Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 154

The choice of a suitable oilstone is one of the greatest difficulties that present themselves to the woodworker when selecting his tools. The degree of hardness is important, oilstones having a tendency to become harder after being in use for a time. Many of the American oilstones are manufactured from fine grit, cemented together. Generally they are even in grain, but are often too coarse, and although they sharpen the tool quickly enough, the cutting edge is not sufficiently keen for woodworking, and should be finished on a stone of finer texture. Natural stones are often uneven in grain, but, with care in selection, they can be obtained far better and more lasting than artificial stones. If a natural stone is wetted, the grain will show up clearly, and if it is uneven, or if there are fossils embedded in the stone, unequal wear will be the result, and it will be necessary to rub it down frequently. The colour also forms a guide to a slight extent; if this is variable, the wear will probably be variable. In choosing an oilstone from a number of the same variety, the cutting properties can be judged by rubbing the surface with the thumb nail, but this is only a comparative test, as a rougher surface will always be found on new or freshly rubbed down stone than on one that has been in use for sharpening tools for some time. For this reason, sharpening a tool on a new stone is not a true test of its cutting properties. If a tool-dealer’s catalogue is examined, several varieties of oilstone will be found enumerated in it, the prices of which may be anything from 6d. to 15s. In purchasing an ordinary tool, paying a good price generally procures a good article; but this is not so with oilstones, as bad ones are often to be found among high-priced articles.

Figs. 437 to 440.—Oilstone Slips.