Patent Application
20070237590
This invention relates to a rotary tool for performing a plurality of operations on a workpiece and more particularly to a rotary drill of the type having a unitary shank adapted to fit into the chuck of an electric drill, a drill bit and a frusto conical file between the shank and drill bit all of which are disposed along a common longitudinal axis.
Rotary tools for performing a plurality of operations on a workpiece have been known for many years. For example, a U.S. Pat. No. 3,346,894 of Lemelson entitled, “Apparatus For Controlling Rotary and Longitudinal Movements Of A Combination Tool Carrying Spindle,” discloses a combination tool including a drill and a further portion for performing a secondary operation on a workpiece during or immediately following the cutting of a hole in the workpiece with the drill. As disclosed, the rotary drill includes a twist drill connected to a tapered head. The tapered head is connected to a shank and includes a plurality of replaceable blades.
A more recent U.S. Pat. No. 5,282,705 of Shiga et al. is entitled “Burnishing Drill.” The Shiga et al. patent discloses a cylindrical shank and a drill body connected to the shank. Drilling edges, reaming faces and reaming edges are formed on a first reduced diameter portion, a second reduced diameter portion and a third reduced diameter portion located at a foremost end of the drill body respectively. The reaming faces which are located axially at rearward positions of the drilling edges and the reaming edges extend radially outward from the foremost end of the drill and incline axially in the rearward direction with respect to the rotational direction. Since an inner surface of the hole is drilled and reamed by the drilling edges and the reaming edges can be further smoothed by the reaming faces, the surface roughness of the finished hole can be improved.
Notwithstanding the above, it is presently believed that there may be a commercial market for an improved rotary drill in accordance with the present invention. There should be a commercial market for such tools since they offer improved cutting by a frusto conical file which is durable and which provides an improved cutting edge over an extended period of time. Further, the rotary tools in accordance with the present invention can be manufactured with different degrees of coarseness for different purposes and at a competitive price.
In addition, the rotary tools in accordance with the present invention are made of a hard steel and have a high resistance to breakage and are capable of maintaining a sharp cutting edge and are resistant to fracture. Further, it is presently believed that the composition of a rotary tool in accordance with the present invention can be adjusted to optimize the performance of the tool with respect to the composition of the workpiece.
In essence, the present invention contemplates a one-piece or unitary rotary tool for performing a plurality of operations on a workpiece. The rotary tool or drill includes an integral hardened steel shank adapted to fit into a chuck of a manual or preferably an electric drill for rotation thereby. The tool also includes an integral drill bit and a frusto conical file between the shank and the drill bit all of which are disposed on a common longitudinal axis. The frusto conical file includes an outer peripheral surface (including a plurality of teeth) which form or define an angle of between about 15° and 55° with respect to the longitudinal axis of the tool. In addition, the composition of the steel includes from about 0.45 weight percent to about 0.65 weight percent of carbon in order to increase the strength of the tool. The composition also includes between about 2.25 percent silicon and about 0.4 percent to about 1.4 percent by weight molybdenum. The latter of which increases the hardness. In addition, the composition includes between about 1.5 percent by weight to about 3.25 percent by weight chrome for increasing the friction resistance of the tool. Further, the composition includes less than 0.45 weight percent of sulfur and phosphorous which would otherwise contribute to the breakage of the tool. It is also contemplated that small amounts of less than about one weight percent each of nickel, tungsten and cobalt may be included as will be well understood by persons of ordinary skill in the art of tool making metallurgy. Such metals may improve the tools ability to withstand higher temperatures and provide improved cutting. In addition, the steel compositions are preferably hardened by heat treatment at a temperature of between about 1,330° F. to about 1,350° F. In a preferred embodiment of the present invention the frusto conical file includes a plurality of crowned teeth about its periphery and wherein each of the plurality of teeth have a front cutting side and a back side and in which each tooth includes a plurality of sharp serrations extending longitudinal of each tooth formed on the backside of the tooth adjacent to the cutting edge.
The invention will now be described in connection with the accompanying drawings wherein like references numbers will be used to define like parts.
A one-piece rotary tool 10 for performing a plurality of operations on a workpiece is illustrated in
As shown in
A second embodiment of the invention is illustrated in
An important feature in the present invention resides in the use of a frusto conical file as opposed to a frusto conical element which includes abrasive media or removable blades attached thereon. A preferred form of a file as used in the present invention is illustrated in
In the preferred embodiment of the invention the rotary drill comprises a unitary or one-piece hardened steel shank which is adapted to fit into the chuck of an electric drill. The tool also includes a drill bit and a frustoconical file disposed between the shank and drill bit along a common longitudinal axis. In this embodiment of the invention, the frustoconical file includes an outer periphery that defines an angle of 35° or about 35° with respect to the common longitudinal axis of the tool. In this embodiment the composition of the steel tool includes about 0.55% by weight carbon, about 2.25% by weight silicon, 0.9% by weight molybdenum, 2.4% by weight chrome and less than 0.45% by weight sulphur and phosphorous and wherein the frustoconical file includes a plurality of crowned teeth about its periphery. In addition, each of the plurality of teeth have a front cutting side and a backside and each tooth includes a plurality of sharp serrations extending longitudinally of each tooth and formed on the backside of each tooth adjacent to cutting edge thereof.
As shown in
Another embodiment of the invention is illustrated in
Further embodiments of the invention are shown more clearly in
TABLE
In addition, it also contemplated that the rotary tools in accordance with the present invention may be provided in sets of drills with different size and shaped file portions and different size drill bits. Thus, the use of a two-piece structure allows the use of a particular size and shaped file portion with different drill bits for different applications. For example, different shaped file portions 51, 51 prime and 51 double-prime are illustrated in
It is also contemplated that a drill bit may be replaced by a removable screw that may be left in the work piece. In this application, the screw may be threaded into the file portion XX or placed therein with a crosscut or slot with a Philips head or regular screw head which is magnetized so that the screw is held in place.
While the invention has been described in connection with its preferred embodiments, it should be recognized that changes and modifications may be made therein without departing from the scope of the appended claims.
