Читать книгу The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking - Paul N. Hasluck - Страница 159

When an oilstone has been in use for some time its surface is apt to become hard, especially if certain oils—paraffin in particular—are used on it. The reason is that the pores of the stone are closed by the viscid or gummy oil, which contains particles of steel rubbed off in sharpening; when the stone is in this condition it is not touched by the tool, which rides upon a substance as hard as itself; therefore the stone fails to cut the tool. A mixture of oil and turpentine is often applied to hard stones to clean them and make them cut; for this purpose, also, they are sometimes boiled in soda water. Hard oilstones may be made to cut and give edges to tools by sprinkling a very little flour emery on them after the oil has been applied, but in this case it is the emery and not the stone that cuts.

Fig. 445.—Oilstone Case, Moulded.