Cutters – for shaping – Rotary cutting tool – Face or end mill
Reexamination Certificate
1999-12-14
2001-05-22
Wellington, A. L. (Department: 3722)
Cutters, for shaping
Rotary cutting tool
Face or end mill
C407S063000, C408S230000, C408S067000
Reexamination Certificate
active
06234725
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cutting tool, and, more specifically, to a rotary milling cutting tool particularly adapted for cutting an expanded synthetic resinous material such as a Styrofoam plastic.
2. State of the Prior Art
As set forth in U.S. Pat. No. 5,429,460 issued in the name of the present inventor, expanded plastic forms are typically hand cut to shape from cast starting blocks of material. A larger starting block of the material is conveniently fabricated by laminating together two or more cast blocks. When a typical hand tool, saw or a grinding-type cutter is used to profile cut the block or to dress the outside surface, a relatively rough finish surface results, primarily from the cellular or bead nature of the foam or expanded plastic material which cause beads or cells to pull away from the stock block being machined.
The aforementioned U.S. Pat. No. 5,429,460 sets forth the details of a machine for cutting expanded plastic work pieces. The basic parameters of the cutting tool are also disclosed which include a rotary cutter having a plurality of generally radially extending openings which fluidly communicate with the axial bore through the cutter. A source of vacuum in the machine entrains cutting material debris in air for evacuating through the radial openings and axial bore.
U.S. Pat. No. 5,626,444, also issued in the name of the present inventor, discloses a rotary cutting tool including features described in the aforementioned patent. This patent also defines the tool as having intersecting cutters disposed at the intersections of right-hand and left-hand flutes in the tool shank which creates components of force in opposite directions along the axis of the tool. In addition, successive axial rows of cutters will overlap diametrical cutting paths alternating between cutters on the leading edges of a right-hand and left-hand helical flute. These oscillating cutting forces in combination with instant evacuation of the material being removed from the workpiece produces a clean, fine, finished work surface.
However, it would still be desirable to provide an improved rotary cutting tool of the kind disclosed in the aforementioned patent which has greater cutting efficiency, particularly at the lead end of the tool in the bottom of a cut hole or bore. It would also be desirable to provide a rotary cutting tool of the aforementioned kind which can be easily inserted into a hole without excess cut material buildup on the tool or below the leading edge of the tool.
SUMMARY OF THE INVENTION
In its basic form, the cutting tool has a longitudinally extending cylindrical shank with an axially extending evacuation bore. Individual cutters are attached to or are an integral part of the shank, and generally radially extending ports pass air entrained with chip or material debris from the cutting flutes to the evacuation bore during the cutting-machining of a workpiece.
In one preferred embodiment of the invention, right-hand, longitudinally extending helical flute grooving and left-hand longitudinally extending helical flute grooving is formed at an angle of 30-60° to the axis of the cylindrical body of the tool shank. An arrowhead shaped cutting flute or intersecting cutters is resultant at the plurality of intersections formed by these right-hand and left-hand helical flute groovings. Also preferably, a radial relief angle and a radial clearance angle are introduced across the top periphery of each flutes land.
The right-hand and left-hand helical flute groovings extend from a mounting flange at one end of the tool shank toward the opposite or lead end of the shank. The right-hand helical grooves extend continuously to the lead end. However, the left-hand helical flute groovings extend from the mounting flange to an end spaced from the lead end of the tool shank.
With this arrangement of intersecting cutters along right-hand and left-hand flutes there will be components of force in opposite directions along the axis of the tool, and that successive axial rows of cutters will overlap diametrical cutting paths alternating between cutters on the leading edges of a right-hand and a left-hand helical flute. These oscillating cutting forces in combination with instant evacuation of the material being removed from the workpiece produces a clean, fine finished work surface.
The elimination of the left-hand flute for a spaced portion extending from the lead end of the tool shank, will remove the opposed component of force along this portion of the tool shank, which is more than compensated for, since the long length of the tool shank provides sufficient opposing forces by the left-hand and right-hand helical flutes to balance the cutting forces applied by the tool shank to the workpiece.
Specifically, the elimination of the left-hand flutes at the end portion of the tool shank extending from the lead end of the tool shank simplify the insertion of the tool shank into a hole while minimizing clogging of the lead end or the buildup of cut material on or adjacent to the lead end of the tool shank. In addition, the provision of only right-hand flutes at the lead end portion of the shank makes the removal of cut material in this portion of the cutting surface of the workpiece more efficient as there will no longer be a component of downward force exerted on the workpiece at the lead end of the tool shank.
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Ergenbright Erica
Wellington A. L.
Young & Basile PC
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