WO2008088925A2

WO2008088925A2 - Grinding assemblies for use with handheld power tools

Info

Publication number: WO2008088925A2
Application number: PCT/US2008/050001
Authority: WO
Inventors: Dennis David Woods; Dennis Clifford Woods; Mark Tretter
Original assignee: I.T., Inc.
Priority date: 2007-01-12
Filing date: 2008-01-01
Publication date: 2008-07-24
Also published as: US20080171498A1; WO2008088925A3

Abstract

Grinding assemblies for use with handheld power tools are disclosed herein. More specifically, the assemblies disclosed herein can include a hub, disc, grinding surface and locking nut and can be used with most available handheld grinders for grinding flat surfaces.

Description

GRINDING ASSEMBLIES FOR USE WITH HANDHELD POWER TOOLS

CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims priority to U.S. Application Serial No. 11/623,051, filed on January 12, 2007, entitled "Grinding Assemblies for use with Handheld Power Tools". The disclosure of this prior application is considered part of the disclosure of this application and is hereby expressly incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

[002] The present invention generally relates to grinding assemblies and attachments for use with a handheld power tool, such as an angle grinder. In general grinding assemblies and the attachments described herein can be used to more easily smooth hard surfaces and alleviate dust build up within the power tool.

BACKGROUND

[003] In the construction and remodeling industry, after concrete foundation is laid and hardened, it is still rough and needs to be smoothed. Large grinders are generally used to smooth out rough concrete floors and working areas, see U.S. Patent No. 5,908,224, to Santos. The grinding surfaces of many grinders designed for large working surfaces are often configured such that they cannot adequately grind close to a wall or other obstruction. Users of these large grinders typically need to provide adequate clearance between the devices 's grinding surface and the wall or obstruction. This disadvantageous design leaves an unfinished or rough working surface area near the wall or obstruction. In addition, large grinders are difficult to move. They are especially difficult to move up stairways in order to smooth upper level floors. For the above reasons, it can be advantageous to utilize a smaller, handheld grinder having a flat grinding surface that is capable of accessing floors and working areas that are otherwise difficult to grind. [004] However, designs for many handheld grinder attachments are problematic. For example, many handheld grinders have a rotating grinding surface attached by a nut that protrudes past the plane of the grinding surface. This design is disadvantageous for grinding flat surfaces, such as floors, because the grinding surface of the grinder must be used at an angle. If a user laid the grinding surface flat against the working surface, the protruding nut would be grinded down. Grinding a flat surface at an angle with a handheld grinder is also problematic as it will cause the rotating grinding surface and/or underlying disc pad to warp. Accordingly, this technique places excessive stress on the grinding surface quickly and requires the user to replace the grinding surface frequently.

[005] Further problems with current grinders is that many utilize a rubber or low-grade plastic disc pad that wears down easily, creates wobble when grinding, and also results in the user replacing the grinding surfaces frequently.

[006] Additional problems are created when the nut, grinding surface, or underlying disc pad are configured to have an opening facing the working surface that allows dust created from the grinding to enter into the rotating spindle. Minimizing the amount of dust contacting the spindle is highly desirable because the dust can quickly build up and harden, thus making it difficult to detach and attach parts to the grinder. Dust can also cause damage to the spindle.

[007] An additional problem with conventional handheld grinders and attachments is that they are susceptible to overheating because they do not have an adequate cooling system for their rotating parts. A further problem of previous grinding attachments is that they are not configured to be attached to most available handheld grinding units.

[008] Accordingly, there is a need in the art to provide grinding assemblies for handheld grinders that minimize the above problems associated with conventional grinder attachments. Accordingly, one object of the invention is to provide new and improved grinding assemblies that are durable and can be used flush against flat working surfaces. A further object of the invention is to provide grinding assemblies that minimize dust from contacting the rotating spindle. Still a further object of the invention is to provide grinding assemblies that cool the rotating parts and grinder as it rotates. Still a further object of the invention is to provide grinding assemblies that are capable of being universal, such that it can attach to most, if not all, available handheld grinders.

SUMMARY OF THE INVENTION

[009] According to certain embodiments, the teachings herein disclose grinding assemblies for handheld grinders. In certain embodiments, the grinding assemblies are configured to be used against a flat working surface, such as a floor, for example. In further embodiments, the grinding assemblies help prevent dust from contacting and collecting on the rotating spindle. In other embodiments, the grinding assemblies provided herein are configured to cool the rotating parts and the grinder as it grinds. In still further aspects, the grinding assemblies described herein can be attached to and used with most, if not all, manufactured handheld grinders.

[0010] The teachings herein are directed to grinding assemblies for attachment to a rotating spindle on a handheld power tool, and include a hub having a vertically traversing channel opening to a topside and underside of said hub and configured to attach to said rotating spindle, and wherein said underside of the hub includes a concave recess, a disc having a substantially planar topside and underside surrounding a concavo- convex frustum having an aperture and configured to conform to said concave recess on the underside of the hub, such that said aperture aligns with the underside opening of the hub, and a locking nut having a top-opening hollowed shaft connected to a base having a solid back, wherein said shaft is configured to fit through the disc aperture and the underside opening of the hub to attach to said rotating spindle such that the back of the locking nut does not protrude past the substantially planar underside of the disc. [0011] According to preferred embodiments, the grinding assemblies provided herein can further include a grinding surface configured to be attached to said disc, such as through a locking nut, for example. According to further embodiments, the hub includes a plurality of grooves around an outer surface, such as bean-shaped grooves, for example. In other more specific aspects, the grinding assemblies provided herein can include a concavo-convex frustum that includes a plurality of slots around said aperture.

[0012] In other preferred aspects said vertically traversing aperture in said hub, is partially threaded at a thread count of 11 threads per inch and is configured to screw onto a spindle having a 5/8 inch (1.6 cm) diameter. The hub can also be threaded to configure to M 14 spindles. Other preferred aspects relate to the underside of the hub having a flat outer periphery.

[0013] Further embodiments are directed to a new improved hub for attachment to a rotating spindle on a handheld power tool, having a stem connected to a base having a concave recessed underside, wherein a central aperture configured to attach to said spindle vertically traverses from a topside opening of said stem and opens to the underside of the base, and wherein said base includes a plurality of grooves on an outer surface.

[0014] In more specific embodiments, the base is shaped as a truncated cone. In further embodiments, the aperture is partially threaded, such as a thread count of 11 per inch. In other embodiments the hub can include bean-shaped grooves, for example. The hub's underside can also include a substantially flat outer periphery that surrounds said concave recess.

[0015] Further embodiments are directed to assemblies for attachment to a rotating spindle on a handheld power tool, and including a hub having a vertically traversing aperture opening to a topside and underside of said hub and configured to attach to said rotating spindle, and wherein said underside of the hub includes a concave recess; and a locking nut comprising a shaft configured to fit through the underside opening of the hub to attach to said rotating spindle such that the locking nut fits within the concave recess of the hub. In even more preferred embodiments, the locking nut has a solid back. In more preferred embodiments, the back end of the locking nuts fits within the concave recess of the hub.

[0016] Further embodiments are directed to a hub having a vertically traversing threaded aperture opening to a topside and underside of said hub and configured to attach to said rotating spindle, and wherein said underside of the hub includes a concave recess; and a locking nut comprising a back end and an externally threaded shaft, wherein said externally threaded shaft is configured to fit through the underside opening of the hub and screw into said hub's aperture, such that the back end of the locking nut fits within the concave recess of the hub.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] It will be appreciated that the drawings are not necessarily to scale, with emphasis instead being placed on illustrating the various aspects and features of embodiments of the invention, in which:

[0018] Figure 1 is an exploded view of one embodiment of a preferred grinding assembly and an angle grinder.

[0019] Figure 2 is an angled view of a preferred hub of a grinding assembly.

[0020] Figure 3 is an angled view of a preferred locking nut of a grinding assembly.

[0021] Figure 4 is an angled view of a preferred disc of a grinding assembly.

[0022] Figure 5 is a cross-sectional view of a spindle secured to a hub and locking nut.

[0023] Figure 6 is a cross-sectional view of a spindle secured to an alternative hub and locking nut.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS [0024] Embodiments of the present invention are described below. It is, however, expressly noted that the present invention is not limited to these embodiments, but rather the intention is that modifications that are apparent to the person skilled in the art and equivalents thereof are also included.

Grinding Assemblies

[0025] In preferred embodiments, the teachings herein are directed to new and improved grinding assemblies for use with a handheld angle grinder. Embodiments of the invention will now be described with reference to the accompanying figures, wherein like numerals refer to like elements throughout. The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive manner simply because it is being utilized in conjunction with a detailed description of certain specific embodiments of the invention.

[0026] FIG. 1 provides a particular advantageous embodiment of a handheld grinder 2 and a grinding assembly. According to this preferred non-limiting embodiment, the grinding assembly typically includes four pieces: a hub 20, a disc 30, grinding surface 40, and a locking nut 50. Other grinding assemblies provided herein can include fewer or more pieces.

Handheld Grinder

[0027] The grinding assemblies described herein can be coupled to available handheld grinders or other power tools having with a rotating spindle. FIG. 1 depicts one embodiment of an angle grinder that is compatible with the assemblies provided herein. Those with skill in the art will readily recognize that most available grinders can be used with the teachings herein. The assemblies are not limited to being attached to the specific grinder depicted in FIG. 1. The angle grinder in FIG. 1 includes an extension cord 14 compatible with an electrical outlet, a handle 8, an ON/OFF trigger 4, a housing 12 that includes an electric motor, a gear box 16, and a rotatable spindle 6 for connecting to a grinding assembly or other attachment. In general, a power source provides power to the electric motor that in turn drives the appropriate gears configured to rotate the spindle 6. Although not depicted in FIG. 1, many angle grinders that can be used with the teachings herein often have a second handle that protrudes from the side of the housing 12 or gearbox 16.

[0028] In preferred embodiments, the grinding assemblies provided herein are attached to the threaded spindle 6 of the grinder 2. While spindle length can vary according to different models of angle grinders (preferably within the range of ¹A inch and 2.5 inches), the current standard in the industry for many spindles is a thread count of 11 per inch and a 5/8 inch (1.6 cm) diameter in the United States. For Europe and countries utilizing the metric system, M 14 is the most common thread count and diameter. Accordingly, in preferred embodiments, and as will be discussed in more detail below, the grinding assemblies provided herein are configured to attach to spindles having either a 11 - 5/8 inch (1.6 cm) or M 14 thread count and diameter, regardless of the spindle's length. Those with skill in the art will readily appreciate that the dimensions of the grinding assemblies described herein can readily be adapted to attach to non standard, or unique spindles having differing thread counts, diameters and lengths, including diameters of ¹A inch (.6 cm) and 1/2 inch (1.25 cm), for example.

[0029] The grinding assemblies described herein can be used with any suitable handheld power tool or grinder, non-exclusively including an angle grinder. Nonexclusive examples of handheld grinders that the grinding assemblies described herein can be used with include those disclosed in Design Patent No. D522,826 to Aglassinger, U.S. Patent No. 6,632,128, to Berger et al, and U.S Patent No. 6,120,362 to Etter et al, and D527,966 to Hayakawa et al., for example. All of these patents are expressly incorporated herein by reference in their entireties.

[0030] In preferred embodiments, the handheld power tools, to be used with the grinding assemblies provided herein are sufficiently lightweight, such that they can be lifted by a user's hands and be easily moved from one working area to another. While preferred embodiments herein are directed to the terms "grinder" and "grinding", the assemblies described herein can be configured with any suitable power tool to smooth a workable surface, including tools commonly referred to as sanders. Nonexclusive uses of the assemblies provided herein include grinding concrete, drywall, plastics, fiberglass, hybrid materials, and sanding wood, for example. In more specific embodiments, the assemblies herein can be used to smooth flat working surfaces, such as floors, including rough, unfinished concrete floors, for example.

Hub

[0031] In preferred embodiments, the hub 20 includes a stem 22 and a base 28 in the shape of a truncated cone. In advantageous aspects, the stem 22 is configured to connect with the threaded spindle 6 of the handheld grinder 2 such that the spindle 6 functions as an axis upon which the hub 20 rotates around. In preferred embodiments, the hub's stem 22 includes an aperture 24 (or channel) that continues through the base 28 and opens to the underside of the hub 20. In more specific aspects, the aperture 24 includes threads 25 configured to screw onto the threads of the spindle 6. In even more specific embodiments, the aperture 24 has a thread count of 11 threads per inch, and is configured to screw onto spindles having a 5/8 inch (1.6 cm) diameter, the standard thread count and diameter for many spindles in the United States. In other preferred embodiments, the aperture 24 is configured to screw onto a spindle having an M14 thread count and diameter. Skilled artisans will recognize that the dimensions of the hub and its components described herein can readily be adapted to attach to spindles having differing thread counts, diameters and lengths, including diameters of ¹A inch (.6 cm) and 1/2 inch (1.25 cm), for example.

[0032] In more specific embodiments, the bottom of the aperture 24, opening to the underside of the hub 20, is configured to receive the shaft 52 of a locking nut 50. According to even more specific embodiments, it is preferred that the aperture 24 is not entirely threaded. It is instead preferred that the top of the aperture has between 2, 3, 4, or 5 threads 25, and the bottom of the aperture has a non-threaded or smooth section to receive the shaft 52 of the locking nut 50. According to this preferred embodiment, the locking nut 50 is not screwed into the aperture 24, but slid into it. This smooth section in the aperture can preferably correspond to the approximate height of the locking nut's shaft 52, and can non-exclusively be approximately 7/8, 5/6, or 1 inch (2.2, 2.1, or 2.5 cm) in height, in advantageous aspects.

[0033] FIG. 5 depicts the shaft 52 of a preferred locking nut 50 securing a spindle 6 within the aperture 24 of a hub 20. This depiction is provided only to show a general view of how the locking nut 50 secures the rotating spindle 6. In preferred working embodiments, the grinding assembly could include a disc 30 and a grinding surface 40 secured between the hub 20 and the locking nut 50.

[0034] In further embodiments, the hub can be configured to include 6, 7, 8, or 9 threads at the top of the aperture. In still further embodiments and as depicted in FIG. 6, the bottom of the hub's aperture is not smooth, but threaded to couple with an externally threaded nut. According to this embodiment, the nut includes external threads 60 configured to engage with the threads located at the bottom of the hub's aperture. This embodiment is particularly advantageous for nuts having a short stem. Short stems can be less than ^xh inch in length, and can be approximately ¹A inch or 1/3 inch in length, for example. Nuts having a short stem preferably include 2, 3, or 4 threads (external and/or internal) and can therefore be installed and removed to allow the user to more quickly change the grinding surface.

[0035] The underside of the hub preferably includes a generally flat surfaced periphery 27 and an inner concave recess 23. More specifically it is preferred that they are both concentric to the aperture 24, in the middle of the underside of the hub 20. The generally flat-surfaced periphery 27 is preferably approximately 1/8 inch (.3 cm) in width (measuring from the outer rim of the base towards the aperture 24), but can be any suitable distance non-exclusively including approximately 1/16, 3/16 or 1/4 inches, (.2, .5 or .6 cm) for example. The concave recess 23 preferably recesses (rises) towards the center aperture 24. In preferred embodiments, the concave recess 23 is configured to conform to the shape of the frustum center 36 on the topside of the disc 30 such that the periphery 27 of the hub lays level on the topside 34 plane of the disc 30. In even more preferred embodiments, the concave recess 23 rises toward the aperture at a 25 degree angle. In further embodiments, the concave recess can rise at various other angles including the approximate range of 15-60 degrees (e.g., 15, 20, 30, 35, 40, 45, 50, and 55 degrees).

[0036] Those with skill in the art will readily appreciate that the aperture's 24 height, diameter and/or thread count can be modified to accommodate other spindles having non-standard thread counts and diameters. Similarly, the hubs and locking nuts described herein can attach to a particular rotating spindle by any suitable means available.

[0037] In preferred embodiments, the base 28 of the hub 20 includes grooves 26 for enhancing airflow. These embodiments are desirable as they help alleviate dust build up within the grinder and its components, including the bearings, for example. The grooves are also helpful for cooling down the grinder and its components. While any suitable shape of groove capable of enhancing air flow can be used with the hubs provided herein (e.g., circular, rectangular, elliptical, square, curved), in preferred embodiments, the grooves 26 are rounded and curved as depicted in FIG. 2. The shape of the grooves shown in FIG. 2 will be referred to as "bean-shaped" for simplicity. In more specific embodiments, the hub can include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more grooves capable of enhancing air flow. In more preferred embodiments, the hub 20 includes six bean-shaped grooves 26 around the base 28.

[0038] In more specific aspects, the hub-enhanced air flow can work in conjunction with a hood cover and vacuum system that is coupled to the grinder to remove the generated dust. In general, a vacuum system sucks out grinder- generated dust and includes a hose in working operation with the handheld grinder.

[0039] The hub 20 can be of any suitable height to accommodate a particular length spindle. In preferred non-exclusive embodiments the hub 20 has a total height from its underside periphery 27 to the top of the stem 22 of approximately 1 and 5/8 inches (4.1 cm). In other preferred non-exclusive embodiments, the diameter of the underside of the base 28 is approximately 2 and 1/2 inches (6.4 cm).

[0040] The hub 20 can be made of any suitable metal, alloy, or plastic, but in preferred embodiments, the hub 20 is made out of steel, aluminum, or high-grade plastic. Metals and alloy based parts can be manufactured according to any suitable technique in the art, including but not limited to casting (e.g., investment or die casting). Aluminum is a particularly desirable material to be used with the hub 20 as it can dissipate heat evenly and quickly.

Disc

[0041] In preferred embodiments, the grinding assemblies described herein include a disc 30 that acts as a support backing for the grinding surface 40. In other preferred embodiments, the disc 30 contains a generally flat topside 34 and underside 32 with the exception of a concavo-convex frustum center 36. In more specific embodiments, the center frustum 36 is raised (convex) on the topside of the disc 30 and is recessed (concave) on the underside of the disc 30. In more preferred embodiments, the topside of the frustum 36 is configured to conform to the concave recess 23 of the hub 20. In more advantageous embodiments, the topside of the frustum 36 is raised at a 25 degree angle. In further embodiments, the frustum can rise at various other angles including the approximate range of 15-60 degrees (e.g., 15, 20, 30, 35, 40, 45, 50, and 55 degrees).

[0042] In still further embodiments, the frustum 36 contains an aperture 38 that aligns with the hub's aperture 24, such that the shaft 52 of the locking nut 50 can fit through both apertures (38 and 24). In more specific embodiments, the disc's aperture 38 can be approximately 3/4 inch (1.9 cm) in diameter.

[0043] In certain embodiments, the frustum can be a solid piece without slots (not shown), in other embodiments, the frustum can include slots 37 that separate multiple wedges 39. These slots 37 allow the disc 30 to have more flexibility during grinding, such that it minimizes stress resulting from a quickly rotating spindle 6. [0044] In certain embodiments, the disc 30 is configured to be secured between the hub 20 on its topside and the grinding surface 40 and locking nut 50 on its underside. In further embodiments, the top of the frustum 36 is configured to fit within the concave recess 23 on the underside of the hub, while the hub's outer periphery 27 lays level on the top flat surface 34 of the disc 30. Under this preferred configuration, when the spindle 6 is screwed into the threads of the hub 20 and the locking nut 50, the disc 30 is secured between the two pieces.

[0045] In other preferred embodiments surface of the disc 30 is relatively thin, having a thickness of approximately 1/16 (.2 cm) of an inch. Other non-exclusive approximate thickness can include 1/8 (.3 cm) and 3/16 (.5 cm) of an inch, for example. Skilled artisans will recognize that the dimensions of the disc 30 provided herein can readily be adapted to accommodate different dimensions of spindles, locking nuts, grinding surfaces, and hubs.

[0046] In advantageous embodiments, the disc 30 can be made of any suitable metal, alloy, or plastic, but in preferred embodiments, the disc 30 is made out of steel, aluminum or high-grade plastic. Metals and alloy based parts can be manufactured according to any suitable technique in the art, including but not limited casting (e.g., investment or die casting). Aluminum is a particularly desirable material to be used with the disc 30 as it can dissipate heat evenly and quickly.

Grinding Surface

[0047] The grinding assemblies provided herein can be used to smooth any hard surface including concrete, asphalt, wood, fiberglass, for example, and a suitable grinding surface 40 can be used accordingly. Suitable grinding surfaces are readily available in the art and can non-exclusively include grinding paper and sand paper, for example. In general grinding surfaces include some type of abrasive material, or grit, on the surface to be used to smooth down a working surface. Suitable grinding surfaces non-exclusively include coarse, medium, fine, very fine, extra fine, and super fine sanding paper, for example. In certain embodiments, the grinding surface 40 can include any suitable abrasive including ceramic, aluminum oxide, alumina oxide, garnet, or silicon carbide, for example. Any suitable grinding surface that can be used to smooth a hard surface can be used with the teachings herein.

[0048] While the grinding surface can be attached to the disc's underside 32 by any suitable means, in preferred embodiments, the grinding surface 40 has a center aperture 42 configured to allow the shaft 52 of the locking nut through. According to this configuration, the grinding surface can be tightly secured against the disc 30 through the use of the locking nut 50. In further embodiments, the grinding surface includes multiple slots 44 around the aperture 42, so the center of the grinding surface will be held within the recess on the underside of the frustum 36. In still further embodiments, the hubs and locking nuts described herein can be used with any rotatable grinding, sanding, or cutting attachment.

Locking Nut

[0049] In preferred embodiments, the locking nut 50 functions to secure the grinding surface 40 and the disc 30 to the hub 20 and the spindle 6 of the handheld grinder 2. In more specific embodiments, the locking nut 50 can include a hollow, internally threaded shaft 52 having an upward opening 58 connected to a base 53 having a generally flat back 56. In other embodiments, the shaft does not include internal threads and instead includes external threads 60 configured to engage with threads within the hub's aperture. In other embodiments, the shaft can include both internal threads configured to screw onto the spindle, and external threads configured to screw onto the threads within the hub's aperture.

[0050] In more preferred embodiments, the opening 58 does not continue to the back 56 of the locking nut 50. In advantageous embodiments, the base 53 can be the shape of a truncated cone, rising towards the shaft 52. In preferred embodiments the angle of the base 53 is equivalent to the angle of the frustum 36 of the disc 30, including 25 degrees for example. In further embodiments, the base can rise at various other angles, including the approximate range of 15-60 degrees (e.g., 15, 20, 30, 35, 40, 45, 50, and 55 degrees). In other embodiments, the base can be flat, having a single height.

[0051] In preferred aspects, the shaft 52 is configured to attach to the spindle 6. In more specific embodiments, it is preferred that that the inside of the shaft 52 is threaded to screw onto the spindle 6. While spindle length can vary according to different models of angle grinders, the current standard in the industry for many spindles is a thread count of 11 per inch and a 5/8 inch (1.6 cm) diameter or M 14, including diameters of ¹A inch (.6 cm) and 1/2 inch (1.25 cm), for example. Accordingly, in preferred embodiments, the internally threaded shaft is configured to attach to spindles with these standard thread counts and diameters, regardless of the spindle's length. In preferred embodiments, the shaft is approximately 1 inch (2.5 cm) long and can non- exclusively include 9, 10, 11, or 12 threads. In alternative embodiments, the internal shaft is not threaded and the external shaft is. Preferably the external shaft only includes 2, 3, or 4 external threads that are configured to screw onto threads located in the lower part of the hub's aperture.

[0052] In further preferred embodiments, the back 56 of the locking nut 50 is a planar, solid piece, without holes, to prevent dust or debris from entering into the shaft 52, the hub 20, or the spindle 6. This particular embodiment of a "closed nut" is advantageous as it substantially prevents dust build up in the spindle 6, which can damage the spindle 6 and make removing grinding attachments difficult. Preferred nonexclusive dimensions include a back 56 with a diameter of approximately 1 and ^xh inches (3.8 cm), a shaft 52 with a ³A inch (1.9 cm) outer diameter, and a total height of the nut 50 (shaft and base) at approximately 1.145 inches (2.9 cm).

[0053] In other preferred embodiments the back 56 of the nut includes means for unlocking the nut. In more preferred embodiments, the means are notches 54 along the circumference of the base 53. A wrench, or other suitable tool, can be used with said means for unlocking the nut. [0054] In more specific aspects of the teachings herein, the locking nut 50 is configured to be secured with the spindle 6 such that the back 56 of the locking nut 50 is secured within the concave recess on the underside of the frustum 36, and within the underside recess 23 on the hub 20. Under these preferred configurations, the locking nut's back 56 does not protrude past the plane of the grinding surface 40, or the planar underside 32 of the disc 30. Accordingly, under this advantageous configuration, the user can direct the entire grinding surface flat against a working surface without grinding the back 56 of the locking nut 50.

[0055] While most preferred embodiments herein relate to grinding assemblies for grinding or sanding, skilled artisans will also recognize that the hub 20 and the locking nut 50 could also be used with any suitable cutting attachment.

[0056] In advantageous embodiments, the locking nut 50 can be made of any suitable metal, alloy, or plastic, but in preferred embodiments, the locking nut 50 is made out of steel, aluminum, or high-grade plastic. Metals and alloy based parts can be manufactured according to any suitable technique in the art, including but not limited to casting (e.g., investment or die casting). Aluminum is a particularly desirable material to be used with the locking nut 50 as it can dissipate heat evenly and quickly.

[0057] Skilled artisans will recognize that the dimensions of the locking nut 50 provided herein can readily be adapted to accommodate different dimensions of spindles, discs, grinding surfaces, and hubs.

[0058] All measurements provided in United States customary units herein include metric equivalents. The invention may be embodied in other specific forms besides and beyond those described herein. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting, and the scope of the invention is defined and limited only by the appended claims and their equivalents, rather than by the foregoing description.

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Claims

CLAIMS:What is claimed is:

1. A grinding assembly for attachment to a rotating spindle on a handheld power tool, comprising: a hub having a vertically traversing channel opening to a topside and underside of said hub and configured to attach to said rotating spindle, and wherein said underside of the hub includes a concave recess; a disc having a substantially planar topside and underside surrounding a concavo- convex frustum having an aperture and configured to conform to said concave recess on the underside of the hub, such that said aperture aligns with the underside opening of the hub; and a locking nut having a top-opening hollowed shaft connected to a base having a solid back, wherein said shaft is configured to fit through the disc aperture and the underside opening of the hub to attach to said rotating spindle such that the back of the locking nut is within the concave recess of the hub and does not protrude past the substantially planar underside of the disc.

2. The grinding assembly of Claim 1, further comprising a grinding surface configured to be attached to said disc.

3. The grinding assembly of Claim 2, wherein said grinding surface is attached to said disc by said locking nut.

4. The grinding assembly of Claim 1, wherein the hub includes a plurality of grooves around an outer surface.

5. The grinding assembly of Claim 4, wherein the hub comprises bean- shaped grooves on said outer surface.

6. The grinding assembly of Claim 1, wherein said concavo-convex frustum comprises a plurality of slots around said aperture.

7. The grinding assembly of Claim 1, wherein said vertically traversing channel in said hub, is partially threaded at a thread count of 11 threads per inch.

8. The grinding assembly of Claim 1, wherein the underside of the hub includes a flat outer periphery.

9. An assembly for attachment to a rotating spindle on a handheld power tool, comprising: a hub having a vertically traversing aperture opening to a topside and underside of said hub and configured to attach to said rotating spindle, and wherein said underside of the hub includes a concave recess; and a locking nut comprising a back end and a shaft, wherein said shaft is configured to fit through the underside opening of the hub to attach to said rotating spindle such that the back end of the locking nut fits within the concave recess of the hub.

10. The assembly of Claim 9, wherein said back end of the locking nut comprises a solid back.

11. The assembly of Claim 9, wherein said vertically traversing aperture and said rotating spindle are threaded such that said hub can be screwed onto said rotating spindle.

12. The assembly of Claim 11, wherein said vertically traversing aperture includes a top section that is threaded such that said hub can be screwed onto said rotating spindle and a smooth bottom section configured to receive said shaft of the locking nut.

13. The assembly of Claim 9, wherein said hub includes a flat surfaced underside.

14. The assembly of Claim 9, wherein said hub includes a stem and a base in the shape of a truncated cone.

15. An assembly for attachment to a rotating spindle on a handheld power tool, comprising: a hub having a vertically traversing threaded aperture opening to a topside and underside of said hub and configured to attach to said rotating spindle, and wherein said underside of the hub includes a concave recess; and a locking nut comprising a back end and an externally threaded shaft, wherein said externally threaded shaft is configured to fit through the underside opening of the hub and screw into said hub's aperture, such that the back end of the locking nut fits within the concave recess of the hub.

16. The assembly of Claim 15, wherein the back end of the locking nut comprises a solid back.

17. The assembly of Claim 15, wherein said vertically traversing aperture and said rotating spindle are threaded such that said hub can be screwed onto said rotating spindle.

18. The assembly of Claim 15, wherein said hub includes a flat surfaced underside.

19. The assembly of Claim 15, wherein said hub includes a stem and a base in the shape of a truncated cone.