Holtzapffel on Pit Sawing

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The long saw, pit saw, or whip saw, which follows in the table, is also the next saw that is commonly applied to the piece of timber, which is then placed over the saw-pit, in order that the saw may he used in the vertical position by two men, called respectively the top-man and the pit-man, the former of whom stands upon the piece of timber about to be sawn.

The positions of the men are highly favourable, as they can give the saw a nearly perpendicular traverse of three or four feet; and in the up or return stroke, the saw is removed a few inches from the end of the saw cut, to avoid blunting the teeth, and to allow the sawdust free escape.

holtapffel_01The long saw varies from about six to eight feet in length, according to the size of the timber. To adapt it to the hands of the sawyers, it has at the upper part a transverse handle or tiller, fig. 673, and at the lower a box, fig. 674. The tiller consists of a bar of iron, divided at the lower part to receive the blade, to which it is fixed by a square bolt passing through the two, and fastened by a wedge; and at the upper end, the tiller is sometimes formed as an eye for a wooden stick, or else it is made as a fork, and the handle is riveted on.

holtapffel_02The handle at the lower part, fig. 674, is simply a piece of wood four or five inches diameter, and twelve to sixteen long, turned as a handle at each end; a diametrical notch is made half way through the center to admit the saw blade, which is fixed by a wooden wedge. Sometimes the bottom handle of the long saw is a flat iron loop, as in fig. 675, with a space for the fixing wedge, and an eye for the wooden handle. Occasionally a screw box is used, or one like fig. 674, but with the one handle screwed in, so that its point may bear upon the saw, in place of the wedge. In all cases it is desirable the lower handle should be capable of being easily removed.

The pit frame-saw, fig. 676, is commonly used for deals, and for such pieces of the foreign hard woods as are small enough to pass between its frame, which is about two feet wide.

holtapffel_03The frame-saw blade has two holes above or at the wider end, and one below, and is attached to the wooden frame by two iron buckles or loops, which are split about half way round. The upper buckle fits squarely and firmly to the top head, and receives, above its lower side, two pins passing through the holes in the saw. The lower buckle is similarly cleft, and receives one pin only; this buckle is drawn tight by a pair of equal or folding wedges, beneath the bottom transverse piece.

The blade is usually five or six feet long, and thinner than that of the whip saw, which latter although it may be used for the widest timbers, is more wasteful. In some few cases, where the double frame, fig. 676, is inapplicable, as in removing a plank from outside a very large log, the single frame, 677, is used; but this latter is generally narrow, and employed alone for small curvilinear works.

It is now proposed to give some few particulars of the sawpit, and the modes employed by the sawyers in marking out the timber preparatory to sawing.

The sawpit varies from about twenty to fifty feet in length, four to six feet in width, and five to six feet in depth; it has two stout timbers running the whole length, called side strakes, and transverse pieces at each end, called head sills, upon which the one end of the timber rests, whilst the other end is supported on a transome, or a joist lying transversely upon the strakes: a second transome, is used in case of the first breaking; this is called a trap transome.

Sometimes holdfasts, or L-formed iron brackets, are added to the head-sills, by which thick pieces of plank are fixed horizontally; screw chops are also used for fixing short pieces of hardwood vertically or edgeways, for slitting them.

In cutting deals into thin boards, three deals, which from being as many as the frame of the saw will include, are called a pit-full, are placed vertically against the stake, and are securely attached to it by a rope passed once round the deals and the lower end of the stake, and strained by a binding-stick.

Foreign timbers and hard woods are mostly squared with the axe or adze, for the convenience of transport and close stowage on shipboard, and such square pieces are readily marked out with the chalk line into the scantling, or the planks and boards required. More skill is called for in setting out the lines upon our native timbers, which are mostly converted into plank, or the various pieces, without being previously chopped square.
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The converter determines in which direction the tree can be cut most profitably into plank, and the section chosen is usually that, which when opened, shows the greatest curvature or irregularity; this section is supposed to be shown longitudinally by a, b, c, d, fig. 678, and, on a larger scale and transversely, by e’ e, fig. 679; the central points a and b, and the line b c, being given by the converter, who also gives instructions as to the thicknesses desired in the planks. The sawyer’s first object is accurately to mark the margins of the irregular central plane, a b c d, so truly, that when the lines are followed with the saw, the surface shall be true and thoroughly out of winding or twist.

The sawyer gets the timber on the sawpit, with the hollow side upwards: that being always first marked: it is plumbed upright, or, so that the plumb-line, suspended by the hand at z, exactly intersects the line b c, which has been marked on the end. The butt is then secured from rotating, by dogs or staples, s s, fig. 679, driven both into the end of the timber and into the vertical face of the head-sill; for which purpose the two ends of the dogs are bent at right angles, both to each other and to the intermediate part of the dog, the extremities of which are pointed with steel, made chisel-form, and hardened.

A chalk-line is now stretched in the dotted line from a to b, and pulled vertically upwards, exactly in the plane in which it is desired to act; the string is then let go, as in discharging an arrow, and striking the timber, it leaves thereupon a portion of the white or black chalk with which the line was rubbed.

Should the curvature of the timber be such that, as in the example, the chalk-line would scarcely reach the hollow, it is strained on the dotted line a, b, and left there; the plumb-line is held in the hand at z, and an assistant holds a piece of chalk on the top of the timber at the point e. The principal then observes, in the same glance, that the plumb-line z, intersects the string a b, the line b c, and also the point of the chalk, showing them all to be in the plane of vision; a mark is then made at e. Marks are similarly made at f and g, or as many places as may be required; and, lastly, the points a g, g f, f e, and e b, are connected by short lines struck with the chalk-line around the curve.

The required thickness of the planks is then taken in the compasses, with a little excess for the waste of the saw, and two, three or more planks are pricked off on each side the center e’ e, fig. 679; until, from the circular section of the timber, its surface becomes so inclined, that the compasses would measure a slanting instead of a horizontal distance, and which would diminish the thickness assigned to the boards.

The sawyer then holds the compasses as at y, and fixing his eye on the part of the wood perpendicularly beneath the off leg of the compasses, he removes the instrument and pricks a mark therewith; after which the compasses are replaced as at y, to see that the mark is correct. This is repeated at different points in the length, and the chalk-line is stretched from point to point thus set out with the compasses, and marks the edges of the intended saw cuts with sufficient certainty.

The timber is now turned over, or with c to d, fig. 678, uppermost and the end line exactly perpendicular as before. Should the piece be very crooked or high-backed, the sawyer may be unable to see over it, and observe the central marks at the ends of the timber; such being the case, the points e,f, g, are transferred to e’, f’, g’, on the top of the timber, by the mode explained by the figure 679, supposed to be a section through the plane e e’. A dog is driven into the timber near e’, and from the dog a plumb-line, x’ x, is suspended; the distance e x, is then measured with a common rule, and measured backwards from x’ to e’, by which process e’ becomes exactly perpendicular to e; the points f and g are similarly treated to obtain the points f’ g’; after which the central line is made at four operations, through c, e’, f’, g’, d; the plank lines are set out with the compasses as before explained.

Large timber is usually cut into plank as in fig. 679; the planks are sometimes flatted or their irregular edges are sawn off and for the most part wasted; but this is not generally done until the wood is seasoned and brought into use.

When many planks are wanted of the same width, it is a more economical mode, first to leave a central parallel balk, as in fig. 680, by removing one or two boards from each side, and then to flat the balk, or reduce it into planks. The central line is in this case transferred from the lower to the upper side, by aid of the square and rule, instead of by the plumb-line.

According to Hassenfratz, the setting out shown in fig. 681 is employed in large wainscot oak, in order to obtain the greatest display of the medullary rays which constitute the principal figure in this wood; and the same author strongly advocates the method proposed by Moreau, and represented in fig. 682, in which he says one-sixth more timber is obtained than by any other mode, and also that the pieces are less liable to split and warp; but on examination there does not appear to be any inducement to incur the increased trouble in marking and sawing the timber on this method.*

* Traité de l’Art du Charpentier, par J. H. Hassenfratz. 4to. Paris, 1804. Plate 12.

When the timber has been properly marked out, the sawyers take their respective places, upon the timber and in the pit: the saw is sloped a little from the perpendicular; that is, supposing the piece about eighteen inches through or deep, the saw when it touches the top angle, is held off about two inches from the bottom. A few short trips are then very carefully made, as much depends on the saw entering well; and should it fail to hit the line, the blade is sloped to the right or left at about the angle of 45 degrees, to run the cut sideways and correct the incision in its earliest stage. It is usual to take all the cuts as in figs. 679 and 680, to the depth of three or four feet, and then the whole of them a further distance, and so on.

When the saw has penetrated three or four feet, a wooden heading wedge is driven into the cut, to separate the timber, for the relief of the saw; and when, from the length of the cut, the timber is sufficiently yielding, the hanging wedge is used, which is a stick of timber about twelve to twenty inches long and an inch square, with a projection to prevent the wedge from falling through. The wedges lessen the friction upon the saw; but if too greedily applied they split the wood, and tear up the loose parts sometimes observed in planks.

In sawing straight boards, it is advantageous that the saw should be moderately wide, as it the better serves to direct the rectilinear path of the instrument; but for curvilinear works, as the felloes of carriage wheels, the sawyer employs a much narrower saw, to enable him to follow the curve. The blade of one kind of felloe-saw is about five feet long, and it tapers from nearly four inches at the wide, to two inches at the narrow end; it is used with a tiller and box, exactly the same as the ordinary long saw, and also without a frame.

The more general felloe-saw, or pit-turning saw, has a blade about 1¼ inch wide, and is stretched in a frame exactly like those represented in figs. 676 and 677. The turning-saw with two side-rails is the best where it can be applied; sometimes the frame is obliged to be made single, and with a wire and screw nuts, by which the saw is strained as in fig. 677.

In cutting-out very small sweeps, as in the small wheels or trucks for wooden gun-carriages, no frame whatever can be used, and slender blades about five or six feet long, five-eighths of an inch wide, with a handle at each end, were employed for this purpose during the late war. In using the various pit-turning saws, the thick plank having been sawn out in the ordinary manner, the work is marked off on one side from a pattern or templet, and then held down, upon the head-sill of the saw-pit and one transom, by means of the holdfast before noticed.

Charles Holtzapffel

Turning and Mechanical Manipulation – Volume II – 1847

 

The included engraving comes from the Book of Trades, a British illustrated children’s book first published in London during the 1790’s. This anonymously authored text consists of a description of trades and professions, a sort of “what shall I be when I grow up?” guide for youths approaching the age of apprenticeship. Some enterprising printer got this idea from the Germans and put together a series of these volumes. It proved so popular that there were many imitators and the text and illustrations were copied and expanded for the next fifty years or more. The image at the top of this post is from the 1806 edition of the book. Included below are a revered copy from 1807, a revision by a different artist from the English Book of Trades 1818, and a copy of the revision from the Young Tradesman 1839 (the head and arms look a bit off…).

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—Jeff Burks

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