JPH02311211A - Cemented carbide drill - Google Patents

Abstract

PURPOSE:To prevent the occurrence of tipping and elongate the life of a drill by coating titanium, aluminum, nitride or the like on a negative land in the outer peripheral end of a cutting edge while setting a radial rake angle to angle of -20 deg. or more and -7 deg. or less. CONSTITUTION:The radial rake angle alpha of a negative land 4 on the outer peripheral side end of a cutting edge 3 of a cemented carbide drill is a negative rake angle set to the range from -7 to -20 deg.. Further, the edge of the drill is coated with 2.5-3.5mum thick film of titanium, aluminum, nitride or the like. Thus, the heat resisting property is improved while the heat conducting property is improved so that the rake angle can be enlarged and tipping is prevented from occurrence while the antiwear property is improved.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a carbide drill in which a negative land portion is formed at the outer peripheral end of a cutting edge.

[Prior art and technical problems of the invention]

Solid drills, which are generally called carbide drills and are used for cutting operations such as drilling steel materials, are coated with titanium nitride to suppress wear on the cutting edge and extend tool life. There are many. Further, in order to deal with the problem of chipping due to the "brittle" nature of the carbide itself, a negative run ridge is usually formed at the outer peripheral end of the cutting edge. At present, the radial rake angle of this negative run portion is set within a positive range from about -5°. From the perspective of preventing chipping, it would be better to make the negative value even larger, but the larger the negative radial rake angle, the more heat will be generated, which will actually promote wear on the cutting edge. This is due to the fact that it would shorten the tool life. In particular, titanium nitride (TiN), which constitutes the two series of coating films, is not very desirable in terms of thermal conductivity, and as a result, such a coating film has a negative land area with a large radial angle. The present invention has been devised to effectively solve the above-mentioned technical problems regarding the radial rake angle and heat generation of the negative land portion. An object of the present invention is to effectively suppress the occurrence of chipping by increasing the radial rake angle of the negative land portion than before, and to effectively diffuse the heat generated due to the increase in the rake angle, thereby extending the tool life. The object of the present invention is to provide a carbide drill that can prevent deterioration.

[Means to solve the problem]

The carbide drill according to the present invention solves the technical problems such as "duplex" and has the following configuration in order to achieve the objective. That is, in a carbide drill in which a negative land portion is formed at the outer peripheral end of the cutting edge, a coating of titanium aluminum nitride (hereinafter referred to as TiAIN) is applied, and the radial direction of the negative land portion is coated with titanium aluminum nitride (TiAIN). The rake angle is set to -20° or more and -7° or less.

[Action and effect of the invention]

The TiAIN coating film in the carbide drill according to the present invention has excellent heat resistance, and
Since the thermal conductivity is 4 to 5 times higher than that of the iN coating film, the increased amount of heat generated due to the increase in the rake angle can be diffused and dissipated more effectively than before. Therefore, the radial rake angle of the non-cutting blunt portion is increased to a negative value, and the eye is tilted to about 120'. For example, if the angle exceeds -20° and the negative value becomes larger, the strength of the tool itself increases and the chipping resistance improves, but on the other hand, the cutting resistance also increases and thermal wear increases. From around the above-mentioned ``--limit value'', a decrease in tool life due to an increase in thermal wear begins to occur, rather than the improvement of chipping resistance. On the other hand, the lower limit is around -7°, and if the angle is more positive than this value, the life will be shortened due to chipping. In addition, since TiAIN has a higher hardness than TiN, its wear resistance is also improved in this respect.

【Example】

A preferred embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a side view of the cutting edge shape of the carbide drill according to the present invention;
FIG. 2 is a side view of the carbide drill according to the present invention. The part of the chip discharge groove formed in a normal drill that does not have a sub-groove is defined as a 1 m main groove, and further cuts are made from around the innermost part of this 1 m main groove toward the chisel part 2 to form a sub-groove 1 s.
The chip discharge groove 1 of the trill according to the present invention in a state where
is formed. Therefore, the cutting edge 3 is composed of a main cutting edge 3m formed by the main groove 1m, and a sub-cutting edge 3s formed by the sub-groove 1s. Further, as shown in Fig. 1, the main cutting edge 3m is curved in a substantially concave shape with respect to the rotation direction, and has a non-cutting edge at the outer peripheral end to prevent chipping of the cutting edge. A blunt portion 4 is formed. The radial rake angle α of this negative land portion 4 is given a negative rake angle, and ranges from -7° to -200°.
It is set within the range up to. Furthermore, the drill bit has
TiAIN coating has a film thickness of 2.5 μm to 3.5 μm
It is carried out in Because the main cutting edge 3m is curved, the cross-sectional shape of the chips coming out of the main cutting edge 3m is also curved, and the chips themselves have increased rigidity and become difficult to bend. It flows along the scooping surface for a long time without winding up in a tendril shape. On the other hand, in this embodiment, the auxiliary cutting edge 3s itself is also formed slightly concavely curved, or the angle between the main cutting edge 3m and this auxiliary cutting edge 3s (the angle between the respective tangents) θ is 10
It is set to be 0° or more. This θ is 100
If larger than
The chips coming out of the auxiliary cutting edge 3s are drawn toward the auxiliary groove 1s side by the force that tries to roll the chips coming out of the auxiliary cutting edge 3s toward the center, and together with the chips coming out of the auxiliary cutting edge 3s, the chips are drawn into the inner circumferential wall surface of the auxiliary groove 1s. can be collided with. In that case, the chips coming out of the main cutting edge 3m flow along a long path without leaving the rake face too much and collide with the inner circumferential wall surface of the sub-slot 1s, so the collision occurs elastically as in the case of a spiral shape. It does not absorb force, and when it collides, it bends in a state close to buckling and breaks completely into small pieces. Incidentally, if this angle θ becomes smaller than 1000, the chips coming out of the main cutting edge 3m and the chips coming out of the auxiliary cutting edge 3s will be separated, and the chips coming out of the auxiliary cutting edge 3s will roll toward the center. This force cannot be applied to the chips coming out from the main cutting edge 3m, and the chip holding from the sub-cutting edge 3s collides with the inner peripheral wall surface of the sub-slot 1s, causing the chips coming out from the main cutting edge 3m to The debris flows along the 1m main groove and is no longer broken into small pieces. Note that if the main cutting edge 3m and the auxiliary cutting edge 3s intersect as they are, the cutting edge shape at the intersection point P1 will become extremely sharp, which obviously causes chipping. The cutting edge shape in is rounded, which is very common sense. FIGS. 3 and 4 are graphs showing the results of a life test when the radial rake angle α of the negative land portion 4 was variously changed in a drill having a cutting edge shape as shown in FIG. 1, respectively. It is a diagram. The tool life in each test was determined by the number of holes drilled at the time the cutting edge chipped. The specifications and test conditions of the drill used in the test shown in Figure 3 are as follows. Drill specifications Trill material P2O Blade TiAIN coated drill Diameter 6 Scrap blade
Part length: 41 mm Overall length: 80 mm Tip center thickness: 0.94 mz Torsion angle: 30° Main groove center thickness taper O Groove width ratio: 0.9:1 Test conditions Cutting speed: 60 m/min Cutting feed: 0, 2 mu/rev Work material 850 C (II8230-2
50) Cutting length 13vrrtr through cutting
The specifications and test conditions of the trill used in the test of Kuzuura Emulsion Figure 4 are as follows. Drill specifications Trill material P2O Blade TiA] N coating = 8- Drill diameter 10zII+
Blade length 60mttr Total length 10571z Tip core thickness ]
, 24 am Torsion angle 30° Main groove core thickness taper 0 Groove width ratio 0.9:] Test conditions Cutting speed 50u/n+in Cutting feed 0, 2 ttrm/rev Work material S 50 C (HB230-250) cutting From the results shown in Figures 3 and 4, if the radial rake angle α of the negative runt portion 4 is between -7° and J-20°, the life expectancy will be It can be seen that there is a marked increase in the number of people. Here, when the drill diameter is D, the core thickness dimension of the main groove forming portion in the drill of this embodiment is set in the range of 0.25D to 0.4D. With this dimension, the main cutting edge is 3m.
Intersection point 1) 1 of the minor cutting edge 3s, that is, the position of the outermost peripheral edge of the minor cutting edge 3s. The effective range in which the chips coming out of the blade 3s can be made to flow toward the center of the drill is O, /II
) is below. The core thickness dimension of the minor groove forming portion is set in the range of 0.0/ID to 0.17D. This dimension corresponds to the set value range of the core thickness dimension of the main groove forming part, but it is the set value range of the dimension that can sufficiently reduce the cutting force (thrust) without thinning the chisel part. This is a set value range of dimensions that can ensure a sufficient length for the sub-groove 1s. The length dimension of the sub groove 1s is set in the range of 0.51) to ], ]D. These dimensions ensure a minimum re-grinding area, and in particular, allow the chips coming out of the main cutting edge of 3m to roughly follow the rake face without bending too much in the direction of coiling, and yet In order to form a sub-groove 1s to the point where it collides with the chips that are drawn in by the chips coming out of the trill and flow toward the center of the drill, the minimum value is 0.5D or more, and the necessary limit value to ensure drill rigidity. As 1. It is considered to be below the ID. Regarding these two limit values, the dimensions are such that a sufficient life can be obtained in terms of the relationship between the trill rigidity and the life. In the trill of this example, the groove width ratio is 08:1 to 1.7.1.
It is possible to set the groove width ratio over a wide range, and is effective over almost the entire range of groove width ratios that can be realistically set. Note that, as shown in FIG. 1, by cutting off the heel portion and enlarging the main groove space, it is possible to improve the evacuation of chips and to improve the penetration of the cutting curve. Instead of thinning, the sub-grooves 1s are formed to sufficiently reduce the chisel portion 2, so there is no need for thinning during repolishing. Since sufficient chip space can be ensured by forming the sub-groove 1s, it is particularly suitable for deep hole machining.

[Brief explanation of drawings]

FIG. 1 is a side view of the cutting edge shape of the carbide trill according to the present invention;
FIG. 2 is a side view of the carbide trill according to the present invention, and FIGS.
It is a graph diagram that does not show the results of a life test in which the radial rake angle of the negative land portion was varied in various ways. 1...Chip discharge groove, 1m...Main groove, 1s...Minor groove, 2 chisel section, 3. Cutting edge, 3m Main cutting edge, 3s.Minor cutting edge, 4.Negative land section, α.・Radial rake angle of negative land part

Claims (1)

[Claims] (1) A carbide drill in which a negative land portion (4) is formed at the outer peripheral end of the cutting edge (3), and the negative land portion (4) is coated with titanium/aluminum nitride. Radial rake angle (α)
A carbide drill characterized in that the angle is set to -20° or more and -7° or less.