SAW-Mills. The most beneficial improvement of the operation of sawing was the invention of saw-mills, which are driven either by water or by wind. Mills of the first kind were erected so early as the fourth century, in Germany, on the small river Ruer. The art of cutting marble with a saw is very ancient. According to Pliny, it was invented in Caria. Stones of the soap-rock kind, which are softer than marble, were sawn at that period; but it appears that the harder kinds of stone were also then sawn; for we are informed respecting the discovery of a building which was encrusted with cut agate, carnelian, lapis lazuli, and amethysts. There is, however, no account in any of the Greek or Roman writers of a mill for sawing wood; and as modern authors speak of saw-mills as new and uncommon, it appears that the oldest construction of them has been forgotten, or that some interesting improvement has made them appear entirely new.
Becher says that saw-mills were invented in the 17th century, which is a mistake; for when the infant Henry
sent people to settle in the island of Madeira, discovered saw-mills in 1420, he gave orders for saw-mills to be erected, for the purpose of sawing into deals the various species of excellent timber with which the island abounded, and which were afterwards exported to Portugal. There was a saw-mill in the city of Breslau about the year 1427, producing a yearly rent of three marks; and in 1490, the magistrates of Erfurth purchased a forest, in which they erected a saw-mill, besides renting another in the neighbourhood. The first saw-mill in Norway was erected about the year 1530. In the year 1552 there was a saw-mill erected at Joachimsthal, the property of a mathematician called Jacob Geusen. In 1555, the bishop of Ely, ambassador from Queen Mary of England to the court of Rome, having seen a saw-mill in the vicinity of Lyons, the writer of his travels gave a particular description of it. The first saw-mill was erected in Holland at Saardam in 1596, the invention of which is ascribed to Cornelius Cornelissen.
The first mill of this kind in Sweden was erected in the year 1653. At present, that kingdom possesses the largest perhaps ever constructed in Europe, where a water-wheel, 12 feet broad, drives at the same time 72 saws.
In England, saw-mills had at first a similar fate with printing in Turkey, the ribbon-loom in the dominions of the church, and the crane at Strasburg. When attempts were made to introduce them, they were violently opposed, because it was apprehended that the sawers would thus be deprived of the means of procuring subsistence. An opulent merchant in 1767 or 1768, by desire of the Society of Arts, caused a saw-mill to be erected at Limehouse, driven by wind; but it was demolished by the mob, and the damage was sustained by the nation, while some of the rioters were punished. This, however, was not the only mill of the kind then in Britain; for at Leith there was one driven by wind, some years before.
Saw-mills are very common in America, where the moving power is generally water. Some have been constructed on a very extensive plan; one in particular, we have been informed, has been erected in the province of New Brunswick, in British America, for the purpose of cutting planks for the English market. This machine works 15 saws in one frame, and is capable, it is said, of cutting annually not fewer than 8,000,000 feet of timber.
The mechanism of a sawing mill may be reduced to three principal things; the first, that the saw is drawn up and down as long as is necessary, by a motion communicated to the wheel by water; the second, that the piece of timber to be cut into boards is advanced by an uniform motion to receive the strokes of the saw; for here the wood is to meet the saw, and not the saw to follow the wood, therefore the motion of the wood and that of the saw ought immediately to depend the one on the other; the third, that where the saw has cut through the whole length of the piece, the whole machine stops of itself, and remains immovable; left having no obstacle to surmount, the moving power should turn the wheel with too great velocity, and break some part of the machine.
Saw-mills have been distinguished into two kinds, viz. those which have a reciprocating and those which have a rotatory motion.
Saw-mills.
Plate
CCCCLXIX.
Fig. 1.
Fig. 1. represents the elevation of a reciprocating saw-mill. AA is the shaft or axle, upon which is fixed the wheel BB (of 17 or 18 feet diameter), containing 40 buckets to receive the water by which it is impelled. CC a wheel fixed upon the same shaft containing 96 teeth, to drive the pinion No 2. having 32 teeth, which is fastened upon an iron axle or spindle, having a coupling box on each end that turns the cranks, as DD, round: one end of the pole E is put on the crank, and its other end moves on a joint or iron bolt at F, in the lower end of the frame GG. The crank DD being turned round in the hole E, moves the frames GG up and down, and these having faws in them, by this motion cut the wood. The pinion, No 2. may work, two, three, or more cranks, and thus move as many frames of faws. No 3. an iron wheel having angular teeth, which one end of the iron K takes hold of, while its other end rolls on a bolt in the lever HH. One end of this lever moves on a bolt at I, the other end may lie in a notch in the frame GG so as to be pushed up and down by it. Thus the catch K pulls the wheel round, while the catch L falls into the teeth and prevents it from going backwards. Upon the axle of No 3. is also fixed the pinion No 4. taking into the teeth in the under edge of the iron bar, that is fastened upon the frame TT, on which the wood to be cut is laid: by this means the frame TT is moved on its rollers SS, along the fixed frame UU; and of course the wood fastened upon it is brought forward to the faws as they are moved up and down by reason of the turning round of the crank DD. VV, the machine and handle to raise the sluice when the water is to be let upon the wheel BB to give it motion. By pulling the rope at the longer arm of the lever M, the pinion No 2. is put into the hold or grip of the wheel CC, which drives it; and by pulling the rope R, this pinion is cleared from the wheel. No 5. a pinion containing 24 teeth, driven by the wheel CC, and having upon its axle a sheave, on which is the rope PP, passing to the sheave No 6. to turn it round; and upon its axle is fixed the pinion No 7. acting on the teeth in an iron bar upon the frame TT, to roll that frame backwards when empty. By pulling the rope at the longer arm of the lever N, the pinion No 5. is put into the hold of the wheel CC; and by pulling the rope O it is taken off the hold. No 8. a wheel fixed upon the axle No 9. having upon its periphery angular teeth, into which the catch No 10. takes; and being moved by the lever attached to the upper part of the frame G, it pushes the wheel No 8. round; and the catch No 11. falls into the teeth of the wheel, to prevent it from going backwards while the rope rolls in its axle, and drags the logs or pieces of wood in at the door Y, to be laid upon the moveable frames TT, and carried forward to the faws to be cut. The catches No 10, 11. are easily thrown out of play when they are not wanted. The gudgeons in the shafts, rounds of the cranks, spindles, and pivots, should all turn round in cods or bushes of brass. Z, a door in one end of the mill-house at which the wood is conveyed out when cut. WW, walls of the mill-house. QQ, the couples or framing of the roof. XXX, &c. windows to admit light to the house.
Saw-mills for cutting blocks of stone are generally, though not always, moved horizontally: the horizontal alternate motion may be communicated to one or more
faws, by means of a rotatory motion, either by the use of cranks, &c. or in some such way as the following. Saw-mills.
Fig. 2.
Let the horizontal wheel ABDC (fig. 2.) drive the pinion OPN, this latter carrying a vertical pin P, at the distance of about one-third of the diameter from the centre. This pinion and pin are represented separately in fig. 3. Let the frame WSTV, carrying four faws, marked 1, 2, 3, 4, have wheels V, T, W, W, each running in a groove or rut, whose direction is parallel to the proposed direction of the faws; and let a transverse groove PR, whose length is double the distance of the pin P from the centre of the pinion, be cut in the saw frame to receive that pin. Then, as the great wheel revolves, it drives the pinion, and carries round the pin P: and this pin, being compelled to slide in the straight groove PR, while by the rotation of the pinion on which it is fixed its distance from the great wheel is constantly varying, it causes the whole saw frame to approach to and recede from the great wheel alternately, while the grooves in which the wheels run confine the frame so as to move in the direction Tt, Vv. Other blocks of stone may be fawn at the same time by the motion of the great wheel, if other pinions and frames running off in the directions of the respective radii EB, EA, EC, be worked by the teeth at the quadrantal points B, A, and C. And the contrary efforts of these four frames and pinions will tend to soften down the jolts, and equalize the whole motion.
The same contrivance, of a pin fixed at a suitable distance from the centre of a wheel, and sliding in a groove, may serve to convert a reciprocating into a rotatory motion: but it will not be preferable to the common conversion by means of a crank.
When faws are used to cut blocks of stone into pieces having cylindrical surfaces, a small addition is made to the apparatus. See figs. 4. and 5. The saw, instead of Fig. 4. & 5. being allowed to fall in a vertical groove as it cuts the block, is attached to a lever or beam FG, sufficiently strong; this lever has several holes pierced through it, and so has the vertical piece ED, which is likewise moveable towards either side of the frame in grooves in the top and bottom pieces AL, DM. Thus, the length KG of the radius can be varied at pleasure, to suit the curvature of NO; and as the saw is moved to and fro by proper machinery, in the direction CB, BC, it works lower and lower into the block, while, being confined by the beam FG, it cuts the cylindrical portion from the block P, as required.
When a completely cylindrical pillar is to be cut out of one block of stone, the first thing will be to ascertain in the block the position of the axis of the cylinder, then lay the block so that such axis shall be parallel to the horizon, and let a cylindrical hole of from one to two inches diameter be bored entirely through it. Let an iron bar, whose diameter is rather less than that of this tube, be put through it, having just room to slide freely to and fro as occasion may require. Each end of this bar should terminate in a screw, on which a nut and frame may be fastened: the nut frame should carry three flat pieces of wood or iron, each having a slit running along its middle nearly from one end to the other, and a screw and handle must be adapted to each slit: by these means the frame-work at each end of the bar may readily be so adjusted as to form equal isosceles or equilateral triangles; the iron bar will connect two corresponding
Saw-mills. responding angles of these triangles, the saw to be used two other corresponding angles, and another bar of iron or of wood the two remaining angles, to give sufficient strength to the whole frame. This construction, it is obvious, will enable the workmen to place the saw at any proposed distance from the hole drilled through the middle of the block; and then, by giving the alternating motion to the saw frame, the cylinder may at length be cut from the block, as required.
If it were proposed to saw a conic frustum from such a block, then let two frames of wood or iron be fixed to those parallel ends of the block which are intended to coincide with the bases of the frustum, circular grooves being previously cut in these frames to correspond with the circumferences of the two ends of the proposed frustum; the saw being worked in these grooves will manifestly cut the conic surface from the block. This, we believe, is the contrivance of Sir George Wright.
The best method of drilling the hole through the middle of the proposed cylinder seems to be this: on a carriage running upon four low wheels let two vertical pieces (each having a hole just large enough to admit the borer to play freely) be fixed two or three feet asunder, and so contrived that the pieces and holes to receive the borer may, by screws, &c. be raised or lowered at pleasure, while the borer is prevented from sliding to and fro by shoulders upon its bar, which are larger than the holes in the vertical pieces, and which, as the borer revolves, press against those pieces: let a part of the boring bar between the two vertical pieces be square, and a grooved wheel with a square hole of a suitable size be placed upon this part of the bar; then the rotatory motion may be given to the bar by an endless band which shall pass over this grooved wheel and a wheel of a much larger diameter in the same plane, the latter wheel being turned by a winch handle in the usual way. See Boring of ORDNANCE.
Circular saws, acting by a rotatory motion, have been long known in Holland, where they are used for cutting wood used in veneering. They were introduced into this country, we believe, by General Bentham, and are now used in the dock-yard at Portsmouth, and in a few other places: but they are not, as yet, so generally adopted as might be wished, considering how well they are calculated to abridge labour, and to accomplish with expedition and accuracy what is very tedious and irksome to perform in the usual way. Circular saws may be made to turn either in horizontal, vertical, or inclined planes; and the timber to be cut may be laid upon a plane inclined in any direction; so that it may be sawn by lines making any angle whatever, or at any proposed distance from each other. When the saw is fixed at a certain angle, and at a certain distance from the edge of the frame, all the pieces will be cut of the same size, without marking upon them by a chalked line, merely by causing them to be moved along and keeping one side in contact with the side of the frame; for then, as they are brought one by one to touch the saw revolving on its axle, and are pressed upon it, they are soon cut through.
Mr Smart, of Ordnance-wharf, Westminster-bridge, has several circular saws, all worked by a horse in a moderate sized walk: one of these, intended for cutting and boring tenons used in this gentleman's hollow masts, is represented in fig. 6. NOPQR is a hollow frame,
under which is part of the wheel-work of the horse-mill. Saw-mills. —A, B, D, C, E, F, are pulleys, over which pass straps or endless bands, the parts of which out of sight run upon the rim of a large vertical wheel: by means of this simple apparatus, the saws S, S', are made to revolve upon their axles with an equal velocity, the same band passing round the pulleys D, C, upon those axles; and the rotatory motion is given to the borer G by the band passing over the pulley A. The board I is inclined to the horizon in an angle of about 30 degrees; the plane of the saw S' is parallel to that of the board I, and about a quarter of an inch distant from it, while the plane of the saw S is vertical, and its lowest point at the same distance from the board I. Each piece of wood K out of which the tenon is to be cut is four inches long, an inch and a quarter broad, and 5-eighths of an inch thick. One end of such piece is laid so as to slide along the ledge at the lower part of the board I; and as it is pushed on, by means of the handle H, it is first cut by the saw S', and immediately after by the saw S: after this the other end is put lowest, and the piece is again cut by both saws: then the tenon is applied to the borer G, and as soon as a hole is pierced through it, it is dropped into the box beneath. By this process, at least 30 tenons may be completed in a minute, with greater accuracy than a man could make one in a quarter of an hour, with a common hand-saw and gimblet. The like kind of contrivance may, by slight alterations, be fitted for many other purposes, particularly all such as may require the speedy sawing of a great number of pieces into exactly the same size and shape. Gregory's Mechanics, II.