JPH08155713A - Twist drill - Google Patents

Abstract

PURPOSE: To provide a twist drill consisting of a cemented carbide that performs drilling of a steel material and is provided with superior drilling accuracy. CONSTITUTION: A twist drill with double margins consists of single material out of coated cemented carbide, cermet, and coated cermet and the first margin 5 along a twist groove 2 is set to a two-stage back taper. As for the size of the back taper, the range (B) in the base side is set larger the range (A) in the tip side. The second margin 6 arranged apart from the first margin 5 has its range (C) set almost same size of the range (A) and the diameter (D) and the back taper are set to the same size as the range (A). The length of the range (A) and the range (C) are set to such a necessary minimum size so as to secure regrinding and not to cause too much fretting resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a twist drill made of an ultra-hard tool material, and more particularly to a drill capable of drilling a steel material with good hole diameter accuracy.

[0002]

2. Description of the Related Art When drilling with good hole diameter accuracy,
Conventionally, for cast iron, aluminum alloys, etc., a straight blade drill with a so-called double margin has been widely put to practical use, and hole diameter accuracy of IT grade 7 to 8 has been obtained. However, this straight blade drill cannot be applied to steel materials due to problems such as cutting resistance and chip discharge.

Therefore, a twist drill having a twist groove is used for steel materials. This is because the spiral groove makes the rake angle of the cutting edge a regular angle, but the hole diameter accuracy obtained by machining cannot be said to be satisfactory. Generally, the improvement of hole diameter accuracy by twist drill is
This has been achieved by increasing the tool rigidity. For example, techniques such as shortening the total length of the tool to form a stub drill, or increasing the core thickness of the drill and reducing the cross-sectional area of the groove to achieve high rigidity are available.

[0004]

However, even with the twist drill having the increased tool rigidity as described above,
For steels, at best, an IT grade of accuracy of only 9-10 is guaranteed. If a twist drill with a so-called double margin can be realized, such a problem can be solved, but in a twist drill made of a super-hard tool material, the resistance due to rubbing at the margin becomes too large,
The problem of breakage remains.

On the other hand, a twist drill with a double margin made of HSS, which is excellent in toughness, is resistant to breakage, but it can be applied only in the low cutting speed region, and because of the high affinity between HSS and steel material, it is difficult to cut. The blade is likely to have a built-up edge. This configured cutting edge lowers the hole diameter accuracy by widening the hole diameter or raising a tear surface.

[0006]

The present invention has been made in view of the above problems, using a super-hard tool material excellent in wear resistance even at a high cutting speed as a raw material, and breakage hardly occurs, (EN) A twist drill capable of drilling a steel material with good hole diameter accuracy.

In the present invention, any of coated cemented carbide, cermet and coated cermet is used as the drill material, and the twist drill is made of a single material. Then, the land portion is provided with two pairs of margins.
In the first margin along the twist groove, the size of the back taper is two steps, and the back taper in the range B on the base side is larger than the back taper in the range A on the tip side. The size of the back taper at A is (0.02 to
0.1) / 100, and the size of the back taper of the B portion is preferably (0.3 to 0.6) / 100.

The second margin spaced apart from the first margin has its length C substantially equal to A, but its length is 0.5D with respect to the diameter D. ~
2D is suitable. Further, the outer diameter D of the C portion and the size of the back taper are also the same as those of the A portion.

The clearance angle of the first clearance surface at the tip of the tool body is preferably 4 ° or less. More preferably, the oil hole penetrates from the rear end to the tip, and at least the cutting edge portion is provided with an oil hole accompanied by a twist along the twist groove, or the first margin and the second hole are provided. It is formed so that the land portion sandwiched by the margin has a relatively shallow twist groove.

[0010]

The present invention is applied to drilling a steel material by using a twist drill having a positive rake angle by twisting, and aims to secure the hole diameter accuracy of the machined hole by the guide action by the two pairs of margins. To do. The tool material has a high longitudinal elastic modulus and uses a single ultra-hard tool material that does not easily bend, giving it tool rigidity, and it can be used in the high cutting speed range and is unlikely to cause chip welding. You have selected the material.

Further, the first margin has a large back taper from the middle so that the abrasion resistance on the base side is large so that the abrasion resistance is not increased and is broken due to the provision of two pairs of margins. Is decreasing. The second margin also has its length kept to a necessary minimum so that the abrasion resistance does not become excessive.

Further, the oil hole penetrating the inside of the tool body is
This has the effect of forcibly discharging chips to the outside of the hole during drilling, and at the same time reduces the scratch resistance by sufficiently supplying the cutting fluid to the two pairs of margins.
The twisted groove provided between the first margin and the second margin is particularly formed in the second groove when the external groove is used for drilling.
The cutting fluid is sufficiently supplied also to the margin.

The reduction of the clearance angle of the first flank of the drill tip is also for suppressing vibration and improving machining accuracy.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings.

In the twist drill shown in FIGS. 1 to 3, the outer periphery of the tool body 1 is composed of a pair of twist grooves 2 and a land portion 3. The twist groove 2 is in contact with a flank that forms a tip angle θ at the tip, and forms a cutting edge 4. For the tool body 1, a single material among the superhard tool materials, which is made of any one of coated cemented carbide, cermet and coated cermet, is used. These tool materials are
It is a material that can be used in a relatively high cutting speed range in which a built-up edge does not occur and that is also excellent in wear resistance. Further, the affinity with the steel material can be lowered, and the welding can be suppressed.

The land portion 3 has two pairs of margins. Among them, the first margin 5 is along the twist groove 2 like the conventional twist drill, and the second margin 6 is separated from the first margin 5 and twists in the land portion 3. It is arranged with it. In general, the margin is a round land shape that does not escape from the outer periphery and determines the diameter of the drill, and at the same time, it abuts the inner wall of the drilled hole to guide the drill during processing and suppress lateral runout. It has an effect. The two pairs of margins as described above improve the effect as a guide, enhance the stability of the drill, and further improve the hole diameter accuracy.

However, the large number of margins increases the abrasion resistance of the inner wall of the processed hole,
It may cause breakage. The present invention is intended to realize a twist drill for steel materials in which breakage is unlikely to occur by reducing scratch resistance, and in addition to consideration from the shape of the margin, sufficient supply of cutting fluid to the margin is provided. This is an examination of the method.

First, the first margin 5 has a back taper in two steps. That is, the back taper in the range B on the base side is made larger than the range A on the tip side, and the size thereof is (0.02 to 0.1) /
100 is preferred. This is because the amount of change in the diameter D is extremely small and high dimensional accuracy is maintained even when re-grinding is performed from the tip side. In the range B, unlike the high-speed twist drill, unlike the case where the back taper is small and the hole diameter is enlarged to form the escape automatically, it is necessary to positively secure the escape. Here, it is similar to the conventional twist drill made of super hard tool material, or slightly larger (0.3 to 0.6) / 1.
00 is preferred.

The length of the range A is 0.5D with respect to the diameter D.
.About.2D, while ensuring a constant re-grinding allowance, the upper limit is set to a necessary minimum length at which the abrasion resistance does not become too large.

The second margin 6 is in the range C from the tip, the length thereof is almost equal to the range A, the diameter D and the back taper are the same as those of the portion A, and the second margin 6 acts as a double margin. In the case of external oil supply, oil supply of the cutting agent to the second margin 6 is performed through the gap of the land portion 3 sandwiched between the first margin 5 and the second margin 6. Therefore, if the length of the range C is too long with respect to the range A,
It will interrupt the supply of cutting fluid and cause oil shortage. Further, for the same reason, the positional relationship between the first margin 5 and the second margin 6 should not be too narrow. The arrangement angle formed by the axis center and both is preferably 60 ° ± 15 °.

Although the flank forming the cutting edge 4 is formed at the tip of the tool body 1, the clearance angle β of the first flank 7 shown in FIG. 4 is preferably 4 ° or less. According to the experimental results of the present inventor, it has been found that the twist drill having a smaller angle can suppress the expansion allowance of the machined hole to be smaller. This is because in combination with cross thinning, first, since there is an action of making the chisel edge angle α smaller, that is, the chisel edge 8 and the cutting edge 4 are closer to each other, lateral shake is suppressed. Secondly, it is considered that there is an action of preventing the tip angle of the chisel edge 8 from increasing to an obtuse angle, which increases centripetality during cutting.

In the present invention, the passage of the cutting fluid is positively provided so that the cutting fluid can be supplied to the second margin 6 more smoothly.

FIG. 5 shows an embodiment according to claim 4, wherein the tool body 1 of the twist drill shown in FIG.
An oil hole 9 that penetrates from the rear end to the front end is added.
Therefore, the parts other than the oil hole 9 are the same as those in FIG. The oil holes 9 are a pair of holes accompanied by a twist along the twist groove 2 in at least the tool body 1. Since the cutting fluid is internally supplied through the spindle of the machine tool and the tool holder, not only is it sufficiently supplied to the first margin 5 and the second margin 6, but also the action of forcibly discharging the chips through the twist groove 2 There is. Further, since the oil hole 9 is formed along the twist groove 2, the oil hole 9 can be re-ground.
The opening position of has not changed, and the cutting performance unchanged from the beginning is maintained.

6 and 7 show an embodiment according to claim 5, which is sandwiched between the first margin 5 and the second margin 6 of the land portion 3 of the twist drill of FIG. A relatively shallow twist groove 10 is added to the land portion 3. Therefore, the components other than the twist groove 10 are the same as those in FIG. 1 and are designated by the same reference numerals. Cutting fluid is twisted groove 10
Since it is easier to be supplied to the second margin 6 through
It is effective for drilling by external refueling.

[0025]

As described above, according to the present invention, it is possible to realize a twist drill for drilling a steel material having two pairs of margins. The tool material is made of a material that can be used at high cutting speeds, has excellent wear resistance, and is unlikely to cause chip welding, and has two pairs of margin shapes, a cutting fluid supply channel, and a first flank shape. Even if it is used for drilling steel materials, it is less likely to break, and drilling can be performed with good hole diameter accuracy that could not be obtained with conventional twist drills.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a tip portion of FIG.

FIG. 3 is a left side view of FIG. 2;

4 is a cross-sectional view taken along the line AA of FIG.

FIG. 5 is a front view showing an embodiment according to claim 4 of the present invention.

FIG. 6 is a partial front view showing an embodiment according to claim 5 of the present invention.

FIG. 7 is a left side view of FIG.

[Explanation of symbols]

 2 Twisted groove 3 Land part 4 Cutting edge 5 First margin 6 Second margin 7 First flank 9 Oil hole 10 Twisted groove

Claims (5)

[Claims] 1. A pair of twisted grooves 2 are formed on an outer peripheral portion of a tool body 1 made of an ultra-hard tool material, and
The land portion 3 has a first margin 5 along the twist groove 2.
And a second margin 6 spaced apart from the margin 5, the tool body 1 is made of a single coated cemented carbide or cermet or a coated cermet. In the margin 5 of 1, the back taper has two steps, the back taper in the range B on the base side is formed larger than the back taper in the range A on the tip side, and the second margin 6 is used. Has its length C approximately equal to A,
The twist drill is characterized in that the diameter D and the size of the back taper are the same as those of the portion A. 2. The length of the range A is in the range of 0.5D to 2D with respect to the diameter D, and the size of the back taper of the parts A and C is (0.02 to 0.1). The range of the back taper of the B part is (0.3 to
The twist drill according to claim 1, wherein the twist drill is formed in a range of 0.6) / 100. 3. The twist drill according to claim 1, wherein the clearance angle β of the first flank 7 at the tip of the tool body 1 is 4 ° or less. 4. A tool body 1 having a pair of oil holes 9 bored from the rear end thereof and having a twist along at least a twist groove 2 and having an opening at the tip. Item 4. The twist drill according to item 3. 5. The twist drill according to claim 1, wherein the land portion 3 sandwiched between the first margin 5 and the second margin 6 is formed so as to have a twist groove 10.