FIELD OF THE INVENTION
This invention relates to honing jigs and more particularly to a jig for sharpening the cutting edge of a blade in a tool such as a plane and a chisel. In one embodiment of the invention, the jig has provision for adjustment of the inclination of the blade according to the angle of its cutting surface. In another embodiment, the jig has provision for honing a secondary bevel on the cutting edge.
BACKGROUND OF THE INVENTION
The conventional method of sharpening a blade of a chisel or a plane is to clamp the blade to a honing tool having a roller and to push the tool across an abrasive surface such as that of a whetstone. Such a method has a number of shortcomings, one of which is that skill is required to operate the tool properly. Many carpenters and particularly hobbyists lack such skill and do more harm that good to a blade when they attempt to sharpen it by this method.
Anther shortcoming of the method is that the tool tends to run off the whetstone as it is pushed back and forth. Unless particular care is taken to prevent this, the blade can be damaged as it is being pushed. Furthermore, the operator may injure himself since his hand may be struck by the blade if his hand is in its path.
SUMMARY OF THE INVENTION
In one aspect of the present invention, a honing jig for use in sharpening an object generally comprises a base adapted to support an abrasive substance thereon and a carriage assembly constructed for releasably mounting the object to be sharpened. The base and carriage assembly are mounted with respect to each other for obtaining relative translational movement of the object mounted on the carriage assembly and the abrasive substance on the base so that a portion of the object engaging the abrasive substance is sharpened.
In another aspect of the present invention, a honing jig for use in sharpening a blade generally comprises a base adapted to support a whetstone thereon, and guide rails pivotally mounted on the base at one end of each guide rail. A carriage assembly comprises a slider and a fixture pivotally mounted on the slider. The slider is mounted on the guide rails for movement along the guide rails with respect to the base. The fixture is adapted to mount the blade thereon. The slider and fixture include alignable apertures, where at least some of the apertures are located in positions so that the fixture must assume different angles with respect to the slider to align different apertures. A pin receivable in selected aligned apertures can thereby fix the angular orientation of the fixture relative to the slider. A stepped pedestal is adapted to support the guide rails in a first position in which the guide rail makes a first angle with the base, and in a second position in which the guide rail makes a second angle with the base different from the first angle.
In yet another aspect of the present invention, a method of honing a blade generally comprises pivotally moving a blade fixture at a selected angle for the blade. The blade fixture is secured at the selected angle mounting the blade in the fixture at the selected angle, and then the securement of the fixture is released. The blade is moved into engagement with an abrasive substance, and the blade is translated across the abrasive substance to hone the blade.
BRIEF DESCRIPTION OF THE DRAWINGS
The honing jig of the invention is described with reference to the accompanying drawings in which:
FIG. 1 is a perspective view of the honing jig;
FIG. 2 is a fragmentary elevation of a carriage and a swiveling clamp of the jig together with the upper portion of a blade;
FIG. 3 is a plan view of a portion of the swiveling clamp;
FIG. 4 is an exploded perspective view of the components which are illustrated in FIG. 2 and which make up a primary adjusting apparatus;
FIG. 5 is a fragmentary, longitudinal section of the honing jig with parts of a clamp of the swiveling clamp broken away to show internal details;
FIG. 6 is a fragmentary, longitudinal section similar to FIG. 5, but illustrating movement of the blade over the whetstone;
FIG. 7 is a fragmentary, exploded perspective view of the components which make up a secondary adjustment apparatus;
FIG. 8 is an elevation of the honing jig showing a secondary adjustment apparatus in one position;
FIG. 9 is the elevation of FIG. 8, but showing the secondary adjustment apparatus in another, raised position;
FIG. 10 is an enlarged, fragmentary elevation of the honing jig and blade, with the blade in a position corresponding to FIG. 8;
FIG. 11 is the enlarged, fragmentary elevation of FIG. 10, but showing the blade in the position corresponding to FIG. 9.
Like reference characters refer to like parts throughout the description of the drawings.
DETAILED DESCRIPTION
With reference to FIG. 1, the honing jig has a base 10 on which is mounted, at one end, two pairs of spaced supporting blocks 12a,b. An end member 14 has opposing trunnions 16 which extend into bores in each supporting block so that each end member is pivotal with respect to the base. An end of one of a pair of spaced guide rods 18a,b is accommodated in each end member. The opposite ends of the guide rods are mounted to a dual supporting block 20, described more fully below. A sliding tube 22 is mounted for sliding to each guide rod 18a, 18b. A carriage, indicated generally at 24 includes a transverse or adjustment plate 26 which has a passageway 28 at opposite sides for receipt of the sliding tubes. The sliding tubes 22 are pressure fitted into the passageways 28 or otherwise suitably connected so that the carriage 24 is moveable or slidable on the guide rods 18a, 18b. The carriage has a means for removably fastening a blade 32 thereto in the form of a swiveling clamp 30 which swivels relative to the transverse plate. A blade 32 to be sharpened is held firmly by the clamp so that its lower edge 32a is in contact with an abrasive substance such as a whetstone 34. In the description that follows the swiveling clamp 30 is sometimes referred to as the “primary angle-adjusting apparatus” of the jig. A pair of collars 36 acts as stop points for the carriage 24. Set screws 38 permit the position of the collars to be moved. The collars 36 are mounted on one of the guide rods 18b, but may be mounted on different rods, or located off the rods.
The whetstone is seated on base 10 and is located on the base by stop members 40a,b at each of its ends. Stop member 40a is immovably fixed to the base while stop member 40b is moveable in a T-slot 42 in the base 10 by loosening thumbscrew 44 so that the spacing between the two stop members can be adjusted to accommodated whetstones of different lengths. Whetstones of different lengths can be commonly encountered in the market, and the honing jig of the illustrated embodiment is capable of accommodating them.
With reference to FIGS. 2 to 4, the swiveling clamp 30 is composed of lower and upper jaws 46, 48 respectively. The jaws are interconnected by a pair of threaded studs 50 which are fixed to the lower jaw 46 and pass through openings in the upper jaw 48. Knobs 52 are threadably connected to the studs 50 and loosening of the knobs allows the jaws 46, 48 to be manually separated to receive blade 32. Conversely, tightening of the knobs 52 causes the jaws 46, 48 to immobilize the blade 32 in position for sharpening. Extending beneath the lower jaw is a block 54. The block is one of the components of the primary angle-adjusting apparatus and is sometimes referred to below as the “angle-adjusting block”. The block 54 has trunnions 55 which extend outwardly from its oppositely facing side walls and into openings in spaced apart ears 58 which extend outwardly from a rear wall 26a of the transverse plate. The front wall 54a of the angle-adjusting block 54 closest to the adjustment plate 26, as it extents downward, curves anyway from the adjustment plate so that the block is free to pivot without interference by the adjustment plate. As angle-adjusting block 54 pivots, so too do the lower and upper jaws 46, 48 of the clamp 30. The position of the block 54 accordingly governs the inclination of the jaws 46, 48 and the inclination of the blade 32.
A number of apertures 56 extend through the adjustment plate 26. The apertures 56 are spaced apart from each other and extend from the front wall 26b through the rear wall 26a. A series of apertures 60 extend inward from the curved area of the block 54 and are arranged, as illustrated in FIG. 3, such that the first aperture 60a is highest and each aperture next in succession is lower than the immediately preceding aperture, the last aperture 60b being the lowest. Each aperture 60 formed in the block 54 aligns with a corresponding aperture 56 in the adjustment plate 26. The first aperture 60a in the block 54 aligns with the first aperture 56a in the plate 26, the second aperture 60c in the block aligns with the second aperture 56b and so on. However, since the apertures 56 in the plate 26 are arranged on a horizontal line whereas the apertures 60 in the block 54 are on a line at an angle with the horizontal, the block must be pivoted to bring each of the pairs of apertures into alignment. In one embodiment, the positioning of adjacent apertures 60 may correspond to roughly a 5° change in angulation of the blade 32 held by the jaws 46, 48.
In FIG. 4, the first aperture 56a in the plate 26 is in alignment with the first aperture 60a in the block 54. In order to bring the second aperture 56b in the plate 26 into alignment with the second aperture 60c in the block 54, the block must be pivoted clockwise. It will be understood that only one aperture 56 in the adjustment plate 26 will align with one aperture 60 in the angle-adjusting block 54 at any given angle of the block. The next aperture in the plate will only align with the next aperture in the block when the block is be pivoted sufficiently and as the block is pivoted, the first apertures will move out of an alignment.
In summary, each aperture 56 in the adjustment plate 26 will align with only one aperture 60 in the angle-adjusting block 54 at any one time and when an aperture in one is in alignment with an aperture in the other, no other apertures will be in alignment. Only by pivoting the block will other the apertures 56, 60 in turn be brought into alignment. Pivoting of course causes jaws 46, 48 to conjointly pivot with resulting pivoting of the blade 32 so that the inclination of the blade relative to the whetstone 34 will vary according to which apertures 56, 60 in the plate 26 and block 54 are in alignment. The shank of a locating pin 64 is receivable in any one of the pairs of apertures 56, 60 in alignment. The pin 64 acts to rotationally lock the block 54 relative to the plate 26. Such immobilization causes a like immobilization of the blade 32.
With reference to FIG. 5, angle 66 is a measure of the inclination of blade 32 relative to the upper surface of the whetstone 34. As indicated previously, that angle is adjustable according to which apertures 56, 60 in the plate 26 and block 54 are in alignment. The locating pin 64 serves to immobilize the block 54 and when the block is so immobilized, it is at a so-called “stop point”. The number of stop points will of course equal the number of apertures 60 in the block 54. Movement of the block 50 from one stop point to the next causes an incremental change in the inclination of the blade 32. The number of apertures 56, 60 may be other than illustrated within the scope of the present invention.
The operation of the locating pin 64 is as follows: first an operator immobilizes the swiveling clamp 30 relative to the adjustment plate 26 at a predetermined angle by inserting the pin through selected aligned apertures 56, 60. He then positions the cutting edge of a blade 32 to be sharpened on the whetstone 34 and secures the blade to the swiveling clamp 30. He then removes the pin 64 to allow him to force the cutting edge into firm and solid contact with the whetstone so that the whetstone can sharpen the edge. the angle of the blade 32 relative to the whetstone set by the pin 64 is not materially changed. The operator can then move the blade 32 back and forth on the whetstone in order to sharpen the cutting edge. Friction between the cutting edge 32a and the whetstone 34 will hold the blade at the same angle.
Should the operator desire to alter the existing angle of the cutting edge 32a, he would disconnect the blade 32 from the swiveling clamp 30, set the swiveling clamp at the new angle by means of the locating pin 64, place the blade so that its cutting edge 32a is in contact with the whetstone 34, secure the blade to the swiveling clamp and finally, remove the locating pin. The cutting edge 32a of the blade 32 is then ready to be sharpened as before, but at a new angle.
As previously indicated, the location of the apertures 60 in the block 54 will determine the angle of the blade 32 at each stop point. It is preferred that the angle at each stop point be an integer and the angle between successive stop points be always the same. For example the angle at the stop points can be 15, 20, 25, 30 degrees and so on. However, other angles may be used without departing from the scope of the present invention. In FIG. 6, the carriage 24 has moved to the right from the position illustrated in FIG. 5 and the lower wall of the blade 32 has moved along the upper surface of the whetstone 34.
With reference again to FIG. 1, the primary angle-adjusting apparatus is the swiveling clamp 30 as previously indicated. The secondary angle-adjusting means is the dual supporting block 20 in conjunction with a pedestal 68, described below. With reference to FIG. 7, block 20 is in one piece and both guide rods 18a, 18b are attached to it. The block 20 is seated on pedestal 68 which is slidable on base 10. A handle 70 is provided for facilitating the sliding. The pedestal 68 has a pair of slots 72 for receipt of threaded studs 74 which are fixed to the base 10 and project upwardly therefrom. The pedestal 68 has a stepped upper wall, the inner step 68a being lower than the outer 68b.
The dual supporting block 20 has a pair of apertures 76 for receipt of studs 74. Knobs 78 are threadably received on the upper ends of the studs 74. Tightening of the knobs 78 immobilizes both the supporting block 20 and the pedestal 68. Loosening of the knobs 78 allows the supporting block 20 to be raised so that the pedestal 68 is free to slide forward or backward with the studs 74 moving in the slots 72. The pedestal 68 can be slid from the position illustrated in FIG. 8 in which the supporting block 20 is resting on the lower step 68a to the position illustrated in FIG. 9 in which the supporting block is resting on the upper step 68b.
The ends of the guide rods 18a, 18b opposite the dual supporting block 20 are pivotally connected by end members 14 to supporting blocks 12a,b as previously indicated. Sliding of the pedestal 68 from the position illustrated in FIG. 8 to the position illustrated in FIG. 9 causes the dual supporting block 20 when again supported on the pedestal 68 to be disposed higher with resulting tilting of the guide rods 18a, 18b and raising of the swiveling clamp 30. As the swiveling clamp rises, the blade 32 tilts with respect to whetstone.
In FIG. 10, blade 32 is shown as it would appear when the pedestal is in the rear position illustrated in FIG. 8. FIG. 11 shows the blade as it would appear when the pedestal is in the forward position illustrated in FIG. 9. From the foregoing description it would be understood that the secondary angle-adjusting means, i.e. the dual supporting block 20 and pedestal 68 permits fine adjustment of the inclination of the blade 32 (e.g., on the order of about 10 in the illustrated embodiment) from the inclination of the blade at each said stop point of the swiveling clamp 30. When the blade 32 is in the position illustrated in FIG. 11, its forward edge 32b is below its rear edge 32c. Sliding of the blade along the whetstone will form a secondary bevel on its forward edge. A secondary bevel would be desirable, for example, when the blade was being used with hard woods and therefore required relatively frequent resharpening. By positioning the blade 32 in the position shown in FIG. 11, just the tip 32b with be resharpened. This can be carried out relatively quickly in comparison to resharpening the entire cutting edge 32a. The tip 32b could be sharpened several times before it would be again necessary to sharpen the entire cutting edge 32a.
It will be further understood, of course, that modifications can be made in the structure of the honing jig of the invention without departing from the scope of the invention as defined in the following claims.
Patent Application
20090004956
