JPH1029107A - Drill with step - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely divide chips produced from a step cutting edge section into pieces by forming a level difference among a part of a small diameter part sub cutter edge, a step part cutter edge and a large diameter part sub cutter edge and producing a breaker wall equivalent to a breaker projection in the vicinity of the step cutter edge. SOLUTION: A groove for lowering the positions of a part of the end side of a small diameter part sub cutter edge 10, a step cutter 4 and a large diameter part sub cutter 11 connected to the outer end of the former cutter edge more than the sub cutter edge side groove surface of a chip discharge groove 5 is provided in the chip discharge groove 5, and a breaker wall 17 is provided in the vicinity of the step cutter edge 4 so as to be raised from the position of a cutter edge face 9 toward the chip discharge groove 5. This breaker wall 17 is extended from the longitudinal middle part of the small diameter part sub cutter edge 10 close to the end of the large diameter part sub cutter edge 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepped drill used for drilling a stepped hole in a metal or chamfering a hole edge simultaneously with the drilling.

[0002]

2. Description of the Related Art In a stepped drill in which the diameter of a drill becomes large in the middle, chips are also generated from a step cutting edge 4 between a small diameter portion 1 and a large diameter portion 2 as shown in FIG. .
The chips flowing out of the stepped cutting portion are generally narrow in width, and unlike the chips flowing out of the main cutting edge 3, the difference between the inside and outside flowing speeds is small, so that little distortion due to the speed difference is applied. , Very hard to break.

[0003] Nevertheless, a typical step drill is shown in FIG.
The step cutting edge 4 is formed at a position where the groove surface of the chip discharge groove 5 is used as the rake face 9 of the step cutting edge as shown in FIG.
There is no function to apply breaking distortion to chips flowing out from the step cutting edge. For this reason, the chips generated at the stepped cutting edge may extend long without breaking, and may stick to the tool.

In order to solve this problem, Japanese Utility Model Laid-Open No. 4-97606 proposes providing a breaker groove in a large-diameter outer peripheral cutting edge (step cutting edge in the present application). Japanese Patent Application Laid-Open No. Hei 4-27513 discloses a chip breaker similar to the initial breaker after re-grinding the stepped cutting edge, in which a plurality of breaker grooves parallel to the stepped cutting edge are provided at a constant pitch in the longitudinal direction of the chip discharge groove. Is proposed.

[0005]

Problems to be Solved by the Invention
In view of the fact that the breaker groove provided on the outer peripheral cutting edge portion of the large-diameter portion of the drill disclosed in Japanese Patent Application Laid-Open Publication No. H11-27139 is considered to be a groove, it is likely that the rake face is simply dug down. However, in such a simple breaker groove, if the chip is made of a soft metal such as aluminum or an aluminum alloy which is easily lifted from the rake face, or if the chip is thin or thinner, the chip gets over the breaker groove, and the chip breaks over the breaker groove. May not function as a breaker. In addition, since chips are also generated from the corners where the step cutting edge and the small diameter portion intersect, there is a problem that chips stay at the corners and clogging of chips occurs.

[0006] The same applies to the drill disclosed in Japanese Patent Application Laid-Open No. H4-275813, and these conventional techniques do not sufficiently solve the problem of sticking chips from tools.

[0007] Therefore, an object of the present invention is to ensure that even if chips generated by a stepped cutting edge are easy to float from a rake face, the chips are cut off.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, according to the present invention, there is provided a stepped cutting portion which is parallel to a small diameter portion minor cutting edge and a large diameter portion minor cutting edge and located between a small diameter portion and a large diameter portion. Equipped with a breaker wall at a position that enters the center of the drill from the inner end of the blade, and a part of the small diameter sub-cutting edge, the stepped cutting edge, and the large diameter sub-cutting edge along the sub-cutting edge of the chip discharge groove Thus, a groove is provided to step down from the groove surface to the rear in the rotation direction of the drill.

[0009]

According to the drill of the present invention, the stepped cutting edge is placed at a position lower than the groove surface of the chip discharge groove, and the breaker projection is formed on the rake face instead of the breaker groove without deteriorating the chip discharge performance. It was made.

[0010] In the case of the breaker groove, no step is formed between the step cutting edge and the chip discharge groove, so that the chip that easily floats from the rake face gets over the breaker groove. If the breaker wall stands and is blocked at the outflow destination, the chip collides with the breaker wall and is surely curled and divided. When the same effect is produced by providing a breaker protrusion in the chip discharge groove, the breaker protrusion hinders the smooth discharge of the chip. Because it is located at a position lower than the groove surface of the groove and the flatness of the groove surface is maintained,
Good chip evacuation is also maintained. In addition, since the breaker wall is provided continuously from the middle of the small diameter portion to the position of the large diameter portion, the chip generated from the corner where the step cutting edge and the small diameter portion intersect is also effectively separated. is there.

[0011]

1 and 2 show an embodiment of a stepped drill according to the present invention. This drill is shown in Figure 1
As shown in FIGS. 1A and 1B, the large diameter portion 2 and the small diameter portion 1 are sequentially connected to the tip of the shank 16 and the main cutting edge 3 and the chisel blade 6 are provided at the tip of the small diameter portion 1 (see FIG. 1C). ) And a thinning groove 7 for narrowing the width of the chisel blade, and a step cutting edge 4 is provided at the boundary between the small diameter portion 1 and the large diameter portion 2. 5 is 18
A chip discharge groove provided at a 0 ° symmetrical position, 8 is a rake face of a main cutting edge, 9 is a rake face of a step cutting edge, 10 is a minor cutting edge rake face,
11 is a large diameter portion secondary cutting edge, 12 is a small diameter portion margin, 13 is a large diameter portion margin, 14 is a small diameter portion round land having the same diameter as the diameter of the small diameter portion 1, and 15 is a same diameter as the diameter of the large diameter portion 2. It is a large diameter round land.

If the chip discharge groove 5 is a straight groove as shown in the drawing, it is easy to make a second cut (relief processing) on the outer periphery of the land portion.
Although the round lands 14 and 15 effective for preventing the steadying of the drill can be easily provided, the present invention is also effective for a twist drill provided with a twist groove.

The main cutting edge rake face 8 is a groove surface of the chip discharge groove 5, and the small diameter portion sub cutting edge 10 is provided with a small diameter portion margin 12 which is not secondly formed with the groove surface of the chip discharge groove 5. Are formed at the intersection ridges.

The above configuration is the same as the conventional step drill. That is, in the present invention, the position of the part on the terminal side of the small diameter portion sub-cutting edge 10, the stepped cutting edge 4, and the position of the large diameter sub-cutting edge 11 connected to the outer end of the cutting edge are shown in FIG. ) And (c), a groove that is lower than the groove surface on the side of the sub-cutting edge of the chip discharging groove 5 is provided in the chip discharging groove 5 so that the stepped cutting edge 4 is formed.
From the position of the step cutting edge rake face 9 in the vicinity of the
, Which is different from the conventional stepped drill. The rake face 9 is the groove bottom face of the groove additionally provided in the present invention, and the breaker wall 17 is the side face of the groove.

The breaker wall 17 is parallel to the small diameter portion minor cutting edge 10 and the large diameter portion minor cutting edge 11 so that the small diameter portion minor cutting edge 10
Of the large diameter portion sub-cutting edge 11 from the middle of the longitudinal direction (near the end) to the vicinity of the end of the large diameter portion sub-cutting edge 11. By doing so, re-grinding for regenerating the step cutting edge and the breaker wall can be performed in the same manner as a normal step drill, and no special equipment is required.
Further, chips generated on the inner end side of the step cutting edge 4 are also satisfactorily treated.

The rake face of the large-diameter sub-cutting edge intersecting with the large-diameter portion margin 13 changes into a stepped cutting rake face by re-grinding. Therefore, here, it was avoided to distinguish between the rake face of the stepped cutting edge and the rake face of the large-diameter sub-cutting edge.

The breaker wall 17 may be a curved surface as shown in FIG. 3 in addition to an angle surface having an angle θ with respect to the rake face 9 as shown in FIG. For angular surfaces,
The value of θ is suitably about 90 ° to 45 °. The step S (see FIGS. 2C and 3) between the step cutting edge 4 and the large diameter sub-cutting edge 11 and the chip discharge groove groove surface is about 0.7 mm, and the width W of the rake face 9 is stepped. Inner end 4a of partial cutting edge 4 (FIG. 2A)
Or (c)), a value that is inward by about 1 mm is appropriate. If θ and S are excessively large or W is too small, the chips tend to be slightly clogged, and conversely θ and S
Is too small or W is too large, the chips tend to grow. Further, as shown in FIG. 4, the rake face 9 may be inclined in a direction in which the edge angle becomes sharp.

As shown in FIGS. 2A and 2B, the stepped drill of the present invention configured as described above has the chip 18 scooped by the stepped cutting edge 4 butting against the breaker wall 17. Curls and is finely divided.

FIG. 5 shows a comparison of the shape of the chip by the step cutting edge between the drill of the present invention shown in FIG. 1 and the conventional drill (without a chip breaker) shown in FIG.

In the comparative test, the diameter of the small diameter portion 1 was 17.5 m.
m, diameter of large diameter part 2 19mm (diameter difference 0.75mm on one side)
Using a drill. Fig. 2 (c)
Was set to 0.7 mm, and the values of W and θ were changed as shown in FIG.

The work material is an aluminum alloy (AC4C-
T6), drilling speed 1900 rpm (peripheral cutting speed V 速度 113 m / min), feed speed 0.15 mm / re
Processing was performed using a water-soluble cutting oil under the condition of v. In this test, the processing area formed by the small diameter portion was previously processed by another drill so that chips were generated only from the stepped cutting edge portion.

As can be seen from FIG. 5, the chips by the conventional drill without a breaker are extended without breaking. On the other hand, the chips (No. 1 to No. 8 in FIG. 5) generated by the step cutting edge of the drill of the present invention do not extend long without cutting. The chips No. 1 to No. 3 tend to be slightly clogged, but are surely separated. Also, No4 to No7
The chips are smoothly curled and finely divided.
Furthermore, although the chip of No. 8 is slightly stretched, unlike the chip of the conventional drill, it curls and is divided into several pieces.
Better results are obtained than with conventional drills.

[0023]

As described above, the stepped drill according to the present invention has a part near the stepped cutting edge by dropping a part of the small diameter subcutting edge, the stepped cutting edge and the large diameter subcutting edge. A chip breaker wall corresponding to the chip breaker projection was formed, so that chips generated from the stepped cutting edge portion without deteriorating the chip discharge performance can be reliably used even when the chip is likely to rise from the rake face. The cutting process can be performed, and the problem that chips are protruded long and stick to the tool can be eliminated, thereby making it possible to eliminate interruption of cutting.

[Brief description of the drawings]

FIG. 1A is a side view showing an embodiment of the drill of the present invention. FIG. 1B is a side view of the same drill at a position rotated by 90 °. FIG.

2A is an enlarged view of a portion surrounded by a chain line frame in FIG. 1A. FIG. 2B is a cross-sectional view taken along a line AA in FIG. 2A. FIG. Figure

FIG. 3 is a sectional view showing a modified example of a breaker wall.

FIG. 4 is a cross-sectional view showing a modified example of a rake face of a groove installation portion.

FIG. 5 is a diagram comparing the shapes of stepped chips between the drill of the present invention and a conventional drill.

FIG. 6A is a side view of a conventional stepped drill. FIG. 6B is a front view of the drill.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Small diameter part 2 Large diameter part 3 Main cutting edge 4 Step cutting edge 4a Inner end of step cutting edge 5 Chip discharge groove 6 Chisel blade 7 Thinning groove 8 Main cutting edge rake face 9 Step cutting edge rake face 10 Small diameter part Sub cutting edge 11 Large diameter sub cutting edge 12 Small diameter margin 13 Large diameter margin 14 Small diameter round land 15 Large diameter round land 16 Shank 17 Breaker wall 18 Chip

Claims (1)

[Claims] 1. A stepped drill having a straight or twisted chip discharge groove, wherein a stepped cutting edge parallel to a small diameter portion minor cutting edge and a large diameter portion minor cutting edge and located between a small diameter portion and a large diameter portion. A breaker wall is provided at a position closer to the center of the drill than the end, and a part of the small diameter sub-cutting edge, the stepped cutting edge, and the large diameter sub-cutting edge are arranged along the sub-cutting edge of the chip discharge groove. A stepped drill characterized in that a groove is provided for stepping down from the rear in the rotation direction of the drill.