TECHNICAL FIELD OF INVENTION

[0001] The claimed invention relates to a rotating abrasive cutting tool for lateral cutting wherein the tip of the rotating cutting tool, used for the initial penetration prior to the primary cutting action, has a concave or hollow point such that the zero surface speed portion of the rotating cutting tool does not perform any cutting directly, and consequently does not wear out before the main cutting part of the tool.

BACKGROUND

[0002] Rotary abrasive tools for cutting and abrading can be made in a wide variety of geometric shapes by those practiced in the art of abrasive tool manufacture, but as the diameter of the rotating tool decreases, the surface velocity of the tool near the rotational axis approaches zero, and equals zero when the axis is reached. Abrasive tools typically need a relatively high surface speed, in comparison with so-called defined edge cutting tools (such as twist drills, endmills, toothed saw blades for example) due to the material removal mechanism of abrasive cutting tools. Abrasive cutting tools abrade a material one abrasive particle at a time, and so a finite number of abrasive impacts per unit time is required at each point of the workpiece-tool interface in order to abrade the material.

[0003] For this reason the great majority of abrasive cutting tools are designed as so-called peripheral cutting tools where the diametrical surface of the tool is the working surface rather than the end of the rotating tool. In accordance with an exemplary embodiment, the claimed invention addresses the problem of abrasive tools that are relatively long in comparison with their diameter where the end of the tool is required to cut at least a portion of the time.

[0004] One solution for penetration tools for the construction industry that is well known is to design an abrasive ring in the form of a cylindrical tool with an abrasive layer at one end. These are called "core drills" because they cut an annular hole as they penetrate into the workpiece. For a blind hole this means that once the tool is withdrawn, a core of material remains, and must thus be removed by other means. A core drill is designed to penetrate only, and cannot cut perpendicular to the axis of tool rotation, because the core of material that remains inside the tool prevents lateral cutting, even if an abrasive medium were affixed to the cylindrical surface of the tool.

[0005] One tool, described by the Switzer design patent D531,650 describes a long thin abrasive cutting tool with abrasive applied in a spiral pattern along the cutting portion of the tool. This tool is intended for lateral cuts, specifically to remove the mortar holding bricks into a masonry structure for localized brick removal or tuck pointing. The Switzer tool has a conventional point design, and as such, the very tip of the tool, having no peripheral velocity, is subject to premature wear, if the tip of the tool is asked to do any significant amount of cutting. No grinding tool is effective without relative motion between abrasive particles and workpiece material, and having no rotational velocity, the very tip is a vulnerable part of the tool. This tool would be best used by penetrating obliquely into the workpiece material in a progressive stroking type motion, to avoid overworking the tip. This is a cumbersome method, and requires a level of both skill and patience that is seldom found in construction workers and home improvement enthusiasts.

[0006] Masonry drills are generally defined as cutting edge penetration tools that drill holes either with or without percussion assistance, but have no ability to cut laterally to the axis of rotation of the drill bit, and therefore have no utility for the intended purpose of making lateral cuts.

OBJECT AND SUMMARY OF THE INVENTION

[0007] The object of the claimed invention is to make a substantial improvement in the task of lateral cutting of brittle materials such as masonry mortar, concrete, brick and similar construction materials. Although counterintuitive (i.e. having no cutting surface at all where material must be removed) at first, it turns out to be a most efficient material removal tool. In accordance with an exemplary embodiment of the claimed invention, the central portion of the abrasive cutting tool is removed entirely at the tip and extended some distance into the tool. The central portion of the workpiece material still is removed by the abrasive cutting tool of the claimed invention, despite the absence of any abrasive particles at or near to its rotational axis.

[0008] In accordance with an exemplary embodiment of the claimed invention, a rotating abrasive tool comprises a tip and a working surface. The rotating abrasive tool has a length that is substantially longer than its diameter. A center portion of the tip is concave or hollow. The rotating abrasive tool further comprises abrasive surface covering a major portion of the working surface except near a rotational axis of the rotating abrasive tool.

[0009] In accordance with an exemplary embodiment of the claimed invention, the working surface of the rotating abrasive cutting tool further comprises a tip surface and a cylindrical surface. The abrasive surface covers a major portion of both the cylindrical and tip surface of the rotating abrasive tool. In accordance with an exemplary aspect of the claimed invention, the abrasive surface comprises diamond abrasive. Preferably, the abrasive surface comprises a mixture of diamond abrasive and a ceramic or carbide abrasive.

[0010] In accordance with an exemplary embodiment of the claimed invention, the abrasive surface on the cylindrical surface of the rotating abrasive tool comprises abrasive applied in a helical pattern to simulate drill flutes.

[0011] In accordance with an exemplary embodiment of the claimed invention, the hollow center portion of the tip communicates with one or more lateral holes behind the tip to provide enhanced swarf evacuation. In accordance with an exemplary aspect of the claimed invention, the hollow center portion of the tip extends to a base of the tool to permit through-tool vacuum or coolant delivery.

[0012] In accordance with an exemplary embodiment of the claimed invention, the abrasive surface comprises abrasive affixed to the working surface of the rotating abrasive tool by at least one of the following: brazing; entrapment within an electrodeposited metal, the electrodeposited metal being at least one of the following: nickel, copper, tungsten, or alloys thereof; an autocatalytic metal deposition process using at least one of the following metals: nickel, copper, or alloys thereof; or means of compacted metal powder.

[0013] In accordance with an exemplary embodiment of the claimed invention, the tip is capable of making controlled cuts in a direction perpendicular to the rotational axis of the rotating abrasive tool.

[0014] In accordance with an exemplary embodiment of the claimed invention, the tip is operable to penetrate into a workpiece in a direction substantially parallel to the rotational axis of the rotating abrasive tool to make controlled cuts in a direction perpendicular to the rotational axis of the rotating abrasive tool.

[0015] In accordance with an exemplary embodiment of the claimed invention, a rotating abrasive tool comprises a tip and a working surface. The rotating abrasive tool has a length that is substantially longer than its diameter. The rotating abrasive tool further comprises an abrasive surface covering the working surface of the rotating abrasive tool to form a spiral abrasive pattern except near a rotational axis of the rotating abrasive tool.

[0016] Various other objects, advantages, and features of the present invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The following detailed description, given by way of example, and not intended to limit the present invention solely thereto, will best be understood in conjunction with the accompanying drawings in which like components or features in the various figures are represented by like reference numbers:

[0018] Fig. 1 shows a schematic diagram of a blind hol2 hollow tip cutter in accordance with an exemplary embodiment of the claimed invention;

[0019] Fig. 2 shows schematic diagrams of a ventilated hole hollow tip cutter in accordance with an exemplary embodiment of the claimed invention; and [0020] Figs. 3A-B show schematic diagrams of spiral coated cutting tool in accordance with an exemplary embodiment of the claimed invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] Turning now to Fig. 1, there is illustrated a schematic diagram of a cross section of the rotating cutting tool or blind hole hollow tip cutter 1000 in accordance of an exemplary embodiment of the claimed invention. The rotating cutting tool 1000 has an "abrasive crown" 1 100 with a convex face, and a central co-axial hole 1200 in the center of the rotating cutting tool 1000. The length and diameter of the rotating cutting tool 1000 is represented as "L" and "D," respectively in Fig. 1. Although the crown 1100 is exemplary shown as a full radius in cross-section in Fig. 1 , this is neither required or necessary by the claimed invention. The shape of the crown 1100 can be a partial radius, a segment of an arc, or even a series of flats approximating an arc.

[0022] Despite the lack of an abrasive cutting surface at or near the rotational axis 1030 of the rotating cutting 1000, the small nugget of workpiece material (not shown) that remains in the center of the cut when the abrasive crown 1100 penetrates during the initial penetration disintegrates (due to the extreme brittle nature of these construction materials, and the natural lateral vibration that inevitably is part of off-hand cutting) and is pulverized by the abrasive on the perimeter 1040 of the rotating cutting tool 1000. That is, the rotating cutting tool 1000 can advantageously evacuate the small nugget of workpiece from the cut. In this manner, the rotating cutting tool 1000 of the claimed invention avoids the primary mode of failure of the Switzer type of bit, thereby leading to a greatly enhanced tool life.

[0023] Turning now to Fig. 2, there is illustrated schematic diagrams of orthogonal cross sections of a rotating cutting tool or ventilated hole hollow tip cutter 2000 in accordance of an exemplary embodiment of the claimed invention. As shown in Fig. 2, the central co-axial hole 1200 in the center of the rotating cutting tool 1000 extends further down into the rotating cutting tool 2000 than in the blind hole hollow tip cutter 1000 of Fig. 1. The central co-axial hole 1200 of the ventilated hole hollow tip cutter 2000 communicates with a lateral hole 1300 in the side surface of the cutting instrument to facilitate swarf removal. Alternatively the concavity could extend the length of the rotating cutting tool 1000 to permit a through-tool vacuum system for optimum swarf removal and dust control. Such high speed tools with through-the-collet vacuum systems are not however currently commercially available. Although the ventilated hollow tip cutter 2000 penetrated the workpiece material more easily than the blind hole hollow tip cutter 1000, the improvement in cutting speed was relatively small.

[0024] Turning now to Figs. 3A and 3B, there are shown schematic diagrams of spiral coated cutting tools 3000 in accordance with an exemplary embodiment of the claimed invention. The spiral coated cutting tool 3000 has a plurality of abrasive coated surface area 3100 and non-coated surface area 3200 free of abrasive. It is appreciated that any known method of abrasive bonding or attachment can be used to manufacture the rotating cutting tool of the claimed invention, such as by brazing or electroplating. Powder metallurgical methods are also possible if the rotating cutting tool can be manufactured to tough, durable and aggressive standards required by such tools.

[0025] Tools used for cutting concrete use diamond abrasive, due to the extreme hardness and durability of diamond as an abrasive. When cutting into masonry walls however, the cutting tool can sometimes encounter steel brick ties, or other steel anchors of various designs and purposes. Diamond as an abrasive, despite its very high hardness, is a poor choice for cutting steel alloys, due to the well known affinity of ferrous alloys for carbon (diamond is an allotrope of carbon). Since this off-hand operation is performed dry, the heat of grinding destroys the diamond abrasive very rapidly if a steel anchor is encountered by the cutting tool during the cut, if diamond alone is chosen as the abrasive. Although ceramic or carbide abrasive grains lack the ultimate hardness of diamond, most also lack the propensity to dissolve in ferrous alloys, and as such are preferred as abrasives for cutting steel. Although seemingly counter-intuitive, in accordance with an exemplary embodiment of the claimed invention, the claimed rotating cutting tool 1000, 2000, 3000 utilizes a softer ceramic or carbide abrasive to protect the harder diamond abrasive to cut through mortar and steel combinations. The use of a portion of ceramic abrasive (such as tungsten carbide or aluminum oxide, for example) mixed in with the diamond leads to longer life than a tool made with diamond abrasive alone. EXAMPLES

[0026] In accordance with an exemplary embodiment of the claimed invention, several rotating cutting tools were fabricated by vacuum brazing of abrasive grains to air- hardening tool steel alloy shanks of ¹ A" diameter with various tip designs. These rotating cutting tools of the claimed invention were used to plunge holes into various construction materials such as fired clay brick and poured concrete. The braze alloy used in this exemplary embodiment was a commercially widespread alloy comprising elemental copper powder of -325 US mesh (from US Bronze Corp., Flemington New Jersey), tin powder of - 325 US mesh (from US Bronze Corp., Flemington New Jersey) and titanium hydride powder of -230 US mesh from Sumitomo Corporation of Japan. These powders were mixed in the proportions 77/23/10 respectively, and vacuum brazed at a temperature between 870 and 890 Celsius.

[0027] For conventional tip tools both bull nose spherical and 120 degree conical tips were tested, for comparison with the claimed hollow tip cutters. The diamond abrasive used was ABS-3 (from Saint Gobain Corp, Oliphant Pennsylvania) in the grit size of 25/30 US mesh. Reclaimed crushed WC (from Materials Specialties Scandinavia, Virginia Beach Virginia) in 30/40 mesh was used for tests that utilized a mixed abrasive type. The air hardening tool steel was purchased as drill rod from MSC, Manhattan, New York.

[0028] The tools were tested using a high speed miniature router, manufactured by Roto-Zip, (available from Home Depot or other home improvement stores) and capable of no-load speeds of up to 30,000 RPM.

[0029] The standard tool, made according to the Switzer patent is effective at lateral cutting in both brick and poured concrete, but when used purely as a penetration tool, loss of diamond at the tip of the tool was noted after as few as 2 holes were drilled to a depth of 3" each in concrete, and 3 holes in red fired clay bricks. Similar results were obtained whether the tip were rounded or conical, though the conical tip may have worn slightly faster.

[0030] The hollow point tools of the claimed invention, by contrast, with a blind hole 3/8" deep and 0.100" diameter (as measured before the coating of diamond was applied) using identical diamonds as the Switzer bits on the tip, were able to drill 10 holes in both brick and poured concrete with minimal wear on the cutting tip or diminution of cutting speed. Lateral cutting was the same as with the Switzer bits, that is to say extremely effective.

[0031] The testing therefore demonstrated that the hollow point tool of the claimed invention was able to penetrate into concrete and brick for much longer distances than a solid tip tool without wearing out prematurely, this despite having no cutting surface at the rotational center of the cutting tool.

[0032] While the present invention has been particularly described with respect to the illustrated embodiments, it will be appreciated that various alterations, modifications and adaptations may be made based on the present disclosure, and are intended to be within the scope of the present invention. It is appreciated that although the invention has been described with respect to derivative securities with any number of components, the disclosed invention may be similarly applied to derivative securities with one or more components. It is intended that the appended claims be interpreted as including the embodiments discussed above, the various alternatives that have been described, and all equivalents thereto.