Patent Application
20100098505
The present invention relates generally to cutting tools. More specifically, the present invention relates to an improvement in Polycrystalline Diamond (PCD) veined or Polycrystalline Cubic Boron Nitrite (PCBN) veined cutting tools.
Veined cutting tools as described in U.S. Pat. Nos. 4,713,286 and 4,762,445 provide for drills, end mills, reamers and other cutting tools with multiple cutting edges fixed to a tungsten carbide body using a sintered abrasive particulate such as diamond (PCD) or CBN. These tools have proven to be advantageous in drilling, reaming, and milling various advanced composite materials and non-ferrous materials and are now well known as cutting tools.
Generally, the high cost and delicate nature of these tools restrict them to use only where cutting conditions can be closely controlled by computer numerically controlled (CNC) machines to avoid impact, vibrations, and/or variable feed conditions that would destroy the cutting edges.
One area where such veined PCD or PCBN tools are widely used is in drilling advanced carbon fiber reinforced plastic (CFRP) composites and stackups of these materials with aluminum or titanium on CNC equipment for advanced aircraft frames. However, many areas of these planes do not allow for the use of CNC drilling equipment making portable power feed air motors the preferred method of drilling the necessary fastener holes.
Prior to this invention, the use of PCD or PCBN drills with these air motors was not considered feasible for drilling difficult materials like layers of advanced composites and titanium. Typically, these air motors use what is called a hard tooling fixture with guide bushings. PCD or PCBN drills were known to chip the sides or margins of the drill as they were guided by these bushings due to the delicate nature of the exposed PCD cutting edge.
U.S. Pat. No. 5,611,251 also teaches a method of making a PCD or PCBN drill using a brazeable PCD or PCBN blank and makes reference to other variations for brazeable PCD and PCBN drill construction using commercially available blanks from Megadiamond or Debeers.
Such cutting tool construction taught or referenced by U.S. Pat. No. 5,611,251 invariably uses low rake angles to strengthen the cutting edge and to compensate for the ready nature of these edges that tend to chip. Such art does not teach a way of preventing the chipping of the cutting edges.
In view of the limitations of prior art PCD drill bits, reamers, and milling cutting tools, the present invention was developed to address these limitations and is an improved PCD cutting tool having a shielded PCD or PCBN cutting edge.
The present invention relates generally to cutting tools. In the present invention, a PCD or PCBN cutting tool and method of manufacture is provided with a shielded cutting edge leaving only a small portion of the cutting edge exposed to engage the work material.
Such shielding prevents the delicate edges of the PCD from being damaged by bushings or the work material while still providing for additional tool life by removing the shielding material in increments as necessary to expose fresh cutting edges.
To manufacture a cutting tool with a shielded cutting edge, the vein of PCB or PCBN or any other suitable material is angled such that a shield is created for the vein by leaving a portion of the shielding material in front of the vein during the grinding processes used to form the cutting tool.
The embodiments of the present invention will be best understood by reference to the drawings. It will be readily understood that the components of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the cutting tools of the present invention, as represented in
The apparatus and method of the present invention have been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully resolved by currently available cutting tools. The present invention has wide application in machining applications as diverse as reaming automotive engine valve guides as well as drilling stackups of CFRP and titanium airframe parts. The shielding of the delicate cutting edges will open many applications where these cutting tools in the past have not stood up to the various cutting forces.
In
In one embodiment, the helix angle is preferably about 24 degrees and the rake angle 26 is preferably about 4-8 degrees positive to the central axis 28 (
The shielding 20 material is fused directly to the PCD or PCBN with an extremely strong attachment or bond to avoid being peeled back by the force of material flowing across the edge and is best attached during the Ultra High Pressure sintering process used to produce veined tools as disclosed in U.S. Pat. No. 4,713,286.
The material can be varied in the sintering process and can include a number of materials that can both protect the PCD or PCBN cutting edge 14 and provide other beneficial properties such as lower friction. In the simplest form, the shielding 20 material is the same tungsten carbide of the drill 10 used to hold the vein 12. In such cases, the shielded cutting edge 14 results from leaving a portion of the original nib material in front of the vein 12 during the grinding processes. This also has the beneficial effect of lowering the manufacturing costs by avoiding contact between the cutting edge 14 and the vein 12 of PCD or PCBN.
The scope of this invention is not limited to the above-described preferred embodiments. The terms and expressions used are terms of description and there is no intention of excluding any equivalents of the features shown and described, but it is recognized that various modifications, appreciable to one of ordinary skill, are possible within the scope of the invention claimed.
