JP2538864Y2 - Hard film coated drill for difficult-to-cut materials - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard film-coated drill, and more particularly to an improvement in a hard film-coated drill for difficult-to-cut materials having a relatively large ratio of a web thickness to a drill diameter.

[0002]

2. Description of the Related Art It is desirable to increase the thickness of a web for a drill for cutting hard-to-cut work materials such as tempered steel with high efficiency and high speed in order to have high rigidity. Increasing the web thickness increases the length of the chisel edge in proportion to this, but this chisel edge is formed as the intersection of the two flank faces, resulting in a large negative rake angle,
Remarkably poor sharpness. For this reason, thinning processing is performed on the web tip to shorten the length of the chisel edge and increase the rake angle. FIG.
(A) is an S-type thinning,
(B) is N-type thinning and (c) is X-type thinning. In FIG. 3, reference numerals 50 and 52 indicated by oblique lines denote thinned surfaces,
4 and 56 are a pair of cutting edges, 58 and 60 are flank surfaces, and 62 is a chisel edge.

[0003] In order to prolong the tool life, it is common practice to coat the surface of the drill body with a hard film. The hard film is made of, for example, a metal of Group 4a, 5a, or 6a of the periodic table, a carbide or nitride of Si or Al, an oxide thereof, or a solid solution thereof, and is coated in a single layer or a multilayer. By coating with such a hard film, not only the welding resistance is improved, but also excellent wear resistance is obtained.

[0004]

However, the center of the drill has a lower cutting speed than the outer peripheral portion and performs cutting close to crushing. Therefore, the drill receives a large cutting resistance. There is a problem that the formed cutting edge is liable to cause chipping and chipping. In particular, a drill coated with a hard film can obtain excellent wear resistance, but has a reduced toughness, so that the above-mentioned problem becomes remarkable.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hard film coated drill for difficult-to-cut materials which prevents chipping or chipping of a cutting edge formed by thinning. Is to do.

[0006]

According to the present invention, a pair of twist grooves are provided symmetrically with respect to the axis so that a ratio of a web thickness to a drill diameter is relatively large. A hard film coated drill for difficult-to-cut materials, wherein (a) a pair of flank surfaces formed at the tip of the drill and a pair of helical grooves extending from an outer peripheral corner formed by intersecting the pair of twist grooves. (B) Thinning applied to the end of the web to form a straight line and both ends are connected to the outer cutting edge and the chisel edge at an obtuse angle in bottom view, and the length of the chisel edge is drilled. A pair of center-side cutting edges formed so as to have a diameter of 10% or less and a right-angle rake angle being negative;
(C) A rake face, a flank, a margin, and a hard film provided so as to cover the surface of the chisel edge except for the rake faces of the pair of center-side cutting edges.

[0007]

In such a hard film coated drill for difficult-to-cut materials, by increasing the web thickness to, for example, about 25 to 40% of the drill diameter, the groove depth required for chip discharge can be reduced. High rigidity that can withstand a large cutting force while securing is obtained. In addition, by reducing the length of the chisel edge to 10% or less of the drill diameter by thinning, cutting resistance is reduced and chip dischargeability is improved. 10% is the critical point where performance changes significantly. The center side cutting edge formed by thinning is straight, and both ends are connected to the outer side cutting edge and the chisel edge at an obtuse angle in bottom view, and the right angle rake angle is negative, so that Chipping and chipping are greatly reduced as compared with the case where the angles are connected at an acute angle or the right angle rake angle is made positive, and the flow of chips becomes smoother and the welding resistance is improved. In addition, since the rake face, flank face, margin, and chisel edge except the rake face of the center side cutting edge are coated with a hard film, the cutting resistance is relatively large, and the toughness of the center side cutting edge which is easily broken is impaired. Therefore, the welding resistance and wear resistance of the drill can be improved.

As described above, in the hard film coated drill for difficult-to-cut materials according to the present invention, the chisel edge has a diameter of 10% of the drill diameter despite the relatively large web thickness so as to obtain high rigidity.
The cutting resistance is reduced as follows, and the welding resistance and abrasion resistance are improved while preventing chipping and chipping of the center cutting edge, resulting in a dramatic improvement in machining efficiency and machining accuracy for difficult-to-cut materials. You can do it.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a plan view of a hard film coated drill for hard-to-cut materials (hereinafter simply referred to as a drill) 10 according to an embodiment of the present invention, as viewed from the tip side, and FIG. 2 is a front view. The drill body of the drill 10 is provided with a pair of torsion grooves 12 and 14 symmetrically with respect to the axis, and a pair of flank surfaces 16 and 18 are formed at the tip end. A pair of outer peripheral side cutting edges 20 and 22 extending from the outer peripheral corners are formed by ridge lines at which the twist grooves 12 and 14 and the flank surfaces 16 and 18 intersect. The groove depth of the twist grooves 12, 14 is determined so that the web thickness is about 25 to 40% of the drill diameter D. The tip of the web is thinned so that the length of the chisel edge 24 is 10% or less of the drill diameter D.
Central cutting edges 26 and 28 are formed to connect the outer cutting edges 20 and 22 to the outer cutting edges 20 and 22. Center side cutting edge 2
6 and 28 are formed so that the right-angle rake angle is negative and form a straight line, and both ends are the outer peripheral cutting edges 20 and 22 and the chisel edge 24 when viewed from the bottom shown in FIG. Connected at an obtuse angle. Portions 30 and 32 indicated by oblique lines in the drawing are thinning surfaces on which thinning has been performed. Also, the rake faces of the pair of center side cutting edges 26, 28, that is, the thinning faces 30, 3
2, except for the portions near the center side cutting edges 26 and 28,
The rake faces of the outer peripheral cutting edges 20 and 22 formed by a part of the twist grooves 12 and 14, the flank faces 16 and 18, the margins 34 and 36, and the surfaces of the chisel edge 24 have T
A hard film such as iCN is provided in a single layer or a multilayer.

In such a drill 10, the web thickness is relatively large, about 25 to 40% of the drill diameter D. Rigidity is obtained. In addition, since the length of the chisel edge 24 is set to 10% or less of the drill diameter D by the thinning, the cutting resistance is reduced and the chip dischargeability is improved. The center side cutting edges 26 and 28 formed by the thinning process are straight, and both ends are connected to the outer peripheral side cutting edges 20 and 22 and the chisel edge 24 at an obtuse angle in a bottom view, respectively, and the right-angle rake angle is Since it is negative, chipping and chipping are greatly reduced compared to connecting them at an acute angle and making a right rake angle positive, and the flow of chips is smoother and welding resistance is improved. Is improved. Further, since the rake face except the rake face of the center side cutting edges 26 and 28, the flank faces 16 and 18, the margins 34 and 36, and the surface of the chisel edge 24 are coated with a hard film,
Central cutting edge 2 with relatively large cutting resistance and easy to break
The welding resistance and the wear resistance of the drill 10 are improved without impairing the toughness of the drill 6.

As described above, in the drill 10 of the present embodiment, the chisel edge 24 is set to 10% or less of the drill diameter D and the cutting resistance is reduced even though the web thickness is relatively large so as to obtain high rigidity. Reduced and center cutting edge 2
Since the welding resistance and the wear resistance are improved while preventing chipping and chipping of 6, 28, it is possible to dramatically improve the processing efficiency and processing accuracy for difficult-to-cut materials.

The products of the present invention and comparative products I and I shown in Table 1
I and two conventional products were prepared, drilling was performed under the following cutting conditions, and the number of drilled holes until the drill life was reached was examined. The results shown in Table 2 were obtained.
The hardness of the hard film TiCN is 2 in Hv (0.025).
525 to 2544, and the film thickness is 0.0032 to 0.0
048 mm.

[0014]

[Table 1]

(Cutting conditions) Work material: SKD61 (HRC 41-42) Revolution: 900 rpm (24 m / min) Feed: 0.25 mm / rev (225 mm / min) Cutting length: 20 mm through hole Cutting oil: water soluble Solivable oil Machine: Vertical machining center

[0016]

[Table 2]

As is apparent from Table 2, the life of the drill of the present invention is about twice as long as that of the conventional product having X-shaped thinning. The comparative product II, which does not cover the hard film, has remarkable corner wear and extremely short drill life, while the comparative product I, which covers the entire hard film, has a longer service life than the conventional product, but lacks the center side cutting edge. Therefore, the effect of improving the service life of the product of the present invention cannot be obtained.

It should be noted that the above is merely one specific example of the present invention, and the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art.

[Brief description of the drawings]

FIG. 1 is a plan view of a hard-film-coated drill for hard-to-cut materials according to an embodiment of the present invention, as seen from the tip side.

FIG. 2 is a front view of the drill of FIG. 1;

FIG. 3 is a plan view showing a typical example of thinning in a conventional drill.

[Explanation of symbols]

 10: Hard film coated drill for difficult-to-cut materials 20, 22: Outer cutting edge 24: Chisel edge 26, 28: Center cutting edge 30, 32: Thinning surface

Claims (1)

(57) [Scope of request for utility model registration] 1. A hard film coated drill for difficult-to-cut materials, wherein a pair of twist grooves are provided symmetrically with respect to an axis so that a ratio of a web thickness to a drill diameter is relatively large, wherein a drill tip is provided. A pair of outer cutting edges extending from an outer corner formed by ridge lines where a pair of flank surfaces formed in the portion intersect with the pair of twist grooves, and a thinning process performed on a web tip to form a straight line. And a pair formed so that both ends are connected to the outer peripheral side cutting edge and the chisel edge at an obtuse angle in a bottom view, the length of the chisel edge is 10% or less of the drill diameter, and the right angle rake angle is negative. And a hard film provided so as to cover the rake face, flank face, margin, and chisel edge surface excluding the rake face of the pair of center side cutting edges. A hard film coated drill for difficult-to-cut materials.