JPS625724B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a drilling tool such as a drill or an end mill with a bottom blade that performs drilling by cutting down in the tool axis direction, and more specifically, Patent application regarding improvement of "drilling tool".

First, in order to clarify the purpose of this invention, the background to the creation of this invention will be briefly explained.

A typical example of this type of drilling tool is a drill (which is also a solid type), but conventional solid type drills have a chisel edge formed at their tip due to constraints on the cutting mechanism and usage pattern. There is. However, it is also true that the chisel edge caused various problems in cutting. This point is also explained in detail in "Cutting and Grinding Processing, Part 1", pages 332-334, written by Eiji Usui, Kyoritsu Shuppan. Therefore, although a detailed explanation will be omitted here, the problem with chisel edges is that they are prone to breakage accidents such as damage to the cutting edge and breakage of the drill. This is due to the fact that chips are forcibly generated in a state that is closer to a pushing action, and the thrust load is also increased thereby. Second, such breakage accidents occur because the center of the tip of the drill tends to run out during cutting, a so-called "slip motion," and in that case, thrust load and torque load This causes so-called "crack vibration" in which the vibrations vary greatly, resulting in the above-mentioned damage accident.

Therefore, in order to improve the above-mentioned problems caused by chisel edges, a drill forming method generally called thinning has been employed. This thinning is a method of cutting off the tip of the drill, and there are two types of thinning: S-shaped thinning and X-shaped thinning. However, in any of these thinning methods, the actual wall thickness of the tip of the drill becomes thinner, resulting in a decrease in cutting strength and the disadvantage that cutting with a large load cannot be performed.

The solid type drill has been described above, but in addition to the solid type, drills with attached blades are also generally well known. This type of drill has at least one cutting edge that passes through the center of rotation of the drill or through the center of rotation of the drill. Therefore, in the case of such a drill, since the cutting edge is obviously asymmetrical, the cutting force becomes unbalanced, which causes adverse effects such as center run-out of the drill, bending of the hole, and enlargement of the hole when the drill bits. This will affect the

Furthermore, both the attached-edge type and the solid-type drill have a cutting edge at the center of rotation of the drill, and if feed is applied during cutting, the following problems may occur at the center of the cutting edge. occurs.
In other words, when cutting with feed, the closer you get to the center, the larger the relief angle is required, and theoretically no matter how small the feed, the center
Requires clearance angle close to 90°. However, in practice it is impossible to set such a relief angle,
Especially in the case of cemented carbide, the angle is limited to around 10°. For this reason, the center of rotation receives a compressive force (thrust load) equivalent to the feed, and this compressive force causes problems such as crushing of the cutting edge and shell-like peeling, making it difficult to use materials such as cemented carbide. It was hot. Another reason why super-hardening has been difficult is that the cutting speed at and around the center of rotation is zero, which causes welding and peeling.

Therefore, the applicant created a non-cutting area in the center where no cutting action is performed by first separating the inner edge of the cutting edge of the tool body from the center of rotation of the tool body relative to the workpiece. I suggested a drilling tool. This drilling tool will be explained with reference to FIGS. 1 to 3. Since the cavity (non-cutting area) 2 provided in the tool body 1 does not cut the workpiece 3, a minute cylindrical core is formed in the workpiece 3 corresponding to the cavity 2. During the growth process of this cylindrical core, due to the rotation of the tool body 1 (that is, the cavity 2 also rotates), when the cavity width d is within a certain range, The micro cylindrical core cannot withstand the cutting resistance in the direction of the main force and the direction of the back force received from the side walls of the cavity, and is threaded off before it hits the bottom of the cavity, and the width of the cavity d at this time. It was found that 0.2 to 2.5 mm is good. Furthermore, by forming the void portion 2, the inner edges 5a, 5 of the cutting blades 4a, 4b are inevitably formed.
b is located apart from the center of rotation of the tool body 1 relative to the workpiece 3 and symmetrically with respect to the point.
The depth of the cavity 2 in the axial direction may be approximately the same as the width d of the cavity 2, but if re-grinding is required, it must be determined to be deeper in consideration of the re-grinding allowance.

In the case of such a tool body (for example, a drill), "grinding motion" and "crack vibration" are difficult to occur during cutting, and the cylindrical core is threaded during the growth process. However, in the center of the bottom of the hole drilled in work material 3,
A conical protrusion 7 of very small height H is formed, which is the remainder of the threaded core. Thus, according to the drill, cutting can be performed smoothly without applying a large thrust load.

However, it has been found that the tool body 1 as described above has the following concerns.

(1) The intersecting portions of the cutting edges 4a, 4b and the inner edges 5a, 5b are likely to be damaged and abnormal wear may occur.

(2) Sliding that would shear chips is less likely to occur, and welding is more likely to occur.

(3) Built-up cutting edges are easy to form.

Therefore, this invention was made in view of the above-mentioned circumstances, and can solve the various problems that chisel edges have, and also solves the concerns (1) to (3) as described above. The purpose of this invention is to provide a drilling tool that can be used to obtain a hole.

An embodiment of the present invention will be described below with reference to FIGS. 4 and 5.
This will be explained based on the diagram. Note that the same parts as those shown in FIGS. 1 to 3 are given the same reference numerals, and the explanation thereof will be omitted.

4 and 5 are diagrams showing a solid type drill. A cavity 2 is formed at the tip of the drill and at the center of rotation 6, so that cutting edges 10a, 10b and inner edges 11a, 1
1b is formed. In this case, the inner edge 11
The rake faces 12a and 12b, which include a and 11b and extend along the axial direction of the drill, are formed as follows. That is, the portion of the rake faces 12a, 12b including the inner edges 11a, 11b is relative to the plane that includes the rotation center axis and passes through the points P, Q closest to the rotation center 6 of the inner edges 11a, 11b. Center of rotation 6
As a result, the center of rotation 6 of the rake face 12a (12b) is formed as an inclined surface that slopes in the direction of rotation as it goes from the side to the outer circumferential side.
The vicinity portion extends from the rotation center 6 to the inner edge 11a (11
In the direction toward the portion P(Q) closest to the rotation center 6 in b), it gradually protrudes toward the relative rotation direction of the tool body 11 from the rotation center 6 side toward the outer circumferential side. It's summery. Note that a portion of the wall surface of the cavity 2 that includes the inner edge 11a (11b) and continues to the rake face 12a (12b) is formed into a plane having a right angle with the cutting edge 10a (10b).

The operation of the drill configured in this way will be explained. First, at the start of cutting, the workpiece 3
Since the inner edges 11a and 11b bite into the cutting surface of the drill at almost the same time, they are stepped on with both feet, and as a result, the force (center swing) that tends to swing the drill is mutually restricted. In addition, when drilling with the drill, the drill's "grinding motion" and "crack vibration" are less likely to occur, and the drill's cylindrical core grows during cutting. Since the core is threaded due to the cutting resistance in the direction of the principal force and the direction of the back force, the cylindrical core does not remain in the center of the lower part of the workpiece 3, and a conical shape with a very small height is formed. (The same applies to the patent application for "drilling tool" filed on October 2, 1974.) However, in addition to that, in the case of this invention, , a rake face 12 including inner edges 11a and 11b.
a, 12b are formed as inclined surfaces that gradually protrude in the direction of rotation from the rotation center 6 side toward the outer periphery. , 10b and inner edges 11a, 11b
The length of the cutting edge consisting of is increased, which reduces the load per unit length.

(2) Cutting blades 10a, 10b and inner edges 11a, 11b
There will be no damage or abnormal wear at the intersection.

(3) Welding is less likely to occur at the intersection because slipping occurs that shears the chips.

(4) It becomes difficult to form a built-up cutting edge, and chipping of the cutting edge is less likely to occur.

(5) Processing and evacuation of chips becomes better.

Additional effects such as these can be obtained.

Further, in the above embodiment, the rake faces 12a, 12
b and the wall surface of the gap 2 that follows it intersect with each other, but they may be formed on one plane as shown by the dashed line in FIG. Furthermore, in the above embodiment,
Inner edges 11a, 11b of rake faces 12a, 12b
Although the portions including the rake surfaces 18a and 18b are sloped surfaces, the rake surfaces 18a and 18b may be formed by curved surfaces that are convex with respect to the direction of rotation, as shown by solid lines in FIG.

Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, but can be applied to other drilling tools such as drills with blades (brazing type and throw-away type) and end mills with bottom blades. It is.

Drills without a cutting edge in the center include core drills and trepanning tools, but core drills are used to enlarge pre-drilled holes, and trepanning tools are Both methods are essentially different from the present invention in that the core is left uncut until the end and the hole is made.

Next, the attached-blade type drill will be described with reference to FIGS. 7 and 8. This drill with a cutting edge has tips 20a and 20b fixedly attached to the tip thereof with a funnel at an equal distance from the center of rotation 6. These chips 20a, 20b have cutting edges 21.
a, 21b and inner edges 22a, 22b are provided, respectively.

The rake faces 23a, 23b in the axial direction including the inner edges 22a, 22b are formed into inclined surfaces similar to those of the solid type described above, and these rake faces 23a, 23b extend in the direction of the rotational axis of the drill. This is done in parallel.

The drill configured in this manner has the same effects as the solid type drill described above, as well as the following effects. That is, when the cutting edge consisting of the cutting edges 21a, 21b and the inner edges 22a, 22b is worn out, the rake face 23
Tip flank 24 without grinding a, 23b
The cutting edge can be sharpened by re-grinding only points a and 24b.

Furthermore, although the rake faces 23a and 23b in the above-mentioned drill with a cutting edge are formed as inclined surfaces, the present invention is not limited to this, and as shown in FIG. 25
a, 25b may be formed. Even in this case, as shown in Fig. 10, not only can the micro cylindrical core be threaded by the principal force and back force, but also the chip T has a convex curved surface. Since it slides smoothly in the radial direction along the rake surfaces 25a and 25b, welding can be further prevented.

Furthermore, when the tips 20a, 20b are fixed to the drill body by brazing, the tips 20a, 20b may be fixed at an angle in the axial direction as shown in FIG. As shown in the figure, the chips 20a and 20b may be screwed and fixed along the escape groove 13. In this case, especially in the case of a drill in which the tips 20a and 20b are screwed and fixed, the axial cross section in the axial direction is kept constant.

Next, the spade drill will be explained with reference to FIGS. 13 and 14. This spade drill is
A flat tip 60 is detachably attached to a drill body 62 with a bolt 61.
This chip 60 has a cutting edge 63 formed in the shape of a mountain, and a gap 65 is formed in the rotation center 64 of the cutting edge 63. Also, by forming the cavity 65 in the tip 60, an inner edge 66 is inevitably formed as in the solid type drill described above. The axial rake face 67 including the inner edge 66 is formed into an inclined surface similar to that of the solid type drill described above. The spade drill configured in this manner also has the same effects as the solid type drill described above.

In the spade drill described above, the rake face 67 may be formed into a curved surface that is convex in the direction of rotation, as shown in FIG.

Next, the flat drill will be explained with reference to FIGS. 16 to 18. This flat drill has cutting edges 70a and 70b formed by cutting off both sides of the tip of the drill body using an inclined flat surface. A gap 72 is formed at this tip and at the center of rotation 6, and this allows the inner edges 73a, 73b to be opened similarly to the solid type drill described above.
is formed. In particular, the inner edge 73a,
Axial rake faces 74a, 74b including 73b
is formed on an inclined surface similar to that of the solid type drill described above. A flat drill constructed in this manner also has the same effects as the solid type drill described above.

Note that the rake face 74a of the flat drill,
74b may be formed into a curved surface that is convex in the direction of rotation, as shown in FIG. 19.

Next, another embodiment of the drill with a blade will be described with reference to FIGS. 20 and 21. This drill is the tip 2 of the drill with the blade type mentioned above.
The only difference is 0a and 20b, and the other configurations are the same. That is, in this drill, the tip 80a and the tip 80b are butted against each other on the axis of the rotational center 6 and fixed by brazing. In this case, the ends of the chips 80a and 80b that are butted are notched, so that each chip 80a and 80b are cut out.
When a and 80b are butted against each other and fixed, a gap is formed in the rotation center 6. and,
In particular, the inner edge 82 of each of the chips 80a, 80b
Axial rake faces 83a, 83 including a, 82b
b is formed into an inclined surface similar to that of the above-mentioned drill with a cutting edge. A drill configured in this manner also has the same effects as the above-mentioned drill with a cutting edge.

Note that the rake faces 83a and 83b of the drill
may be formed into a curved surface that is convex in the direction of rotation, as shown in FIG.

Further, the drill shown in FIGS. 23 and 24 has a hard member 90 such as cemented carbide buried in the bottom of the cavity formed in the drill with a cutting edge shown in FIGS. 7 and 8. However, the other features are exactly the same as the above-mentioned blade type drill. Note that FIG. 25 shows a case where the hard member 90 is applied to the drill shown in FIG. 9.

Furthermore, in each of the above-mentioned embodiments, the case where drilling is performed by rotating the tool has been described, but the present invention is not limited to this, and the invention is not limited to this; Of course you can go.

As described above in detail, the present invention is a drilling tool such as a drill that has two cutting edges at the tip of the tool body and performs cutting down in the axial direction, leaving a core at the center of rotation. (However, the conical protrusion remains), the inner edge of the cutting edge is equal and dotted within a range of at least 0.1 mm or more and less than 1.25 mm from the center of rotation of the tool body relative to the workpiece. It is installed symmetrically, and
At least a part of the rake face along the axial direction of the tool body including the inner edge of the cutting blade is directed from the rotation center side to the outer peripheral side in a direction from the rotation center to the part of the inner edge closest to the rotation center. Since the cutting edge is configured to gradually protrude in the direction of relative rotation of the tool body, the length of the cutting edge becomes longer and the load per unit length can be reduced.
High feed rate is possible without chipping or abnormal wear of the cutting edge, and it also prevents welding by causing slippage that shears chips, making it difficult to form built-up edges and making it difficult to chip the cutting edge. Moreover, it is possible to improve the processing and discharge of chips, and also to improve the hole accuracy.

[Brief explanation of the drawing]

Figures 1 to 3 show conventional drills;
The figure shows a bottom view of a conventional solid type drill.
Figure 2 shows the side view, Figure 3 shows the situation when drilling a hole in the work material with the drill, and Figure 3A
is its enlarged bottom view, Figure 3B is its enlarged sectional view,
4 to 25 show a drilling tool according to the present invention, FIG. 4 is a bottom view of a solid type drill, FIG. 5 is a side view thereof, and FIG. 6 is a bottom view showing another example. Figure 7 is a bottom view of a drill with a cutting edge, Figure 8 is a side view, Figure 9 is a bottom view of another example, and Figure 10 is a hole drilled into a workpiece using the drill shown in Figure 9. Enlarged bottom view when
The figure is a side view when the tip is fixed at an angle in the axial direction, Fig. 12 is a bottom view when the twisted tip is fixed along the twist groove, Fig. 13 is a bottom view of the spade drill, and Fig. 14 is a bottom view when the tip is fixed along the twisted groove. Its side view, Fig. 15 is a bottom view showing another example, Fig. 16 is a bottom view of the flat drill, Fig. 17 is its front view, and Fig. 18 is a bottom view of the flat drill.
The figure is a side view, FIG. 19 is a bottom view showing another example, FIG. 20 is a bottom view showing still another example of the drill with a blade, FIG.
The figure is a bottom view showing another example, FIG. 23 is a bottom view showing a drill in which a hard member is provided on the drill shown in FIG. 7, FIG. 24 is a side view thereof, and FIG. 25 is a bottom view showing another example. It is a diagram. 1, 11... Tool body, 2, 65, 72... Gap, 3... Work material, 6... Rotation center, 10
a, 10b, 16a, 16b, 21a, 21b,
63, 70a, 70b...cutting blade, 11a, 11
b, 22a, 22b, 66, 73a, 73b, 8
2a, 82b...inner edge, 12a, 12b, 1
7, 18a, 18b, 23a, 23b, 25a,
25b, 67, 73a, 73b, 74a, 74
b, 83a, 83b... rake face, P, Q... part closest to the center of rotation of the inner edge.

Claims (1)

[Scope of Claims] 1. A drilling tool such as a drill that has two cutting edges at the tip of the tool body and performs down cutting in the axial direction, and does not leave a core in the center of rotation (provided that (a very small conical protrusion may remain), the inner edge of the cutting edge is provided point-symmetrically and equally spaced within a range of 0.1 to 1.25 mm from the center of rotation of the tool body relative to the workpiece. , and furthermore, at least a part of the rake face along the axial direction of the tool body including the inner edge of the cutting blade is arranged from the rotation center side to the outer periphery in the direction from the rotation center to the part of the inner edge closest to the rotation center. A drilling tool characterized in that it is configured to gradually protrude toward the relative rotational direction of the tool body as it goes to the side. 2 The part of the rake face near the center of rotation is
Claims characterized in that it is formed into a single or multi-step inclined surface or convex curved surface that is inclined with respect to a plane that includes the rotation center axis and passes through the portion of the inner edge closest to the rotation center. The drilling tool described in item 1.