JPH0440810Y2 - - Google Patents

Description

[Detailed explanation of the idea] <Industrial application field> The present invention relates to improvements in hole saws.

<Prior art> A hole saw is generally composed of a cylindrical body with a cutting edge provided on the tip edge and a guide drill extending from the inside of the cylindrical body to the tip, and by rotating both in unison, This is to drill a hole in the workpiece under the guidance of a guide drill that has approximately the same external shape as the cylindrical body. At this time, the hole drilled in the object to be cut is, of course, circular. Therefore, when drilling a circular hole, the preconception that it is most preferable for the cylindrical body of the hole saw to be circular has prevailed among those skilled in the art.

<Problems to be Solved by the Invention> However, when a circular hole is drilled in a cylindrical body, the gap between the cut hole and the tube is extremely small. Therefore, chips generated during cutting are not properly discharged, resulting in clogging of the cutting blade. In particular, this clogging becomes more serious when the thickness of the workpiece is large or when a large amount of chips are generated from the workpiece. For example, when the workpiece to be cut is soft iron, this problem becomes apparent when the thickness of the workpiece exceeds 10 mm, or when the workpiece is an ALC plate that generates a lot of chips.

As a general means for solving the problem of the generation of chips, it is known to form spiral grooves for removing chips on the outer periphery of the cylindrical body. However, this groove is usually formed by cutting, which complicates the manufacturing process of the hole saw. Further, the effective depth of the groove for removing chips needs to be 1.0 to 1.5 mm or more, and in order to form the groove, the thickness of the entire cylindrical body needs to be about 3.0 mm. Therefore,
The complexity of the manufacturing process and the increase in plate thickness are factors that push up manufacturing costs.

<Means for Solving the Problems> Therefore, the present invention solves the above problems by providing the following modified hole saw.

The modified hole saw according to the present invention is provided with a plurality of cutting blades 5 on the tip edge of a cylindrical body 3, and by rotating this cylindrical body 3, a circular hole is made in a workpiece.

In its cross section, the entire cylindrical body 3 from its base end to its distal end has a plurality of circular arc portions 3a having approximately the same radius as the radius of the target hole, and 3a', 3a' between the ends of the circular arc portions. a plurality of rectilinear or curved receding portions 3b arranged and retracted in the radial inward direction;
3b', 3b''.The difference between the radius of the circular arc portion 3a and the shortest distance from the center of the cylindrical body at the retreated portions 3b, 3b, 3b'' is greater than or equal to the thickness of the cylindrical body 3. It is set to .

<Function> In contrast to conventional hole saws, the cross section of the cylindrical body is a perfect circle, and the position of the cutting blade formed at the tip of this perfect circular cylindrical body is changed. In the present invention, the cylindrical body itself has an arcuate portion 3a and retracted portions 3b, 3b', 3b''.
Therefore, the change in the position of the cutting blade formed at the tip of the cylindrical body can be dramatically increased. Therefore, a circular groove with a large width is cut into the workpiece.

In the present invention, since the cylindrical body is composed of the arcuate portion 3a and the retracted portions 3b, 3b', and 3b'' as described above, the outer circumferential surface of the retracted portion and the inner circumferential surface of the groove formed by cutting A large gap 7c is formed between the inner peripheral surface of the arc portion and the outer peripheral surface of the groove.As a result, chips are received in the large gap 7c, and the cylindrical body and the groove are separated. There has never been a case where chips become tightly packed between the holes, and the cutting (rotation) resistance does not increase.Especially, the entire cylindrical body (i.e., only the tip with the cutting edge) The hole saw is made up of the arcuate part and the retracted part as described above, so even if this hole saw penetrates deeply into a thick workpiece, this large gap will not be created by the tip. Therefore, not only the tip of the cylindrical body but also the entire base end, chips are tightly packed between the cylindrical body and the groove. Once it is put away, there is no damage, and it is possible to keep the cutting resistance small until the end.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a perspective view of a hole saw according to an embodiment, and FIG. 2 is an explanatory diagram of its cutting state.

This hole saw has a base 2 with a shank 1 connected to a power tool (not shown), a cylindrical body 3
and a guide drill 4 are attached. The guide drill 4 extends from the inside of the cylindrical body to its open tip, projects from the end of the tip, and guides cutting by the cylindrical body.

The cylindrical body 3 has a large number of cutting blades 5 at its tip, and rotates to make a circular hole in the object to be cut. The cylindrical body 3 is composed of a circular arc portion 3a and a receding portion 3b in a cross section perpendicular to the axial direction. The arc portion 3a has a circumference that is approximately the same as the circumference of the target hole diameter. The retreated portion 3b has a substantially linear shape that is retreated in the radial direction compared to the arcuate portion 3a, and is located between the ends 3a', 3a' of the arcuate portion 3a.

Therefore, during cutting, a circular groove is cut into the workpiece, which is wider than a normal cylindrical hole saw, and there is a gap between the outer circumference 7a of the groove, the inner circumference 7b, and the cylindrical body 3. In this case, a gap 7c is left open, and chips are allowed to escape into the gap 7c. As a result, it was possible to drill even relatively thick soft iron plates (20 mm or more thick) without clogging with chips.

In the illustrated embodiment, three circular arc portions 3a with a center angle of 70 degrees and three receding portions 3b with a center angle of 50 degrees are arranged alternately, but these angles may vary depending on the type and thickness of the workpiece. , various changes may be made depending on changes in the diameter of the hole saw, etc. Similarly, the number of arcuate portions 3a and retreated portions 3b may be changed as appropriate, such as 2 each as shown in Fig. 3, 4 each as shown in Fig. 4, and 6 each as shown in Fig. 5. The number can be changed as appropriate, such as one by one. Generally, as the diameter of the hole saw increases, it is desirable to increase the number of each hole saw, but if the diameter is small and the material of the workpiece is relatively soft, it is also possible to use one each.

Further, as shown in FIG. 6, vertical grooves 11 or spiral grooves 12 may be provided on the surface of the cylindrical body in order to enhance the chip removal function.

The base 2 and the cylindrical body 3 may be integrally molded, or may be molded separately and then fixed by welding or the like. Alternatively, the base 2 and the cylindrical body 3 may be made removable, and only the cylindrical body 3 may be replaceable.

Although the retreated portion 3b has a substantially straight shape in the embodiment, it is not limited to this, and may be curved. For example, as shown in FIG. 7, it may have a curvature and recede. Furthermore, the eighth
9 and 10, the diameter of the cylindrical body 3 itself is constructed by combining the circumferences of a plurality of concentric circles with different diameters, instead of receding with curvature. It may also form a recessed portion. To be more specific, what is shown in FIG. 8 is the retreating portion 3b.
is made up of a circumference with a constant diameter. What is shown in FIG. 9 is a part further retreated to the retreating part 3b (the number is not limited to the number shown in the figure).
That is, it has the last retraction 3b'. The one shown in FIG.
b'' (the number is not limited to what is shown in the figure).A more preferred embodiment will be shown again using FIG. The cutting blade 5'' arranged at the smallest diameter part of 3b draws a trajectory (i.e., a circle (0)) by rotation.
Position it so that it can be traced on or near it.
This is to cover the part where the number of blades corresponding to a specific part of the surface to be cut is the least, and to reduce the load on the cutting blade at that position. Such considerations are particularly meaningful when the object to be cut is metal. When cutting soft iron, etc., it is common to have a ``crow'' of about 2 mm, and it is desirable that the cutting blade be aligned on a circle with this width. To give an example in detail, when drilling soft iron, the ``clam'' was generally about 2 mm. The number of cutting blades for the cylindrical body 3 with a radius of 2 to 3 cm is 30.
It is around 1 piece.

Other cutting blades are omitted in FIG.

As described above, the present invention is not limited to the illustrated embodiments, but can be implemented with various modifications.

<Effects of the invention> As described above, the hole saw of the present invention has a cylindrical shape in which at least the tip ring portion of the cylindrical body is composed of an arcuate portion and a receding portion. A thick circular groove is cut into the workpiece. As a result, a gap is created between the outer circumference and inner circumference of the groove and the cylindrical body, and chips are allowed to escape into the gap. Therefore, chips can be appropriately removed and good cutting can be performed even on thick soft iron plates, ALC plates, etc. As described above, the present invention has been able to provide a new and useful hole saw that was created by breaking away from the conventional concept of a cylindrical hole saw.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a hole saw according to one embodiment;
The figure is an explanatory diagram of the cutting state of the same hole saw, FIGS. 3 to 5 are explanatory diagrams of the shape of hole saws of other embodiments, and FIG. 6 is a perspective view of a hole saw of still another embodiment. Figure 7, Figure 8, Figure 9, Figure 10
The figures are shape explanatory diagrams showing still other embodiments. DESCRIPTION OF SYMBOLS 1... Shank, 3... Cylindrical body, 3a... Circular arc part, 3b... Receding part, 3a'... End of circular arc part, 4... Guide drill.

Claims (1)

[Claims for Utility Model Registration] A modified hole saw in which a plurality of cutting blades 5 are provided on the tip edge of a cylindrical body 3, and by rotating the cylindrical body 3, a circular hole is made in a workpiece. The entire cylindrical body 3 from its base end to its distal end is arranged in its cross section between a plurality of arcuate portions 3a having approximately the same radius as the radius of the target hole, and end portions 3a', 3a' of the arcuate portions. a plurality of linear or curved recessed portions 3b, 3b',
3b'', and the radius of this circular arc portion 3a and the retreated portions 3b, 3
A deformed hole saw characterized in that the difference between b' and 3b'' from the shortest distance from the center of the cylindrical body is set to be greater than the thickness of the cylindrical body 3.