U.S. patent application number 09/798702 was filed with the patent office on 2001-09-06 for drill bit.
Invention is credited to Eberhard, Helmut.
Application Number | 20010019687 09/798702 |
Document ID | / |
Family ID | 3482733 |
Filed Date | 2001-09-06 |
United States Patent
Application |
20010019687 |
Kind Code |
A1 |
Eberhard, Helmut |
September 6, 2001 |
Drill bit
Abstract
A drill bit, includes a shank and a cutter head connected to the
shank. The cutter head has a center point, and first and second
cutting edges extending radially outwards from opposite sides of
the center point, wherein the first and second cutting edges are
formed along their radial extension with valleys and peaks in
alternating disposition such that in relation to the center point,
as viewed in radial direction, the valleys of the first cutting
edge are arranged at locations where the peaks of the second
cutting edge are disposed, and the peaks of the first cutting edge
are arranged at locations where valleys of the second cutting edge
are disposed.
Inventors: |
Eberhard, Helmut; (St.
Josef, AT) |
Correspondence
Address: |
HENRY M FEIEREISEN
350 FIFTH AVENUE
SUITE 3220
NEW YORK
NY
10118
|
Family ID: |
3482733 |
Appl. No.: |
09/798702 |
Filed: |
March 2, 2001 |
Current U.S.
Class: |
408/211 ;
408/213; 408/224; 408/225; 408/227 |
Current CPC
Class: |
B27G 15/00 20130101;
Y10T 408/909 20150115; Y10T 408/906 20150115; Y10T 408/9065
20150115; Y10T 408/901 20150115; Y10T 408/899 20150115 |
Class at
Publication: |
408/211 ;
408/213; 408/224; 408/225; 408/227 |
International
Class: |
B23B 051/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2000 |
AT |
GM 146/2000 |
Claims
What is claimed as new and desired to be protected by Letters
Patent is set forth in the appended claims:
1. A drill bit, comprising: a shank; and a cutter head connected to
the shank, said cutter head having a center point and first and
second cutting edges extending radially outwards from opposite
sides of the center point, said first and second cutting edges so
formed along their radial extension with valleys and peaks in
alternating disposition that in relation to the center point, as
viewed in radial direction, the valleys of the first cutting edge
are arranged at locations where the peaks of the second cutting
edge are disposed, and the peaks of the first cutting edge are
arranged at locations where valleys of the second cutting edge are
disposed.
2. The drill bit of claim 1, wherein the peaks and the valleys are
formed by a grinding process selected from the group of chip
breaker grinding, wave-shaped profile grinding and knurled
grinding.
3. The drill bit of claim 1, wherein the center point has a
circumference, and further comprising two bar-shaped cutting edges
arranged in 90.degree. offset disposition to the first and second
cutting edges on the circumference of the center point.
4. The drill bit of claim 1, wherein at least one of the peaks has
a tapered cross section in radial extension, as viewed in
opposition to a rotation direction of the drill bit, and wherein at
least one of the valleys has a widening cross section in radial
extension, as viewed in opposition to the rotation direction of the
drill bit.
5. The drill bit of claim 4, wherein the at least one of the peaks
defines a center line and is configured in symmetry to the center
line.
6. The drill bit of claim 4, wherein the cross section of the at
least one of the peaks evenly tapers in opposition to a rotation
direction of the drill bit and defines flanks, with each of the
flanks extending at a constant angle with respect to a normal to
the cutting edges, said valleys being configured as a part of one
of a hollow cylinder and hollow truncated cone.
7. The drill bit of claim 6, wherein the constant angle ranges from
3.degree. to 7.degree..
8. The drill bit of claim 7, wherein the constant angle ranges from
4.degree. to 6.degree..
9. A drill bit, comprising a cutter head having a center point and
two primary cutting edges which extend radially outwards from
opposite sides of the center point, each of the cutting edges
formed with a pattern of alternating valleys and peaks such that
the peaks of one of the cutting edges are formed at locations where
the valleys of the other one of the cutting edges are disposed when
acting on a workpiece during rotation of the cutter head, thereby
splitting a cutting force to be applied on the workpiece into two
portions, with one of the cutting edges applying one portion of the
cutting force, and with the other one of the cutting edges applying
the other portion of the cutting force.
10. The drill bit of claim 9, wherein the peaks and the valleys are
formed by a grinding process selected from the group of chip
breaker grinding, wave-shaped profile grinding and knurled
grinding.
11. The drill bit of claim 9, wherein the center point has a
circumference, and further comprising two bar-shaped secondary
cutting edges arranged in 90.degree. offset disposition to the
primary cutting edges on the circumference of the center point.
12. The drill bit of claim 9, wherein at least one of the peaks has
a tapered cross section in radial extension, as viewed in
opposition to a rotation direction of the cutter head, and wherein
at least one of the valleys has a widening cross section in radial
extension, as viewed in opposition to the rotation direction of the
cutter head.
13. The drill bit of claim 12, wherein the at least one of the
peaks defines a center line and is configured in symmetry to the
center line.
14. The drill bit of claim 12, wherein the cross section of the at
least one of the peaks evenly tapers in opposition to a rotation
direction of the cutter head and defines flanks, with each of the
flanks extending at a constant angle with respect to a normal to
the cutting edges, said valleys being configured as a part of one
of a hollow cylinder and hollow truncated cone.
15. The drill bit of claim 14, wherein the constant angle ranges
from 3.degree. to 7.degree..
16. The drill bit of claim 14, wherein the constant angle ranges
from 4.degree. to 6.degree..
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the priority of Austrian Patent
Application Serial No. GM 146/2000, filed Mar. 3, 2000, the subject
matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates, in general, to a drill bit,
such as a Forstner bit or machine bit, and more particularly to a
drill bit of a type having a shank and a cutting head which has a
central center point and first and second cutting edges extending
radially outwards from opposite sides of the center point.
[0003] Drill bits of this type are mass products for use in hand
drills, drill presses, tap borers, or gang drilling machines, and
produced in great numbers for commercial purposes. Holes of
relatively great diameter can be drilled in a wide variety of
materials such as plastic-coated chipboards, bonded wood panels,
acrylic glass plates and other base materials. Conventional drill
bits suffer, however, shortcomings because drilling machines are
required to apply relatively high drilling forces and torques as
the cutting edges must overcome with their straight edges high
material resistance.
[0004] It would therefore be desirable and advantageous to provide
an improved drill bit to obviate prior art shortcomings and to
increase the efficiency of the drilling process by reducing
drilling forces to be applied.
SUMMARY OF THE INVENTION
[0005] The present invention provides for a drill bit which
includes a shank, and a cutter head connected to the shank and
having a central center point and first and second cutting edges
extending radially outwards from opposite sides of the center
point, with the first and second cutting edges so formed along
their radial extension with valleys and peaks in alternating
disposition that in relation to the center point, as viewed in
radial direction, the valleys of the first cutting edge are
arranged at locations where the peaks of the second cutting edge
are disposed, and the peaks of the first cutting edge are arranged
at locations where valleys of the second cutting edge are
disposed.
[0006] Through the provision of a repeating patterns of peaks and
valleys in staggered relationship on the opposite cutting edges,
the cutting force to be applied is divided, whereby the peaks of
each cutting edge effect concentric, circular cutting tracks around
the center point, while the offset disposition of the of peaks and
valleys on the other cutting edge produces exactly the cutting
tracks in-between. As a result, an overall even borehole is
realized, while each cutting edge provides only half of the entire
cutting energy. In this manner, the drilling procedure can be
implemented at smaller drilling force and smaller torque.
[0007] According to another feature of the present invention, the
peaks and valleys are formed by chip breaker profile, wave-shaped
profile, knurled profile or similar teeth formation. The offset
disposition of the peaks and valleys on both cutting edges leads in
the wave-shaped profile, chip breaker profile, or knurled profile
to the desired effect of reducing the drilling force. Depending on
the material, a modification of the arrangement of the peaks and
valleys provides an optimum cutting performance.
[0008] According to another aspect of the present invention, two
bar-shaped cutting edges are arranged in 90.degree. offset
disposition to the first and second cutting edges on the
circumference of the center point, thereby facilitating a centering
of the drill bit during the drilling procedure and ensuring a
precise drilling action.
[0009] According to another feature of the present invention, at
least one of the peaks may have a tapered cross section in radial
extension, as viewed in opposition to a rotation direction of the
drill bit, and at least one of the valleys may have a widening
cross section in radial extension, as viewed in opposition to a
rotation direction of the drill bit. As a consequence of this
configuration, the flanks of the peaks are prevented from touching
the workpiece, thereby reducing friction and accompanying heat
generation during the drilling procedure. In addition, this
configuration permits a higher rotation speed and/or feed rate
during the drilling procedure as the drill bit encounters less
resistance from the material.
[0010] According to another aspect of the present invention, the at
least one of the peaks may be configured in symmetry to its center
line. The center line extends substantially in circumferential
direction. The symmetric configuration of the peak likewise reduces
the friction on the flanks on both sides of the peak. Suitably, the
at least one peak evenly tapers in opposition to a rotation
direction of the drill bit and defines flanks, with each of the
flanks extending at a constant angle with respect to a normal to
the cutting edges, whereby the valleys are configured as a part of
a hollow cylinder or hollow truncated cone. As a consequence of the
constant angle, the valley may be realized through milling with
slanted milling axis, thereby keeping production costs to a
minimum. It is further contemplated that the constant angle may
range from 3.degree. to 7.degree., preferably from 4.degree. to
6.degree.. This selection ensures that the friction of the flank of
the peak is reduced and an excessive weakening of the peak is
avoided.
BRIEF DESCRIPTION OF THE DRAWING
[0011] Other features and advantages of the present invention will
be more readily apparent upon reading the following description of
preferred exemplified embodiments of the invention with reference
to the accompanying drawing, in which:
[0012] FIG. 1 is a partially sectional side view of a first
embodiment of a drill bit according to the present invention;
[0013] FIG. 2 is a side elevation of the drill bit of FIG. 1;
[0014] FIG. 3 is a top plan view of the drill bit of FIG. 1;
[0015] FIG. 4 is a cutaway view, on an enlarged scale, of a detail
of the cutting head, marked IV in FIG. 1;
[0016] FIG. 5 is a cutaway view, on an enlarged scale, of a detail
of the cutting head, marked V in FIG. 1;
[0017] FIG. 6 is a side view of a second embodiment of a drill bit
according to the present invention;
[0018] FIG. 7 is another side view of the drill bit of FIG. 6;
[0019] FIG. 8 is a top plan view of the drill bit of FIG. 7;
[0020] FIG. 9 is a cutaway view, on an enlarged scale, of a detail
of the cutting head, marked IX in FIG. 8;
[0021] FIG. 10 is a cutaway view, on an enlarged scale, of a detail
of the cutting head, marked X in FIG. 6;
[0022] FIG. 11 is a cutaway view, on an enlarged scale, of a detail
of the cutting head, marked X in FIG. 7;
[0023] FIG. 12 is a representation of the pattern of the two
cutting edges in superimposed disposition to illustrate the peaks
and valleys of the cutting edges in relation to one another;
[0024] FIG. 13 is a representation of another pattern of the two
cutting edges in superimposed disposition to illustrate the peaks
and valleys of the cutting edges in relation to one another;
[0025] FIG. 14 is a fragmentary schematic top plan view of a third
embodiment of a drill bit according to the present invention;
[0026] FIG. 14a is a representation showing a pattern of a cutting
edge of the drill bit in FIG. 14; and
[0027] FIG. 15 is an axonometric illustration of a valley and two
neighboring peaks of a cutting edge of a drill bit, showing a chip
breaker formation.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0028] Throughout all the Figures, same or corresponding elements
are generally indicated by same reference numerals.
[0029] Turning now to the drawing, and in particular to FIG. 1,
there is shown a side view of a first embodiment of a drill bit
according to the present invention, configured in the form of a
Forstner bit. The drill bit essentially includes a shank 2 adapted
for clamping in a, not shown, chuck of a drilling machine, and a
cutting head, generally designated by reference numeral 4 and
connected to the shank 2. The cutting head 4 has a substantially
circular hollow-cylindrical rim 8 and is provided with primary
first and second cutting edges 100, 100' which are separated from
one another by a projecting center point 1 and extend essentially
radially outwards across the rim 8 from the center point 1 in
opposite cutting direction, as shown in particular in FIG. 3.
[0030] As shown in FIG. 2, the center point 1 has a generally
pyramidal configuration to allow a precise positioning of the drill
bit on a marking for drilling a hole. The center point 1 penetrates
hereby the, not shown, workpiece to be drilled to such an extent
that a slippage of the drill bit is prevented, when the drilling
machine is operated. FIGS. 4 and 5 show in more detail the
pyramidal configuration of the center point 1. Of course, this
configuration of the center point 1 is shown by way of example
only, and other configurations, which generally follow the concepts
outlined here, are considered to be covered by this disclosure.
[0031] The cutting head 4 is subdivided in two separate sectors
which are demarcated, on the one hand, by the opposing primary
cutting edges 100, 100' and, on the other hand, by rim portions 3
which extend at an acute angle with respect to the cutting edges
100, 100'. A notch 7 is provided on top of the rim 8 of each
sector.
[0032] Referring now to FIG. 12, there is shown a representation of
the pattern of the two cutting edges 100, 100' in superimposed
disposition to better illustrate the arrangement of a series of
repeating valleys 13 and peaks 14 of the cutting edges 100, 100' in
relation to one another. This representation shows only a sectional
view of the cutting edges in which the valleys and peaks have a
flat configuration, as indicated in FIG. 3 by way of hatching.
[0033] In order to reduce the necessary drilling force, the valleys
13 and the peaks 14 alternate in radial extension of the primary
cutting edges 100, 100', such that relative to the center point 1,
as viewed in radial direction, at the positions of the valleys 13
of the cutting edge 100 are arranged the peaks 14 of the other
cutting edge 100', and at the positions of the peaks 14 of the
cutting edge 100' are arranged the valleys 13 of the other cutting
edge 100. As a consequence, during rotation of the drill bit, the
cutting edge 100 cuts into the workpiece being drilled along those
radii where the cutting edge 100' does not cut, and vice versa.
[0034] In FIG. 12, the cutting edges 100, 100' have a wave-shaped
profile. An alternative is shown in FIG. 13, in which the valleys
13 and peaks 14 of the cutting edges 100, 100' are ground with a
chip breaker profile. Of course, these configurations are shown by
way of example only, and other configurations or patterns, which
generally follow the concepts outlined here, are considered to be
covered by this disclosure. As a consequence of the staggered
arrangement of the valleys 13, and peaks 14 of the cutting edges
100, 100', one of the cutting edges 100, 100' cuts with its peaks
14 those areas on the workpiece over which the other one of the
cutting edges 100, 100' with its valleys 13 passes by.
[0035] Turning now to FIG. 6, there is shown a side view of a
second embodiment of a drill bit according to the present
invention, essentially configured in the form of a multi-spur
machine bit. Parts corresponding with those in FIG. 1 are denoted
by identical reference numerals and not explained again. In this
embodiment, provision is made for a separate arrangement of the
cutting edges 100, 100' which are welded to the cutting head 4,
instead of the single-piece design of the cutting edges 100, 100'
and the cutting head 4 in FIG. 1. The center point 1, which
separates the cutting edges 100, 100' (FIG. 9) and is shown in more
detail in FIGS. 10 and 11 in relation with the cutting edges 100,
100', extends in coincidence with the center axis of the shank 2
and projects out from the cutting head 4. As shown in particular in
FIG. 8, the cutting head 4 has two solid sectors 6 which are
separated from one another, with the cutting edges 100, 100'
respectively attached to opposite end faces of the sectors 6 and
thereby supported during rotation of the drill bit. In a manner, as
described above, the cutting edges 100, 100' have a series of
repeating valleys 13 and peaks 14, which so alternate in radial
extension of the primary cutting edges 100, 100', that relative to
the center point 1, as viewed in radial direction, at the locations
of the valleys 13 of the cutting edge 100 are arranged the peaks 14
of the other cutting edge 100', and at the locations of the peaks
14 of the cutting edge 100' are arranged the valleys 13 of the
other cutting edge 100.
[0036] In order to improve the centered run of the drill bit, the
cutting head 4 is provided with two circumferential secondary
bar-shaped cutting edges 9 in 90.degree. offset disposition to the
primary cutting edges 100, 100', as shown in FIGS. 7 and 8, for
providing a cutting action at the outer boundary of the respective
borehole during the drilling procedure.
[0037] Turning now to FIG. 14, there is shown a fragmentary
schematic top plan view of a third embodiment of a drill bit
according to the present invention. Parts corresponding with those
in FIG. 1 are denoted by identical reference numerals and not
explained again. In this embodiment, provision is made for a
tapered configuration of the cross section of the peaks 14 of each
cutting edge 100, 100' (only one cutting edge is shown here), in
opposition to the rotation direction D of the drill bit, as viewed
in radial direction. Such a tapered peak configuration results in a
distancing of the flanks of the peaks 14 from the part of the bore
material which is not elevated as a consequence of the valleys
during rotation of the drill bit. Thus, friction is effectively
eliminated on the flanks of the drill bit, thereby reducing heat
generation during the drilling procedure. A decrease of heat and
required energy can be accompanied by an increase of the rotation
speed and/or feed rate compared to conventional drill bits so that
the time for carrying out the overall drilling procedure can be
shortened. A decreased heat generation lessens also the risk of
excessive heating of the drill bit.
[0038] A simple construction of the drill bit is implemented when
the peaks 14 and the valleys 13 are designed in symmetry to their
center line M, with the cross section of the peaks 14 having an
evenly tapered configuration, whereby the flanks of the peaks 14
extend at an angle .alpha. with respect to the normal N upon the
cutting edge. Suitably, the magnitude of the angle .alpha. is so
selected that the distance between the flanks of the peaks 14 is
sufficient to prevent friction and a breakage of the peaks 14 as a
result of a reduced supporting zone of the peaks 14 is
substantially eliminated. Practice has shown a suitable range for
the angle .alpha. from 3.degree. to 7.degree., in particular a
range from 4.degree. to 6.degree.. Hereby, friction and resultant
heat generation is substantially reduced while only insignificantly
reducing the supporting zone of the peaks 14.
[0039] The valleys 13 of the cutting edges 100, 100' can be made in
a simple manner when forming them as part of a hollow cylinder or
hollow truncated cone. In this way, a miller can be used to produce
the valleys 13, whereby the milling axis lies approximately in
circumferential direction of the drill bit. A slanting of the
milling axis allows the miller to remove more material in the part
of the cutting edge 100, 100' positioned in opposition to the
rotation direction D of the drill bit, so that the valley 13 is
wider there. As a consequence, the cross section of the valleys 13
tapers by a constant angle .alpha..
[0040] Through other positions of the milling axis during
fabrication of the valleys 13 or use of formed cutters, other
configurations can be made in a simple manner. A configuration with
tapered peaks of the cutting edges 100, 100 can be provided for any
grinding pattern.
[0041] FIG. 14a shows a pattern of a cutting edge of FIG. 14.
[0042] FIG. 15 shows an axonometric illustration of one valley 13
and the neighboring peaks 14 of a cutting edge 100, 100' of a drill
bit, showing a chip breaker formation.
[0043] While the invention has been illustrated and described as
embodied in a drill bit, it is not intended to be limited to the
details shown since various modifications and structural changes
may be made without departing in any way from the spirit of the
present invention.
* * * * *