FR2610553A1 - CUTTING GRAIN FOR DRILL, IN PARTICULAR FOR MASONRY AND ROCK, AND DRILL BIT EQUIPPED WITH SUCH CUTTING GRAIN - Google Patents

Abstract

DRILL GRAIN USABLE FOR DRILLING MASONRY AND STONE AND OF THE TYPE CONVENTIONALLY INCLUDING A POINT DEFINED BY THE INTERSECTION OF A FIRST AND A SECOND SURFACE, AND ALSO CONSISTING OF FRONT AND SIDE SURFACES PLACED ON OPPOSING SIDES FROM THE SAID POINT IN ORDER TO DEFINE TWO CORNERS RESPECTIVELY LOCATED AT THE INTERSECTION OF THE EDGES BEFORE THE SAID SURFACES; AT LEAST ONE OF THE FRONT EDGES, CONSIDERING THE DIRECTION OF ROTATION OF THE DRILL, DUDIT GRAIN IS CHAMFRED ALONG THE INTERSECTION OF SAID FRONT AND SIDE SURFACES 43, 44 SO AS TO CREATE DOUBLE INTERSECTIONS 46, 47, 52, 53, ADJACENT TO THE MOST ADVANCED PART OF THE GRAIN 1. THE LIFETIME AND EFFICIENCY OF THE CUTTING GRAIN ARE IMPROVED.

Description

The present invention relates to drills and more particularly to a

  cutting grain for use in combination with a masonry bit having a grooved shaft for receiving the grain and for removing chips produced by the rotation of the cutting grain. It is known in the prior art that sharp cutting grains are commonly used in combination with masonry drills where the cutting grain is inserted into the end of a helically grooved rod, which is used to capture and discharge the

  chips generated by the rotation of the cutting grain.

  The cut is made by means of a rotation of the grain as previously described, in a selected direction of rotation, grain in which it is created, in the prior art, a cutting edge on each side of the chisel edge grain by the intersection of a front face of the grain, defined in correspondence with the direction of rotation, and an extreme front surface of the grain;

  grain, defined in correspondence with the sense of penetration

  tration, and in which a flank edge parallel to the axis of penetration of the drill, is established on each side of the tip by the intersection of a front face of the grain and a lateral end face of the grain parallel to the grain penetration axis, and wherein intersections of said cutting edges and side edges create tips on the grain on each side of the chipping edge, said tips constituting the fastest starting and advancing location chipping and attrition that produce wear of the cutting edges and side edges during cutting. Prior art drill bits having the configuration described above are known and have been manufactured by "Vermont American Corporation" as well as by many others. In the prior art, drills are known which comprise a chamfer of the cutting edge in order to increase the resistance to large scaling, but at the cost of increased resistance to penetration. For a specialist in this field, the

  aforementioned chamfer produces what is called a "clearing-

  In the prior art, there is no device that has used a chamfer to produce negative clearance on a flank edge of a grain of grain.

  forest for masonry, as created by the present

the invention.

  An example of a prior art masonry drill bit is disclosed in US Pat. No. 4,026,327 where a grain of a rotary impact drill is illustrated. In the US patent. No. 4,243,113, a drill bit somewhat similar to the arrangement created by the present invention is shown, but without the chamfered edges. Other features of drill bits are described in US Patents 3,106,972 and 3,555,937 and in British Patent 1,062,158, but none of them represent a direct progression masonry drill. The present invention relates to novel, useful and inexpensive arrangements for improving drill bit characteristics for stones and masonry and in particular for increasing the service life of a drill bit used to drill holes in brittle and hard materials. such as masonry and rock and to reduce the strength

  necessary to advance the forest.

  According to a feature of the present invention

  It has been found that, in the case of masonry drill bits, and in particular plane-shaped cutting grains having a tip and flank edges, the cutting edges are advanced in the material to be cut to size. As the drill advances, a rupturing of the cutting grain is initiated most often

  at intersections of cutting edges and flanks. normally

  The wear then progresses along the front cutting edges and the flank edges and causes a withdrawal of the intersection points and a rounding on both edges. A progression of the wear profile gradually increases the force required for penetration until this necessary force is greater

to the force available.

  It has been unexpectedly found that

  Within the scope of the present invention, the wear occurring at intersections of the cutting edges and the respective side edges is remote from said intersections so that more even wear is achieved on a larger surface. edge length and a geometry that increases the structural resistance to chipping and

big fractures.

  Arrangements falling within the scope of the present invention also make it possible to obtain cutting grains having reinforced side edges

  which have been shown to increase sharply and unexpectedly

  due to the service life of the cutting grains.

  Furthermore, it has been unexpectedly found that, by chamfering flank edges, the efficiency of the cutting grain was improved during a drilling of

masonry and stone.

  In summary, the present invention makes it possible to obtain a cutting grain which is supported by a drill so as to rotate in a first s e n s and be used

  for drilling holes in, for example, masonry-

  and grain, the grain being planar and conventionally comprising a point defined by the intersection of a first and a second surface, and also having front and side surfaces placed on opposite sides of said tip to define two corners respectively located at the intersections of the front edges of said surfaces, characterized in that

  minus one of the front edges, considering the direction of rota-

  of the drill, said grain is chamfered along the intersection of said front and side surfaces so as to create double intersections adjacent to the

the most advanced part of the grain.

  According to additional characteristics of the cutting grain according to the invention: said chamfered surface is oriented at an angle of between 7.5 and 70 with respect to said opposite surfaces; said chamfered surface is oriented with respect to said opposite surface; among the two most advanced points created by the aforementioned double intersections, the point created by the intersection of the chamfer and the sidewall surface is between 1/5 and 3/4 of the distance between said opposite faces; - said most advanced point which is created by the intersection of the chamfer and the flank surface is spaced at least 0.25 mm from the front face towards its opposite side; said chamfering makes it possible to obtain

  surface extending only over part of the length

  the flank of said flank; said chamfering makes it possible to obtain a triangular surface inclined with respect to the axis of rotation of the drill;

  only one of said leading edges, considering

  deriving the direction of rotation, is chamfers; - More than one of said front edges, considering the direction of rotation, is chamfered; said chamfers are not equal;

said chamfers are equal.

  Other features and advantages of the invention will be highlighted later in the

  description, given by way of non-limiting example, in

  1 is a perspective view of an example of a cutting grain according to the present invention which is placed in the stem of a drill; FIG. 2 is a plan view of a cutting grain of the prior art; Figure 3 is an elevational view of the cutting grain shown in Figure 2; Figure 4 is a sectional view taken along a plane 1, passing through the line IV-IV of Figure 3; Figure 5 is a sectional view taken along a plane passing through the line V-V of Figure 3; Figs. 6A-6B are plan views of other cutting grains of the prior art; Fig. 7 is a perspective view of another example of a prior art cutter. Figs. 8A and 8B are respectively a plan view and an elevational view of an example of a cutting grain. 9A and 9B are respectively plan views of another cutter arranged in accordance with the present invention; and FIG. 10 is a graphical representation giving the comparison between the drill bit characteristics falling within the scope of the present invention and

  drill bits of the prior art.

  Referring first to Figure 1, this is a perspective view of a cutting grain within the scope of the present invention and placed on a drill stem, as is generally well known in the prior art. In Figure 1, a grain 1, in this case a grain falling within the scope of the present invention as described below, is disposed in a grooved rod 26 of a drill and may consist of

  for example tungsten carbide.

  Grooves 27 are made in a helix in the rod 26 and are provided for the evacuation of chips produced by the cutting edges of the grain 1 as the drill rod 26 rotates while being pushed by a forward force F in the material being drilled. Figures 2 to 6B illustrate drill bits which are known in the prior art. FIG. 2 is a plan view of an example of a cutting grain of the prior art and FIG. 3 is an elevational view.

  of the same grain, which is a solid defined by seven surfaces.

  The surfaces 5A and 7A are arranged symmetrically on each side of an axis of rotation of the grain so that the intersection creates a chipping edge 3 o SA surfaces, 7A intersect at an angle less than '. Similarly, the intersection of the surface 5A with the surface 4 defines a cutting edge 5 while the intersection of the surface 7A with the surface 4 defines a cutting edge 7. In the arrangement shown in FIGS. and 3, the surfaces 5A and 7A extend between the surfaces 4 and 5 at an angle B, for example from 15 to 30e as illustrated in FIGS. 4 and 5, in order to create cutting edges 5 and 7 behind them. strata defined by the intersection of surfaces 5A, 7A and

  side surfaces 6, 4 respectively as shown.

  In the arrangement of the prior art illustrated in FIGS. 1 and 2, sidewall surfaces 10a and 11A are provided that can be flat as shown in FIG. 2, while side edges 10 and 11 are created by 10A and 11A surfaces and surfaces 6 and 4 respectively. The surfaces 10A and 11A can be oriented at an angle C with respect to the surfaces 6 and 4 so as to create a backward clearance

  flank tips 10 and 11, as indicated.

  It is obvious that the extensions of the cutting edges 7 and 7 terminate at their intersections with the side edges 10 and 11 so as to create spikes 13 and 14. In the case of a new grain or drill bit and having no wear, the cutting action is performed by the cutting edges 5 and 7 and the diameter of the hole is determined by the distance between the tips 13 and 14, the side edges 10 and 11 just following the tips 13 and 14. The cutting grain is made of a hard material, for example an agglomerate of small hard particles bonded together appropriately, by

  example of cemented carbide which is commonly used.

  An examination of the fine structure in points 13 and 14 made it clear that the hard particle lying completely outside in each point is bound to the grain body over a range of its length.

  less than that of the immediate particles

  adjacent and that the proportion of bonding of the particle with the body of the grain is a direct function of the solid angle delimited by the surfaces 7A, 6, 10A, and similarly by the suaces 5A, 4, 11A. For example, as shown in Figure 7, the particle 15 whose tip 14 defines a corner is bonded to the grain body by three (3) surfaces while the particle 16 is bound by four (4) surfaces. It is obvious that the particle 15 at tip 14 will be more easily dislodged. The particles 15 and 16 may represent individual hard particles or they may represent an aggregate of particles. During wear, both individual particles and aggregates of

  particles are dislodged. The fact that an individual particle

  dual or an aggregate of particles is dislodged in a specific event is a function of a multiplicity of conditions and events, including constant forces, impact forces, sense of forces, defects in homogeneity in matter being cut, defects in homogeneity in the material of the cutting grain, dimensions and hardness of the discs removed from the workpiece with respect to the dimensions and hardness of the hard particles and the thickness and hardness the bonding material involved in the cutting grain. Whatever the precise combination of the wear phenomena, the resulting wear is initiated on the tips 13 and 14 and then progresses. Finally, the cutting edges 5 and 7 are blunted and the flank edges 10 and 11 are flattened so that the grain of

  cut takes a wedge shape when it is seen in elevation.

  These changes cause an increase in the thrust required to penetrate the drill into the workpiece until the use of the drill bit

become impossible in practice.

  According to a feature of the present invention, it has been unexpectedly found that the physical strength of the cutting edges 5 and 7 at their ends has a great influence on the total wear process and that a strengthening of the end portions of the cutting edges cut 5 and 7 significantly increases the service life of the grain and drill. Other known configurations of prior art grains are also shown in Figs. 6A and 6B. In FIG. 6A, the flank surfaces are composed of two semicircular surfaces 17 and 18 having a diameter D2 equal to the diameter of the hole to be drilled when the drill is rotated in the direction F, so that the edge of The flank of the drill bit is congruent with the surface of revolution generated by the rotation of the drill bit. The chamfered surfaces 19 and 20 are arranged angularly so that their

  back edges are removed from the surface of revolution.

  Fig. 6B shows an arrangement in which semicircular sidewall surfaces 21, 22 are provided with a diameter D2 which is equal to the diameter of the drill bit so that the total flank surfaces

  are congruent with the surface of revolution of the grain.

  Referring now to Figure 1 which shows an assembly using a drill bit within the scope of the present invention and shown enlarged in Figures 8A, 8B, a main feature of the cutting grains falling within the scope of this The invention consists, as shown in FIGS. 8A, 8B, in that the side edges 10A and 11A, shown in FIG. 2, and the surfaces 17 and 18, shown in FIG. 6A, as well as the surfaces 21, 22 shown in FIG. in Figure 6B,

  are replaced by flank surfaces 43, 44.

  According to an essential feature of the present

  the invention, the flank surfaces 10A, 11A of the example

  of the prior art shown in FIG.

  43 and 44, as shown, to create new ridges 46, 47 and new edges 52 and 53 as well as a new set of cutting tips 57, 58, 59 and 60, as shown in the figures. o points corresponding to those designated by

  59, 60 are not provided by the prior art.

  Similarly, the solid angles with vertices indicated at 57, 58, 59, 60 are larger than those with the vertices indicated at 13 or 14 for the example of the prior art and they are linked with the grain body. on a greater proportion of their surfaces than are the extreme elements corresponding to the points 13 and 14 in the cutting grain shown in FIGS. 2 and 3. It has been found that this

  change in geometry made it possible to obtain

  physically more robust in places subject to maximum wear under the effect of chipping

Macro- or microscopic form.

  Another reinforcing consequence resulting from the invention is attributable to the modification of the angle of attack of the cutting edges 63 and 64, as opposed to

26 1 0 553

1 0

  that of the edges 5 and 7 of FIGS. 2 and 3.

  Arrangements also falling within the scope of the present invention are also shown in Figs. 9A and 9B. In Figure 9A, there is provided a cutting grain having side surfaces 70 and 71 provided with side edges 72, 73 which have a diameter D3 corresponding to the diameter of the drill. Chamfers

  74, 75 formed at angles F and G make it possible to

  the advantages of the present invention by defining cutting tips 76-81 which are similar to the tips

  of cutting indicated in FIGS. 8A, 8B.

  FIG. 9B shows another possible arrangement within the scope of the present invention and according to which lateral edges 92, 93 are provided at the same time as semi-circular side edges 82, 83 having a diameter D4 equal to the diameter of the drill bit. and wherein the edges are chamfered at 84, 85 with an arcuate profile, the length of the chamfer being less than the total length of the flank edge so as to define

points 86-91.

  In general, chamfer surfaces falling within the scope of the present invention and which define the faces and points of the cutting grain may be symmetrical with respect to the center of rotation or

  they can be unsymmetrical; they can extend

  They may extend over the entire length of the flanks or only over a portion of the length of the flanks, as indicated, or they may be inclined relative to the axis of rotation of the drill so as to create a triangular chamfer surface. The chamfers may be provided in a cutting grain design in which the flanks are arranged to create a draft relative to the cylindrical surface of rotation of the drill, or in a cutting grain design in which the flanks coincide with the cylindrical surface of rotation of the drill, or in a design of the cutting grain in which the flanks correspond to a combination of clearance and coincidence with respect to

the rotating surface of the drill.

  Drill cutter bits having the features within the scope of the present invention have been tested by comparison with cutting grains of different configurations of the prior art, but uniformly free of the chamfered leading edges of the sidewall surfaces which are provided. in the grains falling within the scope of the present invention, as has been described above. The drills with cemented carbide grains and configurations within the scope of the present invention have been compared with drills made by other manufacturers and having a somewhat similar grain configuration but with no additional spikes. which have been described above. As a result of the tests carried out, it was concluded that an improvement was obtained when the angle was increased from 7.5 and that the depth of the chamfer could be between 1/5 and 3/4 of the depth of the grain, preferably

about 1/3.

  Tests were carried out with three materials, including die-cast concrete with crushed aggregates, concrete containing aggregates of gravel,

  as well as granite, for various advance forces-

  is lying. It has been found that cutting grains in accordance with the present invention make it possible to obtain results

  with a higher rate of

  the speed of penetration compared to that of comparison drills and it was found that the wear rate decreased, resulting in a significant improvement in the service life of the drill, all these results being highlighted in the figure 10 which shows the comparison between the penetration rate of a drill bit in relation to the total depth of the drilled holes. The superiority of the cutting grains falling within the scope of the present invention is

clearly illustrated.

  Although all the reasons for the superiority of the grains of cut falling within the scope of the present invention are not perfectly understood, it is estimated that at least a part of the improvement results from the fact that the cutting forces are distributed over several

  which, thanks to their configuration, are more robust

  as previously described. Some improvement also results from the fact that the cutting edges are oriented so as to direct the cutting forces towards the inside of the grain body and not tangentially to the arc of the cutting path as is the case with

  the grains of the prior art. In addition, by this amendment

  cation direction of the cutting forces, the resistance of the cutting edges is greatly improved. Some improvement can also be achieved because the total lengths of the cutting edges are increased, which reduces the cutting force per unit length of the cutting edges.

cutting edges.

  Naturally, the invention is not limited to the embodiments described above and shown, from which we can provide other modes and other embodiments, without departing from the

framework of the invention.

Claims (12)

  A drill bit operable for drilling masonry and stone and of the type conventionally comprising a point defined by the intersection of a first and a second surface, and also having front and side surfaces placed on opposite sides of said tip to define two corners respectively located at the intersection of the front edges of said surfaces, grain (1) characterized in that at least one of the front edges, considering the direction of rotation of the drill, said grain is chamfered along the intersection of said front and side surfaces (43, 44) so as to create double intersections (46, 47, 52, 53) adjacent to the most forward portion of the grain (1).   2. Cutting grain for drill according to the claim   1, characterized in that said chamfered surface (43, 44) is oriented at an angle of between 7.5 degrees   and 70 degrees to said opposite surfaces.   3. Cutting grain for drill according to the claim   2, characterized in that said chamfered surface (43, 44) is oriented at 45 degrees with respect to said opposite surface.   4. Cutting grain for drill according to claim 1, characterized in that, among the two points (59,60) the most advanced created by the aforementioned double intersections, the tip (59) created by the intersection of the chamfer and the   flank surface is between 1/5 and 3/4 of the distanc- this between said opposite faces.   5. Drill cutter according to claim 4, characterized in that said most advanced point (59,60) which is created by the intersection of the chamfer and the flank surface is spaced at least 0.25 mm of the   front face towards its opposite side.   6. Drill cutter according to claim 1, characterized in that said chamfering (43, 44; 74, 75) provides a surface extending only   on a part of the length of said flank.   7. cutter drill bit according to claim 1, characterized in that said chamfering (43, 44 74, 75) provides a triangular surface inclined relative to the axis of rotation of the drill.   8. Cutting grain for drill according to the claim   1, characterized in that only one of said edges   before, considering the direction of rotation, is chamfered.   9. Cutting grain for drill according to the claim   1, characterized in that more than one of said edges   before, considering the direction of rotation, is chamfered.   10. Cutting grain for drill according to the claim   9, characterized in that said chamfers (43, 44 74, 75) are not equal.   11. Cutting grain for drill according to the claim   9, characterized in that said chamfers are equal. 12. Drill, especially for masonry and rock,   equipped with a cutting grain according to any one of the 1 to 11.