JPS599281B2 - carbide drill - 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 double-flute, a chisel edge (center cutting edge) that does not perform cutting action is created at the center of rotation of the drill head, which causes the hole to be drilled. It is known that during drilling, the center of rotation of the drill head forcibly crushes and removes the workpiece.

Therefore, a two-blade superalloy carbide drill is suitable for drilling relatively soft non-ferrous metals such as cast iron and aluminum, but when drilling hard metals such as steel, it is difficult to crush and cut the workpiece. Double-flute type carbide drills are considered unsuitable because the cutting edge is easily damaged due to strong resistance, and the thrust resistance is large, so single-flute carbide drills that do not produce chisel edges are used for machining steel materials. It's here.

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 been a bottleneck in machining steel materials.

In response to this, recently, in order to solve 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.

In this conventional structure, the cutting blades K1. Fix K2 and cut both cutting blades K1. A gap, that is, a non-cutting zone 2 having a width of about 0.5 mm is formed between K2.

When a drill with this structure is used to drill and cut a hole, a core C is generated because the workpiece falling in the non-cutting zone Z is not cut as shown in FIG. 7, but the core C is about 0. 5
Since it is a small diameter one formed with a gap of about mw,
It is said that the core naturally repeats its growth and shedding during cutting, and is carried away with the chips, so it does not pose a problem to the drilling process.

With this proposed conventional structure, there is no center cutting edge (chisel edge), so cutting that forcibly crushes the workpiece is not performed, which in turn reduces thrust resistance and damage to the cutting blade. However, since the core C of the workpiece that grows in the non-cutting zone 2 during cutting as described above is removed by natural shedding,
Depending on the type of workpiece, the growing core has a high strength and is difficult to fall off, and if the diameter of the core is large, it will not fall off naturally, so the width of the non-cutting zone 2 should not be made too large. Therefore, it is uncertain and unstable that the core C will fall off, and there is no guarantee that the core C will definitely fall off during cutting.

This invention completely eliminates the above-mentioned drawbacks,
An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 indicates a drill body, and a tip face 3 of a drill head 2 in the body 1 has a radial direction with respect to its rotation center axis 0. Two cutting blades 4.5 are fixed at symmetrical positions, and the cutting edge portions 4a. 4
b are on the straight line P1 passing through the rotation axis O, as clearly shown in FIG. 2, particularly in FIG. There is a slight gap between the opposing edges 4b and Sb of 5a, for example, a diameter of 1. EBtm
They are placed opposite to each other with a non-cutting zone 6 of about 100 mm wide therebetween.

Furthermore, as shown in FIG. 3, the cutting edge portions 4a of both cutting blades. 5a
The non-cutting zone 76 is provided on a straight line P2 perpendicular to the straight line P1 passing through the straight line P1, that is, at a position retreating from the cutting edge portion 4a (a position in the counter-rotational direction) and parallel to the cutting edge portion 4a. A projecting edge portion 1a that partially enters the area of
The protruding blade 1 having the above-mentioned cutting blade 1 is formed by extending one of the cutting blades 4 and 5 and integrally formed therewith.

Therefore, the distance l from the rotation axis 0 to the protruding edge 1a of the protruding blade 1
2 is from the rotational axis O to the opposing edge 4b of both blade tips. It is shorter than the distance l1 to 5b.

In addition, in FIGS. 1 and 2, reference numeral 8.9 indicates a hole for discharging chips that is opened in communication with the drill head 2 and the drill body 1, respectively, and 10 indicates a hole 1-' IJ head 2.
This is a drill guide pad that is fixed to the outer surface of the drill.

Next, to describe the phenomena that occur during the drilling and cutting process, as shown in FIGS. 3 and 4, as the cutting progresses by the pair of cutting blades 4.5 rotating in the direction of the arrow,
Naturally, the core C of the workpiece M is generated and grows in the non-cutting zone 6, but the workpiece M is located at the cutting edge 4a of the cutting blade. 5a
The double-edged edge portion 4a. Edge 4b of the tip of both blades, which is the part where 5a does not touch. The distance 71X2 between Sb corresponds to the diameter of the core C to be grown.

However, as described above, the distance l2 from the rotation axis O to the protruding edge 7a of the protruding blade 7 is made shorter than the distance l1 from the rotation axis O to the opposing edge of both blade tips. has entered the area of the non-cutting zone 6, so when the growing core C gradually enters between the opposing edges of both cutting edges, the core C is elastically compressed in the partial width shown by C1 in FIG. The core C is bitten along the blade edge 1a, and when the pressure or sliding friction resistance by the blade 1 is applied to the core C, and the strength (shearing resistance) of the core C is overcome by the friction resistance, the core C is broken off and falls off as shown by the two-dot chain line in Figure 4.

In this case, as shown in FIG. 4, a pressing force in the axial direction is applied to the cutting edge portion 1a of the cutting edge 1 facing the non-cutting zone 6 against the workpiece M, and almost no cutting action is applied. Since there is a possibility that some cutting due to the biting action may be performed, the above-mentioned ridge is chamfered into a flat shape 7'a to prevent cutting due to the biting action, as in the embodiment shown in FIG. Further, it is preferable to form each of them into a rounded (convex curved) shape 7a as in the embodiment shown in FIG.

Therefore, according to the present invention, two cutting blades are provided at the tip of the drill head, each cutting edge is on a virtual straight line passing through the rotation axis, and the edge on the axis side of each cutting edge is on the rotation axis. They are mounted so that they are equally spaced from the center, and a non-cutting zone with a diameter equal to the distance between the facing edges of both cutting edges on the axis side is formed around the rotational axis, creating a so-called chisel edge. This makes it possible to reduce thrust resistance and damage to the cutting blade.

Moreover, according to the present invention, with respect to the non-cutting zone whose diameter is the distance between the opposing edges of the two cutting edges, one of the two cutting blades is provided at a position retreating from the cutting edge. The distance between the rotation axis and the edge of the cutting edge corresponds to the radius of the growing core, which is integrally formed with a protruding edge that is parallel to the cutting edge and partially intrudes into the non-cutting zone. is made to be larger than the distance between the rotational axis and the protruding edge where the core enters, so there is friction or suppression resistance between the gradually growing core and the protruding edge, which causes the core to break off. A torque is applied to the core, and the core can be forcibly broken off and fallen off during the growth of the core.

Therefore, even if the workpiece to be cut, that is, the core, has 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. Even if it is somewhat large, the core can be forced to fall off reliably.

Furthermore, with the conventional device mentioned at the beginning, the width of the non-cutting zone must be delicately determined depending on the strength of the core because the core is removed by natural shedding. However, according to this invention, since the core is forcibly broken off, both cutting blades are mounted at positions where the core is elastically compressed and torque is generated to break it off. This kind of cemented carbide drill is easy to manufacture because it is flexible and does not need to be installed at exactly the same distance from the rotation center axis.

[Brief explanation of drawings]

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 of the same, and is a diagram explaining its operating state, and Fig. 4 is the same as Fig. 3. FIGS. 5 and 6 are cross-sectional views taken along the line A-A in FIG. 3 showing other embodiments of the present invention; The figure is a diagram for explaining the operating state of the present invention, and FIG. 8 is a plan view showing a conventional example, and is a diagram for explaining the operating state. 1...Drill body, 2...Drill head, 3...
Tip surface, 4. 5... Cutting blade, 4a. 5a...Blade tip portion, 4b, 5b...Blade tip portion opposing edge, 6...Non-cutting zone, 1...Tipped edge, 7a. 7'a*7〃a...Tipped edge part, C...Core, 0...Rotation axis center, P1...
・A straight line passing through the rotational axis O, P2... A straight line perpendicular to the straight line P1, l1... From the rotational axis 0 to the opposing edge 4 of the tip of both blades
b. 5b, l2... Distance from the rotation axis O to the protruding edge portion 7a.

Claims (1)

[Scope of Claims] 1. Two cutting blades are provided at the tip of the drill head, and each cutting edge is on an imaginary straight line passing through the rotation axis, and the edge of each cutting edge on the axis side is on the rotation axis. They are mounted so that they are equally spaced from the center, thereby forming a non-cutting zone centered on the rotational axis with a diameter equal to the distance between the opposing edges of the two cutting edges on the axis side. A cutter formed integrally with a ridged edge having a ridge on one of the cutting edges of the blade at a position set back from the edge of the blade, provided parallel to the edge of the edge, and partially penetrating into the non-cutting zone. hard drill. 2. The carbide drill according to claim 1, wherein the protruding edge of the protruding blade, which partially enters the non-cutting zone, is chamfered into a flat surface. 3 Round the edge of the protruding blade that partially intrudes into the non-cutting zone (
The carbide drill according to claim 1, which is chamfered into a convex curved surface.