JP2001328015A - Twist drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tool for promoting guiding performance of a drill and obtaining excellent stability by remarkably lengthening the drill service life without inducing chipping of an edge and breaking of a drill body in a cemented carbide drill when becoming intermittent cutting like the parting surface side of through hole work. SOLUTION: This twist drill composed of cemented carbide or TiCN cermet, is characterized in that another pair of margin parts are arranged on the heel part side for connecting a land part and a cutting discharge groove in a cross- sectional view perpendicular to the axis of the twist drill, and a position of the margin parts is formed in a position of 60 deg. to 105 deg. toward the heel side from the cutting edge corner relative to a straight line joining both cutting edge corners together by passing through the drill center.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention improves chipping resistance and breakage resistance in the processing of a thin plate having a drill diameter of 0.5 D or less for steel and the hole processing accompanied by intermittent cutting such as when a through hole comes out. The present invention relates to a drill capable of prolonging the life of the drill and providing excellent guideability and stability.

[0002]

2. Description of the Related Art In recent years, twist drills made of cemented carbide have been widely used. Carbide drills have excellent wear resistance and can perform high-speed cutting and high-efficiency cutting.However, due to low toughness, they have poor mechanical strength such as bending strength or bending force, and holes with intermittent cutting for steel. In the processing, chipping of the cutting edge and breakage of the drill body are induced, and the life of the drill is remarkably reduced, so that the drill is rarely used. For this reason, in order to improve chipping resistance and breakage resistance in intermittent cutting, it is necessary to supplement guideability. For example, "Drilling Minden" (Cutting Oil Technology Study Group, published) No. 31
Item, Fig. 46, It is well-known that double-margin drills with carbide straight grooves are used for drilling cast iron and aluminum alloys with relatively good machinability, and that one-shot machining can achieve the same accuracy as reaming. It is. However, the straight grooves are not suitable for cutting steel and are not used. Further, in the case of a twist drill, see JP-A-8-155713.
There is a double margin drill described in
A margin along the torsion groove and a second spaced apart
Margins are disclosed.

[0003]

In drilling involving intermittent cutting for steel, carbide drills have poor mechanical strength such as bending strength or bending strength due to the low toughness of cemented carbide. ,
This causes chipping of the cutting edge and breakage of the drill body, thereby significantly reducing the life of the drill. However, when examining the cause of this chipping and breakage, it was found that there is more throughhole drilling than blind hole drilling, especially when the through surface side of throughhole drilling is unbalanced and intermittent cutting is likely. I understood.
Therefore, by providing another pair of margins on the heel side where the land and the chip discharge groove are connected, it is intended to provide a tool that measures the guideability of the drill and provides excellent stability. It is.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention relates to a twist drill made of a cemented carbide or a TiCN-based cermet, wherein the land portion and the cutting discharge groove are connected in a cross section perpendicular to the axis of the twist drill. Another pair of margins are provided on the heel side, and the position of the margins is set to a straight line passing through the center of the drill and connecting the two cutting edge corners (hereinafter, referred to as
Abbreviated as central angle. ), A twist drill formed at a position of 60 ° to 105 ° from the cutting edge corner toward the heel side.

[0005]

First, in the heel portion connecting the land portion and the chip discharge groove in the cross section perpendicular to the axis of the twist drill, another one is provided.
The drill has 4 holes on the inner wall of the hole because of the pair of margins.
The drill is guided by three margins and supports the drill at three locations on the inner wall of the hole against stress from one side during intermittent cutting, so that the center of the drill is prevented from fluctuating due to stress, and intermittent Even in cutting, the cutting depth of the cutting edge is constant, and chipping resistance and breakage resistance are improved. As described above, by increasing the margin of the drill, the centripetality can be improved. Next, in the cross section perpendicular to the axis of the twist drill, the position of the margin portion passes through the center of the drill and, with respect to a straight line connecting both cutting edge corners, moves the other margin portion toward the heel side from the cutting edge corner. It is the angle of the land portion that is set at the position of 60 ° to 105 ° in the central angle. When the angle is less than 60 °, the width of the land becomes too small and the strength is insufficient. Is 75
Degrees, the space for chip discharge becomes small, and problems such as chip lumping tend to occur.
° to 105 °. Furthermore, the width of the margin portion was set to the range of 0.02 to 0.15D of the drill diameter,
If it is less than 0.02D, the margin width is small and there is no substantial effect. If it exceeds 0.2D, the margin width becomes too large and the guideability is improved, but the frictional resistance due to the contact of the margin part becomes large and is ignored. Since it becomes impossible, the width of the margin portion was set to the range of 0.02 to 0.15D of the drill diameter. In addition, the contact length of the drill margin is insufficient,
Even in the processing of a groove plate having a drill diameter of 0.5 D or less, which tends to cause unstable cutting, the guide surface is guided at four places, thereby improving the chipping resistance, breakage resistance and the processed surface roughness.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a preferred embodiment of the present invention, a pair of margins of a tip edge of a drill and corner portions of both outer peripheral cutting edges and a central angle ω = 85 were used by using a drill diameter D = 8.7 mm made of ultrafine cemented carbide.
A pair of margin width = 0.45 mm margin is added at the position of °, and a twist speed of 47 m / min, feed amount per rotation = 5, using five twist drills provided with a total of four margin portions 0.22mm / rev, machining depth = 25m
m (penetration, removal, black scale state), hole pitch = 8.0 mm
(0.7mm intermittent cutting), under wet cutting conditions, S50C
(HB160-180) is machined to 1000 holes, the maximum flank wear of both cutting edge corners after machining, and when chipping etc. occurs, the chipping length is measured.
It is described in Table 1. In the present invention, a cutting test was performed by coating with a TiAlN film. For comparison, five drills at two guide portions were similarly tested as in the prior art, and the results are also shown in Table 1.

[0007]

[Table 1] Sample No. 1 2 3 4 5 Sample of the present invention Right cutting edge Wear Wear Wear Wear Wear Wear 0.23 0.40 0.29 0.34 0.35 Left cutting blade Wear Wear Wear Chip wear 0.31 0.34 0.16 0.25 0.28 Conventional example Right cut wear 1.93 0.89 2.10 1.98 1.60 Left cutting edge Chipping chipping Chipping chipping 1.52 1.43 1.63 1.57 1.45

As shown in Table 1, as shown in the example of the present invention, a drill provided with four guide portions has one chipping out of five samples (1/1).
Not only 10 corners) but also normal wear, whereas in the conventional example, chipping occurred in 4/5 (9/10 corners). In the above embodiment, the margin width is set to 0.5 mm (drill diameter: 0.057D). However, the margin width is increased in the case of a thin plate or a shallow hole, and reduced in the case of a deep hole. By providing a margin portion, stability of the guide property and friction resistance can be adjusted.

[0009]

By applying the present invention, the guideability of the drill is improved, chipping is reduced in intermittent cutting of steel, and stable cutting performance is made possible.

Claims (2)

[Claims] In a twist drill made of a cemented carbide or a TiCN-based cermet, another pair of margins is provided on a heel side where a land portion and a cutting discharge groove are connected in a cross section perpendicular to the axis of the twist drill. A part is provided, and the position of the margin part is 60 ° from the cutting edge corner toward the heel side with respect to a straight line connecting the two cutting edge corners through the center of the drill.
A twist drill formed at a position of up to 105 °. 2. The twist drill according to claim 1, wherein the width of the margin is set to 0.02 to 0.
A twist drill formed in a range of 15D.