JP4554383B2 - Throw-away drill - Google Patents

Description

The present invention relates to a throw-away drill for drilling, and more particularly to a technique for improving chip discharge performance and drill body rigidity.

6 to 8 are a front view, a side view of the tip, and a perspective view of the tip of the conventional throw-away drill, respectively. This conventional throw-away drill has a pocket formed by a tip seat forming surface (9) and a heel forming surface (11) at the tip of the flute groove (2) on the side where the center blade (6) is mounted. 12), the heel forming surface (11) is substantially perpendicular to the tip seat forming surface (9) and located on the outer peripheral side, and the curved surface forming a recess on the axial center side thereof. (11b). By having such a pocket (12), the discharge property of the chip | tip produced | generated by the center blade (6) is improved (for example, refer patent document 1).
JP-A-11-90715

However, in the drill body of the conventional throw-away drill, the curved surface (11b) that forms a recess from the heel proximity surface (11a) to the axial center side, as shown by a Y portion in FIG. Since the corner of the tip seat (3) formed in the notch is close to the tip of the flute groove (2) on the opposite side of (11b) where the outer peripheral blade is mounted, the corner and the drill body (1 ) Where the tip surface intersects the width (T ′) of the sandwiched portion between the curved surface (11b) and the corner, the thickness is very thin and the rigidity is reduced. End up. Therefore, if vibration during processing or excessive cutting resistance occurs, cracks may occur from the intersection of the corner of the tip seat (3) and the tip surface of the drill body (1). There was a possibility that (1) would be damaged.

The present invention has been made in view of the above circumstances, and its purpose is to improve the discharge of chips generated from the central blade and to improve the rigidity of the drill body, in particular, the corner of the tip seat of the outer peripheral blade. An object of the present invention is to provide a throw-away drill with improved crack resistance of the part.

In order to solve the above-described problems, the present invention provides a round rod-shaped drill body rotated about an axis (CL) along the axis (CL) from the front end surface toward the rear end side. A pair of extending flute grooves are provided, and at least a center blade is attached to the tip of one flute groove, and an outer peripheral blade is detachably attached to the tip of the other flute groove so that drilling is performed. In the constructed throw-away drill, a concave portion that forms a recess in the wall surface is formed at the tip of the wall surface facing the rear side in the rotational direction (K) of the flute groove on the side where the throw-away tip that is the central blade is mounted. The concave portion is gradually separated from the corner portion of the tip seat formed in the tip portion of the flute groove on the side where the throw-away tip serving as the outer peripheral blade is mounted as it goes to the tip end side in the axis (CL) direction. It is indexable drill, characterized in that curved so that.

In the above invention, the concave portion has a substantially arc shape in cross section and extends in the chip discharging direction, and at least its tip portion is preferably formed of a spherical surface or preferably only of a spherical surface, The R center of the spherical surface is a position where the corner portion of the tip seat formed in the tip portion of the flute groove on the side where the throw-away tip serving as the outer peripheral blade is mounted opens to the tip surface of the drill body. More preferably, it is located on the rear end side in the axial center (CL) direction within a range of 10% to 80% of the R dimension of the spherical surface.

According to the throw-away drill having the above-described configuration, the concave portion that forms a recess in the wall surface at the tip of the wall surface facing the rear side in the rotational direction (K) of the flute groove on the side where the throw-away tip serving as the central blade is mounted In order to secure a pocket space where the chips generated from the central blade are not crushed, the chips regularly curled in a conical spiral shape are smoothly discharged out of the machining hole. Further, the recess gradually moves away from the corner of the tip seat formed in the tip of the flute groove on the side where the throw-away tip serving as the outer peripheral blade is mounted as it goes to the tip of the axis (CL) direction. Since it is curved, the thickness between the corner and the recess becomes thicker toward the tip side, and the rigidity of this portion is increased. In particular, since the thickness (T) is the thickest at the corner portion opened at the tip end surface of the drill body, the generation or propagation of cracks at the opening portion of the corner portion is suppressed, thereby preventing the drill body from being damaged. The

If at least the tip of the concave portion is formed of a spherical surface or only a spherical surface, the area for removing the wall surface facing the rear side in the rotational direction (K) of the flute groove is reduced, and the rigidity of the drill body is reduced. Reduction is suppressed. With respect to the R center of the spherical surface, with respect to the position where the corner portion of the tip seat formed in the tip portion of the flute groove on the side where the throw-away tip serving as the outer peripheral blade is mounted opens at the tip surface of the drill body, If it is positioned on the rear end side in the axis (CL) direction within a range of less than 10% of the R dimension of the spherical surface, there is a possibility that the effect of improving the rigidity of the crack at the corner opening is not obtained, and 80% If it is located on the rear end side in the axis (CL) direction in a range exceeding 1, there is a risk that the spherical surface cannot be formed up to the vicinity of the tip surface of the drill body, and chip evacuation may be reduced. If an attempt is made to form the vicinity of the front end surface of the main body, the wall surface of the flute groove may be deeply swept away by the spherical surface and the rigidity of the drill main body may be reduced.

Next, an embodiment to which the present invention is applied will be described with reference to the drawings. 1 and 2 are a front view and a side view, respectively, of a tip portion of a throw-away drill to which the present invention is applied. FIG. 3 is a perspective view of the tip portion of the throw-away drill shown in FIG. As illustrated in FIGS. 1 to 3, the round rod-shaped drill body (1) rotated around the axis (CL) has an axis (CL) from the front end surface (1a) toward the rear end side. A pair of flute grooves (2A, 2B) extending with twist along the axis are provided symmetrically about the axis (CL). The tip seat (3A, 3B) is cut out at the tip of the wall surface (2a) facing the front side in the rotational direction (K) of the flute groove (2A, 2B) and drilled in the center of the bottom surface of the tip seat (3A, 3B). The throw-away tip (5A, 5B) is detachably mounted by a tightening screw (4) that is screwed into the provided screw hole. One flute groove (2A) is fitted with a throw-away tip (5A) serving as a center blade (6), and the other flute groove (2B) is fitted with a throw-away tip (5B) serving as an outer peripheral blade (7). . The drill body (1) is provided with an oil hole (8) that penetrates the inside and opens at the tip, so that the cutting fluid can be supplied from the holder side of the throw-away drill. The cutting fluid supplied during cutting not only cools the cutting edge that has become high temperature due to cutting heat, but also has the effect of pushing the chips out of the processing hole using the flute grooves (2A, 2B) as flow paths.

As can be seen from FIG. 3, the tip seat (3A) facing the front side in the rotational direction (K) is cut out at the tip of the flute groove (2A) in which the center blade (6) is mounted. The side including the flat tip seat forming surface (9) and the heel (10) which faces the rear side in the rotational direction (K) and the flute groove (2A) rises and intersects the outer peripheral surface of the drill body (1) And a heel forming surface (11) formed on the surface. The heel forming surface (11) includes a substantially flat heel proximity surface (11a) that is substantially orthogonal to the chip seat formation surface (9) and a recess (11d) that forms a recess in the heel proximity surface (11a). . The concave portion (11d) has a substantially arc-shaped cross section, and is connected to the curved surface (11b) extending in the chip discharging direction along the heel proximity surface (11a) with a substantially constant width, and the leading end of the curved surface (11b). The spherical surface (11c) is configured by a flute groove (2B) on the side where the throwaway tip (5B) serving as the outer peripheral blade (7) is attached as it goes toward the tip in the axial center (CL) direction. ) Is curved so as to be gradually separated from the corner (3s) of the tip seat (3B) (hereinafter referred to as “tip seat corner (3s) of the outer peripheral blade)” formed by cutting out at the tip of the tip. The R center of the spherical surface (11c) is a portion where the corner (3s) opens in the tip surface (1a) of the drill body (1) (hereinafter referred to as “opening portion (3k) of the tip seat corner of the outer peripheral blade)”. .)) On the rear end side in the axial center (CL) direction. More preferably, it is located on the rear end side in the range of 10% to 80% of the R dimension of the spherical surface (11c), and particularly preferably located on the rear end side in the range of 30% to 80% of the R dimension. Furthermore, it is preferable that the spherical surface (11c) reaches the distal end surface (1a) of the drill body (1) and a part of the distal end surface (1a) is cut away. In the heel forming surface (11), the heel proximity surface (11a) is omitted, and a recess (11d) is formed directly on the wall surface (2b) facing the rear side in the rotational direction (K) of the flute groove (2B). May be.

The recess (11d) is processed using, for example, a ball end mill. That is, the curved surface (11b) is processed by cutting and feeding a ball end mill having a ball blade having the same radius of curvature as the cross-sectional arc of the recess (11d) along the direction in which the recess (11d) extends, The spherical surface (11c) is machined at the location where the cutting feed of the end mill is stopped. Moreover, about the cross-sectional shape of a recessed part (11d), it is not restricted to circular arc shape, For example, by using a radius end mill, you may form in the curve shape which made the bottom part linear.

According to the throw-away type drill having the above-described configuration, the recessed portion (11d) serves as a pocket and secures a pocket space where the chips are not crushed. It can be deformed without being crushed, and it is deformed into a conical shape with the axial center point as a vertex. After this, the chips become a chip shape long connected in a regular conical spiral shape, and are spontaneously divided when they reach an appropriate length. Such a conical spiral chip does not entangle with the drill body (1), and is thus smoothly discharged out of the machining hole. In addition, in the front view of the drill, the angle formed between the tip seat forming surface (9) and the heel proximity surface (11a) is 80 ° to ~ in order to maintain a balance between the rigidity of the drill body (1) and the chip dischargeability. It is preferable to set it in the range of 100 °.

Further, since the spherical surface (11c) formed on the heel forming surface (11) gradually moves away from the tip seat corner (3s) of the outer peripheral blade as it goes to the front end side in the axial center (CL) direction, The thickness between the portion (3s) and the concave portion (11d) increases toward the tip side, and the rigidity of this portion is increased. In particular, since the thickness (T) is the largest in the opening (3k) at the tip seat corner of the outer peripheral edge shown in the X part of FIG. 2, the generation or propagation of cracks in the opening (3k) is suppressed. As a result, damage to the drill body (1) is prevented. In particular, this effect is remarkably obtained in a small-diameter throw-away drill in which the wall thickness (T) tends to be thin. The R center of the spherical surface (11c) is located on the rear end side in the axial center (CL) direction with respect to the position of the opening (3k) at the tip seat corner of the outer peripheral blade, but the R dimension of the spherical surface (11c) is 10 If it is located on the rear end side in the axis (CL) direction within a range of less than%, the expected effect of improving the rigidity may not be obtained, and if it is located on the rear end side in the axis (CL) direction in a range exceeding 80%, The spherical surface (11c) cannot be formed up to the vicinity of the front end surface (1a) of the drill body (1), and there is a possibility that chip discharge performance may be reduced. Conversely, the spherical surface (11c) is removed from the drill body (1). If it is going to be formed up to the vicinity of the tip surface (1a), the wall surface (2b) of the flute groove (2B) may be deeply penetrated by the spherical surface (11c) and the rigidity of the drill body (1) may be lowered. In addition, if the front-end | tip part of a spherical surface (11c) is formed so that a part of front-end | tip surface (1a) of a drill main body (1) may be notched, the discharge property of the chip | tip produced | generated from a center blade (6) will be sufficient. Although it is very preferable in terms of the point, in particular, a small-diameter throw-away drill whose rigidity is likely to be lowered may be formed so as to be closed before the tip surface (1a) from the viewpoint of improving the rigidity of the drill body (1). . In this case as well, the R center of the spherical surface (11c) is located at the position of the opening (3k) at the tip seat corner of the outer peripheral blade so as not to reduce the discharge of chips generated from the central blade (6). On the other hand, on the rear end side in the axial center (CL) direction in the range of 10% to 80% of the R dimension of the spherical surface (11c), particularly preferably in the range of 30% to 80% of the R dimension. ) Should be located on the rear end side in the direction.

In the present embodiment, as illustrated in FIGS. 1 to 3, the curved surface (11b) of the recess (11d) reaches the rear end of the heel proximity surface (11a) with a substantially constant width. If the width is formed so as to gradually increase in the chip discharging direction, chip discharging performance is further improved. In addition, the width gradually decreases in the chip discharging direction within a range that does not adversely affect the chip discharging property, or the curved surface (11b) is a heel proximity surface (11a) as illustrated in FIG. ), The rigidity of the drill body (1) is further increased. In particular, in a small-diameter throw-away type drill with low rigidity of the drill body (1), if the curved surface (11b) is eliminated and only the spherical surface (11c) is formed as illustrated in FIG. It is.

Next, the results of comparative experiments on the occurrence of cracks in the drill body (1) at that time are described using a throw-away drill to which the present invention is applied and a conventional throw-away drill. In both throwaway drills, the drill diameter, the shape of the throwaway tip of the center blade (6) and the outer peripheral blade (7), the shape of the flute groove (2), the tip seat forming surface (9) and the heel proximity surface (11a) ) Is the same shape. The cross-sectional shape of the curved surface (11b) formed on the heel proximity surface (11a) is also set to be the same. In the conventional throw-away drill, as illustrated in FIGS. 6 to 8, the heel proximity surface (11 a) is formed with a curved surface (11 b) having a uniform circular arc shape up to the tip surface of the drill body (1). In addition, the thickness (T ′) between the curved surface (11b) and the opening (3k) at the tip seat corner of the outer peripheral blade is thin in the axial center (CL) direction tip view, On the other hand, in the throw-away drill to which the present invention is applied, the spherical surface (11c) connected to the distal end portion of the curved surface (11b) goes to the distal end side in the axial center (CL) direction as illustrated in FIGS. Therefore, it is gradually separated from the tip seat corner (3s) of the outer peripheral blade, and the wall thickness (T) between the spherical surface (11c) and the tip seat corner (3s) of the outer peripheral blade is increased.

The conditions for drilling were as follows: cutting speed Vc = 200 m / min. , Feed rate fr = 0.08 mm / rev. Then, a blind hole having a depth of 45 mm was continuously machined in the work material SCr420 (JIS G4104) by wet cutting using a cutting oil. In addition, since it is difficult to generate cracks with normal drilling, a special feed that increases the number of impacts when biting on the work material by stepping 1 mm, and actively generates cracks. Drilling was performed. As a result, in the conventional throw-away drill, since the thickness of the opening at the corner of the tip seat (3) of the outer peripheral blade (7) is thin, the total depth of the processed holes is 3330 mm (the number of impacts is 3330 times). ), The occurrence of cracks was observed at the corner openings. On the other hand, in the throw-away type drill to which the present invention is applied, the cumulative depth of holes processed by increasing the thickness of the opening (3k) at the tip seat corner of the outer peripheral blade is twice the conventional depth. Even when it reached a certain 6660 mm (number of impacts 6660), no crack was observed in the opening (3k) at the tip seat corner of the outer peripheral blade.

It is a front view of the front-end | tip part of the throw away type drill to which this invention is applied. It is a side view of the front-end | tip part of the throw away type drill shown in FIG. It is a perspective view of the front-end | tip part of the throw away type drill shown in FIG. It is a perspective view of the front-end | tip part of the other throwaway type drill to which this invention is applied. It is a perspective view of the front-end | tip part of the further another throwaway type drill to which this invention is applied. It is a front view of the front-end | tip part of the conventional throwaway type drill. It is a side view of the front-end | tip part of the conventional throwaway type drill shown in FIG. It is a perspective view of the front-end | tip part of the conventional throwaway type drill.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drill main body 2A, 2B Flute groove | channel 2a Wall surface 2b facing the rotation direction front side of a flute groove Wall surface 3A facing the rotation direction back side of a flute groove 3B 3B Tip seat 3s Corner openings 5A, 5B Throw away tip 6 Center blade 7 Outer peripheral blade 9 Tip seat forming surface 10 Heel 11 Heel forming surface 11a Heel proximity surface 11b Curved surface 11c Spherical surface 11d Recess

Claims (4)

The round rod-shaped drill body rotated about the axis (CL) is provided with a pair of flute grooves extending along the axis (CL) from the front end surface toward the rear end side. In the throw-away drill configured so that the center blade is attached to the tip of one flute groove and the outer peripheral blade is detachably attached to the tip of the other flute groove, so that drilling is performed.
At the tip of the wall surface facing the rotational direction (K) rear side of the flute groove on the side where the throw-away tip serving as the central blade is mounted, a recess is formed that forms a recess in the wall surface, and the recess is the axis (CL) As it goes to the front end in the direction, it is curved so as to gradually move away from the corner of the tip seat formed in the front end of the flute groove on the side where the throw-away tip as the outer peripheral blade is mounted. Throw away type drill. The throw-away drill according to claim 1, wherein the concave portion has a substantially arc shape in cross section and extends in a chip discharging direction, and at least a tip portion thereof is formed of a spherical surface. The throw-away drill according to claim 1, wherein the concave portion is formed only of a spherical surface. The R center of the spherical surface is a position where the corner portion of the tip seat formed in the tip portion of the flute groove on the side where the throw-away tip serving as the outer peripheral blade is mounted opens to the tip surface of the drill body. 4. The throw-away drill according to claim 2, wherein the throw-away drill is located on the rear end side in the axial center (CL) direction within a range of 10% to 80% of the R dimension of the spherical surface.

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