U.S. patent application number 15/905047 was filed with the patent office on 2018-08-30 for drilling tool.
The applicant listed for this patent is Kennametal Inc.. Invention is credited to Jurgen Schwagerl.
Application Number | 20180243843 15/905047 |
Document ID | / |
Family ID | 44009806 |
Filed Date | 2018-08-30 |
United States Patent
Application |
20180243843 |
Kind Code |
A1 |
Schwagerl; Jurgen |
August 30, 2018 |
DRILLING TOOL
Abstract
A drilling tool includes at least two chip flutes and a chisel
edge with a thinned region. The thinned region merges continuously
into the chip flutes in such a way that the thinned region forms
the end of the respective chip flute in the region of the chisel
edge.
Inventors: |
Schwagerl; Jurgen;
(Vohenstrauss, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kennametal Inc. |
Latrobe |
PA |
US |
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|
Family ID: |
44009806 |
Appl. No.: |
15/905047 |
Filed: |
February 26, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13576482 |
Oct 23, 2012 |
9901990 |
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PCT/EP2011/000518 |
Feb 4, 2011 |
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15905047 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23B 51/02 20130101;
B23B 2251/18 20130101; B24B 19/04 20130101; B24B 3/32 20130101;
Y10T 408/9097 20150115; Y10T 408/9095 20150115 |
International
Class: |
B23B 51/02 20060101
B23B051/02; B24B 3/32 20060101 B24B003/32; B24B 19/04 20060101
B24B019/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 4, 2010 |
DE |
10 2010 006 797.0 |
Claims
1-13. (canceled)
14. A drilling tool comprising: at least two chip flutes; and a
chisel edge, with a thinned region being disposed on either side of
the chisel edge; and a pair of opposing major flanks disposed on
opposite sides of the chisel edge, wherein the thinned region:
comprises a portion of each of the at least two chip flutes and
forms an end of each of the at least two chip flutes in the region
of the chisel edge, and merges continuously, without any
discontinuities, without any kinks, and without any ridges, into a
remainder of each of the chip flutes in such a way that the thinned
region forms the end of the respective chip flute in the region of
the chisel edge; wherein each of the chip flutes is fully concave
toward a central axis of the drilling tool, when viewed in
transverse cross-section at one or more axial points along the chip
flute; wherein a core diameter is defined between the at least two
chip flutes; the core diameter reducing from a normal core
diameter, at a predetermined axial point along the drilling tool,
to a reduced core diameter of the thinned region; wherein the
normal core diameter does not increase between the predetermined
axial point along the drilling tool and a region of run-out of the
chip flutes.
15. The drilling tool of claim 14 wherein the at least two chip
flutes comprise helical chip flutes with a corresponding helical
thinned region at the end of the chip flute adjacent to the chisel
edge.
16. The drilling tool of claim 14 wherein the thinned region is of
helical shape.
17. The drilling tool of claim 14, wherein the reduced core
diameter corresponds to 0.01 to 0.2 times an outside diameter of
the drilling tool.
18. The drilling tool of claim 14 wherein the thinned region has a
longitudinal extent in the longitudinal direction of the drill
which corresponds to 0.1 to 1.5 times an outside diameter of the
drilling tool.
19. The drilling tool of claim 14 further comprising a curved major
cutting edge.
20. The drilling tool of claim 19, further comprising a protective
chamfer provided at an outer end of each major cutting edge.
21. The drilling tool of claim 14, wherein each of the chip flutes
is fully concave toward a central axis of the drilling tool, when
viewed in transverse cross-section at least at five different axial
points along the chip flute.
22. The drilling tool of claim 14, wherein each of the chip flutes
extends to a first defining axial edge which, when viewed in
transverse cross-section, is disposed adjacent an outer
circumference of the drilling tool.
23. The drilling tool of claim 22, comprising: a protective chamfer
extending helically in a generally axial direction at an outer
circumference of the drilling tool; wherein the defining axial edge
of at least one of the chip flutes comprises an edge of the
protective chamfer.
24. The drilling tool of claim 22, wherein each of the chip flutes
extends to a second defining axial edge which, when viewed in
transverse cross-section, is disposed adjacent an outer
circumference of the drilling tool.
25. The drilling tool of claim 14, wherein the core diameter
reduces steadily from the normal core diameter to the reduced core
diameter.
26. The drilling tool of claim 14, further comprising: a pair of
major cutting edges; wherein each of the chip flutes extends
continuously, without any discontinuities, without any kinks, and
without any ridges, to each of: the chisel edge, a respective one
of the major cutting edges, and a respective one of the major
flanks.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application under 35 USC .sctn. 120 is a continuation
of co-pending U.S. patent application Ser. No. 13/576,482, filed on
Oct. 23, 2012, which is incorporated herein by reference in its
entirety and is a National Stage Entry of International Application
No. PCT/EP2011/000518, filed on Feb. 4, 2011, itself incorporated
herein by reference in its entirety and claiming priority to
Federal Republic of Germany Patent Application No. 102010006797.0,
filed on Feb. 4, 2010, which itself is also incorporated herein by
reference in its entirety.
BACKGROUND
[0002] The invention, in at least one aspect, relates to a drilling
tool of a kind such as known, for example, from EP 1 230 058, which
is likewise attributable to the applicant. In the region of the
drill point of a drilling tool of this kind, two or more major
cutting edges are connected to one another by a chisel edge. The
practice of reducing the size of this chisel edge by applying a
"thinned region" is known in the area of machining technology in
general and from the abovementioned EP 1 230 058, in particular.
Since the cutting rate is equal to zero in the region of the chisel
edge, the mechanical load on the drill point of the drilling tool
is significantly reduced by such a reduction in the size of the
chisel edge.
[0003] In the production of drilling tools, the thinned region of
the chisel edge is generally produced in a multi-stage grinding
process. In a first grinding operation, the chip flutes and, if
appropriate, the minor cutting edges provided at the boundary of
the chip flutes are ground into the drilling tool blank. In a
second process step, the major cutting edges, the chisel edge and
the flanks adjoining the major cutting edges are ground. In a third
grinding operation, the chisel edge is then thinned. For each
grinding operation, the grinding tool, which is generally formed by
a rotating grinding disk, is in each case applied again to the
drill blank to be ground in order to grind the major cutting edges
and the chisel edge, to grind the thinned region and to grind the
spiral flutes. Each new application of the grinding tool to the
drill blank entails the formation of discontinuities during
grinding, thereby giving rise to unwanted ridges on the finished
drilling tool.
[0004] These ridges must either be smoothed and removed afterwards
by complex and costly finish machining processes. If such finish
machining is omitted, the accuracy of running of the drilling tool
may be impaired, and the mechanical loads acting on the drilling
tool during the drilling operation increase, and this inevitably
leads to a reduction in the life of the drilling tool.
[0005] EP 1 230 058 has disclosed a process for grinding a drill
point which prevents the formation of ridges in the region of the
drill point of the drilling tool disclosed there. The disadvantage
with this grinding process is the fact that it is suitable only for
the way, shown there, of grinding the drill point in the region of
the chisel edge.
SUMMARY
[0006] Objects are achieved in an inventive manner by features
found in the claims. The advantageous and modified embodiments
described in addition concern developments of the invention, in at
least one aspect, which are both expedient and inventive per
se.
[0007] The invention, in at least one aspect, is based on a
fundamental consideration that the thinning of the chisel edge and
the grinding of the chip flutes can be performed in a single
grinding operation. To achieve this, the grinding tool also makes
contact with the drill blank only once, thereby eliminating from
the outset the unwanted formation of ridges. The thinned region in
the region of the chisel edge merges continuously and without
ridges into the chip flute. The thinned region is thus, as it were,
part of the chip flute and thus forms the end of the chip flute in
the region of the major cutting edges, i.e. the end of the chip
flute remote from the clamping shank of the drilling tool. The chip
flute walls bounding the chip flute therefore extend continuously
without ridges as far as the end of the drill, i.e. as far as the
respective major cutting edge, as far as the chisel edge and as far
as the "major flank". At the same time, the thinned region means
that the "core diameter" tapers towards the chisel edge. When
viewed in cross section, the chip flute wall is thus uniform, i.e.
without kinks.
[0008] In a preferred development of the drilling tool, the chip
flutes are helical, and therefore the thinned region is likewise of
helical design. In particular, the thinned region adjoins the
chisel edge in a helical shape. The chip flute wall adjoining the
chisel edge in the axial direction therefore has a twist starting
from the chisel edge.
[0009] The core diameter is preferably reduced steadily to a
reduced core diameter (d) at the chisel edge by the thinned region,
i.e. during grinding the path traced leads back successively in a
radial direction from the chisel edge to the grinding disk, and
therefore the core diameter widens successively and no ridges are
formed in the chip flute wall. The term "core diameter" is
generally understood to mean the minimum distance between chip
flute walls at the center of the drill.
[0010] The reduced core diameter corresponds, in particular, to
0.01 to 0.2 times an outside circumference diameter of the drilling
tool, i.e. during grinding the grinding disk is moved up
correspondingly close to the center of the drill in the
single-stage grinding process.
[0011] It is expedient if the thinned region has a longitudinal
extent in the longitudinal direction of the drill which corresponds
to 0.1 to 1.5 times an outside circumference diameter of the
drilling tool. During the grinding process, the grinding disk is
therefore guided continuously over this length from the reduced
core diameter to the normal core diameter adjoining the thinned
region.
[0012] In a preferred development, a step is formed at the
transition from a major flank to the chip flute. This means, in
particular, that the major flank ends at a ridge extending in a
radial direction, which is then adjoined by the chip flute wall
extending in an axial direction.
[0013] The major cutting edge preferably extends outwards in a
curve or an arc in a radial direction from the chisel edge. As an
alternative, a rectilinear profile is provided.
[0014] To obtain a drilling tool, a three-stage production process
is provided. In a first process step, a rotating grinding disk
feeds into the drilling tool blank from the end of the cutting edge
in the region of the drill point. Relative to the drilling tool
blank, the grinding disk is preferably set here at the lead angle
of the chip flute to be ground. To cut a protective chamfer, the
grinding disk is then preferably simply tilted slightly during the
grinding process. As soon as the grinding disk is in engagement
with the drilling tool blank, the grinding disk is moved in a
radial direction of the tool blank in the second process step in
order to grind the thinned region and then makes a continuous
transition to the third process step. In the third process step,
the grinding disk moves in an axial direction along the drilling
tool blank in order to grind the chip flute continuously adjoining
the thinned region. For the transition from the thinned region with
the reduced core diameter to the chip flute, the grinding disk is
moved back again somewhat in a radial direction in a movement
superimposed on the axial movement. In particular, the radial
movement is superimposed on the axial movement from the beginning
during the grinding of the thinned region.
[0015] It is of particular significance here that the grinding of
the thinned region is followed by the grinding of the chip flute in
the same grinding operation without withdrawing the grinding disk.
During this process, the chip flute is ground continuously from the
chisel edge to the shank end of the chip flute.
[0016] In another embodiment, the drill blank performs a predefined
rotary motion during the second process step or during the third
process step or during the second and the third process step. With
the aid of this rotary motion, a helical chip flute is obtained and
the twist of this helical chip flute or spiral flute is determined.
Thus, the process is suitable for producing both drilling tools
with straight flutes and drilling tools with spiral flutes. The
grinding of the thinned region is therefore, in particular, a
superimposed motion involving a radial, an axial and a rotary
component.
[0017] According to a preferred development, there is provision in
a further process step to provide the drilling tool blank preground
in this way with any desired end grinding. In a preferred
embodiment, the grinding of the chip flutes and of the thinned
region is therefore performed first of all in a continuous,
seamless grinding process before the end geometry of the drill is
then ground. As an alternative, it is also possible for the end
geometry to be ground beforehand.
[0018] One advantage of the invention, in at least one aspect, is
the fact that any number of cutting edge versions can be achieved
with a single drilling tool blank, i.e. with a single basic part.
This has a positive effect in terms of low stocking levels of
drilling tool blanks, and this means that the amount of resources
tied up is low. Moreover, it is possible to match the drilling tool
in an optimum manner to any cutting application by means of
appropriate grinding of the drill point. The invention, in at least
one aspect, is therefore also particularly suitable for producing
small batches or small lot sizes, right down to a lot size of 1.
Finally, the invention, in at least one aspect, also makes it
possible to incorporate refinements in the grinding of the cutting
edges of the drill immediately into a running production process.
In an expedient embodiment, provision is therefore also made, in
particular, to produce a large number of drilling tool blanks
initially, in particular to keep these in storage and only later to
carry out end grinding. Another advantage involves the possibility
of configuring the thinned region itself in a helical or twisted
shape. It is also possible to provide a straight chisel edge
initially, which is adjoined by a helical or twisted thinned
region.
[0019] It is also possible to produce special drilling tools, e.g.
drilling tools with core tapering in an axial direction, with a
production process according to at least one aspect of the
invention. The production process claimed is particularly suitable
for producing drilling tools with 5-axis machine tools.
DESCRIPTION OF THE FIGURES
[0020] FIG. 1 shows an illustration of the point of a drilling tool
according to the invention, with the left-hand half of FIG. 1
showing a plan view of the drill point in a longitudinal direction
of the drilling tool and the right-hand half showing a
corresponding side view of the drill point;
[0021] FIG. 2 shows a conventional drilling tool point without
thinning in accordance with the prior art;
[0022] FIG. 3 shows a conventional drill point with thinning in
accordance with the prior art, with the left-hand half of FIG. 3
showing the plan view of the drill point with conventional thinning
in a longitudinal direction of the drilling tool and the right-hand
half showing the side view of this drill point;
[0023] FIG. 4 shows the side view of the profile of the core
diameter of a drilling tool in accordance with the prior art,
[0024] FIG. 5 shows the side view of the core profile of a drilling
tool according to the invention;
[0025] FIG. 6 shows the side view of the core profile of a drilling
tool with a constant bevel;
[0026] FIGS. 7 to 11 show the core profile of the drilling tool
illustrated in FIG. 5 in section at various positions spaced apart
in a longitudinal direction of the drilling tool;
[0027] FIG. 12 shows the position of the grinding disk of a
grinding tool at the beginning of the grinding process according to
the invention as it grinds a curved major cutting edge onto a
drilling tool, in a plan view of the drill point on the left-hand
side and in side view on the right-hand side;
[0028] FIG. 13 shows the views from FIG. 12 with the position of
the grinding disk at the end of the thinned region of the curved
major cutting edge of the drilling tool;
[0029] FIG. 14 shows the illustrations according to FIG. 12 but for
grinding a thinned region on a tool with a straight major cutting
edge, and
[0030] FIG. 15 shows the grinding disk from FIG. 14 at the end of
the thinning operation.
DETAILED DESCRIPTION
[0031] The drilling tool illustrated in FIG. 1 has the two major
cutting edges 1a and 1b with a protective chamfer 12, and the
chisel edge 8, which connects the major cutting edges 1a, 1b and
has the thinned region 2. The continuous transition from the
thinned region 2 into the corresponding chip flute 3 a can be seen
in the right-hand half of FIG. 1. From the left-hand part of FIG. 1
it can be seen that, corresponding to the two major cutting edges
1a, 1b, two chip flutes 3a and 3b are also formed on the drilling
tool. Here, the term "continuous transition" should be understood
to mean that the (chip flute) wall region which directly adjoins
the end of the drill (end face), in particular the chisel edge, and
extends in an axial direction has a smooth surface without ridges
and kinks. Adjoining the major cutting edges 1a and 1b there are
respective major flanks 4a and 4b. These end at a step 20 or ridge,
which forms the transition to the chip flute 3a, 3b. The direction
of rotation 5 of the drilling tool is furthermore indicated by a
corresponding arrow in FIG. 1. The longitudinal direction 6 of the
drilling tool and the radial direction 7 are also shown in FIG.
1.
[0032] FIG. 2 likewise shows a plan view of the drilling point of a
drilling tool, said plan view corresponding to the left-hand view
in FIG. 1, although this is according to the prior art. This prior
art drilling tool too has two major cutting edges 1a, 1b, two
corresponding major flanks 4a, 4b and two chip flutes 3a, 3b.
However, there is no thinned region here. On this prior art tool,
the chisel edge 8 connecting the two major cutting edges 1a and 1b
clearly has a very much greater width in radial direction 7 than
the chisel edge 8 with the thinned region 2 on the subject matter
illustrated in FIG. 1.
[0033] Finally, FIG. 3 shows the drill point of a drilling tool
with conventional thinning in accordance with the prior art. This
known tool too has two major cutting edges 1a, 1b, two chip flutes
3a, 3b and two major flanks 4a, 4b. Also visible, at the transition
from the major cutting edges 1a, 1b to the chisel edge 8, are the
two ground ridges 9 in the region of the major cutting edges 1a,
1b, which are formed by the repeated application of the grinding
disk to the region of the cutting edges during the production of
the thinned region 2 on the conventional tool illustrated in FIG.
3.
[0034] FIG. 4 shows the profile of the core diameter geometry in
side view. In contrast to the profile of the core diameter geometry
according to the prior art, which is shown in FIG. 4, the
embodiment according to the invention, which is illustrated in FIG.
5, has a thinned region 2 with a twist corresponding to the helical
shape of the chip flute 3a, 3b. This thinned region 2 has a
longitudinal extent L in a longitudinal direction 6 of the drilling
tool. The magnitude of this longitudinal extent corresponds to 0.1
to 1.5 times the outside circumference diameter D1 of the drilling
tool. The central diameter d of the thinned region corresponds to
0.01 times to 0.2 times the outside circumference diameter D1. The
actual core diameter D of the drilling tool corresponds to 0.1 to
0.6 times the outside circumference diameter D1.
[0035] Finally, FIG. 6 shows a core profile with a constant bevel.
Here, the longitudinal extent L of the thinned region 2 corresponds
to no more than 1.0 times the outside circumference diameter D1.
The major cutting edges 1a, 1b of this embodiment can be
reground.
[0036] FIG. 7 to FIG. 11 show various "sections" through the
drilling tool illustrated in FIG. 5 along the longitudinal
direction 6 at different longitudinal distances LA. The figures are
computer-generated illustrations in which the peripheral boundary
edge is indicated only by the circular profile of the outside
circumference diameter D1. FIG. 7 shows the view of the drill point
at a longitudinal distance LA=0, and is therefore equivalent to an
end view. FIG. 8 shows the cross section of the drilling tool
illustrated in FIG. 7 sectioned at the point which corresponds to
the longitudinal distance LA from the drill point in the
longitudinal direction 6 of the drilling tool corresponding to 0.11
times the outside circumference diameter D1. The central circle
depicted indicates the periphery of the drilling tool at the level
of this longitudinal distance LA. FIG. 9 shows the same drilling
tool sectioned at the point of the longitudinal distance LA from
the point of the drilling tool corresponding to 0.2 times the
outside circumference diameter D1. FIG. 10 shows the profile at a
longitudinal distance LA amounting to half the value of the outside
circumference diameter D1 from the drilling point. Finally, FIG. 11
shows through the drilling tool at a longitudinal distance LA
corresponding to 1.5 times the outside circumference diameter
D1.
[0037] From a comparison of FIGS. 7 to 9, on the one hand, the
increase in the core diameter d is very clearly visible. On the
other hand, the helical profile of the chip flute wall and hence
also of the thinned region can also be seen. The profile of the
chip flute wall in the section plane is represented by the thick
black lines.
[0038] Finally, FIG. 12 to FIG. 15 show by way of example the
progress of a process for producing a drilling tool. At the
beginning of the production process, the rotating grinding disk 10
feeds into the drill blank 11 from the drill point. Initially, the
grinding disk 10 performs a grinding movement in a radial direction
7 of the drill blank 11 in order to grind the thinned region in the
region of the major cutting edge. For continuous grinding of the
chip flutes 3a, 3b, the grinding disk 10 then moves along the drill
blank 11 in the longitudinal direction 6 of the drilling tool. For
this purpose, the drill blank 11 is moved along the circumference
of the grinding disk in this embodiment, or changes its angular
position relative to the grinding disk. In the first example, shown
in FIGS. 12 and 13, from the angular position of the grinding disk
A=36.918 to the angular position A=20.632. The angular position of
the drill blank 11 therefore varies, i.e. the tilt of the center
line thereof relative to the radial of the grinding disk 10 varies
(when considered in the plane of the drawing). In the second
embodiment, which is shown in FIGS. 14 and 15, the center line is
in alignment with the radial of the grinding disk 10 at the
beginning of the process, in contrast to the preceding example.
[0039] If--as in the illustrative embodiment--a helical chip flute
3a, 3b is to be ground, the drill blank 11 rotates in the direction
of rotation 5 during the grinding movement of the grinding disk
10.
[0040] During the grinding of a curved major cutting edge 1a, 1b,
as shown in FIG. 12 and FIG. 13, the point of disk engagement
changes, beginning from the drill tip to a length in the
longitudinal direction of the drilling tool which corresponds to 3
times the outside circumference diameter D1. The change in the
point of disk engagement changes in a range of from 0.degree. to
120.degree., based on the central longitudinal axis of the drilling
tool 11, relative to the center of the grinding disk 10.
[0041] FIG. 14 and FIG. 15, in contrast, show the case of
production of a straight major cutting edge 1a and 1b.
* * * * *