53. Whetting Beveled Edge Tools.
—The grindstone does not sharpen tools; that is the work of the oilstone. No tool, after it has been ground, is ready for use until it has been whetted.
54. Oilstones.
—Oilstones in common use are of two kinds; those which are of very fine grained natural stone and those which are manufactured by pressing a powdered, metal cutting substance into rectangular forms. In selecting an oilstone it should be remembered that the finer the grain, the keener the edge it will produce but the longer time it takes to produce it.
Manufactured stones are frequently made “two in one,” that is, coarse and medium or medium and fine are put together in such a way that one side gives a rapid cutting and the other a slower but smoother cutting surface. The advantage of such a stone is easily understood.
Oil is used on stones to cleanse the pores of the stone of the little particles of steel cut from the tool. Were it not for the oil’s mixing with and removing these particles, the surface of the stone would soon become smooth and friction so reduced that the cutting power would be greatly interfered with.
While but a part of the stone need be used at one placing of the tool, effort should be made to utilize as much of the surface as possible that the surface may be kept level as long as possible. Stones that have worn uneven may have their surfaces leveled by rubbing them on a piece of sandpaper or emery paper placed on a flat surface.
55. Sharpening the Chisel.
—Hold the tool as shown in [Fig. 103]. Suppose the grinding produced a bevel of about twenty-five degrees, in whetting, effort should be made to hold the blade so as to produce an angle slightly greater than this. The amount shown in [Fig. 107] a and b is exaggerated. The aim at all times should be to keep this second angle as near like the first as is possible and still get a straight bevel to the cutting edge.
