Patent Application
20090155007
This invention relates to the field of rotary tool bits and more particularly to bits for hand-held rotary tools.
Hand-held rotary tools are widely used by many people, including drywallers, professional remodelers, tile installers, homeowners, and artists. These rotary tools typically include an outer housing designed to be easily held within a human hand. The housing retains an electric motor which is operable to drive a rotatable collet or chuck of the rotary tool. An accessory may be releasably coupled with the collet thereby enabling the rotary tool to rotatably drive the accessory.
The widespread use of Hand-held rotary tools is a result, in part, of the wide variety of accessories that may be used with the tools. The accessories include various cutting bits, cut-off wheels, polishing wheels, grinding wheels, and sanding discs. Cutting accessories may further be specifically designed for the particular type of material that is to be cut. For example, U.S. Pat. No. 6,758,639 assigned to Credo Technology Corporation discloses a bit that is designed for use with drywall.
To cut sheetrock or drywall, a spiral bit must be capable of first axially penetrating the drywall panel, and then making a lateral cut in the panel. The drywall bit can be used first to drill through the panel directly adjacent to an electrical outlet box, for instance. The bit is then conveyed in a direction perpendicular to the length of the bit, following the contour of the outlet box. The rotary tool is then manipulated to completely encircle the outlet box to cut the preferred opening in the drywall panel. In order to address these specific needs, the '639 patent discloses a bit with a single helical flute having a particular geometry. In one embodiment, the flute defines a cutting edge within a specific range of helix angles relative to the longitudinal axis of the bit. In another feature, the cutting edge of the flute is situated at a particular rake angle relative to the axis of the bit and the fluted portion of the bit has a web thickness that is based upon the cutting diameter of the bit.
In bits such as the bit disclosed in the '639 patent, cutting edges are defined by the junction of a flute and a land. The cutting edges penetrate the material being shaped and carve out a wedge of the material. While this mechanism is useful in relatively soft, ductile materials, it is not effective in harder and/or more brittle materials. For example, it is exceedingly difficult to cut through materials such as granite or hard crystalline material wherein the hardness of the material being cut approaches the hardness of the cutting bit. Likewise, it is difficult to achieve a cut efficiently and effectively when working with hard and brittle materials such as various types of tile and glass.
Typically, two types of drill bits, the spear point drill bit and the core drill bit, are utilized when cutting ceramics materials. The spear point drill is shaped much like a spear point. The core drill has a hollow core with a cylindrical cutting edge surrounding the core. These bits may be modified to include a diamond abrasive on the cutting edge of the bit. While these bits are useful in boring operations such as making a hole through a material, neither bit can be used to cut along a line in the plane of the material such as to provide cutout areas in a tile.
What is needed is a configuration for an accessory that reduces the problems associated with the cutting of hard or brittle materials such as floor and wall tile.
In accordance with one embodiment of the present invention, there is provided a rotary tool accessory for cutting hard, brittle material, includes a shaft for coupling with a rotary tool, a work portion extending outwardly from the longitudinal axis of the shaft, the work portion including a cylindrical portion and a spherical portion, a nickel based bonding material affixed to the work portion, and a plurality of abrasive particles extending outwardly of the bonding material.
In accordance with another embodiment of the present invention, there is provided a method of drilling a hole in a hard surface. This method includes, spin the accessory at the desired RPM, contact the hard surface with the spherical tip of the rotating accessory to initiate a bore, and rotate the rotary tool in a conical with axis of the tool inclined an angle of at least 15° from the surface normal and with the accessory pivoting at the spherical tip. Keep rotating the tool in this manner until the accessory drill through the material.
In accordance with another embodiment of the present invention, there is provided a method of making cut-outs in a hard material. This method includes, spin the accessory at the desired RPM, keep cylindrical portion of the accessory in contact of the material being cut, reciprocate the bit along the accessory axial direction, and push the accessory along the direction normal to the axis of the accessory to remove material. Keep moving tool in this manner to make cut-outs of any shape and size.
In yet another embodiment, a hand held rotary tool accessory for shaping hard, brittle material includes a rotary tool accessory for cutting hard, brittle material, comprising a steel shaft for coupling with a rotary tool, a work portion extending outwardly from the longitudinal axis of the shaft, the work portion including a first functional area and a second functional area, a nickel based bonding material affixed to the first functional area and the second functional area, a plurality of abrasive particles extruding outwardly of the bonding material on the first functional area and the second functional area.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the invention is thereby intended. It is further understood that the present invention includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the invention as would normally occur to one skilled in the art to which this invention pertains.
As shown in
The functional area 110 and the functional area 112 are coated with a bonding material 114 which is shown more clearly in
The abrasive particles 116 located on the functional area 110 include an embedded portion 118 and an extruding portion 120. The amount of bonding material 114 that is applied to the functional area 110 is controlled to generate the desired binding strength. In this embodiment, the amount of bonding material 114 is controlled to generate a protrusion of between about 30 percent and 55 percent for the abrasive particles 116 located on the cylindrically shaped functional area 110. Thus, while some of the abrasive particles 116 may not be within the desired range, most of the abrasive particles 116 will exhibit an extruding portion 120 that is between about 30 percent and 55 percent of the respective abrasive particle 116.
In addition to controlling the amount of bonding material 114, the amount of abrasive particles 116 may be controlled to provide the desired coverage. In the embodiment of
Operation of the bit 104 is explained with reference to
The rotary tool 100, which may be energized either prior to contacting the target area 130 or after the bit 104 has contacted the target area 130, is then swiveled about the axis 134 in a circular motion as indicated by the arrow 136. The rotary tool 100 may be swiveled in a clockwise direction, a counter-clockwise direction or a combination. In this manner, the grits on the tip of the bit removes material from the target area 130. Accordingly, the swiveling of the rotary tool 100 about the functional area 112 of the bit 104 generates a bore 140 with sloped sidewalls as shown in
Alternatively, the bit 104 may be pivoted within a single plane thereby generating an elongated bore with two straight sides and two sloped end walls. Continued movement in a single direction, however, generates excessive heat. Accordingly, for linear cuts such as the cut 144 in
The bore 140 at the upper portion of the work piece 132 is wider than the bit 104. Accordingly, dust and debris may exit the bore 140 as the bore 140 is being machined. Additionally, the gap between the bit 104 and the bore 140 allows coolant fluid, such as air or water, to cool the portion of the bit 104 that is not in contact with the work piece 132. Debris removal and/or cooling may be further enhanced by movement of the bit 104 inwardly and outwardly of the bore 140.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the invention are desired to be protected.
