JPH03245974A - Highly spontaneous diamond core drill - Google Patents

Abstract

PURPOSE:To facilitate the discharge of a chip, to improve cutting property and to continue a high cutting property at all times until a diamond cutting blade is lost, by providing chips discharging grooves alternately at both parts of the inner and outer faces of a diamond cutting blade. CONSTITUTION:A chips discharging groove 3 in the dimension of more than 1/2 of the thickness (t) in the radial direction is provided more than one alternately on the inner and outer both faces on a diamond cutting blade 2. The discharging of a chip is thus facilitated by providing the chips discharging groove 3 and the punching speed of a diamond core drill is continued at the value of more than 80% of the initial punching speed at all times until this cutting blade 2 is lost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a diamond core drill suitable for drilling.

[Background of the invention]

Conventionally, diamond core drills have a cylindrical body with a plurality of cutting blades containing arc-shaped diamond abrasive grains fixed at intervals at the tip of the body, and these diamond core drills can be attached to the power source of hand-operated power tools to drill the workpiece. Used for drilling work in concrete, rock, asphalt, brick, etc. This diamond cutting blade is made up of diamond abrasive grains that serve as cutting abrasive grains and a metal bond that holds the diamond abrasive grains.The metal bonds are mainly classified into bronze, cobalt, tungsten, or iron. Diamond abrasive grains are distributed relatively uniformly within the cutting edge and maintain a constant level of cutting performance, but the reality is that diamond abrasive grains become worn or chipped with the number of uses, resulting in poor cutting quality. be. The key point is how to maintain stable machinability.

Up until now, the shape of diamond cutting blades has been fixed to the tip of a cylindrical body, so a hexahedron with an arc that follows the body shape has been common, and depending on the intended use, diamond cutting blades may be long in the circumferential direction or in the drilling direction. There are various types such as long ones, but the hexahedral shape remains the same. However, when aiming to improve cutting efficiency, this hexahedral shape has a large contact area with the workpiece, which not only increases cutting resistance but also prevents sufficient chip evacuation. It will stick between the abrasive grains and cause clogging.

On the other hand, the metal bond must have two important functions: holding the diamond abrasive grains during cutting and self-sharpening action. The former metal bond needs to have a strong holding power against the impactful external forces that act during cutting. There is no chemical reaction between the medal bond and the diamond abrasive grains, and they are mechanically held together by pressure from the outer periphery.

In addition, the latter self-growth effect of the diamond abrasive grains requires that the metal bond is constantly worn during cutting, and a certain amount of abrasive grains must always protrude from the surface of the cutting edge.

If the diamond abrasive grains become worn or chipped, the metal bond itself will also wear out, and as the diamond abrasive grains wear out or chip, the height of the diamond abrasive grains and the metal bond will become the same, reducing cutting efficiency and making the metal bond unusable. Furthermore, if chips adhere to or press against the surface of the metal bond between the diamond abrasive grains, the amount of protrusion of the diamond abrasive grains disappears, resulting in a clogging condition and making the metal bond unusable. In this case, redressing is required,
Hand-held power tools can be particularly cumbersome to work with.

Metal bond, which has a high ability to retain diamond abrasive grains, has a dense microstructure and hardness, so it has high wear resistance. This metal bond contains powder of carbides such as tungsten carbide or nitrides to extend the life of the diamond cutting blade. However, since the metal bond has little wear, the amount of diamond abrasive grains forming the cutting edge is small, and the self-sharpening effect is poor, resulting in a decrease in cutting quality when continuous cutting is performed.

On the other hand, if the hardness of the metal bond is low, it goes without saying that the holding power of the abrasive grains is weak, and the wear of the metal bond progresses quickly during cutting, resulting in severe rockfall of the abrasive grains and shortening the service life.

From the above, it has been considered difficult to improve the holding power and self-growth effect of diamond abrasive grains because they are contradictory to each other.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and provide a diamond core drill with excellent cutting performance.

[Summary of the invention]

The present invention provides a diamond core drill in which a plurality of arc-shaped diamond cutting blades are fixed at intervals to the tip of a cylinder, and the drilling speed of the diamond core drill always maintains 80% or more of the initial drilling speed until the diamond cutting blades disappear. This is a diamond core drill that can be used in a very powerful manner. This is a device in which the diamond cutting blade is provided with one or more chip discharge grooves having dimensions of 1/2 or more of the thickness in the radial direction, alternately on both the inner and outer surfaces, and the diamond cutting blade is equipped with a diamond abrasive groove. The grains contain 0.7 to 3.5% by weight, the particle size is from 20 mesh to 60 mesh, and the metal bond generation components are blue U: 20 to 60%, iron: 20 to 60% by weight.
This diamond core drill is characterized by having a composition consisting of 40% cobalt and 20 to 50% cobalt, a Vickers hardness of 150 to 300, and a sintered relative density of 90% or more.

The diamond core drill of the present invention will be explained below with reference to the drawings. Fig. 1 shows a diamond core drill of the present invention in which one or more chip discharge grooves are provided alternately on both the inner and outer surfaces of the diamond cutting edge.
The diamond cutting blade is S-shaped and has a bottom view seen from the cutting edge. 1 has a cylindrical body.
A plurality of diamond cutting blades 2 are fixed at intervals to the tip of this cylinder, and chip discharge grooves 3 are provided in the diamond cutting blades. Figure 2 shows AA when the depth of the chip discharge groove is 1/2 or more of the thickness of the diamond cutting edge in the t direction.
Figure 3 is a BB' cross-sectional view of the part without the chip discharge groove, Figure 4 is an AA' cross-sectional view when the depth of the chip discharge groove is less than 1/2, Figure 5 is a diamond cutting blade with two S-shaped chip discharge grooves alternately provided on the inner and outer surfaces, and the depth of the chip discharge grooves is 172 or more in the thickness direction. Looking at the relationship between the depth of the chip discharge groove provided on the diamond cutting edge of a core drill and the cross-sectional shape of the diamond cutting blade during drilling, there is almost no change in shape when there is no chip discharge groove; The ridgeline of the blade is only slightly worn and has a curved surface. In this case, the chips are discharged from the gap between the diamond cutting edges, resulting in clogging of the chips and poor cutting performance.

On the other hand, if chip discharge grooves with a depth of less than 172 mm are provided alternately on both the inner and outer surfaces of the diamond cutting blade, the inner and outer surfaces with the chip discharge grooves will wear out fastest, and the central portion without grooves will wear out the fastest. This means less wear.

In this case, the central part of the area where there is no chip discharge groove becomes clogged with chips and the cutting efficiency decreases to 80% of the initial drilling speed.
As a result, cutting becomes impossible. Further, when the depth of the chip discharge groove becomes 1/2 or more, the wear progresses evenly, so the diamond abrasive grains in the diamond cutting edge are sharpened, and the self-synthesis action is constantly repeated. - Worn or broken diamond abrasive grains fall off as the metal bond wears, so new diamond abrasive grains are quickly polished. Because of the chip discharge groove provided on the diamond cutting edge, the self-sharpening action progresses efficiently, and since chips are sufficiently discharged, clogging can be prevented, and stable cutting performance can always be obtained.

Next, improvements in the holding power and self-sharpening effect of diamond abrasive grains will be explained. In addition to the above-mentioned shapes, as a result of researching various diamond abrasive grains and netalbonds in diamond cutting blades to obtain high machinability with the aim of improving the retention force and self-sharpening action of the diamond abrasive grains, we have found that the diamond abrasive grains shown below are The above objective could be achieved with the abrasive grain and metal bond composition. That is, the diamond cutting edge contains 0.7 to 3.5% by weight of diamond abrasive grains, the particle size is from 20 mesh to 60 mesh, and the main component of the metal bond is bronze (by weight).
Cu-5n): 20-60%, iron = 20-40%, cobalt: 20-50%, the Vickers hardness of the metal bond is 120-280, and the sintered relative density is 90% or more. That's true.

The content of diamond abrasive grains is set to 0.7 to 3.5% by weight.If the content is less than 0.7%, there are fewer diamond abrasive grains, which improves cutting efficiency, but the entire diamond cutting edge wears out prematurely. This is because the lifespan is short. 3.5
% or more, there will be more than necessary on the cutting surface of the diamond cutting edge, making it difficult to remove chips, and if some diamond abrasive grains are missing, or even if they fall off, the diamond abrasive grains will remain around the metal bond, causing wear of the metal bond. Since this does not progress, a clogging phenomenon will occur.

The composition of medal bond is Blue R: 20-60%, Iron: 20-40%, Cobalt = 20-50%, and the Vickers hardness of the metal bond is 120-28.
0 and the sintered relative density is preferably 90% or more. Bronze is preferably an alloy powder and tin is preferably 40% or less by weight. Bronze is used to prevent thermal damage to diamond abrasive grains and is necessary for low-temperature sintering. In addition, iron is used to obtain the hardness of the metal bond and improve the toughness of the diamond cutting edge. Cobalt is added for the purpose of improving heat resistance. These alloys or single powders are weighed and mixed and sintered to form a diamond cutting edge.The Vickers hardness of the metal bond at this time is considered to be the hardness of the diamond abrasive grains in terms of their holding power and self-growth. The diameter is preferably Hv 120 to 280.

Especially judging from machinability and service life, Vickers hardness Hv
It is 180-230. If the Vickers hardness of the metal bond is less than 180, the metal bond itself is soft and ductile, and therefore diamond abrasive grains are not retained well, causing the diamond abrasive grains to fall off and the metal bond to wear out prematurely. Further, when the Vickers hardness is 280 or more, the metal bond becomes hard and wear of the metal bond does not progress properly, and the sintered relative density is preferably 90% or more. If it is less than this, the toughness will be low and the diamond cutting edge will chip during cutting, or the entire cutting edge will be damaged, so 90% or more is better. Preferably it is 93 to 96%, and if you look at the microstructure of the metal bond within this range, the presence of excessive voids will form a type of chip pocket, making it easier for self-growth to proceed. The cutting quality is good, and the drilling speed of the diamond core drill can always maintain at least 80% of the initial drilling speed until the diamond cutting edge disappears. Other components may be added to the metal bond composition as long as the Vickers hardness and sintered relative density of the metal bond are within the above ranges.

[Embodiments of the invention]

<Example 1> Bronze powder (Cu-10% 5n) 38.
A diamond cutting blade was produced by mixing 5% iron powder, 30% iron powder, 30% cobalt powder, and 1.5% diamond abrasive grains (particle size 30 to 40 mesh) and firing the mixture under pressure. The sintered relative density of the diamond cutting blade was 95%, and the Vickers hardness of the metal bond was Hv200. The shape of this diamond cutting blade is one in which chip discharge grooves with a dimension of 1/2 or more of the thickness are provided alternately on both the inner and outer surfaces, and these are placed at the tip of the steel cylindrical body (diameter 8ON). A diamond core drill was manufactured by fixing multiple pieces at intervals in an arc shape. For comparison, a diamond core drill without a chip discharge groove on the diamond cutting edge was also manufactured in the same manner.

This diamond core drill was attached to a hand-held power tool and a comparative drilling test in concrete was conducted in a wet state. The drilling conditions are drilling depth 150■, pressing force]-0kg
, and the drilling rotational speed was 700 r, p, m.

In the drilling comparison test results, when the drilling speed of a diamond core drill without a chip discharge groove is expressed as 1, the diamond core drill provided with a chip discharge groove achieved a drilling speed of 1.6 times. This is due to the fact that chip discharge grooves are provided alternately on both the inner and outer surfaces of the diamond cutting edge, which makes it easier to remove chips, resulting in improved cutting performance and consistently high machinability until the diamond cutting edge disappears. , and maintained more than 80% of the initial drilling speed.

Next, a diamond core drill manufactured in exactly the same manner as above and subjected to a dry drilling test revealed that the drilling speed of a diamond core drill with a chip discharge groove was 1.5 times the drilling speed of a diamond core drill without a chip discharge groove. The effect of the chip discharge groove provided on the diamond cutting edge is significant, as the 4 times the gain was obtained.Especially in the dry method, there is less clogging of chips between the diamond abrasive grains, and self-growth occurs, resulting in better cutting quality. Ta.

<Example 2> Bronze powder (Cu-20% 5N) 40%, iron powder 30% by weight
, 28% cobalt powder, and 20% diamond abrasive grains (particle size from 30 mesh to 40 mesh) were mixed to produce six types of diamond cutting blades under different pressure firing conditions. The sintered relative densities of these six types of diamond cutting blades and the Pinkers hardness of the metal bond are as follows. Sample No. 1 has a sintered relative density of 85% and a Vickers hardness of Hv 120. Similarly, sample No. 2 has a sintered relative density of 88%, Hv 140, sample No. 3 has a 90% Hv 160, and sample No. 4 has a 93%.
, Hv190, sample N o 5 is 96%, Hv240,
Sample No. 6 is 99% Hv310. The shape of this diamond cutting blade is such that chip discharge grooves with a thickness of 172 mm or more are provided alternately on both the inner and outer surfaces, and these grooves are circularly attached to the tip of the steel cylindrical body (diameter 80 m). A diamond core drill was made by fixing multiple pieces in an arc shape at intervals.

This diamond core drill was attached to a hand-held power tool, and a concrete drilling test was conducted in a wet state. The drilling conditions were a drilling depth of 150 m, a pressing force of 10 kg, and a drilling rotation speed of 700 r, p, m.
The perforation speed of sample No. 1 was expressed as 1, and the ratio thereof was determined. The results are shown in the table below.

As is clear from this result, a material with excellent machinability requires an appropriate sintering relative density and also requires hardness of the metal bond.

Since sample No. 1 had a low sintered relative density, part of the cutting edge fell off during cutting, resulting in poor cutting performance. Also, sample No.
No. 2 was also improved by about 10% compared to sample No. 2, although a portion of the cutting edge was chipped due to the turning part. On the other hand, Samples No. 3.4 and 5 have good cutting edge conditions, that is, the condition of the diamond abrasive grains and the cutting edge shape.

The machinability was improved by about 50% compared to No. 1. In addition, because the hardness of the metal bond was appropriate, self-growth progressed, clogging of chips disappeared, and high cutting characteristics were always exhibited until the diamond cutting edge disappeared. For sample No. 6, the holding power of the diamond abrasive grains is high due to the high sintered relative density, and even if the diamond abrasive grains are chipped during cutting, they do not fall off, so the next new diamond abrasive grains are not sharpened. Cutting performance was poor due to clogging of chips.

〔Effect of the invention〕

According to the present invention, a plurality of arc-shaped diamond cutting blades are fixed at intervals to the tip of a cylinder, chip discharge grooves are provided alternately on both the inner and outer surfaces of the diamond cutting blades, and the diamond abrasive retention force and self-retention are improved. Since the action has been improved, chips can be easily discharged, cutting performance is always stable, and the diamond cutting edge can maintain high cutting performance until it disappears.

[Brief explanation of drawings]

Figure 1 is a bottom view of the diamond core drill, Figure 2 is a cross-sectional view along line AA' when the depth of the chip discharge groove is 1/2 or more in the thickness direction of the diamond cutting edge, and Figure 3 is the chip discharge BB' cross-sectional view of a portion without grooves. Figure 4 is an AA' cross-sectional view when the depth of the chip discharge groove is less than 1/2, and Figure 5 shows two chip discharge grooves provided alternately on both the inner and outer surfaces of the diamond cutting blade. It is a bottom view in case the depth of this chip discharge groove is a dimension of 1/2 or more. In the figure, 1 is the body, 2 is the diamond cutting blade, 3 is the chip discharge groove, 4 is the center line, and t is the thickness of the diamond cutting blade.

Claims (1)

[Claims] 1. A diamond core drill in which a plurality of arc-shaped diamond cutting blades are fixed at intervals to the tip of a cylinder,
The drilling speed of the diamond core drill is capable of maintaining at least 80% of the initial drilling speed until the diamond cutting edge disappears. 2. The highly self-growing diamond according to claim 1, wherein the diamond cutting blade is provided with one or more chip discharge grooves having a dimension of 1/2 or more of the radial thickness alternately on both the inner and outer surfaces. core drill. 3. In claim 1, the diamond cutting blade contains 0.7 to 3.5% by weight of diamond abrasive grains, the particle size is from 20 mesh to 60 mesh, and the main component of the metal bond is bronze: 20% by weight. ~60%, iron: 20-40%,
A diamond core drill having a composition consisting of 20 to 50% cobalt, a Vickers hardness of 150 to 300, and a sintered relative density of 90% or more.