JPH0747245B2 - 2-flute gun drill - Google Patents

Description

TECHNICAL FIELD The present invention relates to a two-blade gun drill provided with two chip discharge grooves extending linearly from the front end to the rear end of a tool body.

“Prior Art” Conventionally, as a two-blade gun drill used for deep hole machining, for example, those shown in FIGS. 9 and 10 are known. This two-flute gun drill 1 is the gun drill body
Equipped with 11. A tip body 12 is brazed to the tip of the gun drill body 11. The chip body 12 is provided with two chip discharge grooves 13, 13 from the front end toward the rear end. The chip discharge groove 13 is formed in a V-shaped cross section with α = 110 °. A cutting edge 14 is provided at the tip of the surface of the chip discharge groove 13 that faces the direction of rotation.
The rake face of the cutting edge 14 is provided with a first chip breaker 15 and a second chip breaker 16 for facilitating the cutting of chips. As shown in FIG. 10 and FIG. 11, the first chip breaker 15 is formed in a step shape from the inner peripheral side end portion to the outer peripheral side end portion of the cutting blade.
As shown in FIGS. 10 and 12, the second chip breaker 16 is provided so as to overlap with the first chip breaker 15 on the rake face of the inner peripheral side end of the cutting edge 14. ing.

"Problems to be Solved by the Invention" In the gun drill 1 described above, as shown in FIG. 13, the chips T are likely to interfere with the wall surface of the chip discharge groove to form a polygonal shape. Similarly, as shown in FIG. 14, polygonal chips T as shown in FIG. 15 are easily formed from the cutting blade 14 in the direction of arrow A. This tendency is particularly remarkable in materials having high toughness such as SCM and SNCM. Therefore, there are problems that the chips are not discharged smoothly, the cutting resistance increases, chatter and vibration occur, and the cutting power becomes unstable. Further, there is a problem in that re-polishing of the chip breakers 15 and 16 requires time and labor, resulting in high cost.

"Object of the Invention" An object of the present invention is to provide a gun drill capable of preventing vibration during cutting and reducing cutting resistance.

"Structure of the Invention" In the present invention, in a two-blade gun drill in which a tool body is provided with two chip discharging grooves extending linearly from the front end to the rear end, the chip discharging groove is formed in an arc shape in cross section. It is characterized by.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

1 and 2 are views showing a gun drill 2 according to the present invention. This gun drill 2 is a gun drill body 21
have. A tip body (tool body) 22 is brazed to the tip of the gun drill body 21. The chip body 22 is provided with two chip discharge grooves 23, 23 having a circular arc-shaped cross section from the front end to the rear end in a linear shape. Of the wall surfaces 24 defining the chip discharge groove 23, the outer peripheral end of the wall surface facing the rotation direction has a narrow flat surface extending from the front end to the rear end.
25 are formed. The angle of the groove width of the chip discharge groove 23, that is, the angle β at which the flat surfaces 24 and 25 at both ends of the chip discharge groove are seen from the axis of the chip body 22 is 90 ° as shown in FIG. It is set. On the other hand, a cutting edge 26 is provided at the tip of the surface of the wall surface 24 facing the rotation direction. The tip surface of the chip body 22 is X-type thinned. The rake face 28 of the inner blade 27 and the rake face 29 of the cutting edge 26, which are newly formed by this X-type thinning, are connected by the R face 30. The R surface 30 may be a chamfered surface. Further, an oil hole 31 for supplying cutting oil is formed in the tip surface of the chip body.

Thus, in this gun drill 2, the tip body
Since 22 is provided with two chip discharge grooves 23, 23 having an arcuate cross section from the front end to the rear end, the chips can be smoothly curled as shown in FIG. Similarly,
As shown in FIG. 5, chips T which are smoothly curled as shown in FIG. 6 are generated from the cutting edge 26 in the direction of arrow B. Therefore, the chips can be easily divided, and the chips can be smoothly discharged. As a result, vibration can be prevented, cutting resistance can be reduced, and cutting power can be reduced. . Further, since the angle β of the groove width of the chip discharge groove 23 is 90 °, the radius of curvature of the chip curling can be reduced. Therefore, it is possible to prevent the chips from coming into contact with the inner wall surface of the cut hole, easily divide the chips, and improve the chip discharging property. Further, since the tip surface is subjected to X-type thinning, the thrust load can be reduced and the centripetality of the drill can be improved. Further, since the rake face 28 of the inner blade 27 formed by X-type thinning and the rake face 29 of the cutting edge 26 are connected by the R face, it is possible to form an edge in cutting a hard and highly tough material such as stainless steel. It is possible to prevent chipping.

Further, since the narrow flat surface 25 is formed at the outer peripheral side end of the wall surface 24 that defines the chip discharge groove 23 and faces the rotation direction, the outer peripheral end portion of the cutting blade 26 and the wall surface 24 are formed. It is possible to prevent chipping from occurring on the outer peripheral side end of the wall surface facing the rotation direction.

By the way, for the above gun drill 2 with an outer diameter of 10φ, the work material …… SCM435 (HRC25), the cutting speed …… V = 70m / min
(N = 2228 rpm), cutting feed ... As a result of a cutting experiment conducted under the condition of f = 0.16 mm / rev, the power value of the conventional gun drill was 6.3 kw, whereas the power value of the gun drill of the present invention was It was 4.4 kW, and it was possible to reduce power consumption by 30% compared to conventional tools. In addition, the chips can be curled smoothly, and the finished surface accuracy was about 12S, which was 7S, and a good finished surface could be obtained.

Although the angle β of the groove width of the chip discharge groove 23 is set to 90 ° in the above-mentioned embodiment, the invention is not limited to this. For example, as in the two-blade gun drill 4 shown in FIG. 7 and FIG. The groove width angle β may be 110 °.

[Advantages of the Invention] As described above, according to the present invention, since the chip discharge groove is formed in an arc cross section, the chips can be smoothly curled, and the chips can be easily divided. Therefore, it is possible to prevent vibration and reduce cutting resistance.

[Brief description of drawings]

FIGS. 1 and 2 are views showing an embodiment of the present invention, in which FIG. 1 is a front end view in the axial direction thereof, FIG. 2 is a side view thereof, and FIG. 3 is an arrow P in FIG. FIG. 4 is an enlarged view of a portion, FIG. 4 is a front view in the axial direction showing a state in which a work material is being cut by the two-blade gun drill shown in FIGS. 1 and 2, and FIG.
6 and 7 are side views showing the generation direction of chips when the work material is cut by the two-blade gun drill shown in FIG. 2 and FIG. 2, and FIG. 6 is a diagram showing chips generated from the cutting blade in FIG. FIG. 8 and FIG. 8 are views showing another embodiment of the present invention.
FIG. 8 is a front view in the axial direction, FIG. 8 is a side view thereof, and FIGS. 9 and 10 are views showing an example of a conventional two-blade gun drill. FIG. 9 is a side view thereof. The figure is a front view in the axial direction thereof, FIG. 11 is a sectional view taken along the line XI-XI in FIG. 10, and FIG. 12 is a sectional view taken along the line XII-XII in FIG.
Fig. 13 is an axial tip view showing the state in which the work material is being cut by the two-blade gun drill shown in Figs. 9 and 10,
The figure is a side view showing the generation direction of chips when the work material is cut by the two-blade gun drill shown in Figs. 9 and 10, and Fig. 15 shows the chips generated from the cutting blade in Fig. 14. It is a figure. 2 …… 2-flute gun drill, 4 …… 2-flute gun drill, 22
…… Chip body, 23 …… Chip discharge groove.

Claims (1)

[Claims] 1. A two-flute gun drill in which a tool body is provided with two chip discharge grooves extending linearly from the front end to the rear end, wherein the chip discharge grooves are formed in an arc shape in cross section. Two-flute gun drill.