The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking. Paul N. Hasluck

is delayed much longer than in Fig. 142, where the facet is on the whole convex instead of concave. Fig. 141 approaches to the hollow razor form (Fig. 143), and for some little time the grinding angle and the sharpening angle will coincide; after awhile it becomes necessary to tip the facet in sharpening (see Fig. 144), and the sharpening angle is gradually rendered more obtuse until regrinding becomes necessary. But in Fig. 142 the sharpening angle is obtuse from the beginning, and regrinding soon is necessary. Moreover, since the angle is so obtuse, a greater expenditure of energy than in the former case is necessary to remove the shavings, there being less penetrative power. This is apparent from the dotted lines, which show the effective angles of the two by comparison. The endeavour, then, should be to preserve the wedge-like form of a tool edge as long as possible, the grinding of the hollow facet being regarded as of the greatest importance. Chisels are often badly sharpened by tilting up the face for the purpose of turning back the wire edge. The result is that the face is like Fig. 145. This again detracts from the wedge form. Worse than that, it destroys the guidance afforded by a perfectly flat face, this being a very important point. The chisel must be tilted before it will cut, and there is no longer that contact of broad faces which is conducive to the guidance of the tool, and the difficulty of cutting surfaces and ends is much increased. No matter how flat the general area of the chisel face is, if there is a second facet, however narrow at the cutting edge, that determines the action of the tool. The tool angle is measured between that and the sharpened facet on the bevelled face. Of course, with all tools the labour of cutting is increased as the wedge form becomes impaired by legitimate wear, that is as their angles become more obtuse. When the amount of this is slight only, the tools need sharpening; but when, by repeated sharpening, the tool angle becomes very obtuse, grinding is necessary to remove material in greater quantity. The grinding and sharpening of chisels are operations practically identical with grinding and sharpening plane irons (see pp. 54 and 55). Fig. 146, however, shows the position in which the chisel is held on the oilstone.

      Fig. 139.—Sash Mortise Chisel.

      Fig. 140.—Socket Lock Mortise Chisel.

      Fig. 141.—Correctly Shaped Chisel Edge.

      Fig. 142.—Incorrectly Shaped Chisel Edge.

      Fig. 143.—Section of Hollow-ground Razor.

      Fig. 144.—Obtuse Angle of Old Chisel Edge.

      Fig. 145.—Badly Sharpened Chisel Edge.

      Fig. 146.—Sharpening Chisel on Oilstone.

      GOUGES.

      A few gouges also (Fig. 147) may be found useful. Their action is that of a chisel, but instead of being flat their sections form arcs of circles. Fig. 148 shows the sectional curves to which gouges are made.

      Fig. 147.—Cast Steel Firmer Gouge.

      Fig. 148.—Gouge Curves.

      DRAWING KNIFE.

      The drawing or draw knife has its typical form illustrated by Fig. 149. It is used for roughing stuff to shape preparatory to working with finer tools.

      Fig. 149.—Drawing or Draw Knife.

      SPOKESHAVES.

      This spokeshave (Fig. 150) is made in various forms; the one illustrated is of box-wood, and the simplest made; but this form is not recommended, many better kinds being made entirely of iron, with screws to regulate the cutting-iron. An iron spokeshave is shown by Fig. 151. The beech-wood spokeshave shown by Fig. 152 has a metal plate in front of the blade, and that shown by Fig. 153 is regulatable by means or the thumbscrews. In principle, the spokeshave is merely a knife or chisel edge in a suitable two-handled holder. In use it may jump if the iron is loose; if the back part of iron touches before the cutting edge; if there is insufficient clearance for the shavings in the mouth; if the cutting edge of the iron is worn to an obtuse angle and requires grinding; or if the face of shave is either too flat or too round; or the defects may simply be due to want of skill. With some kinds of ash it is very difficult to get a level surface with a spokeshave, and a compass plane should be used.

      Fig. 150.—Wooden Spokeshave.

      Fig. 151.—Iron Spokeshave.

      Fig. 152.—Plated Spokeshave.

      Fig. 153.—Spokeshave with Regulatable Blade.

      SHARPENING SPOKESHAVE BLADES.

      It is somewhat trying to the hands of the operator to sharpen the short blades used in iron spokeshaves and small planes. The difficulty, however, may be readily overcome as follows: Procure a piece of hard-wood about 10 in. or