JPS5943244B2 - Spiral drill without chisel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spiral blade drill suitable for high-speed machining and high-feed machining.

Conventional drills leave unresolved contradictions in the chisel part, so drills that focus on cutting quality and chip evacuation lack rigidity, and highly rigid drills have poor cutting quality and are unsuitable for heavy cutting. Met.

In addition, in recent years, work materials have come to include many difficult-to-cut materials and high-hardness materials, and it has become necessary to use cemented carbide for drills. In addition, the cutting speed at the center of the drill is close to zero, and the rake angle of the chisel part is extremely negative, so it cannot be expected to be effective as a cutting tool, and it is also subject to a compressive load equivalent to the feed rate. .

In order to solve this problem, the present inventor previously proposed a spiral rectangular drill.

However, even if the spiral rectangular shape allows for good cutting at the center, if a sufficient rake surface is not formed on the cutting edge near the center, the generated chips will not be discharged smoothly. This causes problems in chip evacuation during high-speed machining and high-feed machining.

In view of these points, it is an object of the present invention to provide a drill that allows cutting in the vicinity of the center of the drill to be carried out smoothly, and also allows for smooth discharge of cutting chips.

In the present invention, when viewed from the bottom of the drill, the pair of cutting edges are arranged symmetrically with respect to each other with their starting ends located at the center of rotation, and each cutting edge has a curve that is convex with respect to the direction of rotation, and a cutting edge on the outer periphery. The cutting edge curve at the center is configured to have a larger curvature than the cutting edge curve, and by forming a recess in the helical groove of the drill near the starting end of each cutting edge, the recess allows the cutting edge near the starting end to A rake face is formed.

Hereinafter, the present invention will be explained with reference to drawings of embodiments.

1.2 is a tip, 3 is a helical groove of the drill, and 31 is an outer peripheral surface of the drill body.The pair of tips 1 and 2 are made of, for example, a plate shape of cemented carbide to form the apex 10 of the conical head of the drill. The tips 1 and 2 are attached to the drill body so that the starting ends of the cutting edges are located at and the cutting edges 4 and 5 are arranged point-symmetrically with respect to each other.

Tips 1 and 2 can be attached by brazing (
Alternatively, it may be attached with bolts and used as a throw-away type.

Further, the cutting edge may be formed integrally with the drill body.

Each of the cutting edges 10 has a curve that is convex in the direction of rotation when viewed from the bottom, and has a spiral curve whose curvature increases as it approaches the center from the outer periphery, and the flank extends from the center to the outer periphery. The rake faces 11 and 12 are at the center (the rake angle is approximately zero and gradually increases toward the outer periphery).

The diagonal angle and the diagonal angle are not limited to those shown in the drawings, and various modifications are possible.

(The cutting surfaces 11 and 12 are formed as extensions of the helical groove 30 surface, but if the inserts 1 and 2 are installed with the helical groove 3 extended to the top of the drill, the cutting edge will be 4° 5° near the center. Since almost no rake face is formed,
Recesses 6 and 7 are formed in the helical grooves near the center, and these recesses form cutting surfaces near the starting ends of the cutting blades 4 and 5.

When drilling holes with this drill, the cutting edges 4 and 5
Because the cutting edge has a large curvature near the center, the moving speed of the cutting blade approaches the center (although it is slow), the cutting is performed reliably at the center, and the cutting edge has a curved line when viewed from the bottom. The tangent line changes from the center to the outer periphery, and because it is inclined outward with respect to the direction of movement, the chips cause a side-slipping phenomenon, so the chips are not pressed against the cutting edge and are smoothly discharged. Coupled with the fact that the chips are thinner, the cutting resistance is also reduced.

These characteristics also made it possible to use not only general tool steel but also cemented carbide.

In other words, the conventional cutting edge shape does not allow proper cutting and chip evacuation, especially when used for steel materials, and cemented carbide cannot be used because chips tend to occur near the center where the cutting speed is slow. However, in the present invention, the cutting resistance is small near the center and the chips slide sideways without being pressed against the blade, so even if cemented carbide is used, no chipping occurs.

Moreover, by using cemented carbide, it is possible to cut difficult-to-cut materials and high-hardness materials, and to improve machinability, the depth of cut per rotation compared to conventional drilling can be increased by 5 to 6 times. This made it possible to process at high speed.

Furthermore, the life of the tool can be increased by about 10 times compared to conventional products.

However, when machining is carried out at high speeds, chip evacuation becomes a problem, especially near the center, and when the rake face is small, the problem arises that chips do not extend smoothly along the rake face.

However, in the present invention, by forming the recesses 6 and 7, the cutting edge near the center is formed with a sufficiently rounded surface, so chips generated near the center extend upward along the recesses 6 and 7 and curl. Therefore, the chips are discharged well even in high-speed machining.

Note that as a means of forming a thick groove near the center, it is possible to make the head 30 of the drill significantly lower than the top surface of the chip. If the head 30 is lowered as shown, the tip 1
, 2 is weak (because it becomes unable to withstand heavy cutting).

However, when the concave portion is formed only in the vicinity of the starting end of the cutting edge in the helical groove as in the present invention, the force supporting the chip is hardly weakened.

As explained above, one aspect of the present invention is to make the shape of the cutting edge spiral to enable high-speed machining and to smoothly discharge chips from the center, which is a problem in high-speed machining. This makes it an excellent high-speed cutting drill.

[Brief explanation of the drawing]

FIG. 1 is a front view of a drill tip showing an embodiment of the present invention;
2 is a right side view thereof, FIG. 3 is a bottom view thereof, and FIG. 4 is a sectional view taken along the line IV--IV in FIG. 3. 1.2...Tip, Total...Twisted groove, 4
, 5... Cutting edge, 6, 7... Concavity, 10
・・・・・・Start of the cutting edge.

Claims (1)

[Claims] 1. When viewed from the bottom of the drill, the pair of cutting edges are arranged symmetrically with respect to each other with their starting ends located at the center of rotation, and each cutting edge has a curve that is convex with respect to the rotation direction, and the cutting edge curve of the outer periphery is The cutting edge curve at the center is configured to have a larger curvature, and by forming a recess in the helical groove of the drill near the starting end of each cutting edge, the recess creates a rake face on the cutting edge near the starting end. A chisel-less spiral blade drill characterized by a chisel-less spiral blade.