Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR HONING
AN EhONGATE ROTARY TOOK
BACKGROLTN D
The invention concerns a method of treating
an elongate rotary tool that presents a sharp cutting
edge, an apparatus for treating an elongate rotary tool
that presents a sharp cutting edge, and an elongate
rotary tool with a cutting edge treated according to
the method of the invention.
More specifically, the invention concerns a
method of honing a hard cemented carbide elongate
rotary tool (such as a drill) that presents a sharp
cutting edge, an apparatus for honing a hard cemented
carbide elongate rotary tool (such as a drill) that
presents a sharp cutting edge, and a hard cemented
carbide elongate rotary tool (such as a drill) with a
cutting edge honed according to the method of the
invention.
Heretofore in the manufacture of an elongate
rotary tool which presents a sharp cutting edge, e.g.,
a drill, endmill, hob, or reamer, made from a cemented
carbide, e.g., tungsten carbide cemented with cobalt,
one had to impinge.the as-ground surfaces and hone the
sharp cutting edge with a brush. The typical brush uses
a nylon filament impregnated with a 120 grit (average
particle diameter~of about 142 micrometers (um))
silicon carbide particulates wherein the composition of
the filament is about 30 weight percent silicon
carbide. The brush rotates at a speed of about 750 rpm
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and impinges the selected surfaces and sharp cutting
edges for about 15 seconds. There are, however, a .
number of drawbacks to using the brush process to
impinge the as-ground surfaces and hone the sharp
cutting edge (or edges) of an elongate rotary tool.
One drawback with the brush process itself is
the number of steps that are necessary to brush the
elongate rotary tool. Only through physical
manipulation does the brush impinge upon the various
surfaces including certain edges of the elongate rotary
tool. In the case of a drill, the brush has to impinge
the axially forward cutting edges, the side cutting
edges, the axially forward as-ground surfaces, and
possibly the edges of the flutes. These edges and
surfaces are at different orientations so that at least
several steps are necessary to complete the honing
operation. The necessity of using several processing
steps adds to the cost of, and decreases the
efficiencies associated with, the brush process. In
view of this drawback, it would be desirable to provide
a method for honing an elongate rotary tool that
presents a sharp cutting edge wherein the method
comprises a minimum number of steps so as to decrease
the cost and increase the efficiencies associated with
the process.
Another drawback with the brush process is
that the elongate rotary tool does not present an
axially forward cutting edge that has a consistent edge
preparation, i.e., edge condition, across the face of
the elongate rotary tool. For example, in the case of a
drill with diametrically opposed axially forward
cutting edges treated with the brush process, these
cutting edges do not have a consistent edge
preparation. More specifically, the surface roughness
as well as the presence of broken or chipped edges is
not consistent between each cutting edge. When an
elongate rotary tool such as a drill has axially
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forward cutting edges that are inconsistent, the drill
has the tendency to wobble about its longitudinal axis
during the cutting, i.e., drilling, operation. The
existence of this wobble during drilling results in the
holes (or bores) becoming eccentric or oval in shape or
cross-section so as to lose their circularity.
Another drawback with the brush process is
that while the edge preparation for an elongate rotary
tool may have been within the specification, it still
presents a certain degree of inconsistency along the
entire length of the cutting edge. For example, one
length of the cutting edge may experience maximum
deviation from the nominal parameter in one direction
and another length of the cutting edge may experience
maximum deviation from the nominal parameter in the
other direction. Although each location along the
cutting edge is within the specified parameter, the
extent of this variation from the nominal parameter
along the entire length of the cutting edge results in
less than optimum performance of the elongate rotary
tool such as, for example, the wobbling of the drill
during the cutting operation.
Another drawback with an elongate rotary
tool, e.g., a drill, treated according to the brush
process occurs in precision drilling applications. In
this type of application, while the resultant holes or
bores essentially maintain their roundness, they still
experience some deviation from the nominal diameter due
to deviations from the nominal parameter in the drill.
In a precision drilling application, any deviation from
- the nominal diameter is an undesirable feature since
the hole or bore may lose its circularity.
The above drawbacks regarding the
inconsistency of the edge preparation or extent of
deviation from the nominal parameter for the cutting
edge by the brush process demonstrate that improvements
over the brush process are desirable. It would be
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desirable to provide a method for honing an elongate
rotary tool, as well as an apparatus for carrying out
the method and the resultant elongate rotary tool,
wherein the elongate rotary tool presents a honed ,
cutting edge that has a consistent edge preparation,
especially in the case of an axially forward cutting
edge that spans the face of the elongate rotary tool.
It would also be desirable to provide a method of
cutting that uses the resultant elongate rotary tool so
as to produce a hole or bore with satisfactory
circularity, especially with respect to precision
cutting applications.
Still another drawback with the brush process
is that after honing an elongate rotary tool such as a
drill, the intersection between the surface (or side
edge) defining the outside diameter of the drill and
the axially forward cutting edge of the drill is honed
to an excessive extent. Oftentimes, the extent of
honing is so great so as to "over hone" this
intersection. By exceeding the specification for the
size (or extent) of the hone at this intersection the
cutting edge is rounded, i.e., it loses its sharpness.
The consequence of the rounded cutting edges (i.e.,
loss of a sharp edge at the juncture of this surface
and the axially forward cutting edge) is that the drill
does not have optimum cutting ability so that
additional pressure, i.e., force, was needed to drill
using an "overhoned" drill. The use of additional force
has the tendency to shorten the useful life of the
drill.
Another drawback with the brush process is
the excessive rounding of the forward (or nose) cutting
edge~of an elongate rotary tool such as a drill. The
presence of excessive rounding of the forward cutting
edge results in a reduction of the cutting ability of
the drill. Like for the overhoned condition, the
additional pressure necessary to adequately operate a
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drill with a rounded forward cutting edge has the
tendency to shorten the useful life of the drill.
The drawbacks regarding the overhoning of the
elongate rotary tool and the rounding of the forward
cutting edge shows that it would be desirable to
provide a method for honing an elongate rotary tool, as
well as an apparatus for carrying out the method and
the resultant elongate rotary tool, in which the
elongate rotary tool is not overhoned and the forward
cutting edge is not excessively rounded during the
honing process.
Another drawback with the brush process is
the inability to remove grinding marks from the as-
ground surfaces (or faces) of the elongate rotary tool.
I5 These grinding marks result from the initial grinding
operation that forms the axially forward surfaces and
the cutting edges. The brush process does not eliminate
these grinding marks, but instead, leaves many of the
grinding marks in the surface of the elongate rotary
tool. Each grinding mark represents a stress riser.
Each stress riser increases the potential for the
elongate rotary tool to have a shortened useful life
due to chipping. This drawback reveals that it would be
desirable to provide a method for honing an elongate
rotary tool, as well as an apparatus for carrying out
the method and the resultant elongate rotary tool, that
significantly reduces (if not essentially eliminates)
stress risers in the form of grinding marks in the as-
ground surfaces of the elongate rotary tool. The
significant reduction, or even the elimination, of the
' grinding marks increases the potential that the
elongate rotary tool will have a longer useful life.
Earlier patent documents disclose various
methods and structures by which an abrasive impinges
the surface of a workpiece. However, none of these
patent documents discuss a method or apparatus for
treating or honing an elongate rotary tool that
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presents a sharp cutting edge such as, for example, a
drill, endmill, hob or reamer. Thus, while.these patent
documents address this technology in a general way,
they do not present any solutions to the above ,
drawbacks. A brief description of these patent
documents now follows.
Referring now to the patent documents, U.K.
Patent No. 1,184,052 to Ashworth et. al. presents a
method by which one can eliminate tin plating of alloy
IO pistons that were cast and then machined prior to
plating. The method provides for the wet blasting of
the machined pistons with an abrasive. The surface
produced by the wet blast of abrasive resists scuffing
and improves the lubricating properties of the abraded
surface.
U.S. Patent No. 5,341,602 to Foley addresses
a slurry polishing method for removing metal stock from
a complex part such as a turbine blade. The '602 Patent
presents a structure which deflects the high pressure
slurry over the surface of the turbine blade so as to
consistently remove metal stock thereby reducing the
need for hand blending and additional slurry polishing
to correct for inconsistent metal removal.
U.S. Patent No. 4,280,302 to Ohno concerns a
structure for using hone grains to grind a workpiece.
The structure permits the workpiece to be rotated, as
well as moved upwardly and downwardly, to achieve the
necessary grinding of the workpiece.
U.K. Patent No. 1,236,205 to Field pertains
to a method of slurry abrading the surface of a bore in
a tube. A slurry of abrasive and liquid is propelled
along the bore of the tube by compressed gas thereby
impinging the surface of the bore of the tube. The
result is a bore surface that has a finish within a
specified range.
U.K. Patent No. 1,266,140 to Ashworth
mentions the use of a slurry of abrasive to treat the
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surface of a workpiece. More specifically, this patent
p provides for placing an enclosure around the workpiece,
applying suction to the enclosure so as to induce a
flow of primary air into the enclosure, entraining a
slurry of abrasive and liquid in the primary air flow,
directing the abrasive-liquid slurry against the
surface of the workpiece, and removing the slurry. This
process is supposed to provide for a more gentle
abrading process than a dry abrasion.
U.S. Patent No. 2,497,021 to Sterns shows a
structure for grinding or honing using a spray slurry.
The structure uses a cylindrical member with helical
passages to regulate the flow of the abrasive slurry to
the workpiece.
U.S. Patent No. 3,039,234 to Batman shows a
structure that is used to hone the interior surface of
a passage by reciprocating the abrasive fluid through
the passage.
U. S. Patent No. 3,802,128 to Minear et. al.
concerns a structure that removes metal from a
workpiece by extruding through it abrasive particles.
The abrasive particles are in mechanical contact with
the workpiece so as to remove metal therefrom.
U.S. Patent No. 4,687,142 to Sasao et al.
shows a structure to hone the interior passages of a
fuel discharge port by directing an abrasive fluid
against the surface. The abrasive fluid also smooths
the valve seat and rounds the intersection of the
discharge port and the valve seat.
U.S. Patent No. 4,203,257 to Jamison et al.
shows a method of drilling holes in printed circuit
boards and then cleaning the hole with an abrasive
' slurry.
While the brush process produced hard members
with overall adequate performance, the above
description of the drawbacks with the brush process,
and the lack of any patent documents that address these
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drawbacks, reveals that there is room for improvement in the
treating or honing of hard members with sharp cutting edges.
SUMMARY
It is an object of the invention to provide an
improved method of honing an elongate rotary tool that
presents a sharp cutting edge wherein the method comprises a
minimum number of steps.
It is another object of the invention to provide
an improved method of honing an elongate rotary tool that
presents a sharp cutting edge, as well as an apparatus for
carrying out the method and the resultant elongate rotary
tool, wherein the elongate rotary tool presents a honed
cutting edge that has a consistent edge preparation.
It is an object of the invention to provide an
improved method of honing an elongate rotary tool that
presents a sharp cutting edge, as well as the elongate
rotary tool, wherein the juncture of the forward cutting
edge and the side cutting edge is not overhoned, but is
sharp.
Finally, it is another object of the invention to
provide an improved method for honing an elongate rotary
tool that presents a sharp cutting edge, as well as an
apparatus for carrying out the method and the elongate
rotary tool, wherein the face of the elongate rotary tool
does not have grinding marks which function as stress
risers.
In one form thereof, the invention is a method of
treating an elongate rotary tool that has at least one nose
portion that presents at least one sharp cutting edge and an
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elongate portion that presents at least one other sharp
cutting edge, the method comprising the steps of: emitting
under pressure from a nozzle assembly an abrasive fluid
stream comprising at least one abrasive entrained in at
least one liquid; and impinging the abrasive fluid stream
against the sharp cutting edges of the elongate rotary tool
for a preselected time so as to transform the sharp cutting
edges into relatively uniformly honed edges.
In another form thereof, the invention is an
apparatus for treating an elongate rotary tool that presents
at least one sharp cutting edge, and an elongate portion
that presents at least one other sharp cutting edge, the
apparatus comprising: at least one fixture releasably
holding the elongate rotary tool; at least one nozzle
assembly being in communication with at least one source of
an abrasive slurry comprising at least one abrasive
entrained in a liquid so as to be able to emit under
pressure an abrasive stream; and the at least one nozzle
assembly and the elongate rotary tool being moveable
relative to each other so that during the emission of the
abrasive stream the abrasive stream impinges the entire
length of the sharp cutting edges so as to transform the
sharp cutting edges into relatively uniformly honed cutting
edges.
In still another form thereof, the invention is an
elongate rotary tool that has at least one nose portion that
presents at least one sharp cutting edge and an elongate
portion that presents at least one other sharp cutting edge,
produced by a process comprising the steps of: emitting
under pressure from a nozzle assembly an abrasive fluid
stream comprising at least one abrasive entrained in at
i n
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least one liquid; and impinging the abrasive fluid stream
against the sharp cutting edges of the elongate rotary tool
for a preselected time so as to transform the sharp cutting
edges into relatively uniformly honed edges.
BRIEF DESCRIPTION OF THE DRAWINGS
The following is a brief description of the
drawings that form a part of this patent application:
FIG. 1 is a top view of a prior art drill treated
according to the prior art method of brush honing;
FIG. 2 is a side view of a prior art drill treated
according to the prior art method of brush honing;
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FIG. 2A is an enlarged view of the juncture
of the axially forward cutting edge and the side edge
of the specific embodiment shown in FIG.2 hereof;
FIG. 3 is a schematic-perspective view of a
specific embodiment of an apparatus for honing the
sharp edge of a hard member with a portion of the
enclosure removed to reveal the components of the
apparatus;
FIG. 4 is a top view of a specific embodiment
of the invention treated according to the method of the
invention;
FIG. 5 is a side view of a specific
embodiment of the invention treated according to the
method of the invention;
FIG. 5A is an enlarged view of the juncture
of the axially forward cutting edge and the side edge
of the specific embodiment shown in FIG.5;
FIG. 6 is a photograph of the axially forward
end of a cemented tungsten carbide (WC-Co) drill
treated by the brush process (the white scale marker in
the lower left-hand corner of the photograph equals
about 1 millimeter (mm) thus the magnification is about
12X) ;
FIG. 7 is a photograph (the white scale
marker in the lower left-hand corner of the photograph
equals about 1.6 mm thus the magnification is about
7.5X) from the side of the axially forward end of the
cemented tungsten carbide drill of FIG. 6;
FIG. 8 is a photograph (the white scale
marker in the lower left-hand corner of the photograph
equals about 0.23 mm thus the magnification is about
56X) from the side of the axially forward end of the
cemented tungsten carbide drill of FIG. 6; '
FIG. 9 is a photograph (the white scale
marker in the lower left-hand corner of the photograph
equals about 0.28 mm thus the magnification is about
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46X) from the top of the axially forward end of the
cemented tungsten carbide drill of FIG. 6;_
FIG. 10 is a photograph (the white scale
marker in the lower left-hand corner of the photograph
equals about 1.1 mm thus the magnification is about
12X) taken from the top of the axially forward end of a
cemented tungsten carbide (WC-Co) drill treated by the
process of the invention;
FIG. 11 is a photograph (the white scale
marker in the lower right-hand corner of the photograph
equals about 1.7 mm thus the magnification is about 9X)
from the side of the axially forward end of the
cemented tungsten carbide drill of FIG. 10;
FIG. 12 is a photograph (the white scale
marker in the lower left-hand corner of the photograph
equals about 0.25 mm thus the magnification is about
54X) from the side of the axially forward end of the
cemented tungsten carbide drill of FIG. 10; and
FIG. 13 is a photograph (the white scale
marker in the lower left-hand corner of the photograph
equals about 0.28 mm thus the magnification is about
43X) from the top of the axially forward end of the
cemented tungsten carbide drill of FIG. 10.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In order to appreciate the meaningful
advantages which this invention provides, applicant
sets forth FIGS. 1 and 2 which illustrate the structure
of a drill (tungsten carbide cemented with cobalt)
honed according to the typical prior art method, i.e.,
brush honing. Applicant also includes FIG. 6 through
FIG. 9 which are photographs of a tungsten carbide
' drill that was honed according to the brush process. As
a consequence, FIGS. 1, 2 and 6 through 9 are
identified as being "PRIOR ART".
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Referring to the nature of these drills, the
drawings and photographs illustrate a two-fluted style
of drill that has coolant channels. The typical types
of materials that this two-fluted coolant channel style r
of drill cuts includes carbon, alloy and cast steel,
high alloy steel, malleable cast iron, gray cast iron,
nodular iron, yellow brass and copper alloys.
It should be appreciated that other styles of
elongate rotary tools are within the scope of the
invention and include without limitation endmills,
hobs, and reamers. It should also be appreciated that
various styles of drills are within the scope of this
invention. In this regard, other styles of drills
include without limitation a triple fluted style of
drill and a two-fluted style of drill that does not
have coolant channels. The triple fluted style of drill
typically cuts gray cast iron, nodular iron, titanium
and its alloys, copper alloys, magnesium alloys,
wrought aluminum alloys, aluminum alloys with greater
than 10 weight percent silicon, and aluminum alloys
with less than 10 weight percent silicon. The two-
fluted without coolant channels style of drill
typically cuts carbon steel, alloy and cast steel, high
alloy steel, malleable cast iron, gray cast iron,
nodular iron, yellow brass and copper alloys. In
addition to the metallic materials mentioned above, the
drills, end mills, hobs, and reamers may be used to cut
other metallic materials, polymeric materials, and
ceramic materials including without limitation
combinations thereof (e. g., laminates, macrocomposites
and the like), and composites thereof such as, for
example, metal-matrix composites, polymer-matrix
composites, and ceramic-matrix composites.
A typical material for the substrate 10 is
tungsten carbide cemented with cobalt. Other typical
materials include tungsten carbide-based material with
other carbides (e.g. TaC, NbC, TiC, VC) present as
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simple carbides or in solid solution. The amount of
a cobalt can range between about 0.2 weight percent and
about 20 weight percent, although the more typical
range is between about 5 weight percent and about 16
weight percent. Typical tungsten carbide-cobalt (or
tungsten carbide-based/cobalt) compositions used for a
drill or other hard member (e.g., a reamer) include the
following compositions and their properties.
Composition No. 1 comprises about 11.5 weight
percent cobalt and the balance tungsten carbide. For
Composition No. 1, the average grain size of the
tungsten carbide is about 1-4 micrometers (um), the
density is about 12,790 ~ 100 kilograms per cubic meter
(kg/m3), the Vickers hardness is about 1350 ~ 50 HV30,
the magnetic saturation is about 86.5 percent (~ 7.3
percent) wherein 100 percent is equal to about 202
microtesla cubic meter per kilogram-cobalt (uTm3/kg)
(about 160 gauss cubic centimeter per gram-cobalt
(gauss-cm3/gm)), the coercive force is about 140 ~30
oersteds, and the transverse rupture strength is about
2.25 gigapascal (GPa).
Composition No. 2 comprises about 11.0 weight
percent cobalt, 8.0 weight percent Ta(Nb)C, 4.0 weight
percent TiC and the balance tungsten carbide. For
Composition No. 2, the average grain size of the
tungsten carbide is about 1-8 um, the density is about
13,050 t 100 kg/m3, the Vickers hardness is about 1380
~ 50 HV30, the magnetic saturation is about 86.4
percent (~ 7.2 percent), the coercive force is about
170 ~15 oersteds, and the transverse rupture strength
' is about 2.5 GPa.
Composition No. 3 comprises about 6.0 weight
' percent cobalt, 1.6 weight percent Ta(Nb)C, and the
balance tungsten carbide. For Composition No. 3, the
average grain size of the tungsten carbide is about 1
um, the density is about 14,850 ~ 50 kg/m3, the Vickers
hardness is about 1690 ~ 50 HV30, the magnetic
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saturation is about 86.6 percent (~ 7.4 percent), the
coercive force is about 240 ~30 oersteds, and the .
transverse rupture strength is about 2.6 GPa.
Composition No. 4 comprises about 9.5 weight .
percent cobalt and the balance tungsten carbide. For
Composition No. 4, the average grain size of the
tungsten carbide is about .8 um, the density is about
14,550 ~ 50 kg/m3, the Vickers hardness is about 1550 ~
30 HV30, the magnetic saturation is about 86.5 percent
(~ 7.3 percent), the coercive force is about 245 ~20
oersteds, and the transverse rupture strength is about
3 . 6 GPa .
Composition No. 5 comprises about 8.5 weight
percent cobalt and the balance tungsten carbide. For
Composition No. 5, the average grain size of the
tungsten carbide is about 2.5 um, the density is about
14,700 ~ 100 kg/m3, the Vickers hardness is about 1400
~ 30 HV30, the magnetic saturation is about 86.8
percent (~ 7.6 percent), the coercive force is about
150 ~20 oersteds, and the transverse rupture strength
is about 3.0 GPa.
Composition No. 6 comprises about 9.0 ~ 0.4
weight percent cobalt, about 0.3 to 0.5 weight percent
tantalum and no greater than about 0.2 weight percent
niobium in the form of Ta(Nb)C, no greater than about
0.4 titanium in the form of TiC and the balance
tungsten carbide. For Composition No. 6, the average
grain size of the tungsten carbide is about 1-10 um,
the density is about 14,450 ~ 150 kg/m3, the Rockwell A
hardness is about 89.5 ~ .6, the magnetic saturation is
about 93 percent (~ 5 percent), the coercive force is
about 130 t30 oersteds, and the transverse rupture
strength is about 2.4 GPa. '
Composition No. 7 comprises about 10.3 ~ 0.3
weight percent cobalt, about 5.2 ~ 0.5 weight percent
tantalum and about 3.4 ~ 0.4 weight percent niobium in
the form of Ta(Nb)C, about 3.4 ~ 0.4 weight percent
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titanium in the form of TiC and the balance tungsten
_ carbide. For Composition No. 7, the average grain size
of the tungsten carbide is about 1-6 um, the porosity
is A06, B00, C00 (per the ASTM Designation B 276-86
entitled "Standard Test Method for Apparent Porosity in
Cemented Carbides"), the density is about 12,900 ~ 200
kg/m3, the Rockwell A hardness is about 91 ~ .3 HV30,
the magnetic saturation is between about 80 percent and
about 100 percent, the coercive force is about 160 ~20
oersteds, and the transverse rupture strength is about
2.4 GPa.
Composition No. 8 comprises about 11.5 ~ 0.5
weight percent cobalt, about 1.9 ~ 0.7 weight percent
tantalum and about 0.4 ~ 0.2 weight percent niobium in
the form of Ta(Nb)C, no greater than about 0.4 titanium
in the form of TiC and the balance tungsten carbide.
For Composition No. 8, the average grain size of the
tungsten carbide is about 1-6 um, the porosity is about
A06, B00, C00 (per ASTM Designation B 276-86), the
density is about 14,200 ~ 200 kg/m3, the Rockwell A
hardness is about 89.8 ~ .4, the magnetic saturation is
about 93 percent (~ 5 percent), the coercive force is
about 160 ~25 oersteds, and the transverse rupture
strength is about 2.8 GPa.
Composition No. 9 comprises about 10.0 ~ 0.3
weight percent cobalt, no greater than about 0.1 weight
percent tantalum and about 0.1 weight percent niobium
in the form of Ta(Nb)C, no greater than about 0.1
titanium in the form of TiC, about 0.2 ~ 0.1 weight
percent vanadium in the form of vanadium carbide and
' the balance tungsten carbide. For Composition No. 9,
the average grain size of the tungsten carbide is less
than about 1 ~.zm, the porosity is about A06, BO1, C00
(per ASTM Designation B 276-86), the density is about
14,500 ~ 100 kg/m3, the Rockwell A hardness is about
92.2 i- 0.7, the magnetic saturation is about 89 percent
(~ 9 percent), the coercive force is about 300 ~50
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oersteds, and the transverse rupture strength is about
3.1 GPa.
Composition No. 10 comprises about I5.0 ~ 0.3
weight percent cobalt, no greater than about 0.1 weight
percent tantalum and about 0.1 weight percent niobium
in the form of Ta(Nb)C, no greater than about O.I
titanium in the form of TiC, about 0.3 t 0.1 weight
percent vanadium in the form of vanadium carbide and
the balance tungsten carbide. For Composition No. 10,
the average grain size of the tungsten carbide is less
than about 1 um, the porosity is A06, BO1, C00 (per
ASTM Designation B 276-86), the density is about 13,900
~ 100 kg/m3, the Rockwell A hardness is about 91.4 ~ .4
the magnetic saturation is about 84 percent (~ 4
percent), the coercive force is about 300 t20 oersteds,
and the transverse rupture strength is about 3.5 GPa.
It should be appreciated that other binder
materials may be appropriate for use. In addition to
cobalt and cobalt alloys, suitable metallic binders
include nickel, nickel alloys, iron, iron alloys, and
any combination of the above materials (i.e., cobalt,
cobalt alloys, nickel, nickel alloys, iron, and/or iron
alloys).
In brush honing, a rotating multi-filament
brush impinges selected surfaces of the drill including
the as-ground axially forward surface. The as ground
axially forward surface contains grinding marks, and as
will become apparent, the brush process does not remove
all of the grinding marks. The brush also impinges the
sharp cutting edges of the drill so as to hone the
sharp cutting edges thereof. The cemented tungsten
carbide drills of FIGS. 1,2 and 6 -9 were treated in
the following way. The filaments were silicon carbide-
impregnated Nylon with a silicon carbide content of
about 30 weight percent. The silicon carbide was in the
form of about 120 grit (average particle diameter of
about 142 um) silicon carbide particulates. The speed
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of rotation was about 750 rpm and the duration of
impingement was about I5 seconds.
Referring to FIGS. 1 and 2, as well as FIGS.
6 through 9, these drawings and photographs illustrate
the structure of a two-fluted drill (with coolant
passages), generally designated as 20, which has been
honed according to the brush process of the prior art.
As is apparent from FIG. I, the S-shaped nose 22 of the
drill 20 has been rounded by the prior art process. In
this regard, FIG. 6 also shows this rounding of the S-
shaped nose.
In addition, there are grinding marks 24 in
the forward arcuate surface 26 of the drill 20. These
grinding marks were the result of the process involved
with forming the point by the grinding machine. More
specifically, the grinding marks were produced by the
diamond wheel that was used to accurately grind the
drill nose form. The brush process did not remove all
of the grinding marks so that grinding marks remain.
These grinding marks 24 extend across the entire length
of the forward arcuate surface 26. FIG. 9 shows the
presence of these grinding marks with excellent
clarity. As is apparent from the drawings and
photographs, there are many grinding marks in the face
of the prior art drill. Each grinding mark constitutes
a stress riser which increases the potential to shorten
the useful life of the drill because of chipping.
As is apparent from FIGS. 2 and 2A, the
intersection (or juncture) 30 of the surface 32 that
defines the outside diameter of the drill 20 and the
' nose cutting edge 34, which has an angular orientation
relative to the longitudinal axis a-a of the drill 20,
is overhoned. The presence of the overhoned condition
is also shown with excellent clarity in FIGS 7 and 8.
In other words, the brush process removed more material
than was specified from this intersection 30, i.e., the
intersection was overhoned. The result is that greater
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force or pressure is needed to operate the drill so
that it cuts in an adequate fashion. The use of such
greater force typically shortens the useful life of the
drill.
Referring to the drawing of the specific
embodiment of the apparatus of the invention (FIG. 3),
this drawing presents a view (partially in perspective
and partially in schematic) of one specific embodiment
of the apparatus for treating (or honing) the drill
L0 (hard member) that presents a sharp cutting edge with
an abrasive fluid stream. The specific honing apparatus
is generally designated as 50. Honing apparatus 50
includes an enclosure 52, which FIG. 3 illustrates a
portion thereof. The enclosure 52 contains the
components, i.e., the grit and the fluid (e. g., water),
of the abrasive fluid stream throughout the honing
process.
The honing apparatus 50 further ir~cludes a
chuck assembly generally designated as 54. Chuck
assembly 54 includes a base member 58 which is capable
of rotation (see arrow Y). Chuck assembly 54 further
includes a holder 56 which holds the hard member 59
(drill) via a set screw. A receiving opening in the
forward end of the base member 58 receives the holder
56 along with the drill 59 secured thereto. Tnlhile the
holder 56 and the receiving opening are hexagonal in
shape, it should be appreciated that other geometries
or shapes would be suitable for use herein.
Honing apparatus 50 further includes a first
spray nozzle assembly generally designated as 60 which
includes a nozzle 62, a source of abrasive slurry 64 '
(illustrated in schematic) and.a source of pressurized
air ~6 (illustrated in schematic). A hose 68 (shown -
partially in perspective and partially in schematic)
places the source of abrasive slurry 64 in
communication with the nozzle 62. Another hose 70
(shown partially in perspective and partially in
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schematic) places the source of pressurized air 66 in
communication with the nozzle 62. The source of
abrasive slurry 64 and the source of pressurized air 66
are external of the enclosure 52. Although the specific
embodiment presents a nozzle, it should be appreciated
that any structure that would emit a directional stream
of abrasive slurry would be within the scope of this
aspect of the invention.
The nozzle 62 mounts to a piston-cylinder
arrangement generally designated as 72. The nozzle 62
is angularly adjustable via a set screw 74 so that the
angular position of the nozzle 62 is adjustable. One
can loosen the set screw 74 to set the attack angle
of the nozzle, and then tighten the set screw 74 to
secure the nozzle 62 in position. In other words, the
angle of attack " " with respect to the horizontal of
the abrasive fluid stream emitted from the bore of the
nozzle 62 is adjustable with respect to the drill 59.
The typical attack angle is about 45 degrees with
respect to the horizontal.
The piston-cylinder arrangement 72 includes a
cylinder 76 and a piston rod 78. One or spacers 80 may
be positioned near the bottom of the piston rod 78 so
as to select the vertical location of the nozzle 62
relative to the drill. The cylinder 76 is rotatable
about its longitudinal axis (see arrow X), as well as
movable along its longitudinal axis, so as to be able
to selectively position the nozzle 62 prior to or
during the honing operation. Along these lines, while
the specific embodiment shows a piston cylinder
arrangement, it should be appreciated that other
devices may perform the same basic functions. In this
regard, theses functions are to move the nozzle along a
vertical axis and to rotate the nozzle about this
vertical axis, as well as, to vary the angular
orientation of the nozzle with respect to the vertical
axis.
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A first microprocessor 84 receives signals
from the chuck assembly 54 and the first nozzle
assembly 60 so as to control the relative movement of
the nozzle 62 and the drill 59. FIG. 3 illustrates in
schematic the connection between the chuck assembly 54
and the first nozzle assembly 60. Applicant
contemplates that other arrangements to synchronize the
movement of the nozzle (via the piston cylinder
arrangement) and the movement of the drill (via the
chuck) would be suitable. A mechanical coupling between
the chuck and the piston-cylinder arrangement or the
synchronization of members that function independently
are suitable for, and are contemplated to within the
scope of, the present invention.
I5 Honing apparatus 50 further includes a second
spray nozzle assembly generally designated as 90 which
includes a nozzle 92, a source of abrasive slurry 94
(illustrated in schematic) and a source of pressurized
air 96 (illustrated in schematic). A hose 98 (shown
partially in perspective and partially in schematic)
places the source of abrasive slurry 94 in
communication with the nozzle 92. Another hose 100
(shown partially in perspective and partially in
schematic) places the source of pressurized air 96 in
communication with the nozzle 92. The source of
abrasive slurry 94 and the source of pressurized air 96
are external of the enclosure 52.
The nozzle 92 mounts to a piston-cylinder
arrangement generally designated as 102. The nozzle 92
is angularly adjustable via a set screw 104 so that the
angular position of the nozzle 92 is adjustable like
nozzle 62. In other words, the angle of attack with
respect to the horizontal of the abrasive fluid stream
emitted from the bore of the nozzle 92 is adjustable
with respect to the drill 59. The typical attack angle
is zero degrees with respect to horizontal.
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The piston-cylinder arrangement 102 includes
a cylinder 106 and a piston rod 108. The cylinder 106
is rotatable about its longitudinal axis (see arrow Z)
so as to be able to rotate the nozzle 92 prior to or
during the honing operation. The piston-cylinder
arrangement 102 is functional so as to move the nozzle
92 in a direction along its longitudinal axis during
the honing operation. While a microprocessor may
control the function of the piston-cylinder arrangement
102, a pair of spaced-apart movable magnetic reed
switches could also control the movement of the piston-
cylinder arrangement 102, and hence, the nozzle 92.
A microprocessor 104 receives signals from
the chuck assembly 54 and the second nozzle assembly 90
so as to control the relative movement of the nozzle 92
and the drill 59 treated according to the method of the
invention. FIG. 3 illustrates in schematic the
connection between the chuck assembly 54 and the second
nozzle assembly 90.
It should be appreciated that other structure
may be suitable for use in place of the nozzle, 92, the
piston-cylinder arrangement 102 and microprocessor 104
along the same lines as discussed above for the nozzle
62, the piston-cylinder arrangement 72 and the
microprocessor 84. Furthermore, it should be
appreciated that in the honing apparatus 50, the
mounting of the nozzles (62 and 92) to the piston-
cylinder assemblies (72 and 102, respectively) may be
accomplished by any one of a variety of structures. The
specific point of connection, whether on the cylinder
or on the rod, is also subject to variation.
Furthermore, the piston-cylinder assemblies 72, 102 may
be connected to .positioned within the volume of the
enclosure in a variety of ways. Overall, it is apparent
that the specific application for which the apparatus
is used may dictate the type of mounting connection
between the nozzle and the piston-cylinder assembly, as
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well as the position or orientation of the piston-
cylinder assembly. This is also true for the position .
of the chuck assembly 54 in that the position of the
chuck assembly 54 may vary depending upon the specific
application.
It should also be appreciated that the moving
parts inside the enclosure 52 may be protected from
contamination by the abrasive grit. For example, a
protective boot may enclose either or both piston rods
(or both complete piston-cylinder arrangements) to
protect it from contamination.
Referring to FIGS. 4 and 5, these drawings
illustrate the structure of a drill which has been
treated, or honed, according to the method of the
invention. In regard to the specific method, the
operating parameters for the specific honing process
are set forth as follows: the abrasive was about 320
grit (average particle size of about 32 um) alumina
particulates, the concentration was about 2.3 kilograms
(kg) [5 pounds (lbs.)] of alumina particulates per 26.5
liters (1.) [7 gallons (gal.)] of water, the air
pressure was about 275 kiloPascals (kPa) [ about 40
pounds per square inch (psi)], and the duration of
impingement was about 35 seconds.
It should be appreciated that these operating
parameters, as well as the type of abrasive and fluid,
can vary depending upon the specific application and
the desired resultant edge preparation. In regard to
the abrasive, it can include, in addition to alumina,
silicon carbide, boron carbide, glass beads or any
other abrasive particulate material. In addition to
water, the fluid may include any liquid or gas
compatible with the abrasive. In some cases, one may
want to coat the abrasive with a wetting ages':.
Drill 59 includes an elongate body 122 that
has a forward (or nose) end 124. There are a pair of
nose cutting edges 126 which depend from the apex of
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the drill 59. Near the apex of the drill 59 there is an
S-shaped nose 128. The cutting edges 12& blend into a
sharp continuous cutting edge 130 along the length of
the drill 59. The sharp continuous cutting edge 130
takes the form of a helix and continues for a
preselected distance along the length of the elongate
body 122. Drill 59 further includes an arcuate forward
surface 132. There is an intersection 134 between the
surface 136 that defines the outside diameter of the
drill 59 and the nose cutting edge 126.
As is apparent from FIG. 4, the S-shaped nose
of the drill has been slightly rounded by the process,
but not nearly to the extent as is the typical case by
the brush honing process. A comparison of FIG. 10 (the
invention) with FIG. 6 (prior art) clearly shows that
the S-shaped nose of the drill is much sharper in FIG.
10 than in FIG. 7. In this regard, the greater
reflection of light in FIG. 6 at this point
demonstrates that it is more rounded.
The forward arcuate surface of the drill
presents a relatively uniformly smooth surface, and
does not contain grinding marks as is the case with the
brush honing process of the prior art. The absence of
grinding marks in the drill honed according to the
invention is very apparent from a comparison of FIGS. 6
and 9 (prior art) with FIGS. 10 and 13, (the invention)
respectively.
As is apparent from FIGS. 5 and 5A, the
intersection (or juncture) of the surface that defines
the outside diameter of the drill and the nose cutting
' edge, which has an angular orientation relative to the
longitudinal axis a-a of the drill, is not overhoned.
' FIGS.-11 and 12 show the absence of overhoning. This
absence of overhoning is especially apparent when one
compares the condition of the juncture in FIGS. 6 and 7
with the corresponding location in FIGS. 11 and 12. The
honing process of the invention does not remove too
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much material at the intersection, but instead, removes
only enough material to hone the sharp cutting edge
without overhoning. By the honing process of the
invention, the intersection (or juncture) still keeps .
its sharpness.
Referring to the operation of the honing
apparatus 50, the first nozzle 62 is positioned at an
attack angle " " so that it directs the abrasive fluid
stream toward the sharp nose cutting edges 126 of the
drill 59. During the emission of-the abrasive fluid
stream, the chuck assembly rotates the drill 59 and the
piston-cylinder arrangement moves the nozzle 62 in a
direction that is generally parallel to the axial
length of the drill 59. The first microprocessor 84
coordinates the movement of the nozzle 62 relative to
the drill 59 so that the abrasive fluid stream
uniformly impinges upon the nose cutting edges 126 for
a preselected duration.
The second nozzle 92 has an orientation
(attack angle " ") such that it directs the abrasive
fluid stream toward the sharp continuous cutting edge
that is in the elongate body of the drill 59. During
the emission of the abrasive fluid stream, the chuck
assembly rotates the drill 59 and the piston-cylinder
arrangement moves the nozzle 92 in a direction that is
generally parallel to the axial length of the drill 59.
The second microprocessor coordinates the movement of
the nozzle 92 relative to the drill 59 so that the
abrasive fluid stream uniformly impinges upon the
continuous cutting edges 94 for a preselected duration.
In regard to the microprocessors 84, 104, the
control of the honing operation by these
microprocessors is known to those skilled in the art.
The microprocessors are able to take the signal inputs
regarding the relative position and movement of the
nozzle and the drill, and then control these relative
movements so as to provide for the proper extent of
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impingement of the abrasive stream on the appropriate
cutting edge.
Once the drill has been honed it is in a
condition to be used either with or without a coating.
In this regard, typical coatings include hard
refractory coatings such as, for example, titanium
carbide, titanium nitride, titanium carbonitride,
diamond, cubic boron nitride, alumina and boron
carbide. The coating scheme can comprise a single layer
or multiple layers. The coating scheme can comprise
layers applied by chemical vapor deposition (CVD) or
physical vapor deposition (PVD). The scheme can also
include at least one layer applied by CVD and at least
one layer applied by PVD.
The patents and other documents identified
herein are hereby incorporated by reference herein.
Other embodiments of the invention will be
apparent to those skilled in the art from a
consideration of the specification or practice of the
invention disclosed herein. It is intended that the
specification and examples be considered as
illustrative only, with the true scope and spirit of
the invention being indicated by the following claims.
