Background of the Invention
1. Technical Field
The subject invention relates to a cutting insert and, more particularly, to a cutting insert of the type for cutting rounded corners in a workpiece.
2. Description of the Prior Art
Numerous cutting inserts are known in the prior art, each having a specific geometrical configuration for performing a specific cutting or milling operation. A large group of cutting tools are dedicated to drilling holes, e.g., drill bits. One such tool is shown in U.S. Pat. No. 4,568,227 to Hogg to include a pointed cutting tip with asymmetrical flutes on either side.
However, there are a wide variety of cutting inserts for cutting convex rounded corners and the subject invention provides an improved geometrical configuration for such a cutting insert.
Summary of the Invention and Advantages
A cutting insert comprising first and second oppositely facing, parallel faces interconnected by bottom, side and top walls perpendicular to the faces with the side walls being parallel to one another. The cutting insert has a center axis centrally disposed between the walls and first and second flutes disposed on opposite sides of the center axis. A first of the flutes extends in an arc from the top wall to one of the side walls and a second of the flutes extends in an arc from the top wall to the other of the side walls. The first flute presents a flute surface extending in the arc and disposed at an angle sloping downwardly from the first face to the second face along the entire arc thereof to define intersections with the top wall and one of the side walls respectively which are disposed at an angle other than 90.degree. relative to the faces. The second flute likewise presents a flute surface extending in the arc and disposed at an angle sloping downwardly from the second face to the first face along the entire arc thereof to define intersections with the top wall and the other side wall respectively which are disposed at an angle other than 90.degree. relative to the faces.
Brief Description of the Drawings
Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
FIG. 1 is a side elevational view of the cutting insert of the subject invention mounted in a tool holder;
FIG. 2 is a view taken along line 2--2 of FIG. 1;
FIG. 3 is a view taken along line 3--3 of FIG. 2;
FIG. 4 is a front elevational view of the cutting insert of the subject invention;
FIG. 5 is a view taken along line 5--5 of FIG. 4;
FIG. 6 is a view taken along line 6--6 of FIG. 4; and
FIG. 7 is a view taken along line 7--7 of FIG. 4.
Detailed Description of the Preferred Embodiment
Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a cutting tool assembly is shown in FIGS. 1 through 3 comprising an elongated tool holder or shaft 12 having an axis of rotation A and a first end defining a pocket portion 14 having a pocket 16 and a second end defining a support portion 18 for support in a machine. A cutting insert, generally indicated at 20, is disposed in the pocket 16. The elongated tool holder 12 is circular in cross section with the pocket portion 14 having a first diameter smaller than the diameter of the support portion 18.
The cutting insert 20 has first 22 and second 24 oppositely facing, parallel faces interconnected by bottom 26, side 28 and top walls 30 with the side walls 28 being parallel to one another. The cutting insert 20 has a center axis B centrally disposed between the side walls 28 and axially aligned with the axis of rotation of the tool holder 12.
The cutting insert 20 has a first 32 and second 34 flutes disposed on opposite sides of the center axis. The first flute 32 extends in an arc from the top wall 30 to one of the side walls 28 and the second flute 34 extends in an arc from the top wall 30 to the other of the side walls 28. The first flute 32 presenting a flute surface disposed at an angle sloping downwardly from the first face 22 to second face 24. In like geometry, the second flute 34 presents a flute surface disposed at an angle sloping downwardly from the second face 24 to the first face 22 whereby the flutes 32 and 34 are asymmetrical relative to the center axis. The cutting insert 20 has a hole 36 extending between the faces and a fastener 38 extends through the hole 36 and engages the tool for securing the cutting insert 20 in the pocket 16. The hole 36 is offset 0.005 inch from the axis of the fastener 38 to force the insert 20 downward into the pocket 16.
The top wall 30 lies in a plane which is perpendicular to the center axis and the side walls 28 to define non-cutting intersections 40, 42 and 44 between the top wall 30 and the faces and the flutes 32 and 34.
The flute surface of the first flute 32 slopes from the first face 22 to second face 24 at an acute angle relative to the first face 22 to define a first line intersection 42 with the top wall 30 which is disposed at an angle other than 90.degree. relative to the faces 22 and 24. The flute surface of the second flute 34 slopes in the opposite direction from the second face 24 to first face 22 at an acute angle relative to the second face 24 to define a second line intersection 44 with the top wall 30 which is disposed at an angle other than 90.degree. relative to the faces 22 and 24 and parallel to the first line intersection 42. Therefore, the line intersections 42 and 44 and the first 22 and second 24 faces define a parallelogram as viewed from the top, i.e., FIG. 5. The flute surface of the first flute 32 slopes from the first face 22 to second face 24 along the entire length of the arc thereof at an acute angle relative to the first face 22 to define a third line intersection 46 with one of the side walls 28 which is disposed at an angle other than 90.degree. relative to the faces 22 and 24. In like fashion, the flute surface of the second flute 34 slopes from the second face 24 to first face 22 along the entire length of the arc thereof at an acute angle relative to the second face 24 to define a fourth line intersection 48 with the other side wall 28 which is disposed at an angle other than 90.degree. relative to the faces 22 and 24. More specifically, and by way of example, when the distance between the side walls 28 is one and one quarter inches, the radius of the arcs of the flutes 32 and 34 is between 9/32 to 3/8 inch and the slope at the line intersections 42, 44, 46 and 48 is five degrees (5.degree.) whereas the slope at the midlength of the arcs, as illustrated in FIG. 7, is ten degrees (10.degree.). Therefore, each of the flute surfaces slopes downwardly at a greater angle at the center of the arc thereof than at the ends of the arc thereof. Also, the first, second, third and fourth intersections 42, 44, 46 and 48 are all disposed at the same predetermined angle of slope, i.e., five degrees (5.degree.).
The elongated tool holder 12 is circular in cross section with the pocket portion 14 having a first diameter smaller than the distance between the side walls 28 of the insert and a support portion 18 at the second end having a second diameter substantially the same as the distance between the side walls 28 of the insert. In the size exemplified above, the distance between the side walls 28 is one and 1.25 inches, plus or minus ten thousandths, and the diameter of the support portion 18 is between 1.2498 and 1.2495 inches. Other sizes are:
1. Mini-Series 1/2 inch diameter holder having inserts with 0.010 Rad.; 0.015 Rad.; and 0.020 and 0.025 Rads.;
2. 3/4 inch diameter holder having inserts with 1/32, 1/16, 3/32 and 1/8 Rads;
3. 1.00 inch diameter holder having inserts with 5/32, 3/16, 7/32 and 1/4 Rads;
4. 1.25 inch diameter holder shown in application; and
5. 1.50 inch diameter holder having inserts with 13/32, 7/16, 15/32 and 1/2 Rads.
To secure the insert into the pocket 16, the bottom 26 is V-shaped and the pocket 16 includes a complementary bottom engaging the V-shaped bottom 26. Also, the V-shaped bottom 26 has an included angle of 112.degree. and the edges thereof are beveled at 50 between the V-shaped bottom 26 and the faces 22 and 24.
The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.
Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described.