Fig. 2171. Fig. 2172. Fig. 2173. Fig. 2174. Fig. 2175.
The diamond point chisel, [Figs. 2171] and [2172], may be made in two ways. First, as in [Figs. 2173] and [2174], for shallow holes, and as in [Figs. 2171] and [2172] for deep ones. In shallow holes the chisel can be leaned over, as in [Fig. 2176] at y, whereas in deep ones it must be held straight so that the chisel body may not meet the other side of the hole, slot, or keyway. The form shown in [Fig. 2172] is the strongest, because its point is brought into line with the body of the steel, as shown by the line q. The side chisel, [Fig. 2175], for cutting out the sides of keyways or slots, should be bevelled from w to the cutting edge for the reasons already given, and straight from w to v, the line v w projecting slightly above or beyond the body u. An application of the cow mouth chisel is shown at l, and one of the side chisel is shown at z in [Fig. 2176]. All these chisels are tempered to a blue color.
Fig. 2176.
The chisel that is driven by hammer blows may be said to be to some extent a connecting link between the hammer and the cutting tool, the main difference being that the chisel moves to the work, while the work generally moves to the cutting tool. In many stone-dressing tools the chisel and hammer are combined, inasmuch as that the end of the hammer is chisel shaped; an example of this kind of tool being given in the pick that flour millers use to dress their grinding stones. On the other hand we may show the connection between the chisel and the cutting tool by the fact that the wood-worker uses the chisel by driving it with a mallet, and also by using it for a cutting tool for work driven in the lathe. Indeed, we may take one of these carpenter’s chisels and fasten it to the revolving shaft of a wood-planing machine, and it becomes a planing knife; or we may put it into a carpenter’s hand plane, and by pushing it to the work it becomes a plane blade. In each case it is simply a wedge whose end is made more or less acute so as to make it as sharp as possible, while still retaining strength enough to sever the material it is to operate upon.
Fig. 2177.