. Teacher's handbook of Slöjd . JD. and absorbs a portion of the surplus water. The stone mustalways be turned toiuards the worker and towards the edgeof the tool, which must be moved steadily, and with equalpressure from side to side, across the whole breadth of thestone, to prevent the formation of scratches or depressions onits circumference. The bevelled edge produced by grindingmust present either a flat or a concave surface to the convexsurface of the stone. It must never be convex. The con-straight cavc form of the bevelled edge is advantageous, because it^^^^ materially lightens the fi
. Teacher's handbook of Slöjd . JD. and absorbs a portion of the surplus water. The stone mustalways be turned toiuards the worker and towards the edgeof the tool, which must be moved steadily, and with equalpressure from side to side, across the whole breadth of thestone, to prevent the formation of scratches or depressions onits circumference. The bevelled edge produced by grindingmust present either a flat or a concave surface to the convexsurface of the stone. It must never be convex. The con-straight cavc form of the bevelled edge is advantageous, because it^^^^ materially lightens the final sharpening on the oilstone. The edge must also be quite straight unless a curved edge isactually required. As it is difiicult, especially for the inexperienced, to hold the steel steadily enough against the stone, a grinding sup- Accurate port has been invented. Such a support of American make grinding, ^g sliowu in Fig. 84. It cousists of au iron frame into which the plane-iron or the chisel is screwed. A small wheel below. Fig. 84. Grinding-support, or grinding-rest. i. the frame revolves upon the grindstone, and the desired angleon the edge of the tool is obtained by fastening it in withthe edge at a shorter or longer distance from the frame. Bymeans of this simple contrivance even an inexpert pupil isable to grind a plane-iron correctly. A very common fault in grinding is to make the anglewhich the bevelled edge makes with the face of the tool too TOOLS. 117 great, , to make the edge too thick. This is often doneby beginners in their haste to be relieved from grinding. The tool must be ground till a raw edge appears, , the rhe rawvery thin film or hair produced by the grindstones remov- ^^^•ing the very edge of the steel. This, in its turn, is removedby the oilstone. Sharpening with the oilstone is necessary, because the edgeproduced by the coarse-grained grindstone is neither fineenough nor even enough for immediate use. ^ The oilstone is a 1|F ^^^^^^^^^^^Bi
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