To assist in keeping the arms steady, they are pressed firmly to the sides of the body as far as the elbows; and to traverse the tool across the face of the stone, the workman swings bodily from side to side without moving his foot, so as to shift the tool gradually, and almost constantly, without disturbing the position of the arms, which would be liable to grind a second facet upon the bevil of the tool, or otherwise to grind the edge rounding instead of in a right line. The grinding should be continued until nearly the whole of the bevil made in the sharpening on the oilstone has been removed, but unless the iron be notched, it is advisable to avoid grinding it to an absolute edge, which would be liable to produce a wiry film, the removal of which is troublesome.
To ensure the bevel being ground flat, it is in all cases necessary that the tool should be held at the same angle throughout, and also that the edge of the tool should be applied at the same height above the axis of the grindstone. Should the edge of the tool be shifted upwards a little during the grinding, a second facet would be ground somewhat more acutely, and if shifted downwards another facet somewhat more obtusely; the combination of the two movements would produce a rounded instead of a flat chamfer, whereas if the tool be held quite steady, the chamfer will be ground slightly concave, from the circular form of the stone, and which is desirable in tools for wood, as they then cut more keenly.
Carpenters' chisels are ground in exactly the same manner as plane irons, but chisels below about half an inch wide are more difficult to grind square, as the oblique position of the tool in plan, is not so readily detected in narrow chisels.
Carpenters' gouges are ground in the same manner as chisels, except that while the fingers of the left hand are held quite steady to give the requisite pressure, the tool is rotated in the right hand, backwards and forwards, in an arc of about one third of a circle, much the same as in boring a hole with a bradawl. Gouges that are sharpened from the inside do not admit of being ground on a flat stone, they are therefore in general thinned with a slip of gritstone in the same manner as the moulding plane irons explained in the next paragraph. Moulding plane irons are not generally ground because from heir complicated forms they would require grindstones fashioned expressly to suit nearly every kind, but preparatory to sharpening with the oilstone slip, the bulk of the material is removed either with files, or narrow slips of gritstone applied in much the same manner as the file. The irons of moulding planes like those of ordinary planes are always made principally of iron, with a thin facing of steel to constitute the cutting edge, the file may therefore be successfully applied to remove the bulk of the iron, leaving little more than the thin steel edge to be abraded by the oilstone slip. As mentioned at page 493 of Vol. II. care is required in restoring the edges of moulding plane irons to keep the figure of the cutter in the proper position to fit the plane. Concave plane irons may be successfully ground on the conical grinders employed for concave turning tools, and explained in the fourth section of this chapter.
The soft wood turning chisel is ground with two bevils meeting at an angle of from 25 to 40 degrees as explained on page 513 of Vol. II. and as there shown the edge is placed oblique at an angle of about 25 degrees. In grinding this chisel the stone should revolve towards the edge of the tool, the rest is not generally employed, but for the one bevil the handle is grasped with the right hand, whilst the pressure is applied with the fingers of the left, much the same as in grinding the plane iron; but the shaft of the chisel must be held at an angle in order to place the edge square upon the grindstone. When the chisel is turned over to grind the second bevil, of course the angle at which the shaft is held must be reversed, and also the position of the hands, the left then grasping the handle and the right supplying the pressure. As in the plane iron it is desirable not to grind the tool quite to an edge, but to leave a narrow line of the facet produced in sharpening.
In grinding a turning gouge, which requires to have an elliptical edge as noticed on page 512 Vol. II. the stone generally travels from the operator. The tool is held much the same as a turning chisel, except that the oblique position of the shaft is uncalled for, and to give the elliptical form to the edge, the gouge is twisted in the hand half a turn backwards and forwards; and it is at the same time traversed across the face of the stone, not in a straight line against the rest, as for most rectilinear tools, but out of contact with the support, and in a semicircular path like an inverted arch, the sides of the gouge being applied nearer to the top of the stone than the middle of the gouge; a few trials will render this action familiar.
Flat tools for turning hard wood, ivory, and steel, are ground with the stone running towards the operator, and the tool is applied face upwards on the rest, and inclined vertically to the suitable angle for the edge, which is generally from 60 to 80 degrees, but flat tools and chisels must be held square horizontally to avoid producing oblique edges. The handle of the tool is grasped in the right hand whilst the fingers of the left applied near the edge serve to steady the tool, which is gradually traversed across the face of the stone, but to keep the edge straight care must be taken that both hands are moved equally, or parallel with the axis of the stone, otherwise the edge of the tool will become rounded.
Right and left side tools are most conveniently ground with the stone running backwards, and the tool is applied at the top of the stone, with its face or upper surface towards the operator, and its shaft parallel with the axis of the stone, the tool being inclined backwards in order to give the required bevil. For grinding the end, the stone travels forwards as usual, and the tool is applied on the rest as in grinding a flat tool.