JPS6234484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in carbide drills, particularly for deep hole cutting.

In this type of carbide drill, when the cutting blade attached to the drill head is a two-flute type, a chisel edge (center cutting edge) that does not perform cutting action occurs at the center of rotation of the drill head, and this causes the drilling process. It is known that the workpiece is forcibly crushed and removed at the center of rotation of the drill head. Therefore, a two-blade carbide drill is suitable for drilling relatively soft nonferrous metals such as cast iron and aluminum, but when drilling hard metals such as steel, it requires a powerful tool to crush and cut the workpiece. Two-flute type carbide drills are considered unsuitable because the cutting edge is easily damaged by resistance and the thrust resistance is large, so single-flute carbide drills that do not produce chisel edges have been used for machining steel materials. . Naturally, the cutting amount and feed rate of a single-flute carbide drill is lower than that of a two-flute type, and the machining efficiency is inferior to that of a two-flute type, which has become a bottleneck in machining steel materials.

Recently, in order to overcome the above-mentioned drawbacks of the two-blade type drill, a drill has been proposed in which a non-cutting zone is actively formed between the two blades attached to the drill head. This is the structure shown in FIG. This conventional structure is a drill head H.
The cutting blades are radially aligned with each other across the rotation center axis O.
K ₁ and K ₂ are fixed and the width is approximately 0.5 mm between both cutting blades K ₁ and K ₂ .
This is formed by forming a gap of about 100 degrees, that is, a non-cutting zone Z. When drilling and cutting with a drill of this structure, the workpiece falling in the non-cutting zone Z is naturally not cut, as shown in Figure 8, so the core C
However, since the core C has a small diameter and is formed with a gap of approximately 0.5 mm, the core will naturally grow and fall off during cutting, and will be carried away with the chips. It is said that it will not cause any problems.

With this proposed conventional structure, there is no central cutting edge (chisel edge), so cutting that forcibly crushes the workpiece is not performed, and thrust resistance and damage to the cutting blade can be reduced accordingly. , as mentioned above, the non-cutting zone Z during cutting
The core C of the workpiece that grows is removed by natural shedding, so depending on the type of workpiece, the core that grows is strong and difficult to fall off, and the core C. If the diameter is large, it will naturally not fall off, and for this reason, the width of the non-cutting zone Z cannot be made very large, and therefore the core C falling off is uncertain and unstable, and it is difficult to ensure that it will fall off during cutting. There is no guarantee that core C will fall off.

The present invention completely eliminates the above-mentioned drawbacks, and an embodiment of the present invention will be described below with reference to the drawings. In FIG. The tip surface 3 has a diameter line P with respect to its rotation center axis O.
The two cutting blades 4 and 5 are fixed at substantially symmetrical positions in the direction, and the two cutting blades 4 and 5 are not butted against each other at the rotation center axis O, as clearly shown in FIG. 2, and particularly in FIG. 3. , are arranged opposite to each other with a slight gap, for example, a non-cutting zone 6 having a diameter of about 1.5 mm, between both cutting blades 4 and 5. As shown in FIG. 3, the cutting edge portions 4a and 5a of both cutting blades 4 and 5 protrude tangentially from above the diameter line P to each other by a protruding amount a of, for example, about 0.5 mm. As a result, the distance l1 between the cutting edges 4a and 5a, more precisely, the distance between the corners of the cutting edges, is made slightly larger than the distance _l2 between the two cutting blades 4 and 5, more precisely, the distance between their opposing end surfaces, _l2. So,
Furthermore, the cutting edge edge portions 4b and 5b facing the non-cutting zone 6 are formed as non-cutting edge portions that do not perform cutting action (see FIG. 4). In FIGS. 1 and 2, numerals 7 and 8 are holes for discharging chips that are opened in communication with the drill head 2 and the drill body 1, respectively, and 9 is a drill guide fixed to the outer surface of the drill head 2. It is a pad for use.

Next, to describe the phenomenon that occurs during the drilling and cutting process, as shown in Figs. 3 and 4, as the cutting progresses by the pair of cutting blades 4 and 5 rotating in the direction of the arrow, a non-cutting zone naturally occurs. 6, the core C of the workpiece M is generated and grows, but the workpiece M is cut with the cutting edge parts 4a, 5a of the cutting blade, and the core C is formed in the non-cutting zone 6, which is the part where the double-edged edge parts 4a, 5a do not touch. C will grow, that is, the distance l ₁ between the two cutting edge portions 4a and 5a corresponds to the diameter of the core C to grow. However, both cutting blades 4,
As mentioned above, the distance l ₂ between the opposing end surfaces of No. 5 is shorter than the distance l ₁ between the cutting edge portions, and
b and 5b do not perform cutting action, so when the growing core C gradually enters between the opposing end surfaces of both cutting blades, the core C is elastically compressed in the partial width shown by C ₁ in Fig. 3 and is bitten. , the clamping action by both cutting blades 4 and 5, in other words, the sliding friction resistance
When the strength (shearing resistance) of the core C is exceeded by the frictional resistance, the core C becomes threaded and falls off.

In this case, as shown in FIG. 4, the ridges 4b and 5b of the opposing end faces of the cutting blades 4 and 5, which face each other with the non-cutting zone 6 in between, are formed at the non-cutting edge portions as described above. Only a pressing force in the axial direction is applied to the object M, and almost no cutting action is applied. However, there is a risk that some cutting will occur due to the biting action, so the biting action shown in the embodiment shown in FIG. The non-cutting edge portions 4'b and 5'b are chamfered into a flat shape at the ridge corners of the opposing end faces to prevent cutting due to the cutting action, and are also rounded (convex curved surfaces) as in the embodiment shown in FIG. Non-cutting edge portion 4″
It is preferable to form them at 5″b and 5″b, respectively.

Furthermore, as the cutting progresses, the boundary between the part of the workpiece M that is cut by the cutting edge parts 4a and 5a and the part that is not cut (core C), specifically the corner part of the cutting edge part (e in FIG. 3), As shown in the example of FIG.
The two cutting edge portions 4a and 5a, which are formed so as to protrude from the diameter line P in the tangential direction, are further formed to protrude in the tangential direction, and the rotation center axis side portions of the two cutting edge portions are connected to the central axis O. It is preferable to form the cutting edge portions 4c and 5c chamfered in the direction to increase the strength of the central cutting edge portion.

Therefore, according to the present invention, the cutting blades are attached to the drill head at substantially symmetrical positions in the diametrical direction with respect to the rotation center axis, and a non-cutting zone is formed between both the cutting blades. The chisel edge can be removed, reducing thrust resistance and damage to the cutting edge.

Moreover, according to the present invention, by forming the cutting edge portions of both cutting blades so as to protrude from each other in the tangential direction from the above-mentioned diameter line, the distance between the cutting edge portions corresponding to the diameter of the growing core can be set. Make sure that the distance is larger than the distance between the opposing end surfaces of both cutting blades where the core enters.
In addition, since the ridge corner of the cutting blade end face facing the non-cutting zone is formed in the non-cutting edge part, frictional resistance, that is, torque for threading the core, is applied between the two cutting blades to the gradually growing core. During the growth of the core, the core can be forcibly screwed off.

Therefore, even if the workpiece to be cut, that is, the core, has a high strength, it can be reliably removed and completely carried away with the chips, and even if the core diameter generated is large, that is, the width of the non-cutting zone is small. The core can be reliably forcibly removed, no matter how small or large, and this means that the central cutting edge (chisel edge) that does not contribute to the cutting action is completely removed.

Furthermore, with the conventional device mentioned at the beginning, the width of the non-cutting zone must be carefully determined depending on the strength of the core, etc., because the core is removed by natural shedding.
To do this, both cutting blades must be installed accurately from the center axis of rotation, but since the core is forcibly threaded according to this invention, the core is elastically compressed and the torque for threading is increased. It is only necessary to mount both cutting blades at positions where the cutting edge is generated, and there is no need to mount them at exactly the same distance from the rotation center axis, which makes manufacturing this type of carbide drill easier.

[Brief explanation of the drawing]

Fig. 1 is a front view showing an embodiment of the present invention, Fig. 2 is a plan view of the same, Fig. 3 is a plan view of the main part, and is a diagram explaining its operating state, and Fig. 4 is a longitudinal cross-section of the main part. 5 and 6 are longitudinal sectional front views of main parts showing other embodiments of the present invention, and FIG. 7 is a diagram illustrating another embodiment of the present invention. FIG. 8 is a plan view illustrating the operating state of the conventional example, and FIG. 9 is a plan view showing the conventional example, and is a diagram illustrating the operating state. 1...Drill body, 2...Drill head, 3...
... Tip surface, 4, 5 ... Cutting blade, 4a, 5a ... Cutting edge part, 4b, 4'b, 4"b, 5b, 5'b, 5"b
...Edge corner portions of opposing end faces of cutting blades 4 and 5, 4c and 5c
...Chamfered cutting edge part, 6...Non-cutting zone,
C...Core, O...Rotation center axis, P...Diameter line,
l ₁ ... Distance between both cutting edges 4a and 5a, l ₂ ... Distance between opposing end surfaces of both cutting blades 4 and 5, a... Cutting edge section 4a,
The amount of protrusion of 5a from above the diameter line P in the tangential direction.

Claims (1)

[Scope of Claims] 1. Cutting blades are attached to the drill head at substantially symmetrical positions in the diametrical direction with respect to the rotation center axis, and a non-cutting zone is formed between both cutting blades, and a non-cutting zone is formed between both cutting blades. By forming the respective cutting edge portions to protrude from each other in the tangential direction from the above-mentioned diameter line, the distance between the two cutting edge portions is set larger than the distance between the opposing end surfaces of both cutting blades, and the cutting edge faces the non-cutting zone. A carbide drill in which the edge of the blade edge is formed on the non-cutting edge part. 2. The non-cutting edge portion is formed by chamfering the ridge corner portion of the cutting blade end face into a planar shape.
Carbide drill described in section. 3. The carbide drill according to claim 1, wherein the non-cutting edge portion comprises a portion obtained by chamfering the ridge corner portion of the cutting edge end face into a radiused (convex curved surface) shape. 4. A cutting edge in which the above-mentioned both cutting edge portions are formed to project in a tangential direction from above the diameter line and further project in a tangential direction, and the rotation center axis side portions of both cutting edge portions are chamfered in the direction of the central axis. Claim 1, 2 or 3 formed into a part
Carbide drill described in section.