This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
The form of the cutting edge as seen in the side of the axe is often convex. The line across the face in Fig. 417 indicates the extent of the steel, and the corresponding line in Fig. 407 the bevel of the cleaving edge. It will be noticed that the cutting edge in each case is curved. The object of this is to prevent not only the jar and damage which might be done by the too sudden stoppage of the rapid motion of the heavy head in separating a group of fibres, but also to facilitate that separation by attacking these fibres in succession. For, assuming the axe falls square on its work in the direction of the fibres, a convex edge will first separate 2 fibres, and in so doing will have released a portion of the bond which held adjoining fibres. An edge thus convex, progressing at each side of the convexity which first strikes the wood, facilitates the entrance of successive portions from the middle outwards. If the edge had been straight and fallen parallel to itself upon the end of the wood, none of this preliminary preparation would have taken place; on the contrary, in all probability there would have been in some parts a progressive condensation of fibres, and to that extent an increase in the difficulty of the work.
The equally inclined sides of the wedge-form of edge hitherto alone described as belonging to axes, and the equal pressure this form necessarily exerts upon each side if a blow is given in the plane of the axe, suggest what will be the action of an axe if the angle of the wedge is not bisected by the middle line of the metal. Assume that one face only is inclined, and that the plane of the other is continuous to the edge, then let the blow be struck as before. It will be obvious that the plane in the line of the fibres cannot cause any separation of these fibres, but the slope entering the wood will separate the fibres on its own side. Supposing a hatchet sharpened as previously described, and one as now described, are to be applied to the same work, viz. the cutting from a solid block the outside irregularities - say to chop the projecting edges from a square log and to prepare it for the lathe. It may be briefly stated that the hatchet described in the second case would do the work with greater ease to the workman, and with a higher finish than the ordinary equally inclined sides of the edge of the common hatchet.
Coach-makers have much of this class of hatchet-paring work to do, and the tool they use is shaped as in Fig. 416. The edge is bevelled on one side only, and under where the handle enters the eye, may be noticed a piece rising towards the handle; on this the finger of the workman rests in order to steady the blade in its entrance into the timber in the plane of the straight part of the blade, and to counteract the tendency of the wedge side pressing the hatchet out of its true plane.
The principal forms of axe and hatchet, illustrated below, are as follows: - Fig. 406, colonial felling axe; Fig. 407, Australian felling axe; Fig. 408, wheelers' axe; Fig. 409, north country ship axe; Fig. 410, Dutch side axe; Fig. 411, Brazil axe; Fig. 412, broad axe; Fig. 413, Kent axe; Fig. 414, Scotch axe; Fig. 415, blocking axe; Fig. 416, coach-makers' axe; Fig. 417, coopers' axe; Fig. 418, long felling axe; Fig. 419, common ship axe; Fig. 420, Kentucky wedge axe; Fig. 421, Canada hatchet; Fig. 422, American shingling hatchet, with claw; Fig. 423, shingling hatchet, with hammer head.