U.S. patent application number 14/510407 was filed with the patent office on 2015-01-22 for rotary cutting tool having pcd cutting tip.
This patent application is currently assigned to KENNAMETAL INC.. The applicant listed for this patent is Kennametal Inc.. Invention is credited to Karthik Sampath.
Application Number | 20150020649 14/510407 |
Document ID | / |
Family ID | 46458681 |
Filed Date | 2015-01-22 |
United States Patent
Application |
20150020649 |
Kind Code |
A1 |
Sampath; Karthik |
January 22, 2015 |
ROTARY CUTTING TOOL HAVING PCD CUTTING TIP
Abstract
A method of forming a cutting tool includes: providing a PCD
coated nib of material formed in the shape of a rotary cutting tip;
brazing the nib onto a generally cylindrical rod member disposed
about a central longitudinal axis, the generally cylindrical rod
member having a number of coolant passages formed therein at a
first helix angle relative to the central longitudinal axis; and
grinding a number of differential flutes of varying helix angles
with respect to the central longitudinal axis into the brazed
cylindrical rod and nib, each differential flute being oriented
such that a corresponding coolant passage of the number of coolant
passages breaks out within a corresponding flute.
Inventors: |
Sampath; Karthik;
(Pittsburgh, PA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kennametal Inc. |
Latrobe |
PA |
US |
|
|
Assignee: |
KENNAMETAL INC.
Latrobe
PA
|
Family ID: |
46458681 |
Appl. No.: |
14/510407 |
Filed: |
October 9, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13105408 |
May 11, 2011 |
8882412 |
|
|
14510407 |
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Current U.S.
Class: |
76/108.6 |
Current CPC
Class: |
B23B 2240/08 20130101;
B23B 51/02 20130101; B23B 2226/315 20130101; B23B 2222/88 20130101;
Y10T 408/78 20150115; B23P 15/32 20130101; B23B 2226/275 20130101;
Y10T 408/9097 20150115; Y10T 408/45 20150115; B23B 2251/046
20130101; B23B 51/06 20130101 |
Class at
Publication: |
76/108.6 |
International
Class: |
B23P 15/32 20060101
B23P015/32; B23B 51/02 20060101 B23B051/02 |
Claims
1-6. (canceled)
7. A method of forming a cutting tool, the method comprising:
providing a PCD coated nib of material formed in the shape of a
rotary cutting tip; brazing the nib onto a generally cylindrical
rod member disposed about a central longitudinal axis, the
generally cylindrical rod member having a number of coolant
passages formed therein at a first helix angle relative to the
central longitudinal axis; and grinding a number of differential
flutes of varying helix angles with respect to the central
longitudinal axis into the brazed cylindrical rod and nib, each
differential flute being oriented such that a corresponding coolant
passage of the number of coolant passages breaks out within a
corresponding flute.
8. The method of claim 7 wherein each differential flute includes a
first portion disposed at or about the first helix angle with
respect to the central longitudinal axis, a second portion disposed
at a second helix angle with respect to the central longitudinal
axis, and a third portion disposed at third helix angle with
respect to the central longitudinal axis; wherein the third portion
is disposed between the first and second portions along the central
longitudinal axis; and wherein the third helix angle is greater
than the first helix angle.
9. The method of claim 8 wherein each coolant passage of the number
of coolant passages breaks out into a respective flute of the
number of differential flutes generally in the third portion of the
respective flute.
10. The method of claim 7 wherein grinding each flute of the number
of differential flutes comprises: grinding a first portion at the
first helix angle, grinding a third portion adjacent the first
portion at a third helix angle, and grinding a second portion
adjacent the third portion and opposite the first portion at a
second helix angle, wherein the third helix angle is greater than
the first portion.
11. The method of claim 10 wherein the first helix angle comprises
an angle of about 30 degrees.
12. The method of claim 10 wherein the third helix angle comprises
an angle of about 45 degrees.
13. The method of claim 10 wherein the second helix angle comprises
an angle in the range of about 15 degrees to about 20 degrees.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The invention relates generally to rotary cutting tools and,
more particularly, to cutting tools, such as drills, having
polycrystalline-diamond (PCD) cutting tips. The invention further
relates to a method for forming a cutting tool having a
polycrystalline-diamond cutting tip.
[0003] 2. Background Information
[0004] Polycrystalline-diamond (PCD) drills have historically been
formed as straight fluted, facet point drills. More recently,
veined PCD drills have been formed having helical flutes and more
complex point geometries similar to solid carbide drills. One of
the major uses of such highly engineered PCD drills is for drilling
in composite materials, such as carbon fiber reinforced polymer
(CFRP) titanium composites.
[0005] Drilling in titanium requires good coolant flow within the
drill to control the heat generated during drilling. As veined PCD
drills are commonly fabricated as a PCD nib and rod which are later
brazed together, it is difficult to have through-coolant holes
breaking out in the flank of the drill. Typically, coolant holes
are formed in the PCD nib an EDM process (electric discharge
machining) that is carried out after the nib has been brazed to the
rod. Such EDM process is typically quite expensive due to necessary
set-up and processing times. Additionally, known veined PCD drills
commonly utilize a central coolant hole through the core of the
drill which feeds the coolant holes formed in the nib via EDM. The
presence of such a central coolant hole generally reduces the
strength, and thus the durability of the drill, a critical aspect
for drills used to drill titanium materials.
[0006] There is, therefore, room for improvement in cutting tools
used for drilling CFRP-titanium, particularly in the manner coolant
is supplied in such drills.
SUMMARY OF THE INVENTION
[0007] Such deficiencies in the prior art are addressed by
embodiments of the invention which are directed to an improved
rotary cutting tool incorporating an improved coolant hole
design.
[0008] As one aspect of the invention, a cutting tool for
performing hole-cutting operations on a workpiece when the cutting
tool is rotated about a central longitudinal axis is provided. The
cutting tool includes a generally cylindrical body having a first
end structured to be mounted to a machine tool and an opposite
second end structured to engage and perform cutting operations on
the workpiece, at least a portion of the second end being formed
from a PCD material. The cutting tool further includes a number of
coolant passages defined in the generally cylindrical body, each
coolant passage of the number of coolant passages disposed at a
first helix angle relative to the central longitudinal axis; and a
number of flutes formed in the generally cylindrical body, each
flute of the number of flutes having: a first portion at or about
the first end of the generally cylindrical body, a second portion
at or about the second end of the generally cylindrical body, and a
transition portion disposed therebetween. The first portion of each
flute is disposed generally at the first helix angle relative to
the central longitudinal axis, the second portion of each flute is
disposed generally at a second helix angle relative the central
longitudinal axis, and the transition portion of each flute is
disposed generally at a third helix angle relative to the central
longitudinal axis, and the third helix angle is greater than the
first helix angle.
[0009] Each coolant passage of the number of coolant passages may
include an opening disposed at or about the transition portion of a
corresponding flute of the number of flutes.
[0010] The number of flutes may include two flutes and the number
of coolant passages may include two coolant passages.
[0011] The first helix angle may comprise an angle of about 30
degrees. The third helix angle may comprise an angle of about 45
degrees. The second helix angle may comprise an angle in the range
of about 15 degrees to about 20 degrees.
[0012] As another aspect of the invention, a method of forming a
cutting tool is provided. The method includes: providing a PCD
coated nib of material formed in the shape of a rotary cutting tip;
brazing the nib onto a generally cylindrical rod member disposed
about a central longitudinal axis, the generally cylindrical rod
member having a number of coolant passages formed therein at a
first helix angle relative to the central longitudinal axis; and
grinding a number of differential flutes of varying helix angles
with respect to the central longitudinal axis into the brazed
cylindrical rod and nib, each differential flute being oriented
such that a corresponding coolant passage of the number of coolant
passages breaks out within a corresponding flute.
[0013] Each differential flute may include a first portion disposed
at or about the first helix angle with respect to the central
longitudinal axis, a second portion disposed at a second helix
angle with respect to the central longitudinal axis, and a third
portion disposed at third helix angle with respect to the central
longitudinal axis. The third portion being disposed between the
first and second portions along the central longitudinal axis and
the third helix angle being greater than the first helix angle.
[0014] Each coolant passage of the number of coolant passages may
break out into a respective flute of the number of differential
flutes generally in the third portion of the respective flute.
[0015] Grinding each flute of the number of differential flutes may
include: grinding a first portion at the first helix angle,
grinding a third portion adjacent the first portion at a third
helix angle, and grinding a second portion adjacent the third
portion and opposite the first portion at a second helix angle,
wherein the third helix angle is greater than the first portion.
The first helix angle may comprise an angle of about 30 degrees.
The third helix angle may comprise an angle of about 45 degrees.
The second helix angle may comprise an angle in the range of about
15 degrees to about 20 degrees.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] A full understanding of the invention can be gained from the
following description of the preferred embodiments when read in
conjunction with the accompanying drawings in which:
[0017] FIG. 1 is an elevational side view of a cutting tool in
accordance with an example embodiment of the present invention;
[0018] FIG. 2 is a cross-sectional view of the cutting tool of FIG.
1 taken along line 2-2 of FIG. 1; and
[0019] FIG. 3 is an elevational end view of the cutting tool of
FIG. 1 looking down the longitudinal axis of the tool toward the
second end.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Directional phrases used herein, such as, for example, left,
right, front, back, top, bottom and derivatives thereof, relate to
the orientation of the elements shown in the drawings and are not
limiting upon the claims unless expressly recited therein.
Identical parts are provided with the same reference number in all
drawings.
[0021] As used herein, the term "number" shall be used to refer to
any non-zero quantity (i.e., one or any quantity greater than
one).
[0022] As used herein, the term "about" shall be used to refer to a
point near, or at, a particular identified point (i.e.,
proximate).
[0023] FIGS. 1-3 depict an example cutting tool 10, in accordance
with a non-limiting embodiment of the present invention, for
conducting cutting operations on a workpiece (not shown) when
cutting tool 10 is rotated about a central longitudinal axis 12.
Although depicted as a drill in the exemplary embodiment described
herein, it is to be appreciated that concepts described herein are
applicable to other cutting tools such as, for example, without
limitation, end mills or other rotary cutting tools that employ
brazed tips.
[0024] Cutting tool 10 includes a first end 14 and an opposite
second end 16. Cutting tool 10 further includes a mounting portion
18 disposed at or about first end 14 for mounting the cutting tool
10 in a chuck mechanism of a machine tool (not shown), a cutting
tip 20 disposed generally at second end 16 for engaging and cutting
a workpiece (not shown), and a body portion 22 of generally
cylindrical shape disposed between the mounting portion 18 and
cutting tip 20. Cutting tip 20 is generally formed from a carbide
nib 24 having a PCD material 25 deposited thereon which is brazed
via a suitable brazing process to body portion 22 at a braze joint
26. Preferably, body portion 22 is likewise formed from a similar
carbide material.
[0025] Cutting tool 10 further includes a number of flutes 28 (two
in the illustrated example) provided in body portion 22. Each flute
28 includes a first portion (shown generally at 30), a second
portion (shown generally at 32), and a transition portion (shown
generally at 34) disposed between the first portion 30 and second
portion 32. The first portion 30 of each flute 28 is disposed
generally at a first helix angle .theta..sub.1 relative to the
central longitudinal axis 12, the second portion 32 of each flute
28 is disposed at a second helix angle .theta..sub.2 relative the
central longitudinal axis 12, and the transition portion 34 of each
flute 28 is disposed at a third helix angle .theta..sub.3 relative
to the central longitudinal axis 12. Preferably, the first helix
angle .theta..sub.1 is at or about 30 degrees (+/-2 degrees), the
second helix angle .theta..sub.2 is in the range of about 15
degrees to about 20 degrees, and the transition helix angle
.theta..sub.3 is at or about 45 degrees (+/-2 degrees). In any
case, the third helix angle .theta..sub.3 is greater than the first
helix angle .theta..sub.1, the desirability of such relationship is
discussed in further detail below.
[0026] As shown in hidden line in FIG. 1, cutting tool 10 further
includes a number of coolant passages 40 (two in the illustrated
example) defined in the generally cylindrical body 22. Each coolant
passage 40 is disposed at a helix angle .alpha..sub.1 relative to
the central longitudinal axis. Preferably, the helix angle
.alpha..sub.1 of the coolant passages 40 is at or about the same
angle as the first helix angle .theta..sub.1 of the flutes 28. It
is to be readily appreciated that such arrangement provides for
each coolant passage 40 to run generally parallel alongside the
first portion 30 of a respective flute 28.
[0027] As shown in FIGS. 1 and 3, each coolant passage 40 comprises
an opening 42 disposed generally in or about the transition portion
34 of a corresponding flute 28. In other words, as a result of the
difference between the first helix angle .theta..sub.1 of the first
portion 30 of each flute (and the helix angle .alpha..sub.1 of the
coolant passages 40) and the transition angle .theta..sub.3 of the
transition portion 34, each coolant passage 40 breaks out of the
drill body 22 generally in or near the transition portion 34, thus
providing coolant to the periphery (not numbered) and cutting tip
20 of the cutting tool 10 without requiring any EDM processing of
the cutting tool 10.
[0028] From the previous description, a person of ordinary skill in
the art would readily appreciate that there are a number of ways
that a cutting tool 10 according to the present invention may be
formed. As an example, a PCD nib may be brazed onto a rod having
coolant passages formed therein and disposed at a helix angle
.alpha..sub.1 of, for example, without limitation, 30 degrees.
After such brazing has been completed, a differential flute of
varying helix angles would then be ground. Such differential flute
including an optimized second helix angle .theta..sub.2 near the
cutting point 20, and a third helix angle .theta..sub.3 that
"transitions" to cut off the coolant holes 40 at a location
generally axially above the cutting lips (not numbered) of the
cutting tool 10.
[0029] It is to be appreciated that the present invention provides
a number of benefits over known PCD drills. Such benefits include,
for example, without limitation, the ability to use existing
coolant hole rods in manufacturing PCD drills, does not require a
central coolant hole (thus stronger), eliminates any need for EDM,
requires less processing time (thus lower costs), and the
differential helix can be readily adjusted to produce favorable
dynamic behavior.
[0030] While a specific embodiment of the invention has been
described in detail, it will be appreciated by those skilled in the
art that various modifications and alternatives to the details
provided herein could be developed in light of the overall
teachings of the disclosure. Accordingly, the particular
arrangements disclosed are meant to be illustrative only and not
limiting as to the scope of the invention which is to be given the
full breadth of the claims appended and any and all equivalents
thereof
* * * * *