JP7058874B2 - Diamond tip for core bit - Google Patents

Description

The present invention relates to a core bit that is attached to a core drill and used to drill a concrete structure, more specifically a cylindrical shank with a mounting portion to the core drill at the top, and a shank at the open end of the shank as appropriate in the circumferential direction. The present invention relates to the diamond chip of a core bit composed of diamond chips that are fixed at intervals of.

FIG. 1 is a front view of a conventional example of the core bit 1, FIG. 2 is a bottom view of the core bit 1, and the core bit 1 is a cylindrical shank 3 having a threaded portion 2 as a mounting portion on the upper portion and the shank. It is composed of a substantially arcuate diamond chip 4 fixed to the opening end of 3 at regular intervals, and the diamond chip 4 is generally made by blending diamond abrasive grains with a metal powder composed of cobalt powder Co and bronze powder Cu-Sn. As the diamond abrasive grains used for the diamond chip 4 of the core bit 1 which is formed and used for drilling a concrete structure, the optimum size of the grain size is # 40/50, that is, 0,635 to 0.508 mm.

As for the diamond tip, there is also known a tip in which unevenness is provided in the circumferential direction of the bottom surface, which is in contact with the cutting surface of the concrete structure during molding, so that the notch does not shake during drilling.

In the conventional core bit 1 shown in FIGS. 1 and 2, when cutting into a concrete structure, unlike a general cone, there is no center that serves as a center of rotation, so there is a tendency to meander while cutting in the radial direction. Therefore, for example, when a tip with a width of 5 mm is used, the width of the incision becomes as large as about 5.2 to 5.4 mm (see Fig. 3), and an extra cut of about 0.2 to 0.4 is made more than necessary, so that the drilling efficiency is increased. There was a problem above.

On the other hand, the above-mentioned tip having irregularities in the circumferential direction of the bottom surface has an advantage that blurring and meandering are less likely to occur at the time of drilling, but such an advantage is a concrete structure only a short time after the start of use of a new product. When an object is cut by about 1 m, the unevenness disappears and the shape of the conventional chip is the same. If the groove is deepened so that it can be used for a long time and the convex portion is raised so that the groove remains even if the convex portion is worn, the convex portion becomes brittle and easily breaks during cutting. Occurs.

An object of the present invention is to provide a diamond tip for a core bit having an increased cutting speed, an increased cutting efficiency, and an improved life.

The invention according to claim 1 is a cylindrical shank and a diamond chip formed by blending diamond abrasive grains with metal powder and fixed to the open end of the shank with an appropriate interval in the circumferential direction. The diamond chip is a relatively hard layer (hereinafter referred to as layer A) in which diamond abrasive grains are mixed with a first metal powder, and diamond abrasive grains are added to a second metal powder. It is characterized by forming a structure in which relatively soft layers (hereinafter referred to as B layer) are laminated in the radial direction of the shank.
Further, the invention according to claim 1 is characterized in that the relatively soft B layer has a structure in which a plurality of relatively hard A layers provided from both sides in the radial direction of the shank are sandwiched and laminated.

Further, in the invention according to claim 1 , the diamond abrasive grains blended in the A layer have a particle size of # 40/50, while the diamond abrasive grains blended in the B layer have a particle size of # #. It is characterized by being a mixture of 40/50 and # 30/40 abrasive grains.

According to the first aspect of the present invention, both the A layer and the B layer are worn while the diamond abrasive grains are dropped off during cutting, but since the amount of wear of the B layer is larger than that of the A layer, both hard and soft A and B A step is created between the layers. When a step is generated, the A layer mainly cuts, and the pressure applied by the A layer to the cutting surface of the concrete structure per unit area increases, so that the A layer cuts into the cutting surface and cuts. And meandering are less likely to occur. As a result, the width of the groove cut into the concrete structure in an annular shape is reduced, cutting is not performed more than necessary, the cutting speed is increased, and the drilling efficiency is improved.

If the step becomes too large, the pressure applied to the cutting surface of the concrete structure of the B layer becomes small and it becomes difficult to wear, and the abrasive grains of the B layer are held without falling off until the wear of the A layer progresses to some extent. .. The wear of the A layer progresses to some extent, the step between the two becomes smaller, the pressing force on the concrete structure of the B layer increases, and when the cutting by the B layer progresses, the abrasive grains of the B layer fall off. When the abrasive grains fall off, the relatively soft layer B wears faster, the amount of wear becomes larger than that of the relatively hard layer A, and the step between the two layers becomes large. As described above, the excessively large step is eliminated by the wear of the A layer, whereby the step between the hard A layer and the soft B layer is maintained so as to be substantially constant. Therefore, the cutting efficiency is improved without causing blurring or meandering, the life of the insert is also improved, and stable cutting performance is maintained for a long period of time.

Further, according to the invention of claim 1 , by firmly pressing the cutting surface of the concrete structure with a plurality of hard A layers, blurring is less likely to occur at the time of cutting, and the B layer between the A layers is almost constant. You will be able to make a dent in the depth of.

The grain size of the abrasive grains and the wear of the metal need to be balanced between the two. The abrasive grains of the B layer are less likely to fall off. When the abrasive grains are difficult to fall off, the expansion of the step between the layers A and B is prevented, which is effective. However, when only the abrasive grains having a large particle size are used, the cutting efficiency in the B layer is lowered. In the invention according to claim 1 , in consideration of this point, not only the abrasive grains having a large particle size but also the abrasive grains having a small particle size are used in combination, whereby the step between the layers A and B is appropriately maintained. This is intended to prevent a decrease in cutting efficiency.

Front view of the core bit. Same bottom view. Sectional view of a concrete structure drilled by a conventional diamond tip. An enlarged perspective view of the diamond chip according to the present invention. Schematic enlarged cross-sectional view of the chip. The schematic diagram which shows the progress state of the wear at the time of cutting. FIG. 4 is a cross-sectional view of a concrete structure drilled by the diamond chips shown in FIGS. 4 and 5.

Hereinafter, the diamond chip for a core bit according to the embodiment of the present invention will be described with reference to the drawings.
FIG. 4 is a perspective view of a diamond chip 11 used in place of the diamond chip 4 of the core bit 1 shown in FIG. 1, and FIG. 5 is a vertical sectional view of the same. FIG. It is formed by blending grains and has a five-layer structure in which a relatively hard A layer and a relatively soft B layer are alternately laminated.

The layer A is # 40/50, which is suitable for cutting the concrete structure 12 as diamond abrasive grains in a first mixed metal powder of, for example, cobalt powder Co 90% and bronze powder Cu-Sn 10%, that is, grains. The B layer is formed by blending abrasive grains D1 having a diameter of 0.635 to 0.508 mm, and the B layer is formed by adding the above-mentioned # 40/50 abrasive to a second mixed metal powder having, for example, cobalt powder Co60% and bronze powder Cu-Sn40%. It is formed by blending grain D1 and diamond abrasive grains in which # 30/40, that is, abrasive grains D2 having a particle size of 0.846 to 0.635 mm are mixed.

In FIG. 5, the abrasive grains D1 having a particle size of # 40/50 are all drawn in the same size for convenience, but in reality, the abrasive grains D1 in the range of # 40/50 are used. The same applies to the abrasive grains D2 having a particle size of # 30/40.
In the B layer, diamond abrasive grains of # 30/40 with a relatively large particle size D2 are sandwiched from both sides by the A layer and are difficult to fall off, but the wear of the A layer progresses and the step with the B layer is reduced. As a result, cutting into the concrete structure by the B layer proceeds, and as a result, the abrasive grains D2 of the B layer fall off. When the abrasive grains D2 fall off, the wear of the B layer formed of the soft metal material becomes faster than that of the A layer, and the dents in the B layer increase. When the dent increases and the step between the layers A and B becomes large, the amount of wear in the layer B decreases until the wear in the layer A progresses to some extent, and by repeating this, the step between the layers A and B becomes almost the same. It will be kept constant.

The B layer also compensates for the decrease in cutting efficiency due to the # 30/40 abrasive grains used in combination with the # 40/50 abrasive grains, which are blended with the # 30/40 abrasive grains and have a relatively small particle size.

FIG. 6 shows the wear state of the diamond chip 11 when cutting the concrete structure 12, and when the chip 11 is new, both the A layer and the B layer have the cutting surface on the bottom surface of the concrete structure flush with each other. However, as the cutting progresses from the start of cutting, both the A and B layers wear while the abrasive grains fall off, but the B layer, which is formed of a soft metal material, progresses more than the A layer, so the B layer Is dented, and a step is formed between both layers A and B. This step will be maintained substantially constant as described above and as shown in the figure.

FIG. 7 shows drilling by a core bit using the diamond tip 11 shown in FIG. 4, in which three hard layers A firmly press the cutting surface to perform cutting without causing blurring or meandering. Since drilling is performed, therefore, when a 5 mm wide tip is used, the width of the incision is within a range slightly larger than 5 mm, and extra cutting more than necessary is hardly performed, so that compared with the one shown in FIG. Cutting speed increases and cutting efficiency improves.

The diamond chip 11 of the above embodiment has a five-layer structure in which hard layers A and soft layers B are alternately arranged, but in another embodiment, it is further configured by a three-layer structure sandwiching the B layer. In the embodiment of the above, it is composed of a hard and soft two-layer structure or a four-layer structure. When composed of an even number of multiple layers, a B layer that is not sandwiched between the A layers is generated. In such a B layer, it is expected that wear and dropout of abrasive grains will be large, but it will contribute to the improvement of cutting efficiency and chip life by the A layer to some extent.

In the above embodiment, a mixture of cobalt powder Co and bronze powder Cu-Sn is also used as the metal powder, but metal powder made of other materials can also be used, and the abrasive grains used in the B layer can be used. As for D1, abrasive grains having a particle size other than # 40/50 can be used, and the blending ratio thereof can be arbitrarily changed.

Explanation of the sign

11 ... Diamond chip 12 ... Concrete structure A layer ... Relatively hard layer B ... Relatively soft layers D1, D2 ... Abrasive grains

Claims (1)

The diamond tip of a core bit composed of a cylindrical shank and a diamond tip formed by blending diamond abrasive grains with metal powder and fixed to the open end of the shank at appropriate intervals in the circumferential direction. hand,
In the diamond chip, a relatively hard A layer in which diamond abrasive grains are mixed with a first metal powder and a relatively soft B layer in which diamond abrasive grains are mixed with a second metal powder are laminated in the radial direction of the shank. It has a structure that is
The B layer has a structure in which a plurality of layers are provided from both sides in the radial direction of the shank and are sandwiched and laminated.
The diamond abrasive grains blended in the A layer have a particle size of # 40/50, while the diamond abrasive grains blended in the B layer have grain sizes of # 40/50 and # 30/40. A diamond chip for core bits characterized by being made of a mixture of .

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