This term has been given to a variety of convenient modern instruments, especially adapted to the sharpening of knives at table, but particularly carvers, and are intended as substitutes for the common steel. For these instruments several patents have been obtained, and a considerable manufacture of them has been established.
Fillton's Patent Sharpener, without its usual accompanying ornaments, is represented in the annexed cut; it consists of two horizontal rollers, placed parallel to each other, which revolve freely upon their axes, (represented by the two black dots;) at uniform distances, there are fixed upon each roller, narrow cylinders or rings of hard steel, the edges of which are cut into fine teeth, and thus form circular files; the edges of the files in the opposite rollers overlap each other a little, so that when a knife is drawn longitudinally between them, the edge of the knife is acted upon on both of its sides at once. The rollers turn round with the slightest impulse, consequently, they wear uniformly, and will last a considerable time. A good edge is given to a knife by just drawing it from heel to point two or three times between the rollers; and thus obviates the necessity of imi-tating the skill exercised by a butcher upon his steel.
Westby's Knife-sharpener, which was patented in 1828, is a very pretty and ingenious instrument; an immense quantity of them have been sold, and it is said, have been the means of greatly enriching the proprietor of the patent. in the engraving on the next page, Fig. 1 exhibits an end elevation of the instrument, and Fig. 2 a side elevation of the bars, with a section of the boxes a and b, to show the interior. The same letters in each figure have reference to similar parts; a is a small oblong box, surmounted by a smaller box b; in the top of the latter there is a slit made throughout its length, and of sufficient width to receive the square steel bars c c. The box a has two similar slits. The surfaces of the bars are draw-filled,they pass through the slit in b, and alternately through both slits in a, so as to cross each other. as shown in Fig. 1. The lower ends of therse bars are supported upon a plate of metal d, which can. be elevated, so as to9 a bring a different portion of the bars into operation, by means of the screw underneath; ff are two screws passing through the holes in d, to preserve its parallel motion, and likewise to support the bottom of the box; h is a tightening screw to steady the bars c c.
The mode of operating with this instrument is merely to place the edge of the knife upon the bars, so as to bisect the angle formed by them, and then draw the knife backward and forward. As the surfaces of the bars wear away, different sides can be presented, or they can be shifted from end to end, so as to present fresh surfaces to the knife.
Church's Patent Knife-sharpener consists of two very flat truncated cones, fixed with their smaller surfaces together, and with several rectangular projections in the one, fitting into similar cavities in the other. The conical surfaces of both pieces are serrated with a series of very fine teeth extending angularly towards their centres; these are placed upon the shank of the fork, between the shoulder and the handle, with which they correspond in diameter so nearly as to constitute an ornamental finish to the small end of the handle. In the position and size of these consist the principal merit of the sharpener. When used for sharpening scythes, or other large cutting instruments, the conical pieces are made larger, and fitted on an axis between two prongs of a forked apparatus, with an appropriate handle.
The extraordinary success attendant upon Mr. Westby's contrivance for sharpening table-knives induced him to figure a second time as a patentee, "for certain improved apparatus to be used for the purpose of whetting or sharpening the edges of the blades of penknives, razors, and other cutting histruments." The first improvement mentioned in the specification consists in the application to a hone, or oil-stone, of a guide to keep the edge of the razor, or other cutting instrument, at the same angle with respect to the surface of the hone, during the operation of whetting. This is effected in two ways; first, by placing over the hone a plate of metal extending its whole length, and adjustable, at any required distance parallel to its surface, by set screws; now, in the operation of sharpening, the back of the instrument is kept resting upon the guide-plate, while the edge is applied to the hone. The second method consists in the application of two hones placed in an erect position, with a space between them for the razor, which is to be fixed by screws into a small horizontal frame, made to slide upon a circular rod, so that the edge can be applied alternately to the hones; these can be elevated and depressed at pleasure, so that their surfaces may be uniformly worn while in use.
The patentee also mentions in his specification a method of attaching to his hone a leather strap which is made double, and kept stretched by adjusting screws attached to the frame of the hone, or else to the end of a rod extending lengthways between the two folds of leather. This last contrivance does not appear to us to be scientifically adapted to the object in view, as the pressure of the edge of the instrument upon a strap of leather only supported at its extremities, must produce a tendency in the leather to wrap round the acute angle of the edge of the instrument, and render it obtuse.