US 3858671 A
An excavating tool or bit for drilling holes in earth formations in which the bit has a body with a working face on one end that is provided with hard wear resistant carbide inserts. The inserts on the working end of the body include peripheral gauge inserts and disposed in the side of the body, preferably in axial alignment with the gauge inserts, are other inserts also for holding gauge and advantageously having square outer ends with the diagonals of the squares arranged vertically and horizontally. More than one row of the side gauge inserts can be provided in the bit body.
Description (OCR text may contain errors)
llnited States Patent [191 Mita et a1.
1 1 EXCAVATING TOOL  Inventors: John F. Kita, Bedford; David C.
Johnstone, Claysburg RD, both of  Assignee: Kennametal 1nc., Latrobe, Pa.  Filed: Apr. 23, 1973  Appl. No.: 353,357
hull I I 1 ,lan.7, 1975 Primary Examiner-John E. Murtagh Assistant ExaminerRichard E. Favreau Attorney, Agent, or FirmMelvin A. Crosby  ABSTRACT An excavating tool or bit for drilling holes in earth formations in which the bit has a body with a working face on one end that is provided with hard wear resistant carbide inserts. The inserts on the working end of the body include peripheral gauge inserts and disposed in the side of the body, preferably in axial alignment with the gauge inserts, are other inserts also for holding gauge and advantageously having square outer ends with the diagonals of the squares arranged vertically and horizontally. More than one row of the side gauge inserts can be provided in the bit body.
7 Claims, 4 Drawing Figures PATENTEU JAN 71975 FIG-2 FIG-3' PEG-4 EXCAVATING TOOL The present invention relates to excavating tools, particularly in the form of bits, and is especially concerned with an improved arrangement for mounting gauge controlling inserts in a bit body and to the formation of the gauge controlling inserts.
Tools for drilling holes in earth formations are known and comprise steel bodies which are preferably provided with hard wear resistant inserts mounted in the working face of the bit body. Such hard wear resistant inserts include at least one row about the periphery of the working face serving as gauge inserts so that as drilling proceeds, the sides of the bit will not wear away rapidly and cause a hole to be tapered. A tapered hole is particularly disadvantageous because if a bit becomes worn it must be removed from a hole and replaced by another, a tapered hole can create problems because a new full size bit will be likely to wedge in the tapered hole.
The inserts mounted in the working face of the bit are extremely hard and wear resistant, generally being formed of a cemented tungsten carbide material, and will wear away only slowly, so that the gauge inserts provided tend to maintain the gague of a hole being drilled for a substantial period of time.
It has been found, however, that the gauge inserts will sometimes wear off more rapidly than is desired, particularly when hard formations are encountered so that even with hard wear resistant gauge inserts the bit may wear away somewhat more rapidly than desired and produce a tapered hole.
With the foregoing in mind, a primary objective of the present invention is the provision of an arrangement for adding further gauge controlling inserts in a bit body so as materially to increase the life of the bit in which the added inserts are mounted and particularly with respect to holding gauge.
Another object of the invention is the provision of special gauge inserts mounted in the side of a bit body which present upwardly and downwardly facing sharp edges so that the added inserts can assist in cutting operations and can also serve to assist in breaking up overburden which may collapse on top of the bit during drilling operations.
These and other objects and advantages of the present invention will become more apparent upon reference to the following detailed specification taken in connection with the accompanying drawings in which:
FIG. 1 is a side view of a typical bit according to the present invention.
FIG. 2 is a fragmentary vertical sectional view indicated by line II-II on FIG. 1 and drawn at enlarged scale.
FIG. 3 is a view looking in from the side of FIG. 2 as indicated by arrow 3 thereon.
FIG. 4 is a perspective view showing a typical gauge insert according to the present invention.
BRIEF SUMMARY OF THE INVENTION According to the present invention, a bit body which may comprise a steel forging, for example, has one end in the form of a working face and the other end adapted for connection to a drive mechanism. The working face of the bit is ordinarily provided with hard wear resistant inserts distributed thereover in order to assist in breaking up the formation being worked and to reduce the rate at which the bit body wears in use.
One popular type of bit is a bit in which the inserts are rod-like elements having domed outer ends and either press fitted or brazed into holes provided therefor in the bit body. The holes are distributed over the area of the work face and include at least one row of inserts about the periphery of the working face and usually extending angularly to the plane of the working face so as to hold the gauge of the hole being worked by the bit.
The gauge inserts protrude radially from the peripheral wall of the body and axially from the working end of the body and thereby are effective for engaging and reducing the material being worked.
According to the present invention, the peripheral wall of the body is provided with at least one further row of circumferentially distributed radially extending inserts which protrude radially from the peripheral wall of the bit body and advantageously to a distance slightly less than the radial protrusion of the gauge inserts.
The further inserts when consisting of one row are advantageously arranged in axial alignment with respective ones of the gauge inserts. The further inserts preferably have the protruding radially outer ends thereof squared with the diagonals of the square extending vertically and horizontally so that as further insert has a radial cutting edge on each of the axially upwardly and axially downwardly facing sides thereof.
It is possible to provide at least one further row of the further inserts in the peripheral wall of the bit body, and when such a further row is provided, this row is axially displaced from the first mentioned row of further inserts and the inserts thereof are circumferentially staggered relative to the further inserts of the first mentioned row thereof.
DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings somewhat more in detail, the bit body is designated at 10 and has one end 12 adapted for connection to a driving instrumentality while the other end 14, and which may be considered the front end, forms a working face which is generally planar and perpendicular to the longitudinal axis of the bit body. The bit body comprises a peripheral wall 16 extending rearwardly from front end 14 and advantageously tapering inwardly slightly in the rearward direction.
Rearwardly of peripheral wall 16, the bit body reduces in diameter for the flow of reduced material backwardly along the bit body and the bit body may, furthermore, be provided with axial flutes 18 for the flow of reduced material taken by the bit.
The front working end of body 10 is provided with a plurality of axial holes 20 in which are mounted rodlike inserts 22 having domed outer ends 24 which protrude axially outwardly from working face 14. Inserts 22 may be press fitted in bores 20 or may be otherwise affixed therein, as by brazing. The inserts 22 are distributed radially and circumferentially over face 14 and thereby reduce a formation against which the bit is impacted.
Near the juncture of peripheral wall to, with forward end 114 of the bit body, there are provided axially inclined bores 26 in which are mounted inserts 28 which also have domed outer ends 30. Inserts 28 may be identical with inserts 22 if desired.
It will be seen in the drawings, particularly in FIG. 2, that the outer ends of inserts 28 not only protrude axially from front end 14 of the bit body, but also protrude radially as well. Inserts 28, which are distributed about the circumference of the bit body, thus, serve as gauge inserts and tend to maintain the size of the hole being drilled by the bit substantially constant.
This is important because, if the bits wear in the circumferential direction as drilling proceeds, the hole formed by the bit will be tapered, and it will not be possible to introduce a new bit into the hole. The gauge inserts, thus, have an extremely important function to carry out during the operation of the bit.
According to the present invention, the holding of the gauge of a hole being drilled is enhanced by the provision of at least one further row of inserts, indicated at 32 and extending radially into the periphery of bit body within the range of peripheral wall 16 and spaced axially rearwardly from the forward end 14 of the bit body. The inserts are distributed circumferentially about the body and, as will be seen in FIG. 3, each gauge insert 28 preferably has a respective further insert 32 in axial alignment therewith.
Inserts 32 protrude radially from peripheral wall 16 about the same distance as the gauge inserts 28 although, advantageously, the radial outer ends of inserts 32 may be set back a distance of up to about 0.010 inches from the cylindrical envelope in which the radially outermost regions of inserts 28 are disposed.
Still further, the radially outwardly protruding ends of inserts 32 are preferably formed square, as indicated at 34, and when the inserts 32 are installed in body 10, the diagonals of the squared outer ends thereof are arranged vertically and horizontally, respectively.
Each of the inserts 34 is, thus, formed with axial cutting edges, one of which faces vertically upwardly and the other of which faces vertically downwardly. Especially by virtue of the aforementioned axial cutting edges, the inserts 32 can take part in the cutting action, particularly where it is necessary to remove material from the hole being drilled to maintain the gauge.
Still further, in the event that material collapses in the hole upwardly of the bit, thereby placing an overburden on the bit, at least the axially upwardly facing sharp cutting edges referred to assist materially in the extraction of the bit from the hole being drilled.
As will be seen in FIG. 1, in addition to the row of inserts 32, an additional row of inserts 38 can be provided protruding radially from the peripheral wall 16 about the same distance as inserts 32 and also being formed with square ends thereon. This further row of inserts are circumferentially distributed about the bit body and preferably are staggered relative to the inserts The inserts 38, which may be identical with inserts 32 in respect of size andradial protrusion measured from the axis of the bit body, the disposition of the diagonals of the squared ends thereof serve the same function as inserts 32 with respect to assisting in holding the gauge of the hole being drilled and with respect to assisting in extracting the bit from overburden which may collapse thereon.
Where only a single row of the further inserts is provided, it is advantageous to align the further inserts with the gauge inserts as shown in FIG. 3 so that the gauge of the hole being drilled will be accurately maintained for a prolonged period of time.
Modifications may be made within the scope of the appended claims.
What is claimed is:
1. In a mining bit; a bit body having a working face at the front end and a peripheral wall extending rearwardly from said working face, inserts mounted in the front end of said body and distributed over said working face and protruding axially therefrom, at least one row of gauge inserts mounted in the front end of said body near the juncture of said working face and said peripheral wall and extending angularly from the body so as to protrude radially outwardly beyond said peripheral wall and axially outwardly beyond said front end, and at least one row of further inserts extending radially into the peripheral wall of said body in circumferentially spaced relation and spaced axially along said peripheral wall from said gauge inserts, each said further insert having a radially extending sharp cutting edge on each of the axially upwardly and axially downwardly facing sides thereof, the radially outer end of each said further insert being disposed radially inwardly from the cylindrical envelope of the radially outermost points on said gauge inserts a fraction of the amount which the gauge inserts protrude radially beyond said peripheral wall.
2. A mining bit according to claim 1 in which a said further insert is disposed in each axial plane of the bit body which contains a gauge insert.
3. A mining bit according to claim 1 in which the radially outer end of each further insert is rectangular in cross section with a diagonally of the rectangle disposed in a vertical axial plane of the bit body.
4. A mining bit according to claim 1 in which each gauge insert has a said further insert in axial alignment therewith, each said further insert having a radially extending sharp cutting edge on each of the axially upwardly and axially downwardly facing sides thereof.
5. A mining bit according to claim 1 in which the further inserts in said one row thereof are in axial alignment with respective ones of said gauge inserts, and an additional row of said further inserts axially displaced along said peripheral wall from said one row and circumferentially staggered relative to the said further inserts of said one row thereof, the inserts of said additional row thereof also having radially extending sharp edges formed on the axially upwardly and axially downwardly facing sides thereof.
6. An insert according to claim 1 in which said hard wear resistant material comprises cemented tungsten carbide.
7. An insert according to claim 1 in which the radially outer end of each said further insert is disposed about 0.010 inches radially inwardly from the cylindrical envelope of the radially outermost points of said gauge inserts.