JPS61109606A - Twist drill - Google Patents

Abstract

PURPOSE:To aim at enhanced accuracy of machining by means of improved centripedalism of a tool by setting up a relief surface with two steps consisting of the first and second relief surfaces, and forming a band-shaped stand surface on the face extending from the second relief surface. CONSTITUTION:Respective pairs of front cutting edge 5, relief surface 6 and thinning 7 are formed on the tip area of a tool made of sintered hard alloy. The relief surface 6 is set up in two steps consisting of the first relief surface 6a and second relief surface 6b, particularly for the purpose of enhancing its centripetalism. A band-shaped slant surface 9 is in flat with the relief surface 6b and is a result of 'so-called' chamfer to be positioned on its extending face. Provision of such slant surface 9 can enhance the centripetalism of a tool, duly improving the accuracy of machining.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a twist drill made of cemented carbide and suitable for drilling holes in steel, cast iron, aluminum, and the like.

(Prior art) Conventionally, as this type of drill, for example, the
18163, Japanese Patent Publication No. 58-22283, etc. are disclosed. These are cutting edge configuration 1
Excellent cutting performance is recognized due to the presence of a gap near the center of rotation.

However, this method cannot necessarily be applied to small-diameter twist drills, and improvements such as other shapes are desired.

(Problems to be Solved by the Invention) The present invention generally aims to improve the cutting performance of a small-diameter twist drill with a cutting edge diameter of about 3 to 20 m.

Furthermore, the present invention aims to improve the shape of the cutting edge, facilitate its manufacture, and achieve stability in quality.

Furthermore, the aim is to improve chip disposability and life span.

(c) Means for Improving Problems) The present invention has been made in view of the above-mentioned points, and the outer peripheral portion of the tool body made of cemented carbide is provided with a helical groove $1. CF=
A land portion with an i-jin is formed, and a land portion with a tip angle θ is formed at the tip portion.
In the twist drill in which a pair of front cutting edge ridges, a flank face, and a thinning are formed respectively, the flank face is formed by a two-step face consisting of a primary flank face and a secondary flank face, and the thinning is the secondary flank surface.

The front cutting edge is formed in a cross shape or an S shape, and the intersection of the front cutting edge with the thinning near the center of one revolution is chamfered by a narrow belt-shaped inclined surface that is an extension of the secondary flank. 9, and a cutting edge starting edge is formed between the first flank and the first flank.

(Function) In the twist drill of the present invention, the flank face is configured as a two-step face consisting of a primary flank face and a secondary flank face, and when forming the secondary flank face, a band-shaped inclined face is formed on the extension thereof. By being ground.

This has the effect of increasing the centripetal nature of the tool itself.

Mata 1 The twist drill of the present invention has a cutting blade configuration that covers the brittleness of cemented carbide, so it can be applied at high speed to steel cutting, which has not been applied in the past.

(Example) An example of the twist drill of the present invention will be described below with reference to FIG.

In Figure 1 and Figure 2, (1) is carbide.

The tool body is made of an alloy, and its outer circumference is made of an alloy.

Land portions (4) with twisted grooves (2), ridges and margins (3) are respectively formed. At the tip thereof, a pair of front cutting edge ridges (5) having a tip angle θ,
A flank (6) and a thinning (7) are respectively formed. In this case, the flank (6) is particularly configured such that the first flank (6a) and the second flank (6) increase centripetality.
b) It is based on a two-stage surface consisting of.

The thinning (7) is formed on the secondary flank C6b), and is either a so-called cross-shaped thinning like a stone as shown in FIGS. 2 and 4, or an S thinning as shown in FIG.
Formed as something of a shape.

Further, the front cutting edge (5) is formed in a straight line as shown in FIG. 2, or in the form of a portal as shown in FIG.

These are the core thickness and the clearance angle of the primary clearance surface (6a).

It changes depending on the shape of the twisted groove (2), etc.

Furthermore, this front cutting edge ridge (7) has a cutting edge starting edge ridge (8) formed near its rotation center. This cutting edge starting edge (8)
is formed by providing a strip-shaped inclined surface (9) at the intersection with the thinning (7) near the center of one rotation.

And, this band-shaped inclined surface (9) is the secondary flank surface (
It is so-called chamfered so that it is on the same plane as 6b) and located on its extension. This situation is made clear by FIGS. 2 and 3. The chamfer amount δ
varies depending on the tool diameter, but is usually in the range of 0.05 to 0.2B.

The primary flank (6a) is ground to 1, for example 10°, and the secondary flank (6b) is ground to 25°, for example.

Furthermore, in FIG. 5, the S-shaped thinning (7) is formed as described above, but the primary flank (6a) and the secondary flank (6, b) R: r - c ha .

Unlike the two-stage plane mentioned above, it is formed of a two-stage conical surface.

In addition, when the front cutting edge ridge (5) is used for cutting, it is desirable that the ridgeline portion of the remaining part be angled or rounded to match the cutting edge starting edge ridge (8).

This compensates for the brittleness of cemented carbide, which greatly reduces chipping of the cutting edge.

Note that when the twist drill of the present invention is used for steel such as 5550, the ratio (W/R') of the groove width W of the twist groove (2) to the width R of the land portion (2) is usually 0.
It is set in the range of 4 to 1.2.

However, if high rigidity is considered, 0.5 to 0.6 can be adopted. In the case of cutting aluminum, very high rigidity is not required, and rather chip discharge is taken into consideration, so the ratio is increased above the above-mentioned upper limit of 1.2.

Furthermore, the twist drill of the present invention can improve cutting performance and service life by forming a hard coating layer such as TiC or TiN on the surface of the tool body (1). In this case, when 555C is used as the rigid material, the cutting conditions are such that the tool diameter is 3 to 20
m, cutting speed ■; 30 to 70 m/min, feed') f
= o, x s ~ o, s, 7 rev is the standard.

In this embodiment, the tool body (1) k and the shaft 1 yank part (10) are also made of cemented carbide, but only the tip of the tool body (1) is made of cemented carbide, and the rest of the tool body (1) is made of cemented carbide. When brazing to a steel part, a modification in which the shank part (lO) is made of steel can of course be considered.

(Effects of the Invention) As described above, the present invention employs a cutting edge configuration having a rear cutting edge (8), and therefore has the following effects.

First, it shows excellent cutting action when drilling steel. This is because conventional cemented carbide twist drills
That's something I couldn't get. In other words, as a rigid material, 8
55C was set, and the cutting conditions were *V = 40 tn.
/ min, feed j) f = 0.3 m/red, hole depth L) / cutting edge diameter (D) = 2.5, 21 when drilling
This is because even in the case of 0-size machining, the amount of expansion of the hole diameter was small and the damage to the cutting edge was small.

Second, the tool has good centripetal properties. this is.

This is due to the presence of the band-shaped inclined surface (8) mentioned above.

Along with this, large-scale processing accuracy can also be improved.

Thirdly, the magic properties of cemented carbide are covered, and it can be manufactured easily. This is because this can be achieved by the presence of the band-shaped inclined surface (8) and by honing the remaining cutting edge ridge.

[Brief explanation of drawings]

Fig. 1 is a front view showing an embodiment of the twist drill of the present invention, Fig. 2 is an enlarged bottom view of the twist drill, Fig. IEa is a partial side view of Fig. 2, and Fig. 4 is an enlarged view showing a modification. The bottom view, FIG. 5, is an enlarged bottom view showing a modified example. (1)...Tool body (2)...Land part (3)...Margin (4)...
...Twisted groove (5) ...Front cutting edge ridge (6)
...Fleet surface (6a)...Primary flank surface (6b)...Second flank surface (7)...Thinning (8) ...After the cutting edge starting end (9) ...Band-shaped inclined surface

Claims (1)

[Claims] The outer peripheral portion of the tool body (1) made of cemented carbide has a land portion (
2) are respectively formed, and at the tip thereof, a pair of front cutting edge ridges (5) formed by the tip angle θ,
In the twist drill in which a flank face (6) and a thinning (7) are respectively formed, the flank face (6) is a first flank face (6a) and a second flank face (6a).
It is formed by a two-step surface consisting of a secondary flank surface (6b), the thinning (7) is on the secondary flank surface (6b) and is formed in a cross shape or an S shape, and the front cutting edge The ridge (5) is chamfered at the intersection with the thinning near the center of rotation by a narrow strip-shaped inclined surface (9) on an extension of the secondary flank (6b),
A twist drill characterized in that a cutting edge starting edge (8) is formed between the primary flank (6a) and the primary flank (6a).