Triangular tools that are required to cut very keenly, are ground in the same manner as the side tools, and by which the edges are made slightly concave; but when the triangular tool is required to be less penetrative and more durable, it is applied on the top of the stone, at right angles to its axis, and traversed quickly backwards and forwards as in grinding a flat surface. Square tools for turning brass are ground in the same manner as triangular tools. A graver is held point upwards on the rest, with the stone running towards the operator, and it is best to remove the extreme point by grinding a minute triangular facet, at right angles to the principal chamfer, but less in size than a pin's head, the tool performs as well, and the point is considerably strengthened; it requires only a touch on the stone. Many of the tools for metal are used at once from the grindstone, which could not be the case if a film were left upon them, as explained at page 1135.
Point tools are ground in the same manner as flat tools, except that the tool is held horizontally at the suitable angles for the point.
Large pointed drills that cut in the one direction only are ground the same as point tools, except that for the second edge the drill is turned over and applied at the same angle as for the first edge.
Small pointed drills that cut in both directions are generally sharpened on the oilstone without grinding. When the latter process is resorted to, however, the tool is held like a pen near the top of the stone, which runs backwards.
Round tools are held upon the rest much the same as flat tools, except that they are not traversed in a line across the stone, but while the extremity of the tool is kept nearly stationary, the handle is moved horizontally through a semicircle around the part of the tool supported on the rest, and which serves as the imaginary axis.
Round tools that are much bevilled are sometimes ground in a manner similar to the gouge, but without the rotation on the axis of the tool therein called for.
Heel tools for turning iron are supported upon the rest exactly in the position for turning, shown in figs. 415 and 417, page 525, Vol. II., but the handle is a little more depressed, to place the bevil at the suitable angle, and the tool is swept round in a semicircle like the round tools, the point of the heel serving as the axis of rotation.
Slide rest tools for metal turning are generally held upon the rest, and as they are mostly used direct from the grindstone without having recourse to the oilstone, it is desirable in all possible cases that the stone should run towards the edge. They are applied to the grindstone after the same general method as the hand tools of corresponding forms, but as explained in pages 530 to 534 of Vol. II., the fixed tools require additional care to preserve the proper angles for cutting, and the tool-gage, figs. 438 and 439, may with advantage be resorted to for determining the proper forms.
Detached cutters for fitting into cutter bars, such as those shown in figs. 440 to 442, page 535, Vol. II., are too small to be held in the fingers, they are therefore fixed in socket handles of appropriate forms, or otherwise they are grasped in a hand-vice, which serves as the temporary handle for applying them to the grindstone.
Screw tools and moulding tools used by hand, that are cut to their respective forms on steel hobs or cutters, as explained on page 591, Vol. II., are sharpened only upon their upper surfaces, as the forms of the tools would be impaired by grinding their ends. They are frequently sloped off on the face, and this method serves sufficiently well for tools applied to the hardwoods and ivory, but as explained on page 520, Vol. II., the slope increases the angle of the edge; and the method of nicking in the tools, shown in fig. 407, by applying them transversely on the grindstone, is far preferable for screw tools intended for iron and steel.