Popular Science Monthly/Volume 9/June 1876/Axes and Hatchets, Ancient and Modern
TOOLS with cutting-edges are not only numerous and varied in form, but they are also varied in the purposes for which they are formed, and in the mode of using. Hence no very precise statement of what is generally meant by a "cutting-edge" can well be given. Three classes, however, of such tools may be marked out, and into one or other of these it is probable all those tools which can properly be defined as tools with cutting-edges may be arranged.
A first class will comprehend tools which meeting the work at a particular angle continue the path of each portion of the edge in the same straight line. Axes, adzes, gouges, chisels, and planes (as ordinarily used by carpenters), belong to this class. Such tools are brought into action either by impact or by direct thrust. The adaptation of machinery to tools in this class is easy, because the cutting-edge has to describe only a straight line, and this done once, if the place of application be removed, a repetition of impact or thrust in the same direction will suffice.
A second class will comprehend tools which, while as a rule retaining the angle at which they are applied to the work, the path of any portion of the tool is not a straight but a curved line. Tools of Class 2 are seldom acted upon by direct impact, or simple thrust. To adapt them to machine-work requires either a compound motion in the tool, or a motion compounded of the tool and work. When used as handicraft tools, this compound motion is derived from the muscular actions of the body of the workman, or the mechanical contrivances of construction in the tool. Knives, shears, razors, and saws, belong to this class. And to this class belong those tools in which what are mechanical contrivances for causing a "draw cut" are introduced, e. g., certain garden and pruning shears, also, hay and bread cutting knives. There is a motion in the human jaws which gives to the cutting teeth this "draw cut," and so they separate what is between them as draw-cut scissors might do. Indeed, all tools in this class operate most efficiently when acting upon the "draw-cut" system.
Hence, while certain of the human teeth belong to Class 1, others belong to Class 2. The contrivance in the jointing of the lower jaw to the upper in man is a compound one, adapting itself to three motions, one or other of which is found in many tools. There is up-and-down motion, enabling certain of the teeth to cut meat as nippers do. There is also a backward-and-forward motion, producing a saw or file like operation, and there is a lateral or side motion, producing such a result as that of grinding. It is probable that, from observation on the action of the teeth, the "draw cut," so essential to the perfection of tools that really cut, has been suggested.
Class 3 will comprehend those tools in which rotation is more usual than rectilineal motion. The tools in this class are constructed on principles allied to those in the two former classes. All drilling and boring tools belong to this class.
The action of tools with cutting-edges in Class 1, being the most simple, had better be first considered. As axes and adzes belong to this class, and as the structure of habitations probably led our ancestors to the formation of tools, doubtless that form of cutting-instrument which most commended itself to these primitive artificers would be the first to be constructed. Passing by the very early form, we may commence with a consideration of the edge of the axe or adze, when that edge became part of a constructed implement, and not a mere piece of sharp-edged flint. The construction essential to the tool is a handle, or, as it is called, a "helve." The shape of this helve, and the mode in which the head or metal of the axe is attached to it, are well worthy of some preliminary attention.
Perhaps here may be drawn the distinction between narrow and broad axes and hatchets. Axes are tools to be used with both hands; they have long handles, and may be swung as sledge-hammers. Hatchets are to be used with one hand, have short handles, they are much lighter and thinner than axes, and are employed more in the trimming than in the hewing of timber. Both narrow and broad axes are employed in forestry, the woodman's choice being affected by the size of the timber and the character of the fibre. A hatchet is handled with the centre of gravity nearer the cutting-edge than the line of the handle; an axe with the centre of gravity in the line of handle produced. Of this, however, more hereafter.
The mode of attaching a handle to an axe in the bronze age is very instructive to us. The illustrations are suggestive enough, and need only a passing remark. It will be observed that for the purpose of handling, some of these axes are socketed, others wedge-pointed. The socketed ones were evidently handled as we handle socketed chisels. There is, however, one peculiarity, and that worthy of consideration. These bronze hatchets have in many instances a semicircular, ring-like projection [see Figs. 4 and 5), the object of which was for a long time a puzzle, but the suggested mode of handling the implements, if correct as seen in the diagram, points to a knowledge of directions of tension and of pressure, which engineers at the present day cannot but admire. If any one has ever struck a common hatchet to any great depth into timber, and carelessly endeavored to loosen it by raising the extremity of the handle, he may have found the handle separate from the metal near the junction of the two. Now the withe, or lashing, shown in this bronze instrument, has been put, as we should put it at the present day, in order to strengthen the connection at this, the weakest part.
Figs. 3, 4, 5, are examples of the modes of handling these ancient bronze hatchets. Fig. 3 is the most primitive. Fig. 4 and Fig. 5 illustrate the mode adopted to strengthen by tension-cords the weakest part of the handle. A remnant of this tension-cord is probably seen in the increased depth now given to the handle, where it enters the eye. It will be noticed that Fig. 5 is socketed as a carpenter's heavy mortising-chisel. The commendable pride of these prehistoric workmen in the beauty of their tools may be inferred from the ornamentation of these bronze axe-blades.
When we pass from the tool and its contrived handle to the mode of using, and the purpose for which it has been constructed, we find, as a rule, a cutting-edge formed by two inclined surfaces meeting at an angle, the bisecting line of which passes through the middle of the metal. It is very apparent that the more acute this angle is, the greater, under the same impact, will be the penetrative power of the axe into the material against which it is driven. This supposition very soon needs to be qualified, for suppose the material offers a great resistance to the entrance of this edge, then the effect of the blow, upon the principle that action and reaction are equal, will react upon the edge, and the weakest, either edge of axe or object struck, must yield. Here, then, primitive experience would be obliged to qualify the simple tool in which the edge was keen and acute, and would naturally sacrifice the keenness and acuteness to strength.
When early uses of the axe are considered, it will be noticed that, even in fashioning with an axe or adze the same piece of wood, different conditions of edge are requisite. If the blow be given in the direction of the fibre, resistance to entrance of the edge is much less than in the blow across that fibre. So great, indeed, may this difference become, that while the axe in Class 1 seems in all respects a suitable tool, yet as the attention of the workman passes to directions inclined to the fibre at an angle of more than forty-five degrees, he will be induced to lay aside the tools in Class 1, and try those in Class 2; for he will have found that while in the one direction of the wood the edge of his axe continues sound and efficient, yet a few blows on the same timber at right angles to this direction have seriously damaged the perfection of the edge, whatever may be the angle at which the faces meet which constitute the edge.
These remarks apply only to tools used in dividing materials, and not to tools used in preparation of surfaces of materials. This preliminary consideration prepares us for the different circumstances under which these two classes of tools may be respectively used. And as the contrast of the effect of the same tool under different circumstances in the same substance is considerable, great also is likely to be the contrast between the edges of the tools and the manner of using them, e. g., the axe, which is the proper tool in the direction of the fibre, is operated upon by impact, while a saw, which is the proper tool across the fibre, is operated upon by tension or thrust, but never by impact.
The mode in which the axe is used will explain why it is unsuited for work across the fibre. The axe is simply a wedge, and therefore arranged to cleave, rather than to cut, the wood. Now, a calculation of the pressure necessary to thrust forward a wedge, and the impact necessary to cause the same wedge to enter the same depth, would explain why (regarded as a wedge only) the handle proves an important adjunct to the arm of the workman. Any one may test this by using an ordinary-handled hatchet on a soft straight-grained wood, or he may take a small axe with a straight and not a curved edge; let it rest upon a lump of moderately soft clay. Add weights until it has sunk to any decided depth, then take the axe by the head, and by pressure force the edge to the same depth. Next, hold the axe by the handle, first at, say, one foot from the head, then at two feet, then perhaps at three feet, and give blows which seem of equal intensity, and mark the depth. Thus a practical testimony to the value of a handle will be borne by the respective depths.
A few words about the motion of the hands and the handle they grasp; and then a consideration of the curves given to the cutting-edges of axes, adzes, etc.; also to the wedge-like sections of the edges. These will be all that can now be considered.
The motions of the hands on the handle of an axe are similar to those of a workman on that of the sledge-hammer. The handle of a properly-handled axe is curved, that of a sledge-hammer is straight. For present consideration this curvature may be overlooked, although it plays an important part in the using of an axe with success and ease. If the almost unconscious motions of a workman skilled in the use of an axe be observed, it will be noticed that, while the hand farthest from the axe-head grasps the handle at the same or nearly the same part, the other hand, or the one nearest to the head, frequently moves. Let us follow these motions and consider the effect of them. The axe has just been brought down with a blow and entered between the fibres of the wood. In this position it may be regarded as wedged in the wood, held in fact by the pressure of the fibres against the sides of the axe. From this fixity it must be released, and this is usually done by action on or near the head. For this purpose the workman slides his hand along the handle, and, availing himself (if need be) of the oval form of the handle after it has passed through the eye of the metal, he releases the head. The instrument has now to be raised to an elevation; for this purpose his hand remains near to the head, so causing the length of the path of his hand and that of the axe-head to be nearly the same. The effect of this is to require but a minimum of power to be exerted by the muscles in raising the axe; whereas, if the hand had remained near the end of the handle most distant from the head, then the raising of the axe-head would have been done at what is called a mechanical disadvantage. Indeed, if a workman will notice the position of the hand (which does not slide along the handle) before and after the blow has been given, he will find that its travel has been very small indeed. Remembering that the power exerted to raise a body is in the inverse ratio of the spaces passed through by the body, and the point of application of the power, it may thus be obvious how great a strain will be on the muscles if the axe-head be raised by the hands at the opposite extremity of the handle. Reverse the problem. Take the axe-head as raised to such an elevation as to cause the handle to be vertical (we are dealing with ordinary axes, the handles being in the plane of the axe-blade). Now, the left hand is at the extremity of the handle, the right hand is very near to the axe-head the blow is about to be given. The requirement in this case is that there should be concentrated at the axe-head all the force or power possible; hence to ease the descent would be as injudicious as to intensify the weight of the lift. Consequently, while with the hand nearest to the head (as it is when the axe reaches its highest elevation) the workman momentarily forces forward the axe, availing himself of the leverage now formed by regarding the left hand as the fulcrum of motion, he gives an impulse, and this impelling force is continued until an involuntarily consciousness assures him that the descending speed of the axe is in excess of any velocity that muscular efforts can maintain. To permit gravity to have free play, the workman withdraws the hand nearest to the head, and, sliding it along the handle, brings it close to the left hand, which is at the extremity of the handle; thus the head comes down upon the work with all the energy which a combination of muscular action and gravity can effect. The process is repeated by the right hand sliding along the handle, and releasing as well as raising the head.
The form of the axe-handle deserves notice, differing: as it does from that of the sledge-hammer. In the latter it is round or nearly so, in the axe it is oval, the narrow end of the oval being on the side toward the edge of the axe, and, more than this, the longer axis of the oval increases as the handle approaches the head, till at its entrance into the head it may be double what it is at the other extremity. It often has also a projection at the extremity of the handle. The increasing thickness near the head not only gives strength where needed, as the axe is being driven in, but it also supplies that for which our ancestors employed the thongs as illustrated in Figs. 4 and 5. There is, too, this further difference—in a sledge-hammer more or less recoil has to be provided for, and the handle does this; in the axe no recoil ought to take place. The entrance of the axe-edge is, or ought to be, sufficient to retain it, and the whole of the energy-resulting from muscular action and gravity should be utilized. The curvature, too, of the handle is in marked contrast with the straight line of the sledge-hammer handle. The object of this curvature is worthy of note. In my hand is an American forester's axe. The handle is very long and curved. If, laying the axe-handle across my finger where the head and handle balance, I place the blade of the axe horizontally, you may notice that the edge does not turn downward; in fact, the centre of gravity of the axe-head is in the horizontal straight-line prolongation of the handle through the place where my finger is. Now, in sledge-hammer work the face is to be brought down flat, i. e., as a rule, in an horizontal plane. Not so with the forester's axe: it has to be brought down at varying obliquities. If, now, the hewer's hand had to be counteracting the influence of gravity, there would be added to him very needless labor; hence the care of a skilled forester in the balance of the axe-head and the curvature of the handle.
We must now consider the form of the cutting-edge as seen in the side of the axe. It is often convex. The line across the face in Fig. 7 indicates the extent of the steel, and the corresponding line in Fig. 8 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 that the axe falls square on its work
|Fig. 7.||Fig. 8.|
in the direction of the fibres, a convex edge will first separate two 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 outward. 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. Suppose 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. 10. The edge is beveled on one side only, and, under where the handle enters the eye, may be noticed a piece rising toward 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.
On Adzes.—Those whose business requires the forming of lengths of wood into curved shapes, and who rely upon the adze for the preliminary operation, use an Indian form of adze. In India it is held so near the metal that the workman's hand touches the metal. He accomplishes blows chiefly by acting from the elbow. This very general mode of holding gives a pretty uniform length to the radius of the swing, hence the form of the adze in the plane of the swing is nearly that of the circle described. The angle of the handle and the adze is very much the same as that of the handle of the file-maker's hammer and the head.
The Two-handed Adze.—When we look at the adze as used by English wheelwrights or shipwrights, we may well shudder to see how it is handled, especially when the cutting-edge is taken into account. The operation, briefly described, is the following: The workman stands with one foot upon the wood, this foot being in the line of the fibre. He thus assists in steadying (say) the felloe of a wheel. From this felloe much of the wood on which the sole of his shoe rests has to be removed. It will be noticed that the long handle of the adze is curved—the object of this is to permit an efficient blow to be given, and the instrument brought to a stop before the handle strikes any part of the workman's body; in fact, caused to stop by the exhaustion of its impact energy in and among the fibres of wood to be separated. The edge is often so keen as to cut through a horse-hair held at one end and pressed against it.
This instrument is raised by both hands until nearly in an horizontal position, and then not simply allowed to fall, but steadily driven downward until the curved metal, with its broad and sharp edge, enters near to, if not below, the sole of the workman's shoe, separating a large flake of wood from the mass; the handle is rapidly raised, and the blows repeated. This is done with frequency, the workman gradually receding his foot until the end-flakes of wood are separated. It is fearful to contemplate an error of judgment or an unsteady blow. William Tell and the apple on his son's head are, in another form, here repeated.
So skilled do men become in thus using the adze, that some will undertake, with any predetermined stroke in a series, to split their shoe-sole in two.
Curvature op Adze.—Clearly the adze must be sharpened from the inside, and, when the action of it is considered, it is also clear that the curvature of the adze-iron must be circular, or nearly so.
The true curvature of the metal may be approximately deduced from considering the radius of the circle described by the workman's arms, and the handle of the adze.
The edge of the adze is convex (Fig. 12), the projection in the middle being so formed for the same reasons as influenced the curvature of the edge of the axe already alluded to.
The curvature in the blade also serves (though partially) as a fulcrum, for, by slightly thrusting the handle from him, the-workman may release such flakes of timber as are over the adze, and yet so slightly adherent as not to require another blow. Thus the adze when applied lever-fashion discharges its duty as the curvature in the claw
of a hammer does. Fig. 13 is a gouge-formed adze; a modification of this is used in making wooden spouts, and similar hollow work.
Many of the remarks applied to axes and adzes also apply to pick-axes. It may suffice to refer to two forms of this tool; they differ not so much in the operative points as in the size and distribution of the material.
The one used by paviors is long and light, and of large curvature; the other, used by stone-masons and quarrymen, is short-handled and heavy, much material being concentrated in the head. There is also another form of this instrument used on kegs, for the purpose of driving home the wooden wedges; in this form there is no point, the tool
is rather that of an elongated hammer, the ends being provided with "panes" of different forms, set off at different angles. Such tools may properly be consigned to the class of hammers.
The pavior's, the mason's, and the quarryman's picks are the three to be very briefly considered. The first is properly a lever, and no more; its pointed end is for entrance between stones, and then the wooden handle and the unemployed elevated arm of the pick are used as two lever-arms at right angles to each other; thus motion can be had in two planes for the varying character of the pavior's work.
Such an employment is never allotted to the stone-mason's pick. The object of this is to remove chippings from stone much as the single-angled edge of an axe or an adze would do with chips from timber. It is, however, pointed and not edged, because stones are not fibrous. The weight of the iron head corresponds exactly with that of a heavy hammer, and, so far as this particular feature is concerned, the considerations in relation to hammers apply.
There are peculiarities in reference to the points of these tools. The whole of the energy of the workmen is expended upon one point (in the carpenter's axe or the wheelwright's adze this energy is distributed over an edge from four to eight inches in length), hence the rapid wear of this point, and the necessity not of frequent grinding, but of frequent reforging and retempering. Any attempt at grinding up these points would be practically unsuccessful, made as these picks usually are, because of the mass of metal required to give that penetration resulting from the sudden stoppage of heavy weights. The ordinary picks are therefore sent to the smith's to be sharpened. For this purpose they must be removed from the handle; and this has suggested forms of eye and handle which might with advantage be used with some other tools.
The axes and adzes hitherto considered have been chiefly regarded as tools for the greatest amount of heavy work to be accomplished by a workman. They are at one extreme of the scale, the other extreme being the removal of such small flakes as to become shavings of varying thickness. In progressing from great to small, the order would be from the axe or adze with its weighted head to a separation of the cutting-edge and its necessary metal, and the weight which must give the blow. Hence, in this descending scale, we reach the chisel, struck by a mallet.—Journal of the Society of Arts.
- From a lecture delivered before the London Society of Arts.