U.S. patent application number 13/500167 was filed with the patent office on 2012-08-02 for cutting tool inserts.
Invention is credited to Andy Ollerenshaw, Mark Russell.
Application Number | 20120193152 13/500167 |
Document ID | / |
Family ID | 41402780 |
Filed Date | 2012-08-02 |
United States Patent
Application |
20120193152 |
Kind Code |
A1 |
Russell; Mark ; et
al. |
August 2, 2012 |
CUTTING TOOL INSERTS
Abstract
An insert (10) for a cutting tool (100) for use down a well bore
comprises a body of a hard material (tungsten carbide) suitable for
cutting steel. The body is shaped for formation in a mould that
comprises a die (70) and first (74) and second (78) punches and
arranged so that the first punch can eject the body after formation
from an opening of the die closed during formation by said second
punch. The insert has first (12) and second (14) ends whose faces
are defined, at least in part, by corresponding faces of the first
and second punch. Between them is a longitudinal axis (24) of the
insert. The area of the first end is less than the area of the
second end. The body has flanks (16) that form ridges (18)
extending between the first and second ends. The ridges form
cutting edges of the insert. They are separated by V-shaped troughs
(20) of said flanks. The ridges taper and spiral about the
axis.
Inventors: |
Russell; Mark; (Sheffield,
GB) ; Ollerenshaw; Andy; (Sheffield, GB) |
Family ID: |
41402780 |
Appl. No.: |
13/500167 |
Filed: |
September 15, 2010 |
PCT Filed: |
September 15, 2010 |
PCT NO: |
PCT/GB2010/051545 |
371 Date: |
April 4, 2012 |
Current U.S.
Class: |
175/430 |
Current CPC
Class: |
E21B 29/002 20130101;
E21B 10/633 20130101; E21B 10/5673 20130101; E21B 10/627 20130101;
E21B 10/567 20130101; E21B 10/56 20130101 |
Class at
Publication: |
175/430 |
International
Class: |
E21B 10/36 20060101
E21B010/36 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 9, 2009 |
GB |
0917704.9 |
Claims
1. An insert for a cutting tool for use down a well bore,
comprising: a body of a hard material suitable for cutting steel,
the body being shaped for formation in a mould that comprises a die
and first and second punches and arranged so that the first punch
can eject the body after formation from an opening of the die
closed during formation by said second punch, said body having:
first and second ends whose faces are defined, at least in part, by
corresponding faces of the first and second punch and which between
them define a longitudinal axis of the insert, the area of the
first end being less than the area of the second end, and flanks of
the insert extending between the first and second ends comprising
ridges, said ridges forming cutting edges of the insert and being
separated by troughs.
2. An insert of claim 1, wherein the insert has a plurality of
tiers that are of different cross sectional area with steps between
them, each tier having said ridges and troughs that extend between
first and second faces of the tier.
3. An insert of claim 1, wherein said ridges taper from said second
end to said first end.
4. An insert of claim 1, wherein said ridges spiral about said
axis.
5. An insert of claim 4, wherein the degree of spiral is
sufficiently limited, the degree of taper is sufficiently large,
and the angular separation of a ridge and trough in the radial
plane of the axis is so arranged, that the insert is not required
to rotate on ejection from the die.
6. An insert of claim 1, wherein said troughs are V-sections.
7. An insert of claim 1, wherein said troughs diminish in depth,
and said ridges correspondingly diminish in height, from said
second end to said first end.
8. An insert of claim 7, wherein said ridges terminate at or before
said first end.
9. An insert of claim 3, wherein the tapering is not linear.
10. An insert of claim 9, wherein said tapering is convexly curved
with respect to the axis.
11. An insert of claim 2, wherein said tapering is not linear and
is at least partly caused by said steps in the ridges forming said
tiers.
12. An insert of claim 2, wherein the cross section of each tier is
constant along said axis.
13. An insert of claim 2, wherein the ridges of each tier taper
between said first and second faces.
14. An insert of claim 2, wherein the steps between adjoining
ridges form additional cutting faces.
15. An insert of claim 2, wherein there are three tiers.
16. An insert of claim 2, wherein the profiles of the tiers are the
same.
17. An insert of claim 16, wherein adjacent tiers are rotationally
offset about said axis with respect to one another.
18. An insert of claim 1, wherein said hard material comprises
sintered tungsten carbide in a binder matrix.
19. An insert of claim 18, wherein said binder comprises
cobalt.
20. A tool comprising: a substantially cylindrical body having a
working face, wherein the working face has applied thereto within a
fixing matrix a plurality of cutting inserts of said body of claim
1 disposed on the face in a random distribution.
21. A tool of claim 20, wherein the working face is arranged in a
radial plane of the tool.
22. A tool of claim 21, wherein the working face is arranged
substantially perpendicularly to a radial plane of the tool.
23. A tool of claim 22, wherein said working surface may comprise
blades attached to the tool.
24. A tool of claim 21, wherein said working surface may comprise
flutes formed in the side of the tool.
25. A tool of claim 20, wherein said fixing matrix is braze
material.
26. (canceled)
Description
[0001] This invention relates to cutting tool inserts, in
particular to random distribution inserts for use on cutting tools
adapted to remove casings from well bores.
BACKGROUND
[0002] Down hole mills are known for removing casing, packers and
other debris down hole for the purpose of renovating the hole. Such
tools are also referred to as fishing tools and may comprise a
cylindrical body adapted to be rotated about their longitudinal
axis having cutting faces either arranged on the face of peripheral
blades, in which event, the face is perpendicular to the cutting
action (that is, parallel to, or possibly helically inclined to,
the axis of rotation of the tool) or on an end face of the tool, in
which event, the face is substantially parallel to the cutting
action (for example, lying on a radial plane of the axis of
rotation of the tool).
[0003] In either case, the body of the tool is protected by cutting
elements fixed thereto that are made of a material (usually
tungsten carbide composite material) harder than the metal (usually
steel) forming the casing or other component to be cut. The cutting
elements not only protect the tool, but also of course machine the
body being cut. Consequently it is desirable that the cutting
elements present an effective cutting profile to the workpiece. On
the other hand, there are two considerations. Firstly, the milling
of casing and packers by machining them is abrasive to the tool.
The cutting inserts and blades etc on which they are mounted wear
away rapidly in the aggressive environment. Secondly, there is no
requirement for great precision--the application is generally just
the removal of a well casing, and not precision machining.
[0004] There are three currently known options. In a first
arrangement, an array of cutting inserts are carefully oriented and
disposed on the tool in a pattern that results in a most efficient
cutting tool. Each element is aligned so that a sharp edge of the
element, with a desired rake angle, is presented to the workpiece.
The face of the element above a cutting edge may be provided with
surface features that results in shavings from the workpiece
breaking, so that long spirals of shavings are avoided. Such long
shavings run the risk that they bundle together in a "bird's nest",
making removal of the cuttings potentially problematic. If short
chips a few millimeters long break off quickly, bird-nesting can be
eliminated or at least reduced. Furthermore, with regular patterns
it is easy to ensure that, when one element wears away and breaks
off, a following element is equally presented in the most effective
cutting position. However, while the tool is ideal, it is
time-consuming, and thus expensive, to construct.
[0005] A second arrangement is at the other extreme. Old tungsten
carbide inserts recovered from a large number of tools can be
crushed and broken into irregularly shaped fragments. These can be
sorted for size and then randomly distributed over a surface of the
tool that will form the working bit of the tool. The crushed
tungsten carbide is generally attached to a cutting tool by a
brazing process. In this embodiment, the random inserts may be
supplied in a rod of brazing material, and applied to the tool
simply by progressively melting the brazing rod and bonding the
crushed tungsten carbide inserts to the tool. Alternatively, the
inserts may be embedded in a bar, a number of which may themselves
be fixed (eg by brazing) to the tool body. In either case, the
disposition of the crushed tungsten carbide inserts on the tool is
entirely random, as is the presentation of each insert to the
workpiece when cutting. Consequently, despite the obvious cost
savings to be had by this arrangement, the cutting and wear
resistant performance is certainly compromised. Any given insert is
unlikely to present a clean cutting edge, and if it does, long
shavings of the work piece may result. Of course, it has to be said
that clean cutting, as mentioned above, is not really the issue.
With sufficient pressures and torques applied, it is not essential
to have clean cutting edges. It is not necessarily the case that
the grade of material of the all of inserts will be specified for
cutting--some may come from wear applications which use different
grades of tungsten carbide (tungsten carbide is generally the
material of choice at present times). Consequently, while
inexpensive, this arrangement does not perform as well as the first
arrangement described above.
[0006] The third arrangement, however, is a compromise, in which
geometrically shaped inserts are used that have a plurality of
cutting edges and faces so that, even with a random distribution of
them on a tool, they are likely to present an effective cutting
face to the workpiece. Of course, merely square inserts are likely
to simply "tile" onto the tool so that no cutting faces are
presented. Instead the inserts provide a wear resistant face that
does little cutting. The availability of shapes is of course
limited, to some extent, by the process by which inserts are
routinely made. In the case of tungsten carbide inserts, these are
conveniently made by mixing tungsten carbide and other metallic
carbide powders with a binder substance such as cobalt. The mixture
is then filled in to a die and, under high pressure, the tungsten
carbide is pressed to a solid block having the shape of the die and
end punches. Generally, the die is tubular and each end is closed
by a punch that provides the pressure. In order to extract the
formed insert from the mould, the bottom punch is used to push the
insert out of the mould through the mouth of the die. Consequently,
inserts generally have a constant cross-section to enable ejection
from the die. The inserts are then sintered at high temperature
1300-1500 Deg C. to give the final physical properties.
[0007] GB-A-2378670 discloses an insert that is a constant cross
section prism whose ends are rendered concave and, optionally,
provided with dimples or other surface irregularities. The cross
section is a complex polygon having both internal and external
angles of less than 180 degrees that provide corrugations of ridges
separated by grooves in the sides of the insert.
[0008] It is an object of the present invention to provide an
insert that can be made in a conventional manner but which provides
at least one of the following advantages:
[0009] a tendency to generate a more aggressive cutting action,
which may be beneficial for cutting not just metal but other
non-metal components frequently encountered downhole when
milling;
[0010] a tendency to reduce vibration during milling; and
[0011] promotion of tighter coils of cuttings that encourage
break-off and discourage bird-nesting or production of a
multiplicity of fine cuttings which are easily broken up and
circulated out of the hole with the drilling mud.
BRIEF SUMMARY OF THE DISCLOSURE
[0012] In accordance with the present invention there is provided
an insert for a cutting tool for use down a well bore, comprising a
body of a hard material suitable for cutting steel, the body being
shaped for formation in a mould that comprises a die and first and
second punches and arranged so that the first punch can eject the
body after formation from an opening of the die closed during
formation by said second punch, said body having:
[0013] first and second ends whose faces are defined, at least in
part, by corresponding faces of the first and second punch and
which between them define a longitudinal axis of the insert, the
area of the first end being less than the area of the second end,
and
[0014] flanks of the insert extending between the first and second
ends comprising ridges, said ridges forming cutting edges of the
insert and being separated by troughs.
[0015] The insert may have a plurality of tiers that are of
different cross sectional area with steps between them, each tier
having said ridges and troughs that extend between first and second
faces of the tier. Thus the insert tapers from the second end to
the first end in a stepwise fashion.
[0016] Additionally, or instead of having tiers, said ridges may
taper from said second end to said first end. When tiers are
present, the tapering of the ridges is of each tier.
[0017] Optionally, whether there are tiers or not, said ridges may
spiral about said axis.
[0018] Thus, in another aspect, the present invention may provide
an insert for a cutting tool for use down a well bore, comprising a
body of a hard material suitable for cutting steel, the body being
shaped in a die and first and second punches and arranged so that
the first punch can eject the body after pressing from an opening
of the die closed during formation by said second punch, said body
having:
[0019] first and second ends whose faces are defined, at least in
part, by corresponding faces of the first and second punch and
which between them define a longitudinal axis of the insert, the
area of the first end being less than the area of the second end,
and
[0020] flanks that form ridges extending between the first and
second ends, said ridges forming cutting edges of the insert and
being separated by troughs of said flanks, wherein
[0021] said ridges taper from said second end to said first end,
and spiral about said axis.
[0022] The degree of spiral may be sufficiently limited, and the
degree of taper sufficiently large, and the angular separation of a
ridge and trough in the radial plane of the axis is, such that the
insert is not required to rotate on ejection from the die. In this
event, ejection is, of course, in the axial direction. Other
directions are feasible, for example in the direction of taper of
the ridges.
[0023] Preferably, the tapering is not linear. Preferably, it is
convexly curved with respect to the axis.
[0024] In accordance with a third aspect of the present invention
there is provided an insert for a cutting tool for use down a well
bore, comprising a body of a hard material suitable for cutting
steel, the body being shaped in a die and first and second punches
and arranged so that the first punch can eject the body after
pressing from an opening of the die closed during formation by said
second punch, said body having:
[0025] first and second ends whose faces are defined, at least in
part, by corresponding faces of the first and second punch and
which between them define a longitudinal axis of the insert, the
area of the first end being less than the area of the second end,
and
[0026] a plurality of tiers of the insert that are of different
cross sectional area with steps between them, each tier having
ridges that extend between first and second faces of the tier, said
ridges forming cutting edges of the insert and being separated by
troughs that also extend between said first and second faces of the
tier.
[0027] In any case, preferably, said troughs are V-sections. The
troughs may diminish in depth, and said ridges correspondingly
diminish in height, from said second end to said first end. Of
course, the depth of a trough is the same as the height of a ridge,
both being the difference in radial distance from said axis of the
base of the trough and the peak of the ridge. Said ridges may
terminate at or before said first end.
[0028] Preferably, the ridges on each tier spiral between the first
and second faces. Preferably there are three tiers. Preferably, the
steps between them form additional cutting faces of the insert.
Preferably the profiles of the tiers are the same. Preferably, they
are rotationally offset about said axis with respect to one
another. Preferably, the ridges of each tier taper between said
first and second faces. The first face of the smallest tier of the
insert forms said first end of the insert and the second face of
the largest tier of the insert forms said second end. Where a first
and second face of a tier intersect, said second face is internal
of the insert and only exists in a geometric sense because it is
entirely within the confines of the first face of the adjacent
tier. The step is formed where a first face overlaps an adjacent
second face.
[0029] When scattered randomly on a tool, each insert will
generally come to a position in which its flanks rest on the tool
surface, assuming the tool surface is flat and horizontal when the
inserts are applied. The orientation, however, of an insert about
an axis perpendicular to the tool surface is random. Where the
direction of approach of the tool surface with respect to a
workpiece during cutting is perpendicular to the tool surface, this
randomness of orientation is largely irrelevant. Indeed, it is
largely irrelevant, in any event. However, when the direction of
approach of the tool surface to a workpiece is parallel to the tool
surface, that randomness of orientation results in the end faces of
inserts frequently providing the cutting function. Therefore, the
end faces also provide cutting faces, as well as the ridges of the
flanks. The points of the ridges of second end present an
aggressive cutting face. The reduced size of the first end also
presents an aggressive cutting face. Also by curving the flanks, a
shorter cutting edge is presented, which is also more aggressive.
Consequently, inserts shaped as defined are effectively more
pointed, whatever their orientation, leading to a more aggressive
cutting environment that is especially useful where not only the
metal of casing is encountered, but also potentially surrounding
well bore material or backfilled cement. Also, the more pointed
cutting face results in less vibration that occurs when a face
attempts to cut too much material in one go. That leads to
snatching of the tool and, frequently, a consequent premature
break-off of inserts from the tool surface. Finally, by spiraling
and tapering the flank ridges, generally the cuttings that do not
break off are wound into tight curves that more readily break off
and, when they do, are less likely to entangle with other cuttings
forming bird nesting.
[0030] The invention also provides a tool comprising a
substantially cylindrical body having a working face, wherein the
working face has applied thereto within a fixing matrix a plurality
of cutting inserts as defined above disposed on the face in a
random distribution. Preferably, the working face is arranged in a
radial plane of the tool. Alternatively, the working face is
arranged substantially perpendicularly to a radial plane of the
tool. Said working surface may comprise blades attached to the
tool. Said working surface may comprise flutes formed in the side
of the tool. Said matrix may be braze material.
[0031] Said hard material is preferably tungsten carbide optionally
including other metallic carbides. Preferably, a binder for the
tungsten carbide comprises cobalt. Preferably, said tungsten
carbide insert is formed by pressing and sintering.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Embodiments of the invention will now be described, by way
of example only, with reference to the accompanying drawings, in
which:
[0033] FIGS. 1(a) to (d) are respectively a perspective view, a
section on the line A-A in FIG. 1(d), an end view in the direction
of arrow C in FIG. 1(d), and a side view, of an insert according to
a first embodiment of the present invention;
[0034] FIGS. 2(a) to (c) are respectively an end view in the
direction of the arrow A in FIG. 2(b), a side view and a
perspective view, of a second embodiment of an insert according to
the present invention;
[0035] FIGS. 3(a) to (d) are respectively a perspective view, an
end view in the direction of the arrow B in FIG. 3(c), a side view,
and an end view in the direction of the arrow D in FIG. 3(c) of a
third embodiment of an insert according to the present
invention;
[0036] FIGS. 4(a) and (b) are respectively side views of a tool in
which a) inserts are disposed on a perpendicular face with respect
to a work piece surface and b) where inserts are on a parallel face
of a tool with respect to a work surface;
[0037] FIGS. 5(a) and (b) are schematic representations of typical
tools according to the embodiments shown in FIGS. 4(b) and (a)
respectively;
[0038] FIG. 6 is a schematic representation of a sintering die for
producing inserts according to the present invention;
[0039] FIGS. 7(a), (b) and (c) are respectively a perspective view,
a side view and an end view in the direction of the arrow E in FIG.
7(b) of a fourth embodiment of an insert according to the present
invention; and
[0040] FIGS. 8(a), (b) and (c) are respectively a perspective view,
a side view and an end view in the direction of the arrow F in FIG.
8(b) of a fifth embodiment of an insert according to the present
invention.
[0041] FIGS. 9(a), (b) and (c) are respectively a perspective view,
a side view and an end view in the direction of the arrow G in FIG.
9(b) of a sixth embodiment of an insert according to the present
invention.
[0042] FIGS. 10(a), (b) and (c) are respectively a perspective
view, a side view and an end view in the direction of the arrow H
in FIG. 10(b) of a seventh embodiment of an insert according to the
present invention.
[0043] FIGS. 11(a), (b) and (c) are respectively a perspective
view, a side view and an end view in the direction of the arrow J
in FIG. 11(b) of a eighth embodiment of an insert according to the
present invention.
DETAILED DESCRIPTION
[0044] Referring now to FIG. 1, an insert 10 is illustrated
comprising end faces 12 and 14, and flanks 16 consisting of ridges
18 separated by troughs 20, forming faces 19 between them. The
insert 10 has an axis 24 extending between the end faces 12,14,
which are shown as being flat faces perpendicular to the axis 24,
although either face may be concaved, convex or faceted, internally
or externally, or inclined with respect to the axis 24. A section
taken perpendicular to the axis 24, such as the section A-A, has a
regular six pointed star shape profile 30 that is the same from the
small end 12 to the large end 14. The angle between faces 19 is
.alpha., which typically is 60.degree.. However, the ridges 18, and
corresponding troughs 20, spiral about the axis 24 between the ends
14 and 12. Thus, the ridges both taper and spiral between the ends
12,14.
[0045] The degree of taper is, in the case of FIG. 1, non-linear.
That is to say, the radial distance R of the ridge 18 from the axis
24 decreases at an increasing rate from the large end 14 towards
the small end 12. Indeed extrapolating the flange 18 until the
extrapolation coincides with the axis 24 defines a start point or
origin O. The taper provides a curved profile to the insert 10, so
that it is not stable in any position when resting on its flanks
and consequently adopts easily a number of dispositions when lying
on its flanks 16.
[0046] The degree of spiral is such that the ridge 18 (and trough
20) turns through an angle .theta. between the ends 12,14. This
angle is about 20 degrees, but may be between a greater or less
angle, depending on the requirements of manufacture and the ease
with which it is desired that the insert can be ejected from the
die which forms it. This is discussed further below.
[0047] FIG. 2 shows a variation being a second embodiment of the
present invention where insert 10' has tapering ridges 18', as in
the first embodiment, but less tapering troughs 20' so that, at
small end 12' of the insert the section through the insert is
circular. The distance x from the face 12' to the origin O,O' will
be different for each of the trough 20' and ridge 18'.
[0048] With reference to FIG. 3 an insert 10'' is shown being a
further embodiment of the present invention, which differs from the
above embodiments in that the ridges 18'' and troughs 20'' have a
radial distance R with respect to the distance x from its origin O
that is linear.
[0049] FIG. 6 illustrates one possible manufacturing arrangement
for the inserts of FIGS. 1 to 3, or, indeed, those of FIGS. 7 and 8
described further below. The manufacture of inserts according to
the present invention employs conventional techniques, but with
special considerations. A die 70 is formed having the desired
profile 72 of the flanks 16 of the insert to be formed. An top
punch or ejector pin 74 closes a bottom end of the die and has an
end form 76 to form end face 12 of the insert. A bottom punch
(plate) 78 closes a bottom end of the die 70 and has an end-form 80
to form end face 14 of an insert. The joint 82 between die and
punch 78 is shown extending perpendicularly to the axis 24 of the
insert. However, it could be parallel, as is the joint between the
pin 74 and die 70.
[0050] Tungsten carbide inserts are generally made in three steps.
Firstly, the tungsten along with other metallic carbides are milled
along with the metallic binder (usually cobalt) and a wax. This is
then granulated (to give good flow characteristics). The second
step is to press it in a die with a top and bottom punch at room
temperature. The last step is to sinter, in a first stage to drive
off the wax binder, and in a second stage to fully sinter the
carbide and which results in a 20% reduction in volume.
[0051] The die 70 is filled with tungsten carbide and other
metallic carbide powders of appropriate grade already mixed with
binder composition (eg cobalt). The composition of such material is
known per se in the art and needs no further description herein.
The bottom punch 78 closes the die. Punch 74 is pressed against the
material in the die to compress it. After pressing, the die is
opened by withdrawing the bottom punch 78 and ejecting the insert
with the top punch 74. To the extent that the geometry of the
formed insert is such that some rotation of the insert is necessary
during ejection along the axis 24 (in order for the formed ridges
18 to clear the flutes of the die 70) such rotation may be
self-effecting by sliding interaction between the flutes of the die
and the ridges 18 of the insert. Also, however, such rotation can
assisted by corresponding rotation of the pin 74. Some formations
on the end face 12 that assist frictional grip between it and the
pin 74 may in this instance be advantageous.
[0052] Turning to FIGS. 5a,b two alternative arrangements of a tool
incorporating the inserts of the invention are illustrated.
[0053] In FIG. 5a, a tool 100a has a substantially cylindrical body
102 which is fluted at 104 adjacent an end face 106 of the tool.
The end face is coated with multiple inserts 10 (or 10' or 10'',
future references to the insert being only made to the insert 10,
but it is to be understood that the inserts 10' and 10'' are
equally applicable, unless the context discusses otherwise). The
inserts 10 are held in a matrix 108 of braze material, also known
in the art and not described further herein. One method of
application is to supply inserts 10 to the tool manufacturer in
rods of braze material which then need only melting against the
face 106 for inserts to be delivered in approximately the right
volume ratio of braze to insert so that the face 106 can be covered
with at least one layer 110 of randomly arranged insert 10. (In
fact, and insert of the form 10', as shown in FIG. 2, is
illustrated in FIG. 4b, although here they are labeled 10). More
than one layer may be provided. In applying the inserts to the face
106, this is done with the face 106 uppermost and substantially
horizontal. Most of the inserts end up on their sides, as shown at
10a,c in FIG. 4b, but occasionally some will end up standing on
either end 12, 14 (as at 10b) or at some other angle. The
randomness of the arrangement ensures that plenty of sharp edges
and points of the inserts 10 are presented to a work piece 200a. In
the case of the tool 100a, the workpiece 200a is parallel the tool
face 106 carrying the cutting elements 10. In this case, the tool
100a is rotated about its longitudinal axis so that the working
face 106 moves in the direction of the Arrow X in FIG. 4b, that is,
parallel the workpiece surface 200a
[0054] In FIG. 5b, tool 100b also comprises a substantially
cylindrical body 122, but is here provided with a pilot nose 120
designed to fit in and slide inside a casing sleeve (not shown) to
be milled away. The body 122 is provided with blades 124 that are
here shown spiraling around the longitudinal axis of the tool 100b,
but equally they can be parallel that axis, and indeed, this is
simpler to construct. One face 126 of the blades 124 is coated with
randomly distributed inserts 10, distributed in similar manner to
the application to face 106 of tool 100a. Here, however, the coated
face 126 moves with respect to a work piece surface 200b, also in
the direction X parallel with the workpiece 200b, but in this case
perpendicularly to the face 126. Thus fewer inserts perform the
cutting function of the workpiece and accordingly wear away more
rapidly, but they are constantly replenished by new inserts as the
blades 124 are eroded.
[0055] By virtue of the tapered form of the inserts, especially
with exponentially tapering ridges, numerous different orientations
of the insert is possible that present a sharp cutting edge to the
workpiece. Long edges, that might increase the risk of tool
vibration, are substantially eliminated. Nevertheless, a more
aggressive cutting profile is achieved that may be more effective
in respect of mixed workpiece cutting, especially those involving
mineral formations/debris/concrete etc. Moreover, given that a
sloping edge is almost inevitably presented to the workpiece, in
the case of metal cutting, tighter coils of the cut material are
likely to result, whereby the problem of nesting of cuttings can be
reduced.
[0056] Turning to FIGS. 7 and 8, two further alternative
arrangements of inserts 110a,b are illustrated and which differ
from one another only in degree. Here, instead of straight ridges
18, stepped ridges 118 are presented, along with stepped troughs
120. Thus the inserts 110a,b as a whole are stepped having a
plurality of tiers 140a,b,c. Each tier tapers and spirals in a
similar manner to the entire insert 10'' described above with
reference to FIG. 3. However, there is no necessity for the
tapering to be linear and it could be exponentially convex, as per
the FIGS. 1 and 2 arrangements. Indeed, the tapering could be
different for each tier. The degree of spiral is shown being the
same for each tier. Indeed, the start points 142 144 of each ridge
118 and trough 120, respectively, of each tier is shown at the same
angular position as the end points 146,148 of the corresponding
ridge and trough respectively of the adjoining tier. This is shown
by the lines 150 in FIGS. 7 and 8 (c) (the start points 144 of the
troughs 120 are not visible in the end views, although the end
points 148 are).
[0057] This arrangement enjoys the benefits described above but
also has two the further advantages compared with the earlier
embodiments described above. The first advantage is realized on
those occasions when the end face 112 of the insert faces the
workpiece during cutting operations. While the end faces 12 in the
embodiments described above work perfectly effectively, the ridges
18 behind tend to plough into the workpiece without effecting a
cutting action. This is not especially problematic, since the ridge
in that event quite soon wears down and an insert behind will pick
up the cutting action. However, with the inserts 110a,b, there is
not a long ridge behind but a relatively short one followed by a
further effective cutting face 112a, and behind that another face
112b. Accordingly, the problem, such as it is, of the ridge 18, (or
118 in the case of these embodiments), ploughing into the workpiece
and failing to effect a cutting action is avoided.
[0058] This leads also to the second advantage, which is also
experienced when the insert presents other faces to the workpiece,
is that cross-sectionally smaller chips are cut from the workpiece.
That is, instead of one chip being cut by the end face 112, three
chips are cut with the same depth of penetration into the
workpiece. Likewise, three ribbons are cut by the tiers 140a,b when
the side of the insert faces the workpiece. Consequently, even if
long turns are cut, these are thinner and break up more easily in
the melee around the tool during its operation.
[0059] As mentioned above, the only difference between the
embodiments of FIGS. 7 and 8 is in the degree of taper (that is to
say, the size of the steps (112a,b) between tiers). Otherwise they
are the same. It should of course be appreciated that more than
three tiers may be provided, although the more that are provided,
the more the insert approximates the earlier embodiments of the
present invention. It should also be made clear that the step in
the ridges need not be the same as the step in the troughs. Indeed,
there could be no step in the troughs and only steps in the ridges,
and vice versa. Finally, although the start 142,144 and finish
146,148 of ridges and troughs of adjacent tiers are shown in the
same angular position, this is not essential. Any angular
displacement between is permissible provided that the entire rear
face (112x) of a smaller tier is within the profile (112a) of the
adjacent tier (see rear face 112x partially shown in dotted lines
in FIG. 7(c), which face is "virtual" being internal of the insert
110a).
[0060] FIGS. 9 to 10 show further embodiments of the present
invention. In FIG. 9, insert 910 has two tiers 940a,b, each of
whose cross-sections are the same (that is, there is no taper) and
their ridges do not spiral from a first face 912a,b to a second
face 914a,b of the respective tiers. The cross section is, in each
case, a six-pointed star, but rotationally offset with respect to
one another. Of course, a regular six-pointed star having
60.degree. angle ridges and 120.degree. angle troughs is not
essential, any more than it is for the embodiments described
above.
[0061] In FIG. 10, the only difference of the insert 1010 shown
with respect to that of FIG. 9 is a third tier 1040c. In FIG. 11,
the only difference of the insert 1110 shown with respect to that
of FIG. 10 is a middle tier 1140b that is a five pointed star
compared with the tiers 1140a and c that are six pointed stars. Any
combination of cross-sections is possible and, indeed, a variation
in the shape changes the cutting profile of the insert with respect
to the workpiece. The variations shown in FIGS. 10 to 11 in respect
of tier numbers and profiles are, of course, equally applicable to
the embodiments described above with reference to FIGS. 7 and
8.
[0062] While the end faces 12,14 in all the embodiments described
above are shown flat, as well as the intermediate faces 112a,b of
the embodiments described above with reference to FIGS. 7 to 11, it
is feasible to include features in those faces. For example, they
may have dimples or bumps. Likewise, they may be dished, as
indicated at 1175 in FIG. 11(b) in order to improve cutting
performance when the end faces 1112,1114 face the workpiece. A more
aggressive, pointed, cutting profile is achieved.
[0063] Throughout the description and claims of this specification,
the words "comprise" and "contain" and variations of them mean
"including but not limited to", and they are not intended to (and
do not) exclude other moieties, additives, components, integers or
steps. Throughout the description and claims of this specification,
the singular encompasses the plural unless the context otherwise
requires. In particular, where the indefinite article is used, the
specification is to be understood as contemplating plurality as
well as singularity, unless the context requires otherwise.
[0064] Features, integers, characteristics, compounds, chemical
moieties or groups described in conjunction with a particular
aspect, embodiment or example of the invention are to be understood
to be applicable to any other aspect, embodiment or example
described herein unless incompatible therewith. All of the features
disclosed in this specification (including any accompanying claims,
abstract and drawings), and/or all of the steps of any method or
process so disclosed, may be combined in any combination, except
combinations where at least some of such features and/or steps are
mutually exclusive. The invention is not restricted to the details
of any foregoing embodiments. The invention extends to any novel
one, or any novel combination, of the features disclosed in this
specification (including any accompanying claims, abstract and
drawings), or to any novel one, or any novel combination, of the
steps of any method or process so disclosed.
[0065] The reader's attention is directed to all papers and
documents which are filed concurrently with or previous to this
specification in connection with this application and which are
open to public inspection with this specification, and the contents
of all such papers and documents are incorporated herein by
reference.
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