JPH02237712A - Twist drill - Google Patents

Abstract

PURPOSE:To drill a hole without causing burrs or peeling due to reinforcing fibers by forming a twisted groove into a helical shape advancing from the tip side to the base end side in the direction of rotation, forming first and second flanks provided with respective specified relief angles to a tip part, and keeping clearance between a crossover ridge line of both the flanks and a cutting edge at less than 1mm. CONSTITUTION:A twisted groove 2 is formed into a helical shape advancing from the tip side toward the base end side in the direction of rotation, and a first flat flank 4 provided with relief angle of 10 deg.-45 deg. is formed along a cutting edge 3 on the tip part of a drill body 1. Further, a second flat flank 5 provided with relief angle larger by 50 deg. or more than the relief angle of the first flank 4 is formed on the back side of the first flank 4. Tip clearance l between the crossover ridge line 6 of the first and second flanks 4, 5 and the cutting edge 3 is kept below 1mm viewing from the tip in the axis direction. As a result, reinforcing fibers can be cut with good cutting action, and generation of burrs or peeling can thus be efficiently prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a twist drill suitable for use in drilling holes in fiber-reinforced composite materials made of carbon fibers, Kevlar fibers, and the like.

[Conventional technology and its issues] In recent years, the development of fiber-reinforced composite materials has progressed rapidly, and FR
There are many cases where materials made of P etc. are machined. For example, CFRP is a synthetic resin reinforced with carbon fibers, and the tensile strength of the synthetic resin is increased by interposing woven carbon fibers within the synthetic resin.

However, machining of CFRP and the like has been extremely difficult due to the presence of reinforcing fibers inside it. In particular, when drilling with a twist drill (hereinafter abbreviated as a drill), reinforcing fibers remain as burrs and rips on the entry and exit sides of the drill. Moreover, unlike metal materials, synthetic resin is sticky and easily melts due to heat generated by frictional resistance, which can cause the synthetic resin to adhere to the cutting blade or soften the cutting part. For this reason, it has been almost impossible to drill holes in fiber-reinforced composite materials.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a drill that can perform hole drilling without causing the reinforcing fibers to bulge or peel.

[Means for Solving the Problems] Firstly, the drill of this invention has a helical groove first.
It is formed in a spiral shape that progresses in the direction of rotation as it goes from the side to the proximal end, and a flat first flank with a clearance angle of 10' to 45° is formed along the cutting edge at the tip of the drill body. death,
A flat second flank face with a clearance angle 5° or more larger than the clearance angle of the first flank face is formed behind the first flank face, and the intersection of the first and second flank faces is The separation distance between the ridgeline and the cutting edge in the axial direction when viewed from the tip is 1 mm or less. Second, the intersecting ridge lines of the first and second flanks intersect with the cutting edge.

[Function] For example, consider cutting a thin thread with scissors.
If there is a gap between the two blades of the scissors, the thread will not cut properly. In other words, the two blades are strongly pressed against each other, and the thread cannot be cut properly unless it is strongly pinched between the two blades. This is the same when cutting reinforcing fibers such as CFRP with a cutting blade. be. In the drill with the above configuration, the twist direction of the helix groove is opposite to that of conventional drills, so
The axial rake angle of the cutting edge is necessarily negative.

When drilling holes in CFRP, for example, with such a cutting blade, the reinforcing fibers are strongly pressed against the synthetic resin side by the rake face because the axial rake angle of the cutting blade is negative. As a result, the reinforcing fibers and the synthetic resin are cut off as if using scissors, with the synthetic resin as the lower blade and the cutting blade as the upper blade. Therefore, the reinforcing fibers do not remain on the surface processed by the cutting blade, and it is possible to prevent the occurrence of burrs due to the reinforcing fibers.

Furthermore, in the drill having the above-mentioned first feature, the flank is made up of first and second flanks that are flat and have a large clearance angle,
The distance between the intersecting ridge lines of the first and second flanks and the cutting edge is 1 m.
m or less, it is possible to effectively prevent double hit while maintaining the rigidity of the cutting edge, and of course it is possible to prevent synthetic resin welding, etc. The pushing force acting on the cutting material is small, and the reinforcing fibers can be cut with good sharpness, which together with the fact that the occurrence of plucking can be more effectively prevented.

In addition, in the drill having the second feature, since the intersecting ridge lines of the first and second flanks intersect with the cutting blade, the clearance angle of the cutting blade formed at the ridge line portion of the second flank is large. The above-mentioned pushing force can be further reduced.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 5. FIG. 1 is a side view showing a drill according to an embodiment. In the figure, reference numeral 1 indicates the drill body.

The drill body 1 is made of, for example, cemented carbide or a ceramic metal, and is adapted to be rotated clockwise, that is, rightward, when viewed from the base end. Two helical grooves 2 are formed on the outer periphery of the drill body l;
A cutting edge 3 is formed at the tip ridgeline of the wall surface facing the direction of rotation. The above points are the same as conventional drills.

However, the twisted groove 2 is formed in a spiral shape that progresses in the rotational direction from the distal end side to the proximal end side. In other words,
The twisted groove 2 is twisted to the left in a counterclockwise direction when viewed from the tip in the axial direction.

Therefore, the axial rake angle of the cutting edge 3 is negative. Here, the helix angle of the helix groove 2 is 15° ~
The angle is set at 75°, preferably between 20° and 60°, more preferably between 30° and 50°. The lower limit of this numerical limitation is a range that can more effectively prevent the occurrence of cracks and peeling, and the upper limit is a range that allows chips to flow out more smoothly and prevents chip clogging.

Further, at the tip of the drill body 1, a first relief 4 is formed along the cutting edge 3. The first flank surface 4 is. )1′
7. The clearance angle is set to 10' to 45°. Moreover, a second flank surface 5 is formed on the rear side of the first flank surface 4. The second relief 5 is also flat, but its relief angle is set to be 5° or more larger than the relief angle of the first relief. Also, the first and second escapes and 4.
The separation distance σ between the intersecting ridge line 6 of No. 5 and the cutting blade 3 in the axial direction tip view is set to l mm or less.

Further, at the tip of the drill body 1, a rear portion of the second relief 5 is shaved off to form a thinning portion 7 there. The thick core portion of the drill body l is thinned so as to extend linearly from the axis portion toward the outer circumference.
A thinning blade 8 is formed which is located above the cutting edge 3.

The angle γ formed by the cutting blade 8 and the line segment connecting the axis 1i1o and the outer peripheral end of the cutting blade 3 when viewed from the tip in the axial direction is 0.
It is set from 0 to 30'. Also, when viewed from the direction perpendicular to the tingling point 8a along the thinning blade 8 (Fig. 4), the valley line 9 and the edge line 0 are formed between the scooping point 8a and the sharpening point 7a of the cutting part 7. Angle λ is 20°~45
° is set. Further, the angle δ formed between the scoop 8a along the thinning blade 8 and the sharpened tip 7a of the thinning portion 7 is set to 95° to 115°.

Further, the wall surface of the twisted groove 2 facing the rotation direction is formed into a concave curved surface so that the shape in a cross section perpendicular to the axis O is a concave curve concave toward the rear in the rotation direction. For this reason, together with the fact that the helical groove 2 is left-handed, the cutting edge 3 has a shape that is deeply recessed toward the rear in the rotational direction when viewed from the tip in the axial direction, and as a result, the run angle of the cutting edge 3 is greatly increased. direction. In other words, as the axial rake angle of the cutting edge 3 increases toward the negative side, the radial rake angle increases toward the positive side, thereby preventing the cutting resistance from increasing excessively. Here, a line segment connecting the intersection of the cutting blade 3 with a circle centered on the axis O and having a diameter of 60% of the drill diameter and the outer peripheral end of the cutting blade 3;
The angle φ between the axis O and a line segment extending to the outer peripheral end of the cutting blade 3 is set to 5° to 60°, preferably 10° to 5°.
The angle is preferably set to 15° to 400° than 0°.

In addition, by making the shape of the twisted groove 2 a concave curved surface [7],
The cutting edge 3 (FIG. 1) when viewed from the side also has a concave shape toward the proximal end. With such a cutting edge 3, the cutting progresses from the contour line of the hole toward the inner circumference, so it is possible to prevent the hole edge from being peeled off due to cutting thrust. Opening processing can be performed more easily. In addition, in order to obtain the shape of the cutting blade 3 as described above, it is desirable to set the tip angle θ of the cutting blade 3 to 150° or more.
In order to prevent chipping, chipping, and pinging at the outer peripheral end of the cutting edge 3, the tip angle 0 needs to be 175° or less.

In addition, the outer peripheral end P of the cutting blade 3 and the center Q of the tip of the drill body l
The axial distance IT is 15% of the drill diameter.
It is said that In the drill of the example, the center Q of the tip is located closer to the tip than the outer peripheral end P, so if T exceeds 15% of the drill diameter, the mechanical strength of the center Q side of the tip of the cutting edge 3 will decrease. This is because, on the contrary, when the outer peripheral end P is located on the tip side, the mechanical strength of the outer peripheral end P side decreases.

Furthermore, the groove width ratio (groove width; land width) of the twisted groove 2 is 1
．． The core thickness of the drill body 1 is set to 8% to 20% of the drill diameter, and is set larger than that of conventional drills (about 09:1), and is set to be larger than that of conventional drills (about 0.9:1).
) is smaller than << set. This is because the left-handed twisted groove 2 makes it difficult for chips to flow out, so the flow area for chips is increased to improve discharge performance.

Furthermore, the entire outer periphery of the drill body 1 is made into a cylindrical smooth curved surface, and unlike conventional drills, a margin is not formed.
Q per m. A large back taper of 4 mm to 2 mm is provided.

This prevents the reinforcing fibers in the cutting material from getting caught on the outer periphery of the drill body (2), and also reduces the frictional resistance with the hole.

Next, the operation when drilling holes in CFRP, for example, using the drill configured as described above will be explained with reference to FIG. 6. FIG. 6 shows a cross section of the cut material A perpendicular to the cutting edge 3. Innumerable reinforcing fibers F are woven vertically and horizontally in a plan view. As can be seen from FIG. 6, since the axial angle of the cutting blade 3 is negative, the reinforcing fibers F facing the cutting blade 3 during drilling are strongly pressed against the cutting material A by the scooper 3a. In other words, the reinforcing fiber F is combined with the synthetic resin M.
The cutting blade 3 is used as the lower blade and the cutting blade 3 is used as the upper blade to cut as if using scissors. Therefore, no reinforcing fibers F remain on the surface B processed by the cutting blade 3.

Moreover, in the above drill, the flank face is set to the first part with a large clearance angle.
, second flank surfaces 4,5, and first and second flank surfaces 4.5.
Since the distance Q between the intersecting ridge line 6 and the cutting blade 3 is set to 1 mm or less, it is possible to effectively prevent double hit while maintaining the rigidity of the cutting edge, and it is possible to prevent welding of synthetic resin, etc. Not only can this be done, but the pushing force acting on the cutting material A as a reaction force to the cutting thrust is small, and the reinforcing fibers F can be cut with good sharpness. It can be prevented. Note that since the eleventh and second flank surfaces 4 and 5 are flat surfaces, re-polishing can be easily performed, and it goes without saying that fine grinding chips will not occur on the cutting edge 3.

Furthermore, in the above drill, since the tip of the drill body l is thinned as described above, there is less resistance when the chips generated by the thinning blade 8 extend into the helical groove 2, and chip evacuation is improved. Not only can this be improved, but in combination with the core thickness of 8% to 20%, the cutting resistance is small, which prevents heat generation at the cutting part, making it even more effective for welding synthetic resins, etc. can be prevented. Therefore, drilling of fiber-reinforced composite materials can be performed smoothly in the same manner as drilling of metal materials.

Next, FIGS. 7 and 8 show an embodiment of the second feature of the present invention.

The drill shown in these figures is the first twist drill.
, the intersecting ridge line 6 of the second flank 4.5 intersects the cutting edge 3. Therefore, the clearance angle of the cutting edge 3a formed on the ridgeline portion of the second clearance surface 5 is thick, and the pushing force acting on the cut material can be further reduced. Further, as shown in FIG. 8, the cutting edge 3a has a concave curve shape that is deeply concave toward the base end when viewed from the side, so that the cutting edge 3a bites into the workpiece at a more acute angle. This makes it possible to reduce the force of pushing apart the material to be cut due to the cutting thrust, thereby making it possible to more effectively prevent the occurrence of peeling. However, from the axis O to the cutting edge 3a
, 3 to the outer peripheral side boundary of the cutting edge 3 is desirably within 70% of the drill radius R in order to maintain the mechanical strength of the outer peripheral end of the cutting edge 3.

In addition, although the above embodiment is an application of the present invention to a solid drill, the same effect can be achieved even if the present invention is applied to a brazed drill or throw-away drill in which only the cutting edge is made of cemented carbide or the like. be able to. In addition, in the embodiment 11, the drill body 1 is rotated clockwise when viewed from the base end side, so the helical groove 2 is left-handed. However, the drill body 1 is rotated counterclockwise. Of course, when it is rotated, it will be twisted to the right.

[Effects of the Invention] As explained above, the drill of this invention has, firstly,
A helical groove is formed in the direction of rotation from the distal end to the proximal end, and a 10° groove is formed at the distal end of the drill body.
A flat first flank face with a clearance angle of ~45° is formed along the cutting edge, and a clearance angle 50 or more larger than the clearance angle of the first flank face is formed behind the first flank face. A flat second flank is formed, and the separation distance between the intersecting ridge line of the first and second flanks and the cutting edge in the axial direction when viewed from the tip is l m.
Second, since the intersecting ridge lines of the first and second flanks intersect with the cutting blade, the axial rake angle of the cutting blade becomes negative, and the reinforcing fiber It can be cut as if using scissors. For this reason, no reinforcing fibers remain on the surface of the cutting edge, and since there is little frictional resistance between the drill body and the hole, the reinforcing fibers can be cut with good sharpness. It is possible to effectively prevent the occurrence of cracks and peeling at the edges and inner periphery. Furthermore, it is possible to effectively prevent double contact on the flank face while maintaining the rigidity of the cutting edge, which not only prevents the melting of synthetic resin from occurring, but also the reaction of the cutting thrust. The pushing force acting on the work material is small, and the reinforcing fibers can be cut with good sharpness, which together with the fact that the occurrence of peeling can be more effectively prevented.

[Brief explanation of drawings]

1 to 6 are views showing an embodiment of the first feature of the present invention, in which FIG. 1 is a side view showing a drill, FIG. 2 is a view taken in the direction of arrow 11 in FIG. Figure 3 is a view in the ■ direction of Figure 2, Figure 4 is a view in the ■ direction of Figure 3, Figure 5 is a view in the ■ direction of Figure 4, and Figure 6 is a drilling process for FRP. 7 and 8 are cross-sectional views perpendicular to the cutting edge showing the state in which cutting is performed.
The drawings show an embodiment of the second feature of the present invention, and Fig. 7 is a view of the tip of the drill in the axial direction, and Fig. 8 is a view of the drill in the direction of arrow (J). ...1.Rill body, 2.....Twisted groove,...
・Cutting edge, 4...First flank,...Second escape, 6...Cross ridge line, a...Tip sharpened, 8...・Nnnning blade, 1...Zukuiji, 9...Valley line, 0...Axis line.

Claims (5)

[Claims] (1) In a twist drill, a twist groove is formed on the outer periphery of a drill body that is rotated around an axis, and a cutting edge is formed on the tip ridgeline of the wall surface facing the rotation direction of the twist groove. It is formed in a spiral shape that progresses in the direction of rotation as it goes from the side to the proximal end, and a flat first flank with a clearance angle of 10° to 45° is formed along the cutting edge at the tip of the drill body. And behind this first flank,
A flat second flank is formed with a clearance angle that is 5° or more larger than the clearance angle of the first flank, and the intersection ridge line of the first and second flanks and the cutting edge are viewed from the axial end of the cutting edge. A twist drill characterized by having a separation distance of 1 mm or less. (2) A twist drill characterized in that the intersecting ridge lines of the first and second flanks of the twist drill intersect with the cutting edge. (3) A thinning blade is formed in the thick core part of the drill body by thinning, extending linearly from the axis part in the outer circumferential direction and positioned higher than the cutting blade, and the thinning blade and the axis line The angle between the line segment connecting the outer circumferential edge of the cutting blade and the tip in the axial direction is 0° to 30°, and when viewed from the direction perpendicular to the rake face along the thinning blade, the angle between the rake face and the thinning tip is 0° to 30°. A patent claim characterized in that the angle between the valley line with the ground surface and the axis is 20° to 45°, and the angle between the rake face along the thinning blade and the tip ground surface by thinning is 95° to 115°. The twist drill according to item 1 or 2. (4) The wall surface of the helical groove facing the rotation direction is formed into a concave curved surface so that the shape in a cross section perpendicular to the axis is a concave curve concave toward the rear in the rotation direction. The twist drill according to any one of Items 1 to 3. (5) Claims 1 to 4 characterized in that the distance in the axial direction between the outer peripheral end of the cutting edge and the center of the tip of the drill body is within 15% of the drill diameter.
Twist drill described in any of the paragraphs.