Abstract:
The present invention relates to an improved hole saw boss ( 10 ) and in particular, to a boss including a threaded member ( 12 ) adapted to accommodate two hole saws of the same or different bore thread diameters. The present invention allows for a pre-existing aperture ( 22 ) in a work piece to be simply enlarged. This is useful if a new lock mechanism is being installed in a door with a pre-existing aperture where the lock mechanism requires a larger aperture than that which was in existence. Currently the aperture has to be enlarged by manual handwork since there is no centre-point to which a pilot drill may be enlarged. The threaded bore diameters of the present invention correspond with the commonly available hole saw threaded bore diameters. The present invention therefore provides the public with device for enlarging apertures which is simply, cost effective and can be used with currently available hole saws.

Description:
[0001]     The present invention relates to an improved hole saw boss and in particular, to a boss including a threaded member adapted to accommodate two hole saws of the same or different bore thread diameter.  
       BACKGROUND OF THE INVENTION  
       [0002]     Drills are typically used by tradesmen and home handymen to perform a multitude of various tasks. The most common task is generally the drilling of holes into various materials. Drill bits are designed such that they are very effective in this process whereby the rapid rotation of the bit effectively cuts away at the work piece thereby forming an aperture. These drill bits, which are typically locked within a mandrel are effective for apertures of a small diameter, however, it is often required that much larger apertures be drilled.  
         [0003]     This is where the invention of the hole saw came into being which incorporates a cylindrically shaped member including cutting teeth on one end and a threaded bore on the other. This threaded bore engages with an oppositely threaded member connected to the mandrel commonly referred to as a boss. The drill bit is incorporated into the hole saw assembly and protrudes through the boss a distance greater than that of the hole saw member so that it can be used to align the drill with the centre of the circle being cut. That is, when using a hole saw member to drill a hole into a work piece, it is much easier to align a pilot drill with a centre point of a circle than it is to align the cutting teeth of a hole saw member with the perimeter of a circle. The pilot drill forms an initial hole in the work piece until the hole saw teeth reach the material surface where they then proceed to accurately drill the required hole.  
         [0004]     Although this has proven to be an effective method of drilling larger holes, it becomes apparent that when faced with having to increase the diameter of an existing hole, there exists no centre-point to which a pilot drill may be aligned. This provides a problem because as mentioned, it is very difficult to accurately drill a large-diameter hole without some type of centre alignment. In many situations, the handyman is forced to manually hand-work the work piece so that enlargement can be achieved.  
         [0005]     It is an object of the present invention to overcome at least some of the aforementioned problems or to provide the public with a useful alternative.  
         [0006]     Insofar as the applicant is aware, there exists no hole saw boss including a threaded member adapted to accommodate two hole saws of the same or different diameter threaded bore.  
       SUMMARY OF THE INVENTION  
       [0007]     Therefore in one form of the invention there is proposed an improved hole saw boss including:  
         [0000]     a threaded member adapted to accommodate at least two hole saws of different cutting diameters.  
         [0008]     In a further form of the invention there is proposed an improved hole saw boss including:  
         [0000]     a threaded member incorporating at least a first and second threaded portion;  
         [0000]     said first threaded portion adapted to engage a threaded bore of a first hole saw; and  
         [0000]     said second threaded portion adapted to engage a threaded bore of a second hole saw, wherein the cutting diameter of said first hole saw is different to the cutting diameter of said second hole saw.  
         [0009]     Preferably said second hole saw cutting diameter is smaller than said first hole saw cutting diameter.  
         [0010]     Preferably said boss includes a base member to which the threaded member is connected.  
         [0011]     Preferably said threaded member incorporates a first threaded portion and at least one other threaded portion of stepped down diameter to accommodate hole saws of different threaded bore diameters.  
         [0012]     Preferably said first and second threaded portion diameters correspondingly engage with commonly available hole saw threaded bore diameters.  
         [0013]     Preferably at least one threaded portion is of a length capable of accommodating more than one hole saw of different cutting diameters.  
         [0014]     Preferably said base member and said threaded member include a central aperture adapted to allow a drill bit to fit there through.  
         [0015]     Preferably said boss includes a connection means which is configured to engage a mandrel.  
         [0016]     Preferably said second hole saw is chosen to fit snugly within an existing aperture of a work piece.  
         [0017]     Preferably said first hole saw is adapted to drill a hole larger than the existing hole into said work piece.  
         [0018]     Preferably the cutting surface of said second hole saw extends beyond the cutting face of said first hole saw.  
         [0019]     Preferably said cutting surface of said second hole saw contacts the planar face of said work piece before said cutting surface of said first hole saw.  
         [0020]     In yet a further form of the invention there is proposed an improved hole saw boss including:  
         [0000]     a threaded member adapted to accommodate at least two hole saws of different cutting diameters;  
         [0000]     a notched base member; and  
         [0000]     at least one drive pin, said drive pin configured to engage both a notch on said base member and an existing aperture on at least one of said hole saws.  
         [0021]     Preferably said drive pin is magnetised to restrain said drive pin within said aperture on said hole saw. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several implementations of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings,  
         [0023]      FIG. 1  is an exploded perspective view of a hole saw assembly embodying the present invention and including a single threaded member;  
         [0024]      FIG. 2  is a perspective view of the hole saw assembly of  FIG. 1  applied to a work piece;  
         [0025]      FIG. 3  is a perspective view of the double-diameter boss of the present invention including a mandrel connection means;  
         [0026]      FIG. 4  is a side view of the hole saw boss of  FIG. 3 ;  
         [0027]      FIG. 5  is a top view of the hole saw boss of  FIG. 3 ;  
         [0028]      FIG. 6  is a side view of the hole saw boss rotated 90° to that shown in  FIG. 4 ;  
         [0029]      FIG. 7  is an exploded perspective view of a hole saw assembly embodying the present invention and including two drive pins;  
         [0030]      FIG. 8  is a perspective view of the hole saw boss of  FIG. 7 ;  
         [0031]      FIG. 9  is a perspective view of the hole saw boss of  FIG. 7  illustrating the mandrel disengaged from the hole saw boss; and  
         [0032]      FIG. 10  is an end view of the hole saw boss of  FIG. 7 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]     The following detailed description of the invention refers to the accompanying drawings. Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.  
         [0034]     The present invention discloses a hole saw boss  10  including a threaded member  12  adapted to accommodate two hole saws. Moreover, member  12  may be adapted to include a first threaded section  14  and a second threaded section  16  of stepped down diameter, an arrangement that allows for hole saws with differing bore thread diameters to be connected thereto. In both cases, threaded member  12  is adapted to engage both an outer hole saw  18  and an inner hole saw  20  respectively of different diameter cutting sizes. When the diametric enlargement of an existing aperture  22  in a work piece  24  is required, the inner hole saw  20  seeks to minimise any unfavourable lateral movement of the outer hole saw  18  during initial contact with the work piece surface  26 , since it protrudes beyond the outer hole saw  18 .  
         [0035]     Illustrated in  FIGS. 1 and 2  is a hole saw assembly utilising a hole saw boss the subject of the present invention. For details of the hole saw assembly the reader is referred to applicants International Patent Application PCT/AU02/01296 whose content is incorporated by reference herein.  
         [0036]      FIG. 1  illustrates an exploded view of a hole saw assembly including the boss  10  of the present invention. The hole saw assembly  28  includes a shank  30 , a mandrel  32  (or driving means), a drill bit  33 , and an annulus  34  (or locking ring) that locks the boss  10  to the mandrel  32 .  FIGS. 2-6  illustrates the alternate configuration of boss  10  which can be incorporated into the same hole saw assembly  28 . A work piece  24  includes an existing aperture  22  required to be enlarged while dotted line  36  forms an invisible circle perimeter to which enlargement of the aperture  22  is required to extend.  
         [0037]     Using either configuration, the invention allows for a more accurate enlargement of the existing aperture  22  in that the inner hole saw  20  extends a greater distance longitudinally than the outer hole saw  18  and fits snugly within the aperture  22 , thereby acting as a guide or pilot for the outer hole saw  18 . It is the contact between the outer surface  38  of the inner hole saw cylinder with the inner surface  40  of the aperture  22  that minimises the risk of the outer hole saw  18  unfavourably moving as it makes contact with the work piece surface  26 . If it were not for the inner hole saw  20 , the rotating motion of the outer hole saw  18  would cause it to gyrate as soon as it makes contact with the work piece surface  26 .  
         [0038]     The first configuration of boss  10  shown in  FIG. 1  simply includes a single diameter threaded member  12  to which firstly the outer  18  and secondly the inner  20  hole saw are screwed, the two hole saws being of different cutting diameter so that one can fit within the other.  
         [0039]     Boss  10  of the second configuration shown in  FIGS. 2-6  engages the outer hole saw  18  with a first threaded section  14 . Longitudinally extending from the first threaded section  14  is a second threaded section  16  of stepped down diameter adapted to engage the inner hole saw  20 . It is to be understood that in both configurations, the threaded section  14  is fixedly attached to a base member  42 , which is adapted to fit to the mandrel  32  using connection means  44  and  46  locked by annulus  34 . Furthermore, a central aperture  47  through boss  10  allows drill bit  33  to protrude there through.  
         [0040]     The second configuration including a second threaded section  16  of stepped down diameter is provided to accommodate typical hole saws that engage with one of two boss thread sizes, a smaller thread size (typically ½″) or a larger thread size (typically ⅝″). These cover a wide range of hole saw diameters from relatively small hole saws to larger hole saws. Preferably, the threaded sections  14  and  16  are shaped correspondingly to engage these industry standard threads, however, the boss of the invention should not be limited to these sizes as it could well be used for other functions incorporating thread sizes of a different magnitude. For example, the first threaded section  14  could be used to engage a buffing or grinding wheel (not shown) while the second threaded section  16  could be used to engage a locking bolt (not shown) or the like. Threaded sections for this operation may well differ from those used in a typical hole saw operation.  
         [0041]     It is to be also understood that the connection means referred to in this invention need not limit the connection means used, for example, the boss  10  may simply be screwed onto the mandrel  32  whereby both mandrel  32  and base member  42  include engageable threads. Furthermore, any member adapted to be screwed may include flat surfaces adapted to be engaged by a spanner or the like for screwing and unscrewing of the member.  
         [0042]     It should be further understood that the lengths of sections  14  and  16  of threaded member  12  are such that two different sized hole saws may well engage only one of the sections. This would occur, for example, when the diameter of the required enlargement perimeter  36  is only slightly larger than that of the existing aperture  22  and therefore hole saws of relatively similar sizes are used.  
         [0043]     It should now be apparent to those skilled in the art that the use of either of the two configurations of the boss of the present invention in a hole saw assembly, allows the user of such an assembly, when faced with wanting to enlarge a hole on a work piece to simply reach into their toolbox, pick up two hole saws of the same or different size, screw them onto the boss and proceed with drilling. The invention does away with the need to manually enlarge a hole in a work piece. It further eliminates the need to replace the boss when a hole saw of differing bore size needs to be used and it achieves this by including different sized threads on the one boss.  
         [0044]     In a further embodiment the hole saw assembly  28  includes drive pins  50  and  52  as illustrated in  FIG. 7 . The drive pins  50  and  52  are configured to fit within the pre-existing apertures  54  and  56  of the hole saw  18 . These pre-existing aperture  54  and  56  are a feature of all hole saws and are used to engage older hole saw mandrels. The drive pins  50  and  52  engage recesses  58  and  60  on the base member  42  respectively, as illustrated in  FIG. 8 . Alternately, a single drive pin could be used.  
         [0045]     In this way the hole saw  18  is prevented from over tightening on the threaded member  12 . Over tightening can occur when a large hole saw is used on machinery. If drive pines are not used the gears of the machinery can tighten the hole saw  18  onto the threaded member  12  is such as way that the hole saw  18  is difficult to remove from the threaded member  12 . It is then necessary to remove the hole saw boss  10  from the machinery and forcibly disengage the hole saw  18 . In some cases the thread of the treaded member  12  may even be stripped thereby damaging the hole saw boss  10 . The drive pins  50  and  52  therefore bear the load and prevent the hole saw  18  tightening onto the boss  10 . The risk of damage to the threaded member  12  is thereby reduced whilst ensuring that the hole saw  18  can be rapidly engaged and disengaged from the hole saw boss  10 .  
         [0046]     As further illustrated in  FIG. 8 , the drive pins  50  and  52  are held in place during operation of the hole saw assembly  28  by the mandrel  32 . However, when the mandrel  32  is disengaged from the hole saw boss  12 , as illustrated in  FIG. 9 , the drive pins  50  and  52  are no longer restrained within apertures  54  and  56 . The drive pins  50  and  52  therefore have the potential to be lost during removal of the hole saw  18 . Thus it may be desirable that the drive pins  50  and  52  are magnetised so they are restrained within the aperture  54  and  56  even when the mandrel  32  is disengaged. The reader should however appreciate that the present invention is not limited this particular configuration nor to the use of magnetised drive pins.  
         [0047]     It is important that the drive pins  50  and  52  do not interfere with the operation of the hole saw assembly  28  if more than one hole saw is located on the threaded member  12 . Therefore, as illustrated in  FIG. 10  the drive pins engage the aperture  50  and  52  in such as way that they do not protrude excessively into the cavity  62  of the hole saw  18 . This ensures that the ends of the drive pins  50  and  52  do not interfere if a second hole saw (not shown) is attached to the threaded member  12 . Alternatively, the drive pins could be configured to engage both of the hole saws.  
         [0048]     As the skilled addressee will now appreciated the embodiment that incorporates at least one drive pin allows the hole saw boss of the present invention to be used in conjunction with large hole saws on industrial machinery. The use of the drive pins prevents the hole saw  18  from being over tightened onto the boss or damaging the boss by stripping the thread.  
         [0049]     Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.