Abstract:
A guide to center a screw or drill bit in the center of a hole of a countersink in a member to engage a piece under the member, the countersink having a downwardly tapered wall from the member to the hole. The guide has a body with a through hole and a tapered part that is to rest on the member tapered wall to align the through hole generally perpendicular to the piece. In a preferred embodiment the guide body tapered part is at an end of the body and the body is of frangible material and holds a screw in the through hole which fractures the body as the screw is threaded into the piece beneath the member. At least one slot is formed in the body along at least a part of its length between its top and bottom ends to facilitate the fracture of the body.

Description:
FIELD OF THE INVENTION 
     The present invention relates to guides, or pilots, to position a screw or drill bit in the center of a countersink hole and more particularly to one of the type that is of frangible material that is broken and removed after the guiding function has been completed. 
     BACKGROUND OF THE INVENTION 
     One type of operation that is regularly performed in woodworking operations is to provide an entry point for a screw or drill bit that is centered in a hole that is countersunk in a member. A countersink hole is one that is at the termination of a wall that tapers downwardly from the member surface. The screw or drill bit is to be inserted through the hole to engage a wood piece on which the member lies and to which it is to be fastened. For example, a typical leaf type hinge has three or more countersink holes on each leaf. A wood screw is to be inserted into each countersink hole and the screw head is recessed in the countersink. 
     When inserting a screw into the wood piece through a countersink hole, it is necessary that the tip of the screw be precisely centered in the hole. Most often the screw tip is inserted directly into the wood piece but sometime the tip of the screw is placed in a pilot hole that has been drilled in the wood piece. In either case the screw tip or the drill bit that makes the pilot hole must be precisely centered in the hole. Otherwise, when the screw is screwed down, the screw head will not be fully recessed in the countersink. This can also cause misalignment of the hinge. 
     Accordingly, a need exists to provide a simple and inexpensive device to directly center the point of entry of a screw or drill bit in a countersink hole into the wood piece. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment of the invention a guide is provided to center the point of entry of a screw tip or drill bit into a wood piece through a hole of a countersink in a member. The guide has a bottom end that is tapered to generally correspond to the countersink and rests on the tapered wall of the countersink that surrounds the hole. The guide has a passage through which the screw or drill bit extends to engage the wood piece. The matching tapers of the guide and the countersink wall centers the screw tip in the hole so that it can be accurately centered to engage the wood piece. 
     In a preferred embodiment the guide is made of frangible plastic material and houses a screw. As the screw is threaded into the wood it fractures the guide which breaks into pieces that can be removed. In one use of this embodiment, a leaf type hinge can be sold with a set of screws each having the attached guide. This provides a convenience feature for the person attaching the hinge at very little cost. 
     In a modification of this embodiment, the frangible guide can be provided with one of a surrounding flange or extending lugs spaced around the guide. The flange rests on the surface of the member in which the countersink is formed and the lugs fit into corresponding grooves that are formed in the member. The guide tapered bottom end centers the guide in the countersink and the flange or lugs stabilizes the guide so that the screw will enter the wood at a perpendicular orientation. If desired, there can be an adhesive on the lower face of the flange that engages the hinge leaf. 
     In another embodiment of the invention, the guide is inserted in the countersink hole and held in position by a locking ring acting against the underside of the member with the countersink or by an adhesive. In a first form the guide is for a drill bit which passes into the hole in the guide to engage the wood piece to make the pilot hole. The drill bit is withdrawn and the guide is pried out of the countersink hole. In a modification of the foregoing for guiding insertion of a screw, the guide is made in two pieces and after the screw tip passes through the guide central hole into the wood piece, the two pieces of the guide are removed from the countersink hole. 
     OBJECTS OF THE INVENTION 
     An object of the invention is provide a guide to directly center the point of entry of a screw or drill bit tip in a countersink hole in a member into the wood piece under the member. 
     A further object is to provide a guide for centering a drill bit in a countersink hole of a member to drill a pilot hole in a wood piece under the member. 
     Another object is to provide a frangible guide holding a screw that centers its tip in a countersink hole. 
     Yet another object is to provide a guide for use with a member having a countersink hole to center the tip end of a screw or dill bit in the hole. 
     An additional object is to provide an insert to guide a drill bit or screw that is located in a countersink and attached to the member having the countersink by an adhesive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become more apparent upon reference to the following specification and annexed drawings in which: 
     FIG. 1 is a perspective view of a hinge leaf member mounted on a piece of wood to which it is to be fastened illustrating the use of the screw guide embodiment of the invention; 
     FIG. 2 a  is a perspective view of the screw guide of FIG. 1; 
     FIG. 2 b  is a top plan view of the guide of FIG. 2 a;    
     FIG. 2 c  is a top plan view of an alternative form of the guide; 
     FIGS. 3 and 3 a - 3   e  are part perspective and cross-sectional views showing the use of the screw guide of FIGS. 1 and 2; 
     FIG. 3 e  is an elevational view partly in cross section of a modification of the guide; 
     FIG. 4 a  is a top plan view of a hinge leaf modified to use a second embodiment of the guide and FIG. 4 b  is an elevational view of the guide for use with the hinge; 
     FIG. 5 a  is a top plan view of a hinge leaf modified to use a third embodiment of the guide and FIG. 5 b  is an elevational view of the guide for use with the hinge leaf; 
     FIG. 6 a  is a perspective view of a drill guide insert to be inserted in a countersink hole; 
     FIG. 6 b  is an elevational view in cross-section and FIG. 6 c  is a perspective view showing the use of the guide insert of FIG. 6 a;    
     FIG. 7 is a perspective view of a further embodiment of the guide; 
     FIG. 8 is a view of a modification of the embodiments of inserts shown in FIGS. 6 and 7; 
     FIGS. 9 a  and  9   b  are respectively a perspective and a cross-sectional view of an insert to be attached by an adhesive strip to the member having the countersink; and 
     FIGS. 10 a  and  10   b  are respectively a top plan and elevational views of a modification of the embodiment of FIGS. 9 a - 9   b.   
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-3 show a first embodiment of the invention in which there is a piece of wood  10  to which a leaf member of a conventional hinge  14  is to be fastened. The other hinge leaf would also be fastened to another wood piece  14 . The hinge leaf member is typically made of metal and has a plurality of countersinks  16  with respective holes through which a screw  20  is to be inserted to fasten the hinge leave to the wood piece. Each of the countersinks  16  has a wall  16   a  that tapers downwardly from the hinge leaf surface to a hole  16   b . The head  21  of the screw  20  to be inserted through the hole  16   b  has a corresponding taper so that when the screw is fully threaded into the wood piece, as shown in FIG. 3 d , the screw head will be flush with or slightly below the hinge leaf top surface. While the invention is illustratively described with respect to a countersink hole in a hinge leaf, it should be understood that it is applicable to any member having a countersink with a hole through which a screw is to be passed for fastening the member to another piece. 
     If the pointed end  22  of screw  20  is not properly centered in the hole  16   b  before it is threaded into the wood, the screw head  21  will not be fully recessed into the countersink. This can also cause mis-alignment of the hinge leaf on the wood piece. Usually, the person placing the screw will try to center it in the hole  16   b  by eye, which is not always successful. 
     FIGS. 2 a - 2   c  show a preferred embodiment of a guide  30  for centering a screw  20  in the countersink hole  16   b . The guide body is of generally cylindrical shape and has a flat top end  31  and a bottom end  32  that is tapered to correspond to the taper of the wall  16   a  of the countersink  16 . A hole  34  extends through the guide body from its top to bottom ends. A screw  20  is placed in the guide member hole  34 . The guide body hole  34  can be of uniform diameter, have a tapered bottom end or be treaded to accept the screw  20 . In all of the embodiments the screw  20  is illustratively of the conventional wood screw type but it can be of other types, such as an auger point screw. 
     The body of the guide  30  is made of a suitable plastic material that will fracture upon force being applied to it. The guide has fracture aiding slots, which are portions of the guide body from which material is removed. In FIG. 2 b  the slots  36  extend from the outside of the guide body partially toward the hole  34  and in FIG. 2 c  the slots  37  extend from the hole  34  part way toward the guide body outer surface. The slots  36  and  37  are preferably diametrically opposed and also preferably extend for the full height of the center part of the guide body to the beginning of the tapered bottom end  31 . While a single pair of diametrically opposed slots  36  or  37  is shown, it should be understood that there can be three, four or more of such slots. 
     FIG. 3 shows the screw  20  placed in the guide body hole  34  and the pointed end screw tip is at the end of the guide body. FIGS. 3-3 d  show the use of the guide  30 . As seen in FIG. 3 a , the tapered bottom end  32  of the guide  30  is placed in the countersink on the tapered wall  16   a . Since both the guide bottom end  31  and countersink wall  16   a  match, the screw tip end  22  will be at the center of the countersink hole  16   b . FIG. 3 b  shows the screw at the first stage of its threading into the wood piece  10  in which the tapered screw head  21  enters the guide body hole  34 . As force is applied in threading the screw into the wood piece, the screw head  21  moves down on the guide body and causes it to start to fracture. Further threading of the screw, as shown in FIG. 3 c , causes a completer fracture of the guide body into two parts before the screw  20  has been fully inserted into the wood piece  10  and the two split parts are temporarily held between the screw head  21  and the hinge leaf. As the screw threading is continued to completion, as shown in FIG. 3 d , the fractured parts of the guide body are forced outwardly and can be easily removed from the work area. The parts of the split guide body can be manually removed. FIG. 3 d  also shows the screw fully fastened in the wood piece. Since the screw tip was properly centered by the guide  30  before the threading started, the screw head  21  is properly centered and fully recessed in the countersink  16 . 
     FIG. 3 e  shows a second embodiment of the guide. Here, the guide body  30   a  has a flange  38  formed around the circumference of the central cylindrical part of the guide body above the point where the taper of the bottom end  32  starts. In this embodiment, the guide body tapered bottom end  32  rests on the countersink tapered wall  16   a , as described above. The flange  38  seats the guide  30   a  on the upper surface of member  14  and makes certain that the guide hole  34  and screw will be perpendicular to the wood piece  10 . Use of the guide and its fracture is as previously described. If desired, there can be a layer of adhesive on the lower surface of the flange that lies on the hinge leaf. 
     FIGS. 4 and 5 show further embodiments of the guide. In FIG. 4 a  the tapered wall  16   a  of the countersink  16  is provided with spaced recesses  19 , such as by punching, staking or any other conventional process. The recesses  19  can be of any desired shape, such as circular, square or rectangular. They can be of uniform depth or of varying depth with the shallowest part toward the hole  16   b . While three such recesses  19  are shown spaced apart by 120°, it should be understood that there can be fewer or more of the recesses. FIG. 4 b  shows a guide  40  which is substantially the same as the guide  30  previously described except for the addition of lugs  49  on the tapered bottom end  32 . The lugs  49  are of a number and have a shape and spacing corresponding to the recesses  19  in the leaf countersink tapered wall  16   a . In use, the tapered bottom end  32  of the guide is placed in the countersink  16  and the guide is rotated until its lugs  49  line up and fall into the corresponding recesses  19  on the countersink tapered wall  16   a . This locks the guide  40  into the countersink with proper vertical alignment of the guide hole  34  so that the screw will be properly oriented perpendicular to the wood piece. The operation of the guide  40  and its fracture into pieces as the screw is threaded are as previously described with respect to FIGS. 1-3. 
     FIGS. 5 a  and  5   b  show a further embodiment which is a modification of that of FIGS. 4 a - 4   b . Here, recesses  19   a  are on the leaf member spaced away from the countersink  16  instead of on the countersink tapered wall  16   a . The guide body is provided with a surrounding flange  51  on the cylindrical part of the body above the bottom taper  32 . Extending downwardly from the flange  51  are lugs  59  of a number, placement and shape to lock into the recesses  19   a . The operation of this embodiment is similar to that of FIG. 4, in that the guide body rotated until its lugs  59  fit into the recesses  19   a  in the member  12 . 
     In some cases, such as where the wood piece is of hard wood, such as oak, or for other reasons a pilot hole has to be drilled in the wood piece  10  centered in the hole  16   b  of a countersink  16 . FIGS. 6 a - 6   c  show an embodiment of the invention that can be used for this purpose. Here there is an insert guide  60  that is preferably made of a relatively soft plastic resin. The body of guide  60  is of one integral piece and has a flange top  62  that is to lie on the top surface of the member  12  with the countersink  16 , a tapered central portion  64  that matches the tapered wall  16   a  of the countersink and a locking ring  66 . A central hole  67  extends through the guide body  60 . The diameter of the hole  67  is made somewhat larger than the diameter of a drill bit D that is to pass through it. 
     The taper of the central body portion  64  corresponds to the taper of the countersink wall  16   a  and the thickness of the central body portion is substantially the same as that of the hinge leaf  16 . The top flange  62  can be made relatively thick to provide stability and a good aligning surface for the drill bit. The locking ring  66  thickness can be made as thick as desired but should be thin enough so that the guide can be easily removed from the countersink  16  in member  12 . 
     As shown in FIG. 6 b , the guide body is placed into one of the hole  16   b  in the countersink. It is preferred that the material for the body be soft so that ring  66  can deform as it is pushed through the hole  16   b . The ring  66  then returns to its original shape to lock the guide  60  into the countersink  16 . Once the guide  60  is locked in the countersink, it provides a centered guide hole  67  for the drill bit D to make pilot hole in the wood piece, as shown in FIG. 6 c . After the pilot hole is drilled the drill bit is removed from the guide hole  67  and the guide  60  is pried out of the countersink hole  16   b  by the flat blade end B of a screwdriver or similar device. When the screwdriver is removing a guide  60  from a hole  16   b , the locking ring is either snapped off as it is pried upwardly through the hole or it deforms. 
     FIG. 7 shows a modification of the guide insert of FIG. 6 to be used to center a screw to be directly threaded into the wood piece, as in the embodiments of FIGS. 1-4. Here, the guide insert  70  is made in two separate pieces  71  which are placed in a countersink hole  16   b  which centers the insert hole  67  in the countersink hole. The screw  20  is placed into the guide hole  67  and the threading of the screw is started. Once the tip end of the screw is engaged in the wood piece the two halves of the guide insert  70  are removed from the hole, such as by a screwdriver blade tip or a pair of needle-nose pliers. The tip end of the screw will be properly centered because of the matching contours of the tapers of the countersink wall  16   a  and the tapered center body part  64  of the guide insert. 
     FIG. 8 is a modification of the inserts of FIGS. 6 and 7 in which the locking ring  66  has been eliminated. Here, a layer  62   a  of an adhesive is placed on the lower surface of the top flange  62 . The adhesive holds the guide insert  60  in place in the countersink  16 . Once the hole is drilled, the insert is removed from the leaf  16  by prying up on the flange  62  to break the adhesive bond. This embodiment is both simpler to make and use than that of FIGS. 6 and 7 since the locking ring  66  is eliminated and it is not necessary to have to push the locking ring through the hole of the countersink to lock the insert in the countersink. 
     In the embodiment of FIGS. 9 a - 9   b , there is a piece of adhesive tape over the top flange  62  of the insert body  60 , which can be of one piece. Here, the insert is placed in the countersink and the adhesive strip  90  is fastened to the leaf  14 . After the pilot hole is made, the user lifts the adhesive strip  90  from the leaf to remove the insert from the countersink. The tape  90  can be transparent or opaque. In the latter case, a target can be printed to center the pilot hole. 
     In the embodiment of FIGS. 10 a - 10   b  the insert body is made of two pieces as in FIG.  7  and there is the piece of adhesive tape  90  on the top of the flanges of the pieces. As in the case of FIGS. 9 a - 9   b , the insert body  70  is positioned in the countersink  16  and the insert is used for the pilot hole or starting the insertion of the screw as described above. Here, the two pieces  71  of the insert can be removed with the drill or screw in place in the hole in the insert body. 
     In the embodiments of FIGS. 9 and 10 there can be a large rectangular piece of tape or a long strip of tape that is sectioned with a guide insert mounted to each section. The sections are torn from the larger adhesive piece or elongated strip and used as described above. 
     The embodiment of FIGS. 1-5 also can be used as drill guides. That is, the central hole  37  is made of a suitable diameter to accept a drill bit to be used to drill a pilot hole. The tapered guide bottom end  32  alone or in combination with the flange  38  of FIG. 3 b  or lugs and recesses of FIGS. 4 and 5. In this case, the body of the guide does not have to be of frangible material. Also, in all these embodiments the body  30  of the insert can be made with any desired height. 
     Each of the guides described herein can be made by any suitable process, such as injection molding. Thus, they are relatively inexpensive. The screw guides that fracture are disposable items and can be molded with the screws in place or the screws inserted after the molding. The insert and guides used for drill guides can be re-used. 
     Specific features of the invention are shown in one or more of the drawings for convenience only, as each feature may be combined with other features in accordance with the invention. Alternative embodiments will be recognized by those skilled in the art and are intended to be included within the scope of the claims.