Cutters – for shaping – Rotary cutting tool – Including holder having seat for inserted tool
Reexamination Certificate
1996-12-21
2001-04-17
Tsai, Henry (Department: 3722)
Cutters, for shaping
Rotary cutting tool
Including holder having seat for inserted tool
C407S043000, C407S046000, C407S053000, C407S051000
Reexamination Certificate
active
06217262
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a high speed milling tool for deburring and edge radiusing of machine parts.
BACKGROUND INFORMATION
Present cutters available for deburring and edge radiusing are standard concave radius tools. These cutters use multiple concave shaped cutter surfaces. One prior art embodiment uses multiple inserts having a concave shaped cutter area as shown in FIG.
1
. The inserts
1
can be either integral or detachable to the tool
7
and each insert cuts the same surface area on the machine part. These tools work satisfactorily with low rotation per minute (rpm) and low feedrate applications. The feedrate is the relative movement of the tool in the direction of the part axis (inches/minute). The detachable inserts are held on the tool
7
by a set screw
3
or other suitable fastener. A concave shaped cutter area is shown at
9
. The detachable inserts are held on the tool
2
by a set screw
3
or other suitable fastener. A concave shaped cutter area
9
in shown at
4
.
FIG. 2
shows a schematic of a prior art insert
1
with a concave shaped cutter area overlapping the top edge of a machine part
6
having top and bottom edges. Standard concave radius cutters have a large contact area
4
with the part
6
resulting in a sudden and dramatic increase in cutter forces at high rpm's and feedrates, causing the part and cutter to deflect from each other. Their use in high speed milling applications causes deflection and springback between the part and the tool resulting in excessive chatter and unacceptable part surface finish. The chips resulting from a standard concave radius cutter curl then split also producing unacceptable part surface finish. As the edge of the part becomes thinner or the flange gets longer, the amount of chatter or deflection between the part and tool may increase. The feedrate is dependent upon the rigidity of the tool which in turn depends upon its length to diameter ratio. For instance, a tool having a 7:1 length to diameter ratio would require a feedrate of less than about 8 inches per minute on aluminum or in applications where the surface quality is not important. Another limitation of this tool is an application requiring long reach or set length to the cutter surface. Here, the tool becomes less rigid providing less support in high rpm applications.
Machine parts can also be deburred and edge radiused using electric or air powered hand tools. These tools include rotary files and rotary sanders sometimes operating at faster feedrates than using standard concave radius cutters. Rotating files are used to round or radius a parts edge. Rotating sanders use either cylinders or disks to smooth part surfaces. Rotary buffers are used to produce a smooth finish. All hand tools have the disadvantage of potentially undercutting or unintentionally removing part material. Hand tools can also have the disadvantage of limited access to part features that require long reach including edges and ledges.
Previously, it was more cost effective to debur or radius edges by hand due to excessive machine costs. More recently, the availability of high speed machining allowing speeds of at least 10,000 rpm has become economically competitive with hand tools.
SUMMARY OF THE INVENTION
The invention features a milling tool employing a plurality of cutter inserts having corresponding edges whereby each edge mills only a portion of the part radius. This requires a full revolution of the tool to make a complete cut producing a faceted approximation to the cut radius.
Another feature of the invention is to offer significant improvement in part feedrate in applications requiring longer reach or set length.
Still another feature of the invention is to provide a milling tool having a top milling radius cutter.
Still another feature of the invention is to provide a milling tool having a bottom milling radius cutter.
Still another feature of the invention is to provide a milling tool having a top and bottom milling radius cutter.
These and other advantages and features will become more apparent from the detailed description of the invention that follows.
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patent: 5704736 (1998-01-01), Giannetti
patent: 0 620 070 A1 (1993-04-01), None
Nelson Lawrence W.
Tsai Henry
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