For these reasons no method of sharpening which fulfils all conditions satisfactorily has yet been discovered.
The simplest and at the same time the least durable method of sharpening is: 1. That by means of ice-nails or frost-nails ([Fig. 158]). One or two nails are drawn from each branch of the shoe and replaced with ice-nails.
2. Sharp Toe- and Heel-Calks.—The outer calk is split and a small steel wedge welded in. It is then laid upon the edge of the anvil, indented and sharpened from within to without in such a manner that the calk shall be thin from the branch to the ground, and the outer surface shall be in the same vertical plane as the outer edge. If a calk is narrow from its base to its end, and at the same time without flaw, it does not need a sharp cutting edge. The inner calk should never be sharpened except the ground be very slippery. The cutting edge of this inner calk stands at right angles to the length of the branch, and its outer corner should then be rounded to prevent its injuring the opposite foot ([Figs. 159], [160]).
Fig. 159.
Fig. 160.
Outer and inner heel-calks sharpened.
For horses used for heavy draft purposes a toe-calk is welded to the shoe and sharpened. For this purpose we use only steel (toe-steel), which is easily welded to the shoe and remains firm. Toe-calks and steeled heel-calks are tempered, in order, as much as possible, to lengthen their period of durability. This method of sharpening is the oldest and most wide-spread, and is employed on the shoes of all horses of which we require more than light service.
Fig. 161.