U.S. patent application number 11/999324 was filed with the patent office on 2008-06-05 for endmills.
This patent application is currently assigned to SMITH INTERNATIONAL, INC.. Invention is credited to Matt Collier, David DenBoer.
Application Number | 20080131304 11/999324 |
Document ID | / |
Family ID | 37054185 |
Filed Date | 2008-06-05 |
United States Patent
Application |
20080131304 |
Kind Code |
A1 |
DenBoer; David ; et
al. |
June 5, 2008 |
Endmills
Abstract
An endmill having a body formed from a single piece of material
and having a length greater than 1.6 inches and a method for
forming such an endmill are provided. The method includes sintering
a blank with an ultra hard material while in a heater having a
length of at least 1.6 inches.
Inventors: |
DenBoer; David; (Pleasant
Grove, UT) ; Collier; Matt; (Draper, UT) |
Correspondence
Address: |
CHRISTIE, PARKER & HALE, LLP
PO BOX 7068
PASADENA
CA
91109-7068
US
|
Assignee: |
SMITH INTERNATIONAL, INC.
|
Family ID: |
37054185 |
Appl. No.: |
11/999324 |
Filed: |
December 4, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11395969 |
Mar 30, 2006 |
|
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11999324 |
|
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60666860 |
Mar 30, 2005 |
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Current U.S.
Class: |
419/10 |
Current CPC
Class: |
B22F 3/14 20130101; C22C
26/00 20130101; B23C 2226/315 20130101; Y10T 407/1948 20150115;
B22F 2005/001 20130101; B23C 5/10 20130101; B23C 2226/125 20130101;
B23C 2222/28 20130101 |
Class at
Publication: |
419/10 |
International
Class: |
B22F 3/14 20060101
B22F003/14 |
Claims
1. A method for forming an endmill having polycrystalline ultra
hard material comprising: providing a blank having a groove;
placing an ultra hard material in the groove; placing the blank in
a refractory metal enclosure; placing the enclosure in a heater,
said heater having a length greater than 1.6 inches; and pressing
the heater with blank in a press while heating using said heater
for sintering the ultra hard material in the groove forming a
polycrystalline ultra hard material in the groove.
2. The method as recited in claim 1 wherein the heater has a length
of about 2.5 inches.
3. The method as recited in claim 1 wherein providing a blank
comprises providing a blank having a length of at least 1.6
inches.
4. The method as recited in claim 1 wherein the heater has a length
greater than 1.7 inches wherein providing a blank comprises
providing a blank having a length greater 1.7 inches.
5. The method as recited in claim 1 wherein the heater has a length
greater than 1.75 inches wherein providing a blank comprises
providing a blank having a length greater 1.75 inches.
6. The method as recited in claim 1 wherein the heater has a length
of about 2 inches wherein providing a blank comprises providing a
blank having a length no less than about 2 inches.
7. The method as recited in claim 1 wherein the blank is provided
in powder form.
8. The method as recited in claim 1 further comprising machining
the blank to form a flute having a cutting edge defined by the
polycrystalline ultra hard material.
9. The method as recited in claim 1 wherein the press is selected
from the group or presses consisting of belt presses and
piston-cylinder presses.
10. The method as recited in claim 1 wherein the heater does not
include end heating units at opposite ends thereof.
11. A method for forming an endmill having polycrystalline ultra
hard material comprising: providing a blank having a length greater
than 1.6 inches and a groove; placing an ultra hard material in the
groove; placing the blank in a refractory metal enclosure; placing
the enclosure in a heater; and pressing the heater in a press while
heating using said heater for sintering the ultra hard material in
the groove forming a polycrystalline ultra hard material in the
groove.
12. The method as recited in claim 11 wherein providing a blank
comprises providing a blank having a length greater than 1.7
inches.
13. The method as recited in claim 11 wherein providing a blank
comprises providing a blank having a length greater than 1.75
inches.
14. The method as recited in claim 11 wherein providing a blank
comprises providing a blank having a length of about 2 inches.
15. The method as recited in claim 11 further comprising machining
the blank to form a flute having a cutting edge defined by the
polycrystalline ultra hard material.
16. The method as recited in claim 11 wherein the press is selected
from the group or presses consisting of belt presses and
piston-cylinder presses.
17. The method as recited in claim 11 wherein the heater is
elongate and does not include end heating units at opposite ends
thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of application Ser. No.
11/395,969 filed on Mar. 30, 2006, which is based upon and claims
priority on U.S. Provisional Application Ser. No. 60/666,860, filed
on Mar. 30, 2005, the contents of which are fully incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] An endmill typically is used for machining a surface, edges,
grooves, pockets and slots. It can be made of high speed steel, or
solid cemented carbide, but it can also consist of a steel tool
body with cemented carbide inserts as cutting means. For certain
applications, endmills having cutting edges formed of a superhard
material, such as PCD, are usually used for the machining of
non-ferrous alloys such as aluminum, brass, magnesium, composites,
and the like, whereas endmills with cutting edges formed of a
superhard abrasive, such as PcBN, are usually used for the
machining of ferrous materials such as cast iron and hardened steel
and the like.
[0003] There are several types of PCD or PcBN endmills on the
market today. One method of making an endmill includes sintering at
high temperature and high pressure (HPHT) diamond or cBN powder
into veins in a solid cylindrical carbide body, i.e., a blank which
is then brazed onto a shank and finished into an endmill. When the
shank is attached to the endmill blank via brazing or other methods
forming a joint, it results in a tool with an inherent weakness at
the joint. Endmilling applications under normal conditions exert
complex tensile and shear loads on the endmill that can lead to
failure of the endmill at the joint. Consequently, an endmill is
desired that does not have this inherent weakness. A method for
forming such an endmill is also desired.
SUMMARY OF THE INVENTION
[0004] A method is provided allowing for the formation of an ultra
hard material, such as a polycrystalline diamond (PCD) or
polycrystalline cubic boron nitride (PCBN), endmill from a single
solid blank without requiring brazing of the blank onto a shank. In
an exemplary embodiment, the method provides for the formation of
endmills from blanks having a length of at least 1.6 inches. In a
further exemplary embodiment, the method provides for the formation
of endmills from blanks having a length of at least 1.7 inches. In
another exemplary embodiment, the method provides for the formation
of endmills from blanks having a length of at least 1.75 inches. In
yet a further exemplary embodiment, the method provides for the
formation of endmills from blanks having a length not less than 2
inches. In yet a further exemplary embodiment, the method provides
for using longer enclosures in a conventional sintering press, such
as a belt press or a piston-cylinder press. In one exemplary
embodiment, the method allows for the use of longer sintering
enclosures and longer heaters which do not incorporate end heating
units by alleviating the use of end heaters.
[0005] In another exemplary embodiment, a method for forming an
endmill having polycrystalline ultra hard material is provided. The
method includes providing a blank having a groove, placing an ultra
hard material in the groove, placing the blank in a refractory
metal enclosure, placing the enclosure in a heater which has a
length greater than 1.6 inches, and pressing the heater with the
enclosure and blank in a press while heating using the heater for
sintering the ultra hard material in the groove forming a
polycrystalline ultra hard material. In another exemplary
embodiment, the heater has a length of about 2.5 inches. In one
exemplary embodiment, the blank has a length of at least 1.6
inches. In yet another exemplary embodiment, the heater has a
length greater than 1.7 inches and the blank has a length greater
1.7 inches. In yet a further exemplary embodiment, the heater has a
length greater than 1.75 inches and the blank has a length greater
1.75 inches. In another exemplary embodiment, the heater has a
length of about 2 inches and the blank has a length not less than 2
inches.
[0006] In another exemplary embodiment, a method is provided for
forming an endmill having polycrystalline ultra hard material. The
method includes providing a blank having a length greater than 1.6
inches and a groove, placing an ultra hard material in the groove,
placing the blank in a refractory metal enclosure, placing the
enclosure in a heater, and pressing the heater with the enclosures
and blank in a press while heating using the heater for sintering
the ultra hard material in the groove forming a polycrystalline
ultra hard material in the groove. In one exemplary embodiment, the
blank may have a length greater than 1.7 inches. In a further
exemplary embodiment, the blank may have a length greater than 1.75
inches. In another exemplary embodiment, the blank may have a
length of about 2 inches.
[0007] In either of the aforementioned exemplary embodiment
methods, the blank may be provided in solid or in powder form.
Furthermore, either of the aforementioned exemplary embodiment
methods may include machining the blank to form a flute having a
cutting edge defined by the polycrystalline ultra hard material. In
an exemplary embodiment, in either of the aforementioned exemplary
embodiments the heater does not include end heating units at
opposite ends thereof. Furthermore, the presses used may, in an
exemplary embodiment, be a belt press or a piston-cylinder
press.
[0008] In yet a further exemplary embodiment, an endmill is
provided having a body having a length of at least 1.6 inches
including a grip portion and being formed from a single piece of
material. Polycrystalline ultra hard material is bonded to the
body. In another exemplary embodiment, the body has a length of at
least 1.7 inches. In a further exemplary embodiment, the body has a
length of at least 1.75 inches. In yet another exemplary
embodiment, the body has a length of not less than 2 inches. In a
further exemplary embodiment, the polycrystalline ultra hard
material does not extend to the grip portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a side view of a conventional endmill blank having
veins of sintered ultra hard material.
[0010] FIG. 2 is a side view of a conventional endmill blank brazed
onto a shank.
[0011] FIG. 3 is a perspective view of a conventional endmill blank
finished into an endmill.
[0012] FIG. 4 is a partial cross-sectional view of a conventional
heater for use in a sintering process.
[0013] FIG. 5 is a cross-sectional view of an exemplary embodiment
longer heater for use in an exemplary embodiment sintering
process.
[0014] FIG. 6 is a side view of an exemplary embodiment endmill
blank of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0015] This invention relates to a helical endmill with
polycrystalline cubic boron nitride (PcBN) or polycrystalline
diamond (PCD) cutting edges and to a method of making the same.
There are several types of PCD or PcBN endmills on the market
today. One method of making an endmill includes sintering at high
temperature and high pressure (HPHT) diamond or cBN powder into
veins in a solid cylindrical carbide body, i.e., a blank which is
then brazed onto a shank and finished into an endmill. Exemplary
endmills and methods of making the same are described in U.S. Pat.
Nos. 4,991,467, 5,031,484, 5,115,697, and 5,685,671, the contents
of which are fully incorporated herein by reference.
[0016] An endmill is typically formed from a cylindrical tungsten
carbide blank 10 having helical grooves or veins 12 formed
longitudinally on its outer surface, as for example shown in FIG.
1, which are packed with either diamond or cubic boron nitride and
a binder. The blank with the packed grooves is then HPHT sintered
in a refractory metal enclosure, typically referred to as a "can",
such as a can made of Niobium or Tantalum. The sintering takes
place in a press such as a cubic press. During sintering, the
diamond or cBN form polycrystalline diamond (PCD) or
polycrystalline cubic boron nitride (PcBN), respectively and
simultaneously bond to the tungsten carbide blank.
[0017] With current endmills, the length of the blank is very
short, typically less than 1.5 inches. To accommodate for the short
length of the blank and to provide a means for holding the tool,
i.e., the endmill, the blank is brazed onto a shank 16 as for
example shown in FIG. 2. The blank with the polycrystalline ultra
hard material and shank combination is then machined to form flutes
15 thereby forming the endmill having ultra hard material cutting
edges 17 as for example shown in FIG. 3.
[0018] When sintering the blank to form conventional endmills, the
blank with grooves packed with diamond or cubic boron nitride is
placed in a refractory metal enclosure 11 which is then surrounded
by salt 13 and placed in a cylindrical heater 20. Current rings
(not shown) and end disks 26 are coupled to the heater which
provide current to the heater which in turn heats the enclosure
with the blank by resistive heating. The resistive heating is
radial heating (as shown by arrows 22 in FIG. 4) through the
circumferential outer surface of the heater, when the enclosure is
supplied with current through current rings (not shown). The end
disks provide for axial heating as shown by arrows 24. The end
disks 26 are typically resistive types of heaters. The heater with
the enclosure is then placed within the press workspace where it is
subjected to pressure. The temperature provided by the heater and
the pressure provided by the press for sintering are at levels
where diamond and CBN are thermodynamically stable.
[0019] Conventional cubic sintering presses cannot accommodate a
longer heater with end heaters, thus limiting the length of the
blank being sintered. A typical cubic press typically has a working
space having a length of 2.5 inches and can accommodate a
conventional heater which has a length of about 1.60 inches, along
with two end disks 26. A conventional refractory metal enclosure
has a length of about 1.50 inches. The entire heater length is
taken up by the refractory metal enclosure and the salt.
Consequently, the length of endmill blanks produced by conventional
cubic sintering presses and heaters are limited to a length of
about 1.50 inches.
[0020] In attempting to overcome these limitations, Applicants have
discovered that they can sufficiently heat the blank for sintering
using only radial heating without using end heating under
sufficient pressure supplied by a high pressure apparatus. In this
regard, the end disks 26 that are usually used for end heating are
not required allowing more length within the press working space to
accommodate a longer heater 32 (FIG. 5) and thus, a longer blank.
For example, in one exemplary embodiment, Applicants were able to
use a heater having a length of 2.528 inches. This size heater can
be accommodated in a belt press or a piston-cylinder press. With
this heater, Applicants were able to use a longer refractory metal
enclosure to form the endmill blank. With the longer heaters
Applicants have been able to form endmill blanks having a length of
2 inches or greater. By forming a longer blank, the need to braze a
shank to the blank is alleviated.
[0021] In an exemplary embodiment, a blank 40, such as a
cylindrical tungsten carbide substrate is provided with
longitudinally extending helical grooves 42 which are packed with
the appropriate powder, e.g., diamond or cBN powder. The blank with
grooves may be formed using any known method. For example, the
cylindrical blank may be formed using conventional methods and then
machined to form the grooves. Alternatively, the blank may be
molded with the grooves in place. In another exemplary embodiment,
the blank may be provided in powder form such that it is solidified
during the sintering process. In yet another exemplary embodiment,
the blank may be provided in a powder form bound together with a
binder.
[0022] With the exemplary embodiment shown in FIG. 6, the helical
grooves 42 do not extend along the entire length 44 of the blank
body 40. In this regard, when the blank is formed, it is formed
with a portion 46 not having any ultra hard material. The blank
portion including the ultra hard material is then machined to the
appropriate shape without being brazed to a shank. Consequently, an
endmill is formed where the portion 46 defines a grip portion. The
grip portion is used to mount the endmill in different apparatuses,
such as machine collets or holding apparatuses. For example, the
end portion of the endmill may be shrink fitted in a shrink fit
holder which is then mounted onto a tool used for endmilling
purposes. In an alternate exemplary embodiment, a longer blank is
formed having longitudinal helical grooves extending along the
entire length of the blank. In yet a further exemplary embodiment,
the blanks may be formed with only a single groove for receiving
the appropriate ultra hard material.
[0023] Whereas typical endmills require that they be brazed onto a
shank because they have a length less than 1.5 inches, the present
invention provides for forming endmill blanks having a length
greater than 1.6 inches and more preferably greater than 1.7
inches, thus, providing a grip portion and not requiring brazing to
a shank. In an exemplary embodiment, an endmill blank is formed
having a length greater than 1.75 inches. In another exemplary
embodiment, an endmill blank is formed having a length greater than
1.7 inches and up to 2 inches. In another exemplary embodiment, an
endmill blank is formed which has a length of at least 2
inches.
[0024] Although the present invention has been described and
illustrated with respect to multiple embodiments thereof, it is to
be understood that it is not to be so limited, since changes and
modifications may be made therein which are within the full
intended scope of this invention as hereinafter claimed.
* * * * *