U.S. patent application number 10/469768 was filed with the patent office on 2005-06-02 for mult- purpose end-mill.
Invention is credited to Dov, Avi, Volokh, Vladimir.
Application Number | 20050117982 10/469768 |
Document ID | / |
Family ID | 11075204 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050117982 |
Kind Code |
A1 |
Dov, Avi ; et al. |
June 2, 2005 |
Mult- purpose end-mill
Abstract
A multi-purpose end-mill to be used for different machining
purposes, in particularly useful for closed or open contours
machining. The end-mill comprises a cylindrical shank portion
connected to a first cutting portion provided with a plurality of
spaced-apart cutting teeth and a second portion provided with a
plurality of different spaced-apart cutting teeth.
Inventors: |
Dov, Avi; (Ma'alot, IL)
; Volokh, Vladimir; (Ma'alot, IL) |
Correspondence
Address: |
Eitan Pearl Latzer & Cohen Zedek
10 Rockefeller Plaza
Suite 1001
New York
NY
10020
US
|
Family ID: |
11075204 |
Appl. No.: |
10/469768 |
Filed: |
September 4, 2003 |
PCT Filed: |
March 3, 2002 |
PCT NO: |
PCT/IL02/00162 |
Current U.S.
Class: |
408/24 |
Current CPC
Class: |
Y10T 407/196 20150115;
B23C 2210/0492 20130101; Y10T 407/1946 20150115; B23C 5/10
20130101; B23B 51/08 20130101; B23C 2220/605 20130101; Y10T 408/348
20150115; B23C 2210/285 20130101; B23C 2210/203 20130101; Y10T
407/1952 20150115; B23C 2210/405 20130101 |
Class at
Publication: |
408/024 |
International
Class: |
B23B 051/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 2001 |
IL |
141828 |
Claims
We claim:
1. A multi-purpose end-mill particularly useful for closed contour
machining and usable for at least rough machining and finish
machining, comprising a cylindrical shank portion to be gripped in
a machine tool, said shank portion being connected to a first
cutting portion comprising a core supporting a plurality of
spaced-apart cutting teeth for a first type of machining, said
first cutting portion being connected to a second cutting portion
provided with a plurality of spaced-apart cutting teeth for a
second type of machining.
2. The multi-purpose end-mill as claimed in claim 1, wherein said
first type of machining is finishing, and said second type of
machining is roughing.
3. The multi-purpose end-mill as claimed in claim 2, wherein said
finishing portion has a larger number of teeth than said roughing
portion.
4. The multi-purpose end-mill as claimed in claim 2, wherein said
finishing portion has double the number of teeth than said roughing
portion.
5. The multi-purpose end-mill as claimed in claim 2, wherein said
finishing portion has a smaller helix angle than said roughing
portion.
6. The multi-purpose end-mill as claimed in claim 1, wherein the
core diameter of said end-mill varies along the axial length
parabolically, the larger diameter being located near the shank and
the smaller diameter being located near the tool tip.
7. The multi-purpose end-mill as claimed in claim 1, further
provided with a drill-like pointed cutting tip.
8. The multi-purpose end-mill as claimed in claim 7, wherein the
number of cutting teeth at said pointed cutting tip corresponds to
the number of teeth in said second cutting portion.
Description
FIELD AND BACKGROUND OF THE INVENTION
[0001] The present invention relates to the machining of slots by
use of a rotational cutting tool. More particularly, the invention
provides an end mill, which can be used for different machining
purposes by changing the distance between a thin workpiece and the
end mill shank. This change is accomplished either by moving the
workpiece or the cutter.
[0002] A common requirement is to machine a slot, straight or
contoured, in a thin workpiece. "Thin" means that the machined item
is usually no thicker than the tool diameter.
[0003] If the required slot reaches an outer edge of the workpiece,
or the operation to be carried out comprises machining the outer
edge, then the first operation is rough machining, leaving a little
material for finishing, and the following operation is finish
machining to the required size.
[0004] End-mills configured for rough machining are generally
unsuitable for finish machining. During rough machining much
material is removed, and the removal of chips from the cutting area
requires adequate space between cutting teeth. Such space can only
be provided when the number of teeth is low, typically 2-4 teeth
depending on cutter diameter, and the core diameter of the tool is
small, although still large enough to prevent tool breakage. The
smaller core diameter may lead to minor loss of accuracy due to
tool bending under pressure, but this is of little moment for
roughing operations.
[0005] Conditions for finish machining are quite different. A
larger number of teeth will produce a smoother finish, and as only
small quantities of material are removed, little space is needed
between teeth for chip clearance. Accuracy of cut is essential for
finishing operations, and therefor a large core diameter is
desirable to provide the necessary tool rigidity to produce smooth
and accurate surfaces. In choosing an appropriate core diameter,
there is always a need to balance the requirements of chip
clearance and coolant access on the one hand, which call for a
small core diameter, and the demand for tool rigidity and break
resistance which require a large core diameter.
[0006] According to the recommendation of The Cincinnati Milling
Machine Co., no more than two teeth at a time should be engaged in
a cut. This rule corresponds well with our previous remarks. During
roughing fewer teeth are preferred as the cut is deep; during
finishing more teeth are desirable as the cut is shallow.
[0007] There are further differences between roughing and finishing
tools. The ideal tooth helix angle of an end-mill is partly
dependent on the number of teeth. A roughing cutter having few
teeth (2-3) requires a large helix angle (about 25.degree.) to
reduce vibration. However a finishing cutter having more closely
spaced teeth will produce a better finish with a more moderate
helix angle; 10.degree. is usual.
[0008] For these reasons the tool should be changed after
completing the roughing cut and before starting the finishing
operation and changed again for the roughing operation on the next
workpiece. This is tiresome when done by hand, and still time
consuming even when carried out by an automatic machine. The
alternative is to complete all roughing cuts on all the workpieces,
and then carry out the finish machining on the whole batch. This
method however involves clamping and unclamping each workpiece, and
aside from the time needed for this, there is greater risk of
inaccuracy as a result of the workpieces not being clamped with the
same force each time, or as a result of a chip lodged between the
workpiece and a locating surface of the fixture or machine vice or
table.
[0009] If the required slot does not reach an outer edge, then the
first operation is drilling a hole to allow entry for the end-mill.
Many end-mills are provided with cutting teeth at the end face of
the tool, and it is possible to use such an end-mill for drilling.
However such operation requires high pressure, machining time is
extended and the hole produced could be oversize or even off its
intended position. A drill can be used to produce the hole, but of
course this involves more changeover time. After the hole is
drilled, the slot is rough machined and then finish machined as
described above.
[0010] In U.S. Pat. No. 4,411,563 Moon discloses an end mill
provided more than one set of cutting teeth for the purpose of
forming a plurality of steps at the closed extremity of a bored
hole. Although the proposed cutting tool will carry out several
machining tasks, there is no separate provision for rough and
finish machining.
[0011] The same remark applies to the double diameter boring tool
disclosed by Ashbaugh et al. in U.S. Pat. No. 4,793,745. The tool
produces a bore with a stepped diameter at its closed end.
OBJECTS OF THE INVENTION
[0012] It is therefore one of the objects of the present invention
to obviate the disadvantages of prior art cutting tools and to
provide an end mill which can be used for several needed different
machining operations in a workpiece that is thin relative to the
cutter tool diameter.
[0013] It is a further object of the present invention to save most
of the time needed for cutter changing by use of a multi-purpose
tool which executes different tasks in response to movement of the
work table or the cutter spindle.
SUMMARY OF THE INVENTION
[0014] The present invention achieves the above objects by
providing a multi-purpose end-mill particularly useful for closed
contour machining and usable for at least rough machining and
finish machining, comprising a cylindrical shank portion to be
gripped in a machine tool, said shank portion being connected to a
first cutting portion comprising a core supporting a plurality of
spaced-apart cutting teeth for a first type of machining, said
first cutting portion being connected to a second cutting portion
provided with a plurality of spaced-apart cutting teeth for a
second type of machining.
[0015] In a preferred embodiment of the present invention there is
provided a multi-purpose end-mill wherein said first type of
machining is finishing, and said second type of machining is
roughing.
[0016] In a most preferred embodiment of the present invention
there is provided a multi-purpose end-mill further provided with a
drill-like pointed cutting tip.
[0017] Yet further embodiments of the invention will be described
hereinafter.
[0018] The cutter of the present invention can used for machining
most metals, including stainless steel and high temperature alloys
such as Inconel 718 and Rene 41. As with prior-art milling cutters,
tooth clearance angle is about 4 degrees for hard materials, 6
degrees for softer metals and about 11 degrees for easy-to-machine
materials. Rake angles (for a high speed steel cutter) are about 10
degrees for machining hard materials and up to 25 degrees for
magnesium, aluminium and plastics.
[0019] It will be understood that, as with prior art cutters, the
present tool, typically made of high speed steel, can be made
partly of tungsten carbide where production quantities justify the
cost. Also, coolant passages can be provided in the tool, as is
sometimes found on prior art cutters.
SHORT DESCRIPTION OF THE DRAWINGS
[0020] The invention will now be described further with reference
to the accompanying drawings, which represent by example preferred
embodiments of the invention. Structural details are shown only as
far as necessary for a fundamental understanding thereof. The
described examples, together with the drawings, will make apparent
to those skilled in the art how further forms of the invention may
be realized.
[0021] In the drawings:
[0022] FIG. 1 is a perspective view of a preferred embodiment of
the end mill according to the invention;
[0023] FIG. 2 is an elevational view of an embodiment wherein the
tooth helix angle is different for each part of the cutter;
[0024] FIG. 3 is a partly sectioned elevational view of an
embodiment having a parabolically shaped core;
[0025] FIG. 4 is similar to FIG. 2, with the addition of a drill
point;
[0026] FIG. 5 is a perspective view of a workpiece produced by an
end mill of the type seen in FIG. 2; and
[0027] FIG. 6 is a view of a perspective view of a workpiece
produced by an end mill of the type seen in FIG. 4
DETAILED DESCRIPTION OF THE INVENTION
[0028] There is seen in FIG. 1 a multi-purpose end-mill 10
particularly useful for open contour machining, for example
producing a workpiece of the type seen in FIG. 5. The end mill 10
is suitable for both rough machining and finish machining.
[0029] A cylindrical shank portion 12 is arranged to be gripped in
a machine tool (not shown), such as a router or a milling machine,
and in some types of work even a lathe or drilling machine.
[0030] The shank portion 12 is connected to a first cutting portion
14 comprising a core 16 supporting a plurality of spaced-apart
cutting teeth 18 for a first type of machining.
[0031] The first cutting portion 14 is connected to a second
cutting portion 20 provided with a plurality of spaced-apart
cutting teeth 22 for a second type of machining.
[0032] Advantageously from considerations of core support diameter,
the first type of machining is finishing, and the second type of
machining is roughing. This is the arrangement in the shown
embodiment. However, if special considerations so warrant, this
order can be reversed.
[0033] Preferably the first cutting portion 14, which is the
finishing portion has a larger number of teeth than the second
cutting portion 20 which is the roughing portion. Conveniently the
finishing portion 14 has double the number of teeth, for example 4
in the present embodiment, than the roughing portion 20 which has 2
teeth 22.
[0034] If a vertical axis milling machine is being used, movement
in the Z axis to change between roughing and finishing can be
accomplished by raising/lowering the work table, or it may be more
convenient to raise/lower the cutter spindle.
[0035] If a horizontal axis milling machine is being used, the
machine table is moved in the Y axis to change between roughing and
finishing.
[0036] With reference to the rest of the figures, similar reference
numerals have been used to identify similar parts.
[0037] FIG. 2 illustrates a multi-purpose end-mill 24 similar to 10
seen in the previous figure. However the finishing portion 26 has a
smaller helix angle than the roughing portion 28. Tooth helix angle
of an end-mill is partly dependent on the number of teeth; the
following values are however typical. The roughing portion 28 has a
tooth helix angle of about 25.degree. to reduce vibration. The
finishing portion 26 has a more moderate helix angle of about
10.degree. to produce a smooth finish.
[0038] Seen in FIG. 3 is a multi-purpose end-mill 30 wherein the
core 31 diameter, seen shaded, of the end-mill varies parabolically
along the axial length, the larger diameter being located near the
shank 32 and the smaller diameter being located near the tool tip
34. This form is ideal for resisting the bending moment in an
end-loaded cantilever beam, a model approximately representing the
bending stress on the end mill during use.
[0039] Referring now to FIG. 4, there is depicted a multi-purpose
end-mill 36 further provided with a drill-like pointed cutting tip
38. The tip 38 enables quick and accurate drilling of a hole at any
desired point (usually an end point) of a profile path to be
milled. The hole is needed to allow cutter access for rough milling
of a slot 40 of the type seen in FIG. 6.
[0040] In the shown embodiment, the number (2) of cutting teeth 42
at the pointed cutting tip 38 corresponds to the number (2) of
teeth 44 in the second cutting portion 46. The advantage therein is
that the tip cutting edges 42 are well supported and that there are
unobstructed paths for chip clearance between the teeth 44.
[0041] FIG. 5 shows a machined workpiece 48 having one edge
machined as a concave curve 50 and having a slot 52 meeting the
curve 50. Both the slot 52 and the curve 50 have been rough and
finish machined by the multi-purpose end-mill 24 in FIG. 2.
[0042] FIG. 6 illustrates a machined workpiece 54 having one edge
machined as a concave curve 56. The closed path slot 40 required
three machining operations--drilling, rough machining and
finishing. All machining was completed by use of the multi-purpose
end-mill 36 provided with a drill-like pointed cutting tip 38 seen
in FIG. 4, without changing the tool.
[0043] The scope of the described invention is intended to include
all embodiments coming within the meaning of the following claims.
The foregoing examples illustrate useful forms of the invention,
but are not to be considered as limiting its scope, as those
skilled in the art will readily be aware that additional variants
and modifications of the invention can be formulated without
departing from the meaning of the following claims.
* * * * *