge bar 24 in the fitting groove 13 of the body 11. First, the wedge bar 24 is inserted and fitted in the fitting groove 13. Then, the bottom surface 24c is placed on the bottom wall surface 16 of the fitting groove 13, and both ends of the wedge bar 24 are adjusted to be flush with the end surfaces 11a and 11b of the body 11. Then, the blade 21, being curved with the rake face 21d thereof facing the wedge bar 24, is inserted and fitted in an arc-shaped interval between the rear wall surface 15 of the fitting groove 13 and the rear side surface 24b of the wedge bar 24. Then, the bottom surface 21a is pushed against the bottom wall surface 16 of the fitting groove 13, and a surface 21e opposite to the rake face 21d is pushed against the rear wall surface 15. Then, the bolt 19 is inserted in the fitting hole 18 from the side of the entry part 18a. When the bolt 19 is screwed into the threaded part 18b and fastened, a tip of the bolt 19 is inserted in the securing hole 25 formed in the front side surface 24a of the wedge bar 24 and pushed against the wedge bar 24. Then, the blade 21 is pushed against the rear wall surface 15 of the fitting groove 13. As a result, the blade 21 and the wedge bar 24 are firmly secured in the fitting groove 13. The blade 21 is bent in an arc shape and then fitted in the fitting groove 13. In such a handling, it is unnecessary to twist the blade 21. The bottom surface 21a of the blade 21 and the bottom surface 24c of the wedge bar 24 are both flat surfaces. These bottom surfaces are easily put on the bottom wall surface 13 of the fitting groove 13 which is a flat surface as well. In this manner, the blade 21 and the wedge bar 24 can be easily fitted in the fitting groove 13 with a high precision.
The blade 21 is curved in the direction opposite to the direction of rotation R in an arc shape that corresponds to the shape of the fitting groove 13 and securely fitted therein. The flank face 21b of the blade 21c including the cutting edge 21c protrudes by approximately 0.5 mm from the outer peripheral surface of the body 11. The length of protrusion of the edge of the blade 21 from the body 11 and the blade thickness have the following relationship. The blade 21 having the edge protruding by 0.5 mm is suitably 0.5 mm in thickness when any steel material is used as its base material, and suitably 0.3 mm in thickness when any cemented carbide is used as its base material. The blade 21 having the edge protruding by 0.3 mm is suitably 0.3 mm in thickness when any steel material is used as its base material, and suitably 0.2 mm in thickness when any cemented carbide is used as its base material. The blade 21 having the edge protruding by 0.8 mm is suitably 0.8 mm in thickness when any steel material is used as its base material, and suitably 0.6 mm in thickness when any cemented carbide is used as its base material. When any cemented carbide is used as the base material of the blade, the blade can be reduced in thickness as compared to blades of steel materials equally protruding, and the blade can be protruded farther than blades of steel materials equally thick.
A part of the upper surface 24d of the wedge bar 24d on the side of the rear side surface 24b is located on the inner side of the blade 21 by approximately 1 mm. A part of the upper surface 24d on the side of the front side surface 24a is joined to the dented notch 17 exposed from the outer peripheral surface of the body 11 through an equal degree of inclination. By thus suitably providing the upper surface 24d of the wedge bar 24 and the dented notch 17 of the body 11 on the side of the rake face 21d of the blade 21, the discharge of chips generated by the cutting operation is facilitated.
As describe above, after the blade 21 is securely held down with the wedge bar 24 and thereby fitted in the fitting groove 13 of the body 11, a twist angle, which is an angle of inclination of the blade 21 from the shaft center on the outer peripheral surface of the body 11, is a negative twist angle that changes in a curve on the side of the end surface 11a of the body 11 but is a positive twist angle that changes in a curve on the side of the other end surface 11b of the body 11. As illustrated in Fig. 7, regarding the direction of rotation R of the body 11 as a direction of 12 o'clock, the twist angle θ of the blade 21 is positive when the blade is inclined clockwise (CW) from the shaft center but is negative when the blade is inclined counterclockwise (CCW) from the shaft center. The four blades 21 securely fitted in the fitting grooves 13 of the body 11 are subjected to the jointing with grindstone to correct any variability of outer diameters of the cutting edges 21c. Since the blade 21 according to the example is as small in thickness as approximately 0.5 mm, the jointing conventionally targeted for the cutting edge 21c may be performed to all over the outer peripheral flank face 21b. The flank face 21b is accordingly subjected to cylindrical grinding and thereby formed in an arc shape with a constant radius, and the clearance angle γ becomes 0°.
According to the example 1 described so far, the thickness of each blade 21 is reduced to approximately 0.5 mm. This minimizes the use of any costly materials for the blade 21, thereby making the blade 21 available at far lower prices than the conventional blades approximately 3 mm in thickness. By thus reducing the thickness of the blade 21, the example 1 succeeds in making the flank face 21b smaller. As a result, a wear width of the flank face 21b can be controlled to an extent of [blade thickness ÷ cos (rake angle δ) ÷ cos (twist angle θ)]. Comparing the blade 21 to a conventional blade 21X having the thickness of 3 mm illustrated in Fig. 5D, the conventional blade 21X needs polishing again when a cutting edge of the blade 21X is abraded by approximately 1 mm and receded to a line x, whereas the blade 21, even if further abraded, is still usable because the cutting edge 21c of the blade 21 having the clearance angle γ that equals 0° retains its sharpness. According to the example 1, therefore, the blade 21 can still be used even after the cutting edge 21c is receded beyond the limit of the conventional thick blade 21X. Thus, the blade 21 has a service life a few times as long as that of the blade 21X. According to the example 1, the rake face 21d is coated with the hard film 22. This avoids excessive abrasion of the rake face 21d and thereby improves the durability of the blade 21. Further, the abrasion of the flank face 21b of the blade 21 is more aggressive than the abrasion of the rake face 21d. This avoids any heavy contact between the flank face 21b and the work material, thereby reducing the cutting resistance of the blade 21.
According to the example 1, each blade 21 is curved in an arc shape in the direction opposite to the direction of rotation, and the twist angles θ on the sides of the end surfaces 11a and 11b of the blade 21 are negative and positive. Then, the depth of each blade 21 is three-dimensionally large enough in the circumferential direction, and the blade 21 thereby has a higher flexural rigidity than its original flexural rigidity before bending. This technical feature of the example 1 certainly promises such a high flexural rigidity although the thickness of each blade 21 is as small as approximately 0.5 mm. According to the example 1, on the both end sides of the blade 21 are the portions inclined through the positive and negative twist angles. Therefore, oppositely directed forces are laterally applied to the work material during the cutting operation and hence counteract each other. This controls any resistance imposed on the work material during the cutting operation in one of the lateral directions, thereby preventing the work material from moving in the lateral direction. As a result, the cutting operation performed by the cutter head 10 is stabilized.
According to the example 1, the blade 21 is curved in an arc shape in a manner that protrudes in the direction opposite to the direction of rotation R, and the twist angles θ on the both end sides of the blade 21 are negative and positive. Thereby, an inward force from the blade 21 is applied to the work material at the both side edges of the work material during the cutting operation. This effectively prevents the occurrence of burr and/or chipping at the both side edges of the work material. This technical advantage is particularly effective with materials to be cut made of fibrous woods having directionality. According to the example 1, the bent blades 21 are used. This prevents that the whole blade 21 contacts the work material at once, thereby succeeding in noise reduction during the cutting operation. According to the example 1, the base material of the blade 21 is a steel material, a cemented carbide, or a steel material with a cemented carbide used in the edge part of the blade alone. When the cutting resistance is imposed on the blade 21 thus characterized, the blade 21 thereby slightly elastically deforms and warps toward the flank-face side, moving away from the work material. With this technical feature, the example 1 reduces the cutting resistance imposed on the blade 21, thereby enabling the cutting operation to be smoothly performed.
Next, modified examples 1 to 8 of the example 1 are hereinafter described referring to Figs. 8 to 15. The modified examples 1 to 8 describe different arrangements of the blade according to the example 1. The drawings only illustrate the blade alone, omitting the fitting groove and the wedge bar. According to the example 1, the both ends of the blade 21 are situated on a line in parallel with the shaft center. According to the modified example 1, two ends of a blade 21A are not both situated on a line (K) in parallel with the shaft center as illustrated in Fig. 8.
According to the example 1, the blade 21 is symmetric with the apex of curve thereof being positioned at the center in the longitudinal direction. According to the modified example 2, a blade 21B is located with an apex of curve T being displaced to vicinity of the end surface 11a of the body 11 as illustrated in Fig. 9. According to the modified example 2, the twist angles of the cutting edge are always negative and positive at crosswise both ends of any work materials having widths smaller than the length of the body 11. When a work material made of a fibrous wood having directionality, for example, is cut, the modified example 2 effectively controls the occurrence of burr and/or chipping at both side edges of such a work material irrespective of any widths of the work material.
In contrast to the blade 21 having one curved portion according to the example 1, a blade 21C according to the modified example 3 includes two continuous curved and arc-shaped portions forming a wavy shape as illustrated in Fig. 10.
Instead of the blade 21 curved in an arc shape according to the example 1, a blade 21D according to the modified example 4 is symmetrically bent at the center in the longitudinal direction as illustrated in Fig. 11.
A blade 21E according to the modified example 5 is similar to the blade according to the modified example 4 except that an apex of curve U is displaced to vicinity of the end surface 11a of the body 11 as illustrated in Fig. 12. Similarly to the modified example 2, the modified example 5 can effectively prevent the occurrence of burr and/or chipping at the both side edges of the work material irrespective of any widths of the work material.
In contrast to the blade 21D having one bent portion according to modified example 4, a blade 21F according to the modified example 6 includes a plurality of bent portions that are continuously formed as illustrated in Fig. 13.
As illustrated in Fig. 14, a blade 21G according to the modified example 7 has an intermediate portion linearly extending in parallel with the axial direction and arc-shaped portions on both end sides thereof.
Instead of the blade 21C according to the modified example 3, the modified example 8 provides a blade 21H having an S-like wavy shape as illustrated in Fig. 15. Similarly to the example 1, these modified examples 1 to 8 ensure a flexural rigidity with the thin blade 21H. The modified examples 1 to 7 accomplish the effect of burr and/or chipping prevention at the both side edges of the work material. However, the modified example 8 alone fails to accomplish such an effect on the side of one end surface of the body 11.
An example 2 of the invention is hereinafter described referring to Figs. 16 and 17.
Contrary to the blade 21 according to the example 1, a blade 35 according to the example 2 is fitted in a fitting groove 33 in a manner that protrudes in a curved arc shape in a direction of rotation R which is a cutting direction of a cutter head for woodworking 30. In contrast to the cutter head 10 according to the example 1, the cutter head 30 has fitting grooves 33 formed in an outer peripheral surface of a cylindrical body 31 having a shaft hole 32. The fitting groove 33 is curved in an arc shape in the direction of rotation R and has symmetric ends on axial both sides of the body 31 relative to the center of the body 31 in the axial direction. A wedge bar 37 is curved in a direction opposite to the direction illustrated in Fig. 6A.
As illustrated in Figs. 18A to 18C, a blade 35 to be fitted in the fitting groove 33 is an elastically deformable long and thin plate made of the same material as that of the blade 21. The blade 35 has a nearly rectangular shape and a thickness from 0.3 to 0.6 mm. In the illustration of Fig. 18B, a fitting surface 35a on the lower edge side is straight, and a cutting edge 35c on the upper edge side is slightly protruding outward. A flank face 35b of the blade 35 has a clearance angle γ that equals 0°. In the blade 35, a predefined area of a rake face 35d including the cutting edge 35c on one side thereof is coated with a chromium nitride hard film 36. When the blade 35 is inserted and fitted in the fitting groove 33 and pressed down with the wedge bar 37, the blade 35 is curved in a manner that protrudes in the direction of rotation R of the body 31. Then, a twist angle, which is an angle of inclination of the cutting edge 35c from the shaft center on the outer peripheral surface of the body 31, is a positive twist angle that changes in a curve on the side of an end surface 31a of the body 31 but is a negative twist angle that changes in a curve on the side of the other end surface 31b of the body 31. It is noted that the positive and negative twist angles of the cutting edge 35c are similar to that of the example 1.
According to the example 2 described so far, the thickness of each blade 35 is reduced to approximately 0.5 mm similarly to the example 1. This minimizes the use of any costly materials for the blade 35, thereby making the blade 35 available at far lower prices than the conventional blade approximately 3 mm in thickness. In the blade 35 according to the example 2 reduced in thickness to approximately 0.5 mm, the outer peripheral flank face 35b can be downsized. This controls a wear width of the flank face 35b to an extent of [blade thickness ÷ cos (rake angle) ÷ cos (twist angle)]. In the blade 35 according to the example 2, the rake face 35d is coated with the hard film 36. This controls excessive abrasion of the rake face 35d, thereby imparting a better durability to the blade 35. Thus, the example 2 exerts the effects similar to those of the example 1. According to the example 2, the blade 35 is bent in a protruding shape in the direction of rotation R of the body 31, and the twist angles θ of the portions of the blade 35 on the sides of the end surfaces 31a and 31b are positive and negative. Then, the depth of each blade 35 is three-dimensionally large enough in the circumferential direction, and the blade 35 thereby has a higher flexural rigidity than its original flexural rigidity before bending. This technical feature of the example 2 certainly promises such a high flexural rigidity although the thickness of each blade 35 is as small as approximately 0.5 mm.
According to the example 2, on the sides of the end surfaces 31a and 31b of the blade 35 are the portions inclined through the positive and negative twist angles. Therefore, oppositely directed forces are laterally applied to the work material during the cutting operation and hence counteract each other. This controls the cutting resistance imposed on the work material during the cutting operation in one of the lateral directions, thereby preventing the work material from moving in the lateral direction. As a result, the cutting operation performed by the cutter head 30 is stabilized. According to the example 2, the blade 35 is bent in a protruding shape in the direction of rotation R, and the twist angles of the portions of the blade 35 on the both end sides thereof are positive and negative. Thereby, chips generated while the work material is being cut can be discharged sideways from the center of the work material during the cutting operation, and the discharge of the chips is thereby facilitated. This technical feature becomes a particularly great advantage when cutting hard obj ects made of materials such as metals and resins where the occurrence of burr at side edges thereof is less of a problem. According to the example 2, the bent blades 35 are used. This prevents that the whole blade 35 contacts the work material at once, thereby succeeding in noise reduction during the cutting operation.
Referring to Figs. 19 to 26 are described modified examples 9 to 16 wherein the blade 35 according to the example 2 is bent in different manners.
Describing a blade 35A according to the modified example 9 referring to Fig. 19, two ends of the blade 35A are not both situated on a line (K) in parallel with the shaft center.
Describing a blade 35B according to the modified example 10 referring to Fig. 20, an apex of curve V of the blade 35B is displaced to vicinity of the end surface 31a of the body 31.
Describing a blade 35C according to the modified example 11 referring to Fig. 21, the blade 35C includes, instead of one curved portion, two continuous portions that are curved in an arc shape forming a wavy shape.
Describing a blade 35D according to the modified example 12 referring to Fig. 22, the blade 35D is not curved in an arc shape but is symmetrically bent at the center in the longitudinal direction.
Describing a blade 35E according to the modified example 13 referring to Fig. 23, an apex W of curve of the blade 35E is displaced to vicinity of the end surface 31a of the body 31.
Describing a blade 35F according to the modified example 14 referring to Fig. 24, the blade 35F includes, instead of one bent portion, a plurality of bent portions that are continuously formed.
As illustrated in Fig. 25, a blade 35G according to the modified example 15 has an intermediate portion linearly extending in parallel with the axial direction and arc-shaped portions on both end sides thereof.
In contrast to the blade 35C according to the modified example 11, the modified example 16 provides a blade 35H having one curved portion and a nearly half-length curved portion that are continuous in an arc shape, forming an S-like wavy shape as illustrated in Fig. 26. Similarly to the example 2, these modified examples 9 to 16 ensure a flexural rigidity with thin blades. The modified examples 9, 10, 12, 13, and 15 accomplish the effect of facilitating the discharge of chips generated by the cutting operation. On the other hand, the modified examples 11, 14, and 16 fail to accomplish such an effect on the side of one end surface of the body 11.
An example 3 of the invention is hereinafter described referring to Figs. 27 to 30.
The example 3 provides a blade 51 to be used in a router bit for woodworking 40 which is an example of a milling cutter with shaft. The blade 51 is similar to the blade 21 according to the example 1 except that chamfer portions are provided on both end sides of the blade 51 as illustrated in Fig. 27. In the router bit 40, a cylindrical body 41 and a shank unit 42 provided for the body 41 to be mounted in a rotary cutting device are coaxially coupled with each other. The body 41 has fitting grooves 43 formed at symmetric two positions on an outer peripheral surface thereof. The fitting groove 43 has a front wall surface 44 and a rear wall surface 45 respectively located on the forward side and the backward side in a direction of rotation of R of the body 41. The front wall surface 44 is a flat surface extending substantially in a radial direction. The rear wall surface 45 is a surface protrudingly curved in an arc shape in a direction opposite to the direction of rotation. The fitting groove 43 further has a bottom wall surface 46 that is a flat surface in parallel with the axial direction. A wedge bar 55 and a blade receiver 57 are inserted and fitted in the fitting groove 43, respectively on the side of the front wall surface 44 and on the side of the rear wall surface 45. The blade 51 is sandwiched between the wedge bar 55 and the blade receiver 57.
As illustrated in Figs. 31A and 31B, similarly to the blade 21 according to the example 1, a base material used in the blade 51 is a steel material, a cemented carbide, or a steel material with a cemented carbide used in an edge part of the blade alone. The blade 51 is a long and thin plate elastically deformable and approximately 0.3 to 0.6 mm in thickness. A surface of the blade 51 on the upper edge is a flank face 52a. In the blade 51, an intermediate portion 53 is recessed in an arc shape similarly to the example 1, and the flank face 52a continuous from the intermediate portion 53 forms a chamfer portion 54 bulging in a nearly semi-arc shape on each of two end sides of the blade. A bottom surface 52b of the blade 51 on the lower edge is a flat surface. Like the other blades described so far, the blade 51 is easily formed by punching the base metal plate. The blade 51 curved as illustrated in the drawings has a length almost equal to that of the fitting groove 43. In the flank face 52a of the blade 51 mounted in the body 41 and then subjected to the jointing, a clearance angle is almost 0°. In the blade 51, a predefined area of a rake face 52c including a cutting edge 52c on one side thereof is coated with a hard film 52e similarly to the example 1. The hard film 52e is a chromium nitride film containing CrN, Cr₂N or a mixture of CrN and Cr₂N. The thickness of the hard film 52e is approximately 0.5 to 10 µm.
A front side surface 55a of the wedge bar 55 facing the front wall surface 44 is a flat surface. A rear side surface 55b of the wedge bar 55 is a curved surface bulging in an arc shape that corresponds to the shape of the rear wall surface 45, and a bottom surface 55c thereof is a flat surface. An upper side surface 55d of the wedge bar 55 is curved on both sides thereof in the longitudinal direction in a protruding shape that corresponds to the shape of the blade 51. When the blade 51 is curved and fitted along the rear side surface 55b, the whole wedge bar 55 exactly overlaps the blade 51 except its upper cutting edge. The blade receiver 57 is a metal thick plate having a given thickness. The blade receiver 57 is bent in an arc shape that corresponds to the shape of the rear wall surface 45. A front side surface 57a of the blade receiver 57 is a recessed curved surface, and a rear side surface 57b thereof is a bulging curved surface. A bottom surface 57c of the blade receiver 57 is a flat surface. Similarly to the upper side surface 55d of the wedge bar 55, an upper side surface 57d of the blade receiver 57 is protruding on both sides thereof in the longitudinal direction. The front side surface 57a overlaps the blade 51, and the rear side surface 57b closely contacts the rear wall surface 45 of the fitting groove 43. The wedge bar 55, the blade 51, and the blade receiver 57 are inserted and fitted in the fitting groove 43. A bolt (not illustrated in the drawings) is inserted in each of fitting holes 47 formed in the body 41 on the forward side of the fitting groove 43 in the direction of rotation. Then, the inserted bolts are fastened, and the blades 51 are thereby mounted in the body 41.
In the example 3, the intermediate portion 53 of the blade 51 cuts the work material in a manner similar to the example 1, and effects similar to those of the example 1 are achieved. The chamfer portions 54 of the blade 51 on the both end sides thereof chamfer the both side edges of the work material. According to the example 3, the chamfer portions 54 of the thin blade 51 are protruding from the outer peripheral surface of the body 41. The chamfer portions 54 thus protruding are firmly and securely held between the wedge bar 55 and the blade receiver 57, and the blade 51 thereby has a large strength. Thus, the example 3 is advantageous in that the regular cutting operation and chamfering can be performed at the same time with such thin and inexpensive blades 51.
A modified example 17 of the blade according to the example 3 is described referring to Figs. 32A and 32B.
In a blade 51A according to the modified example 17, a middle part 53a of the intermediate portion 53 between the bent chamfer portions 54 has a flat surface, and parts on the outer sides of the middle part 53a are curved in an arc shape. The blade 51A has a flat bottom surface, and the middle part 53a has a flat surface. The intermediate portion 53 has a constant rake angle.
An example 4 of the invention is hereinafter described referring to Figs. 33 to 35. Unlike the curved and bent shapes so far described in the examples and the modified examples thereof, the example 4 provides a blade 71, which is a straight flute, to be fitted in a fitting groove 63 in parallel with the axial direction of a cutter head for woodworking 60. The cutter head 60 has a body 61 formed in an elongated cylindrical shape and made of metal. The body 61 has a shaft hole 62 at the center thereof. The body 61 further has two fitting grooves 63 having an identical shape and formed at two positions radially facing each other on the outer peripheral side of the body 61. The fitting groove 63 is dented in a substantially radial direction of the body 61 and has a nearly rectangular shape when viewed from the side of an end surface penetrating through in the longitudinal direction. Unlike the curved and bent shapes so far described in the examples and the modified examples thereof, the fitting groove 63 is a straight groove extending in parallel with the axial direction. The fitting groove 63 is inclined so that a rake angle stays in the range of positive angles. The fitting groove 63 has a front wall surface 64 and a rear wall surface 65 respectively on the forward side and the backward side in a direction of rotation, and a bottom surface 66. The front wall surface 64 and the rear wall surface 65 are in parallel with each other. The bottom surface 66 is a flat surface perpendicular to the front and rear wall surfaces 64 and 65. An angle of inclination of the rear wall surface 65 from the radial direction is approximately 15°.
The body 61 has dented notches 67 at positions respectively near upper edges of the front wall surfaces 64. The dented notches 67 are dented in an arc shape in the direction of rotation and extending between the both ends in the axial direction. The dented notch 67 is continuous to the upper surface of a wedge bar 73 described later and smoothly connected thereto. The body 61 further has fitting holes 68 structured similarly to the fitting holes 18 described earlier. The fitting holes 68 are formed a little more forward in the direction of rotation than the dented notches 67 at five positions; a middle position and positions near the right-hand left-hand ends in the axial direction, and intermediate positions therebetween.
The fitting grooves 63 are each mounted with a blade 71 and a wedge bar 73. Similarly to the blade 21, the blade 71 is an elastically deformable long and thin plate made of a steel material or a cemented carbide. The blade 71 is formed by punching the base metal plate. The blade 71 is approximately 0.5 mm in thickness and substantially equal in length to the fitting groove 63. In the blade 71, the flank face has a clearance angle that equals 0°, and a predefined area of the rake face including a cutting edge is coated with a hard film; a chromium nitride film containing CrN, Cr₂N or a mixture of CrN and Cr₂N, similarly to the example 1. The wedge bar 73 is a metal member having an elongated square bar shape. The upper surface of the wedge bar 73 is a curved surface recessed in an arc shape that corresponds to the shape of the dented notch 67. The blade 71 and the wedge bar 73 both having a straight shape are easily fitted in the straight fitting groove 63 of the body 61. When a bolt (not illustrated in the drawings) is inserted in each of the fitting holes 68 and fastened, the blade 71 and the wedge bar 73 are firmly secured in the fitting groove 63. The cutting edge at the tip of the blade 71 protrudes by approximately 0.5 mm from the outer peripheral surface of the body 61.
The two blades 71 securely fitted in the fitting grooves 63 are subjected to the jointing with grindstone to correct any variability of outer diameters of the cutting edges. Since the blade 71 according to the example is as small in thickness as approximately 0.5 mm, the jointing conventionally targeted for the cutting edge thereof may be performed to all over the outer peripheral flank face. The flank face is accordingly subjected to cylindrical grinding and thereby formed in an arc shape, and the clearance angle becomes 0°.
According to the example 4 described so far, the thickness of each blade 71 is reduced to approximately 0.5 mm similarly to the example 1. This minimizes the use of any costly materials for the blade 71, thereby making the blade 71 available at far lower prices than the conventional blades approximately 3 mm in thickness. By thus reducing the thickness of the blade 71 to approximately 0.5 mm, the example 4 succeeds in making the flank face smaller. As a result, a wear width of the flank face can be controlled to an extent of [blade thickness ÷ cos (rake angle)] . According to the example 4, therefore, the blade 71 can still be used even after the cutting edge is receded beyond the limit of the conventional thick blades. Thus, the blade 71 has a service life a few times as long as the conventional blades. Because the rake face is coated with the hard film, excessive abrasion of the rake face is prevented, and the durability of the blade 71 is thereby improved. Thus, the example 4 exerts effects similar to those of the example 1. According to the example 4, the base material of the blade 71 is a steel material, a cemented carbide, or a steel material with a cemented carbide used in the edge part of the blade alone. When the cutting resistance is imposed on the blade 71, the blade 71 thereby slightly elastically deforms and warps toward the flank-face side, moving away from the work material. With this technical feature, the example 4 reduces the cutting resistance imposed on the blade 71, thereby enabling the cutting operation to be smoothly performed.
The examples 1 and 2 respectively describe the variously different shapes of the blade in the modified examples 1 to 16. These shapes of the blade are, however, only some examples. The blade fitted in the cutter head may be arranged in other shapes, or these different shapes may be arbitrarily combined. The examples 1 and 2 and the modified embodiments thereof described one cutter head. A plurality of cutter heads may be coupled with each other in the axial direction, wherein blades of the adjacent cutter heads are displaced relative to each other. A plurality of blades may have grooves formed on cutting-edge sides thereof, so that a work material can be cut into separate pieces. According to the examples and the modified examples thereof, the blade according to the invention is applied to the rotary cutting tool. The blade according to the invention may be applied to cutting tools not configured to rotate such as fixed knife planers. The invention has been described and illustrated in detail in the examples and the modified examples thereof. However, the invention is not necessarily limited thereto, and various modifications, additions and alterations may be made to the invention without departing from the spirit and scope of the invention.

INDUSTRIAL APPLICABILITY

The blade according to the invention has the following advantages. The blade reduced in thickness can greatly curtail its material cost and accordingly lower its selling price. The reduction of the flank face in length along the direction of rotation allows the reduction of a wear width to at most an extent of [blade thickness ÷ cos (rake angle)]. By coating the rake face with the hard film, excessive abrasion on the rake-face side of the cutting edge is prevented, which leads to a better durability.

DESCRIPTION OF REFERENCE SYMBOLS

10: cutter head for woodworking
11: body
13, 13A to 13G: fitting groove
18: fitting hole
21, 21A to 21H: blade
21c: cutting edge
22: hard film
24, 24A to 24G: wedge bar
30: cutter head for woodworking
31: body
33, 33A to 33G: fitting groove
35, 35A to 35H: blade
35c: cutting edge
37, 37A to 37G: wedge bar
40: router bit for woodworking
41: body
43: fitting groove
51: blade
55: wedge bar
57: blade receiver
60: cutter head for woodworking
61: body
63: fitting groove
71: blade
73: wedge bar

Claims

A cutting blade to be mounted in a tool body, wherein at least a rake face of the cutting blade is coated with a harder material than a base material used in the cutting blade, and the cutting blade has a thickness from 0.2 mm to 0.8 mm.
The cutting blade according to claim 1, wherein the cutting blade is mounted in the tool body in a manner that protrudes in a direction opposite to a direction where a work material is cut, and twist angles of portions on both end sides of the cutting blade are positive and negative angles.
The cutting blade according to claim 1, wherein the cutting blade is mounted in the tool body in a manner that protrudes in a direction where a work material is cut, and twist angles of portions on both end sides of the cutting blade are positive and negative angles.
The cutting blade according to any one of claims 1 to 3, wherein the base material of the cutting blade is a steel material, a cemented carbide, or a steel material with a cemented carbide used in an edge part of the cutting blade alone.
A rotary cutting tool wherein the cutting blade according to any one of claims 1 to 4 is mounted in the tool body and subjected to jointing.