JPH078447B2 - Drill for thin plate processing - Google Patents

Description

TECHNICAL FIELD The present invention relates generally to drills, and more particularly to drills suitable for drilling thin sheets.

2. Description of the Related Art As a drill suitable for drilling a thin plate, for example, JP-A-58-14
Japanese Patent No. 9115 discloses a drill having a bite portion projecting toward the drill tip side at the center of the drill tip. This drill is shown in Figs. This will be briefly described with reference to the drawings.

FIG. 6 is an end view showing the tip of the drill, and FIG. 7 is a side view of the drill. The tip of the drill is provided with a pair of tip blades and a chisel blade 3 that connects the tip blades. And
Each tip blade is divided into a tip inner blade 1 located radially inside and a tip outer blade 2 located radially outside. The pair of tip inner blades 1, 1 constitutes the biting portion. That is, each tip inner blade 1 has a form in which it projects toward the tip of the drill with respect to each tip outer blade 2 toward the chisel blade 3. Then, first flanks (second face) 5a, 6a and second flanks (third face) 5b, 6b are formed behind the inner tip 1 and the outer tip 2 in the circumferential direction, respectively. Has been done. The second flanks 5b, 6b are formed at an acute angle with respect to the first flanks 5a, 6a, and a chip space is secured here. In the figure, 4 is thinning, and 7 is a margin formed on the outer circumference of the drill tip. The tip angle formed by the pair of tip inner blades 1, 1 is about 105 °, and the shoulder angle formed by each tip outer blade 2 with respect to the plane perpendicular to the drill axis is set to zero. According to the above configuration, the pair of tip inner blades 1,
Since 1 is projected to the tip side of the drill, it has a good biting property with respect to the work material, and has an advantage that it is easy to use, especially in the case of a hand drill.

However, according to the above configuration, the tip flanks are composed of the first flanks 5a, 6a and the second flanks 5b, 6b. As a result, the thickness of the back metal relative to the tip blade, especially the first flank 5a. , 6a
Since the thickness of the back metal is extremely thin with respect to the tip blade of the portion, there is a problem that the cutting edge strength is weak and chipping easily occurs.

Technical Problem of the Present Invention Therefore, the technical problem to be solved by the present invention is to improve the cutting edge strength in the above-described drill having a biting portion.

SUMMARY OF THE INVENTION (Structure / Operation / Effects) In order to solve the above technical problems, in a drill according to the present invention, the inner tip of each tip and the outer edge of each tip are circumferentially behind each other in succession. It forms one flank that extends. In other words, unlike the above-mentioned conventional example, the flanks are not divided into two and are configured by one flank,
By securing a sufficient thickness of the back metal for the tip blade, the strength of the tip blade is improved, and the occurrence of chipping is reduced.

Since the above-mentioned conventional example is not particularly aimed at drilling a thin plate, it is necessary to secure the tip space at the drill tip by intentionally dividing the flank of the drill tip into the first flank and the second flank. This prevents the broken tip (small piece tip) generated due to the constraint of the hole wall surface from being clogged (bite) between the bottom of the hole and the flank. As far as the purpose of drilling is concerned, since almost no breakage type chips are generated, the present invention was completed by focusing on the fact that there is no problem in the chip discharge property even if the second flank face is not intentionally formed. Came to do.

Further, according to the present invention, the diameter dimension formed by the pair of tip inner blades is set to 40% to 50% of the drill diameter. If this diameter dimension is 40% or less of the drill diameter, the thrust load applied to the pair of inner tip blades during machining becomes excessive, so chipping and wear of the inner tip blades are remarkable, and the drill itself has a short life. On the other hand, when the diameter dimension is 50% or more of the drill diameter, the resistance received from the work material increases, and thus the biteability to the work material deteriorates.

According to the invention, the tip angle formed by the pair of tip inner blades is
It is set between 100 and 115 degrees. Since the tip angle of a normal drill is 118 ° to 130 °, the tip angle of the drill according to the present invention is small as compared with this. Therefore, the biting property with respect to the work material is very good.
However, if the tip angle is 100 ° or less, the cutting edge strength of the inner blade at the tip becomes extremely small, which is not preferable. Further, if the tip angle is 115 ° or more, the biting property is deteriorated, which is not preferable.

Further, according to the present invention, the shoulder angle formed by the outer tip of the tip with respect to the plane perpendicular to the drill axis is set to 4 ° to 10 °. As described above, according to the conventional example, this shoulder angle is 0, but in this case, there is a problem that a large burr is generated in the drilled hole, but the shoulder angle is set to 4 ° to 10 °. By doing so, the occurrence of this burr can be almost suppressed.

Further, according to the present invention, the width dimension of the chisel blade is set to 3% to 20% of the drill diameter. By setting the width dimension of the chisel blade within this range, the chisel blade's ability to bite against the work material is improved, and the strength of the inner tip of the tip is large and the wear resistance is good, and the drill life is extended. .

Further, according to the present invention, no margin is formed on the outer circumference of the drill tip and the outer circumference of the drill tip has the same diameter over the entire area. In the above-described conventional example, as shown in FIG. 6, the margin width is extremely small like a normal drill. This is because if the margin width is made too large, the amount of abrasion with the inner peripheral surface of the hole made in the workpiece becomes large and the processing becomes heavy. However, when the material to be processed is a thin plate, if the margin width is small, the guide function of the margin is not sufficiently exerted, and as a result, the accuracy of the processed hole, specifically, the roundness of the finished surface, causes the rough surface There is a problem that it is bad. Therefore, in the present invention, by eliminating the margin, the drill itself is guided by the entire outer circumference of the tip end portion thereof, so that the guide function thereof can be improved and the accuracy of the drilled hole can be improved. In this case, since the material to be processed is a thin plate, the heavy processing does not become a problem.

EXAMPLE An example of the present invention will be specifically described below with reference to FIGS.

As shown in FIGS. 1 to 3, the drill tip is provided with a pair of tip blades and a chisel blade 3 connecting the tip blades. Then, each tip blade is divided into a tip cutting blade 1 located radially inside and a tip outer blade 2 located radially outside. The pair of inner tip blades 1 and 1 forms a biting portion that projects toward the tip side of the drill from the outer tip blades 2 and 2. That is, each tip inner blade 1 has a form protruding from the tip outer blade 2 toward the chisel blade 3 in the drill tip direction.

On the circumferential back surface of each tip inner blade 1 and each tip outer blade 2,
Each of the flanks 5a and 6a is formed so as to extend continuously.

The diameter dimension d formed by the pair of tip inner blades 1, 1 is 40 of the drill diameter D.
% To 50%.

The tip angle b formed by the pair of tip inner blades 1, 1 is set to 100 ° to 115 °.

The shoulder angle a formed by each tip outer blade 2 with respect to the plane perpendicular to the drill axis is set to 4 ° to 10 °.

Further, in this embodiment, no margin is formed, and the diameter is the same over the entire outer circumference of the drill tip. That is, in this embodiment, the outer periphery of the drill other than the drill groove is configured to be in sliding contact with the inner peripheral surface of the hole to be machined during machining. The broken line in FIG. 2 shows the margin and the outer shape of the drill in the conventional example.

In the above configuration, the height dimension h of the inner blade at the tip is 10% to 30% of the drill diameter D.

In the figure, 4 is thinning, and by performing this thinning, the width dimension of the chisel blade 3 is 3% of the drill diameter D.
It is set to ~ 20%. This size range is determined by the balance between the biteability of the chisel blade with respect to the work material, the thrust load, the cutting edge strength, and the wear resistance.

(Experimental Example 1) As shown in FIG. 4, the present inventors actually performed drilling work by using drills having different tip angles b under the following cutting conditions and compared them.

Cutting conditions Machine used: Desktop drilling machine Rotation speed: 610 rpm Feed: Manual feed Cutting length: 1.6 mm Work material: SS41 (plate thickness 1.6 mm) Cutting fluid: None Drill diameter: φ6.5 mm Shoulder angle: 5 ° Diameter: φ2.9 mm As shown in Fig. 4, when the tip angle b is 90 ° to 99 °, the average number of holes per hole is 490 and the tip angle b is 116.
The average number was 819 in the case of ° to 120 °. On the other hand, when the tip angle is 100 ° to 110 °, the average number is 13
In the case of 71 pieces and the tip angle is 111 ° to 115 °, the average number is
In the case of 1371 and the tip angle of 111 ° to 115 °, the average number was 1419. The average number of drills according to the conventional example is 700 before. As a result, the drill according to the present invention is about 2 times larger than the drill according to the conventional example.
It is clear that it has a double lifespan.

(Experimental Example 2) As shown in FIG. 5, the present inventors conducted an experiment with the drill according to the present invention by sequentially changing the shoulder angle a. As already clear, it is clear that the burr length is smallest when the shoulder angle is set to 4 ° to 10 °.

Cutting condition Drill diameter… φ3.5mm Machine used… Handball Work material… SS41 (plate thickness 1.0mm) Rotational speed… 1650rpm Tip angle… 110 ° Inner tip blade diameter… φ1.6mm (Experimental example 3) The inventors In addition, the conditions shown in Fig. 4 (however, the tip angle is 11
At 0 °), when comparing the drill with no margin with the conventional drill, the roundness of the drilled hole by the drill of the present invention is 30μ.
The roundness of the conventional drill was 109 μm, which demonstrates that the inventor's drill can achieve a much higher roundness. In addition, regarding their finished surface roughness,
20 μm Rmax according to the present invention, 3 according to the conventional drill
It was 5 μm Rmax, and it was demonstrated that there was a significant difference between the two.

(Experimental Example 4) As shown in FIG. 8, the present inventors actually performed drilling work by using drills having different diameters d formed by the inner tip of the tip under the following cutting conditions, and compared them. .

Cutting conditions Machine to be used: Desktop drilling machine Rotation speed: 610 rpm Cutting length: 1.6 mm Cutting fluid: None Drill diameter: φ6.5 mm Shoulder angle: 5 ° As shown in Fig. 8, the diameter dimension d formed by the inner tip of the drill is a drill. In the case of 40% to 50% of the diameter D, the number of holes to be drilled was 1100 or more, and it was proved that the drill life was remarkably long as compared with the cases of 39% or less and 51% or more.

(Experimental Example 5) The present inventors further conducted a drilling operation using the drills having different width dimensions (length) of the chisel blade under the same conditions as in FIG. 8 and compared them.

As shown in FIG. 9, when the width dimension of the chisel blade is 3% to 20% of the drill diameter D, the number of holes drilled per one is
It was over 1,000, and it was proved that the peak of drill life appears in this range.

[Brief description of drawings]

1 to 5 show an embodiment of the present invention, FIG. 1 is an end view of a drill, FIG. 2 is a sectional view perpendicular to the axis of a drill tip, FIG. 3 is a side view of the drill, and FIG. 4 is a tip. Fig. 5 is a graph showing the relationship between the part (b) and the life of the drill, Fig. 5 is a graph showing the relationship between the shoulder angle a and the burr length, and Figs. 6 and 7 are end views and side views of the conventional drill respectively. is there. FIGS. 8 and 9 also show an embodiment of the present invention. FIG. 8 is a graph showing the relationship between the diameter dimension of the tip inner blade and the number of holes to be drilled, and FIG. 9 is a graph showing the relationship between the length of the chisel blade and the number of holes to be drilled. It is a graph shown. 1 ... Inner tip blade, 2 ... Tip outer blade, 3 ... Chisel blade, 4
...... Thinning, 5a, 6a …… flank, 7 …… margin,
a: Shoulder angle, b: Tip angle, h: Blade edge height.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliography Sho 54-1648 (JP, Y2) Mechanical Engineering Complete Book 103 “Drilling and Design of Tools for Drilling” Radio Technology Co., Ltd. (Sho 42-6-15 )

Claims (1)

[Claims] 1. A drill tip has a pair of tip blades and a chisel blade (3) for connecting the tip blades, each tip blade being in a radial direction with an inner tip blade (1) located inside in the radial direction. It is divided into the outer tip of the outer blade (2) and the inner blade of each tip (1).
In the drill having a shape in which the tip protrudes in the drill tip direction toward the chisel blade (3) with respect to each tip outer blade (2), the circumference of each tip inner blade (1) and each tip outer blade (2) One flank that extends continuously is formed behind each direction, and the diameter dimension (d) formed by the pair of inner tip blades (1,1) is set to 40% to 50% of the drill diameter (D). , The tip angle (b) formed by the pair of tip inner blades (1, 1) is 100 ° to 11
It is set to 5 °, the shoulder angle (a) made by each tip outer blade (2) with respect to the plane perpendicular to the drill axis is set to 4 ° to 10 °, and the chisel blade (3) width dimension is the drill diameter (D). It is set to 3% to 20% of the above, a margin is not formed on the outer peripheral portion of the drill tip, and the outer peripheral portion of the drill tip has the same diameter over the entire area.