WO2013148765A1

WO2013148765A1 - Masonry drill bit

Info

Publication number: WO2013148765A1
Application number: PCT/US2013/034001
Authority: WO
Inventors: Rainer Lampe; Heinrich Kersten
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 2012-03-27
Filing date: 2013-03-27
Publication date: 2013-10-03
Anticipated expiration: 2014-09-27
Also published as: DE202012003072U1; DE112013001767T5

Description

MASONRY DRILL BIT

The invention relates to a masonry drill bit according to the preamble of claim 1, and to a cutting insert according to the preamble of claim 14.

The masonry drill bit under consideration is intended, in particular, for use in combination with a percussion drill device or hammer drill device. It is suitable for drilling in concrete or reinforced concrete, but also in other masonry, rock or the like.

The usual criteria for the design of masonry drill bits of the type under consideration are ease of centering, the achievable drilling advance per unit of time, long service life and low rate of wear. A masonry drill bit that is optimized in these respects (DE 20 2006 003 539 Ul) and on which the invention is based is provided with a cutting insert that is inserted in a receiving slot and soldered on there.

In the initial state, in a side view, the cutting insert forms a substantially roof-shaped roof portion, which realizes at least one cutting edge and which is adjoined, in the axial direction, by a base portion having outer peripheries that run substantially axially .

In the case of this known masonry drill bit, the geometry of the cutting insert determines the effective drill bit diameter, which determines the resultant drilled hole diameter.

The masonry drill bit under consideration generally has an assigned minimum nominal diameter. The nominal diameter is the minimum diameter that can be produced with the masonry drill bit until the end of its service life. Since, with proper use of the cutting insert, the base portion of the latter is subject to radial wear, the effective drill bit diameter in the initial state - the initial diameter - is always greater than the nominal diameter. When the nominal diameter is attained, the end of the service life of the masonry drill bit has then been attained.

The cutting insert is therefore of very particular importance, not only in respect of the performance features, but also in respect of the service life of the masonry drill bit. The cutting insert is composed of appropriately hard and wear-resistant materials, in particular of a hard metal. Such a hard metal provides good results, both in respect of the performance features and in respect of the service life. However, the costs associated with the use of a hard metal are high .

The invention is based on the object of improving the known masonry drill bit with regard to cost.

The above object is achieved, in the case of a masonry drill bit according to the preamble of claim 1, by the features of the characterizing portion of claim 1.

The invention is based on the consideration of reducing the height of the base portion of the cutting insert insofar as possible, in order to reduce the use of material required for the cutting insert.

According to the proposal, it has been identified that, in the case of the known masonry drill bit, a lower axial part of the base portion of the cutting insert is not instrumental, or is instrumental only to a negligible extent, in the drilling advance. This is manifested, in particular, in that the wear occurring on this lower axial part results primarily in removal of material in the radial direction. This implies that actions of forces in the axial direction, which are actually instrumental in the drilling advance, do not occur in this lower axial part. Accordingly, in principle, it is possible to dispense with this lower axial part .

It is now proposed that the axial height of the base portion be below a maximum height, such that, in the case of proper use and following reduction of the effective diameter to a limit diameter as a result of wear, the contour course of the outer peripheries of the base portion, over its entire axial extent, does not have any portion that is straight and runs axially. This means, in effect, that the corner wear that occurs at the transition between the roof portion and the base portion determines the entire contour course of the outer peripheries of the base portion. The edge wear that results from the side walls of the drilled hole and that could be responsible for maintaining or producing a portion that is straight and runs axially, becomes less important in the case of the masonry drill bit according to the proposal. The cutting insert of the masonry drill bit according to the proposal thus only has portions that are acted upon by axial forces and that, accordingly, are involved in the drilling advance in some manner. It could also be said that the corner wear results in a rounding of the transitional region between the roof portion and the base portion, the rounding extending over the entire axial height of the base portion.

It must be pointed out that the drilling process, as a chaotic system, is subject to a multiplicity of parameters, some of which cannot even be determined in an unambiguous manner. Nevertheless, the simplified explanatory approach given above yields surprisingly good results in practice. The solution according to the proposal results in unusually flat cutting inserts, which, surprisingly, do not involve any limitations in respect of the resultant performance features and the service life. In particular, a base portion height of between approximately 1.5 mm and approximately 5.0 mm, as claimed in claim 5, has proved successful in trials. With the further preferred designs, as claimed in claims 7 to 13, ranges are proposed for the difference between the initial diameter and the nominal diameter, for corresponding nominal diameter ranges in each case. For these configuration variants, the solution according to the proposal has proved to be most particularly successful.

According to a further teaching, as claimed in claim 14, which likewise has independent materiality, a cutting insert for a masonry drill bit as above is claimed as such. Reference may be made to all statements, relating to the masonry drill bit according to the proposal, that are relevant for description of the cutting insert according to the proposal.

The invention is explained more fully in the following with reference to a drawing representing only one exemplary embodiment. In the drawing Fig. 1 shows a masonry drill bit according to the proposal, in a perspective view, and

Fig. 2 shows the drilling head of the masonry drill bit according to Fig. 1, in a highly schematic side view, a) in the initial state and b) at the end of the service life. The masonry drill bit represented in the drawing is used to produce a drilled hole having a minimum nominal diameter. This means that the masonry drill bit according to the proposal guarantees, up to the end of its service life, a drilled hole having at least the nominal diameter N. The terms "drilled hole" and "nominal diameter" in this case are to be understood in a broad sense, and not necessarily in relation to an exactly round drilled hole geometry. In the case of a non-round drilled hole, the nominal diameter denotes the largest possible clear width of the drilled hole.

The masonry drill bit, in the usual manner, has a shank 1 and a drilling head 2, the drilling head 2 being adjoined by a helix 3 for removing drilling dust and, in addition, by an insertion end 4.

On its top side that faces in the direction of advance 5, the drilling head 2 has an inserted cutting insert 6. Depending on design boundary conditions, it may also be provided that the cutting insert 6 is designed as a mounted-on cutting insert 6.

Fig. 2a) shows a side view of a portion of the cutting insert 6 in the initial state. In this view, the not yet worn cutting insert 6 shows a roof portion 8, which is substantially roof-shaped here and preferably realizes two cutting edges 7, and which is adjoined in the axial direction, downward in Fig. 2a), by a base portion 9 having outer peripheries 10. The outer peripheries 10 each extend from the top downward, and here, and preferably throughout the entire service life of the masonry drill bit, they project radially beyond the shank 1. In the present case, the terms "radially" and "axially" are always in relation to the drill bit axis 11. In particular, since the outer peripheries 10 of the base portion 9 here project radially beyond the shank 1, the respectively effective drill bit diameter is determined by the geometry of the cutting insert 6. An "effective drill bit diameter" is understood here to mean the drill bit diameter that determines the diameter of the resulting drilled hole.

In the case of the masonry drill bit according to the proposal, the initial diameter A that exists in the initial state is greater than the nominal diameter N.

Up until the end of its service life, however, the effective drill bit diameter reduces, as a result of wear, down to the nominal diameter N. Upon attainment of the nominal diameter N, the end of the service life of the masonry drill bit has also been attained, as explained above.

Of particular importance for the teaching according to the proposal is the wear of the outer peripheries 10 of the base portion 9 over the service life of the masonry drill bit. In this case, there are two superimposed effects, which are represented schematically in Fig. 2a) .

A first effect is the edge wear, which is due to the friction of the axially extending inner wall of the drilled hole with the outer peripheries 10 of the base portion 9. The general direction of the edge wear is denoted in Fig. 2a) by the reference 12a. The edge wear, of itself, causes wear of the outer peripheries 10 in the radial direction only, in such a way that, in the side view represented in Fig. 2, the outer peripheries 10 run substantially axially.

Thus, if there were to be exclusively edge wear present, a possible concavity angle φ would become "ground away", or an axial alignment of the respective outer periphery 10 would be maintained, with progressive reduction of the effective drill bit diameter in each case. The variation in the outer peripheries 10 that is due exclusively to the edge wear is denoted in Fig. 2a) by a group of substantially axial lines 12.

Superimposed on the edge wear there is then a corner wear, which is due to the fact that the masonry drill bit, when used properly, is pressed in the direction of advance 5, this being associated with rounding of the corner 13 between the roof portion 8 and the base portion 9. The general direction of the corner wear is denoted in Fig. 2a) by the reference 14a. The variation in the outer peripheries 10 due exclusively to the corner wear is denoted in Fig. 2a) by a further group of broken lines 14.

Fig. 2a) shows already that the corner wear can extend far into the base portion 9.

It is now proposed that the axial height a of the base portion 9 be below a maximum height, such that, in the case of proper use and following reduction of the effective drill bit diameter to a limit diameter as a result of wear, the contour course of the outer peripheries 10 of the base portion 9, over its entire axial extent, does not have any portion that is straight and runs axially. This is shown exemplarily by Fig. 2b), which represents the end of the service life of the masonry drill bit.

According to the proposal, however, the height of the base portion 9 is so small that rounding of the corner 13 extends as far as into the lower region of the cutting insert 6. In the case of the masonry drill bit according to the proposal, if the limit diameter mentioned above has been attained there is no straight, axially running lower portion that is determined primarily by the edge wear.

In a particularly preferred design, the limit diameter is the nominal diameter N assigned to the masonry drill bit. Other configuration variants are conceivable.

The solution according to the proposal can be applied to masonry drill bits having differing numbers of cutting edges 7. In a particularly preferred design, the masonry drill bit is a two-cutter bit, the cutting insert 6 realizing two cutting edges 7 that each extend, in opposite directions, from the drill bit axis 11. It is also conceivable, however, for the masonry drill bit to be designed as a three-cutter bit or even to have more than three cutting edges.

Finally, it is conceivable for more than only one cutting insert 6 to be provided. In this case, the design rule according to the proposal is to be applied to at least one cutting insert 6.

Depending on design boundary conditions, differing values for the maximum height of the base portion 9 are advantageous. In trials, a maximum height in a range of between approximately 1.5 mm and approximately 5.0 mm has proved to be successful in the case of a nominal diameter of between approximately 8.0 mm and approximately 15 mm.

For the radial allowance of the cutting insert 6 relative to the nominal diameter N, i.e. for the initial diameter A, differing value ranges have been found to be advantageous, depending on the nominal diameter. Very generally, it is proposed that the difference between the initial diameter A and the nominal diameter N be in a range of between approximately 0.5 % and 10 % of the nominal diameter N. In particular, the difference between the initial diameter A and the nominal diameter N is in a range of between approximately 0.15 mm and approximately 0.4 mm in the case of a nominal diameter N of between approximately 4.0 mm and approximately 6.95 mm.

In the case of a nominal diameter of between approximately 7.0 mm and approximately 10.95 mm, the above difference is preferably in a range of between approximately 0.2 mm and approximately 0.45 mm.

In the case of a nominal diameter of between approximately 11.0 mm and approximately 18.95 mm, the above difference is preferably in a range of between approximately 0.2 mm and approximately 0.5 mm.

In the case of a nominal diameter of between approximately 19 mm and approximately 30.95 mm, the above difference is preferably in a range of between approximately 0.2 mm and approximately 0.55 mm.

In the case of a nominal diameter of between approximately 31.0 mm and approximately 39.95 mm, the above difference is preferably in a range of between approximately 0.25 mm and approximately 0.7 mm.

In the case of a nominal diameter of between approximately 40.0 mm and approximately 51.95 mm, the above difference is preferably in a range of between approximately 0.25 mm and approximately 0.8 mm.

In the case of a nominal diameter of between approximately 52.0 mm and approximately 52.95 mm, the above difference is preferably in a range of between approximately 0.35 mm and approximately 0.95 mm. According to a further teaching, which likewise has independent materiality, the cutting insert 6 of a masonry drill bit according to the proposal is claimed as such. Reference may be made to all statements, relating to the masonry drill bit according to the proposal, that are relevant for description of the cutting insert 6.

Claims

A masonry drill bit for producing a drilled hole that has a minimum nominal diameter (N) , comprising a shank (1) and a drilling head (2), wherein the drilling head (2), on its top side that faces in the direction of advance (5), has an inserted or mounted-on cutting insert (6),

wherein, in the initial state, in a side view, the cutting insert (6) has a substantially roof-shaped roof portion (8), which realizes at least one cutting edge (7) and which is adjoined, in the axial direction, by a base portion (9) having outer peripheries (10) that extend from the top downward,

wherein the respectively effective drill bit diameter is determined by the cutting insert (6) and, in the initial state, has an initial diameter (A) ,

wherein the initial diameter (A) is greater than the nominal diameter (N) , and wherein, up until the end of the service life of the masonry drill bit, the effective drill bit diameter reduces, as a result of wear, down to the nominal diameter (N) ,

characterized in that

the axial height (a) of the base portion (9) is below a maximum height, such that, in the case of proper use and following reduction of the effective drill bit diameter to a limit diameter as a result of wear, the contour course of the outer peripheries (10) of the base portion (9), over its entire axial extent, does not have any portion that is straight and runs axially.

The masonry drill bit as claimed in claim 1, characterized in that the outer peripheries (10) of the base portion (9) project radially beyond the shank (1), throughout the entire service life of the masonry drill bit.

The masonry drill bit as claimed in claim 1 or 2, characterized in that the nominal diameter (N) assigned to the masonry drill bit corresponds to the limit diameter.

The masonry drill bit as claimed in any one of the preceding claims, characterized in that the cutting insert (6) realizes two cutting edges (7) that each extend, in opposite directions, from the drill bit axis (11), and preferably the masonry drill bit as a whole is designed as a two-cutter bit .

The masonry drill bit as claimed in any one of the preceding claims, characterized in that the maximum height of the base portion (9) is in a range of between approximately 1.5 mm and approximately 5.0 mm in the case of a nominal diameter (N) of between approximately 8.0 mm and approximately 15.0 mm.

The masonry drill bit as claimed in any one of the preceding claims, characterized in that the difference between the initial diameter (A) and the nominal diameter (N) is in a range of between approximately 0.5 % and 10 % of the nominal diameter (N) .

The masonry drill bit as claimed in any one of the preceding claims, characterized in that the difference between the initial diameter (A) and the nominal diameter (N) is in a range of between approximately 0.15 mm and approximately 0.4 mm in the case of a nominal diameter (N) of between approximately 4.0 mm and approximately 6.95 mm. The masonry drill bit as claimed in any one of the preceding claims, characterized in that the difference between the initial diameter (A) and the nominal diameter (N) is in a range of between approximately 0.2 mm and approximately 0.45 mm in the case of a nominal diameter (N) of between approximately 7.0 mm and approximately 10.95 mm.

The masonry drill bit as claimed in any one of the preceding claims, characterized in that the difference between the initial diameter (A) and the nominal diameter (N) is in a range of between approximately 0.2 mm and approximately 0.5 mm in the case of a nominal diameter (N) of between approximately 11.0 mm and approximately 18.95 mm.

The masonry drill bit as claimed in any one of the preceding claims, characterized in that the difference between the initial diameter (A) and the nominal diameter (N) is in a range of between approximately 0.2 mm and approximately 0.55 mm in the case of a nominal diameter (N) of between approximately 19 mm and approximately 30.95 mm.

The masonry drill bit as claimed in any one of the preceding claims, characterized in that the difference between the initial diameter (A) and the nominal diameter (N) is in a range of between approximately 0.25 mm and approximately 0.7 mm in the case of a nominal diameter (N) of between approximately 31.0 mm and approximately 39.95 mm.

The masonry drill bit as claimed in any one of the preceding claims, characterized in that the difference between the initial diameter (A) and the nominal diameter (N) is in a range of between approximately 0.25 mm and approximately 0.8 mm in the case of a nominal diameter (N) of between approximately 40.0 mm and approximately 51.95 mm.

The masonry drill bit as claimed in any one of the preceding claims, characterized in that the difference between the initial diameter (A) and the nominal diameter (N) is in a range of between approximately 0.35 mm and approximately 0.95 mm in the case of a nominal diameter (N) of between approximately 52.0 mm and approximately 52.95 mm.

A cutting insert for a masonry drill bit for producing a drilled hole that has a minimum nominal diameter (N) , wherein the masonry drill bit is provided with a shank (1) and a drilling head ( 2 ) ,

wherein the cutting insert (6), when in the mounted state, is inserted or mounted-on on a top side of the drilling head (2) that faces in the direction of advance (5),

wherein the initial diameter (A) is greater than the nominal diameter (N) , and, up until the end of its service life, reduces, as a result of wear, down to the nominal diameter (N) ,

characterized in that

The cutting insert as claimed in claim 14, characterized by the features of the characterizing portion of one or more of the preceding claims.