One machine will cut from eighteen to twenty hundred of square feet of pine timber per day, and two of them maybe driven by a common tub-wheel, seven or eight feet in diameter, having six or seven feet head of water, with a cog-wheel and trundle-head, so highly geared as to give a quick motion to the drums, which should be about four feet in diameter. The machine is so constructed, as to manufacture lumber from four to ten feet in length, and from two to ten inches in width, and of any thickness. It has been introduced into most of the New England states, and has given perfect satisfaction. The superiority of the lumber has, for three years past, been sufficiently proved in this town, (Brunswick Maine,) where there have been annually erected from fifteen to twenty wooden buildings, and for covering the walls of which this kind has been almost universally used. The principal cause of its superiority to mill-sawed lumber, is in the manner in which it is manufactured, viz., in being cut towards the centre of the log, like the radii of a circle; this leaves the lumber feather-edged in the exact shape in which it should be, to set close on a building, and is the only way of the grain in which weather-boards of any kind can be manufactured to withstand the influence of the weather, without shrinking, swelling, or warping off the building.
Staves, and heading also, must be rived the same way of the grain, in order to pass inspection. The mill-sawed lumber, which, I believe, is now universally used in the middle and southern states, and in the West Indies, for covering the walls of wooden buildings, is partly cut in a wrong direction of the grain, which is the cause of its cracking and warping off, and of the early decay of the buildings, by the admission of moisture. That such is the operation, may be inferred, by examining a stick of timber, which has been exposed to the weather; the cracks caused by its shrinking all tend towards the heart or centre, which proves that the shrinking is directly the other way of the grain. It follows, that lumber, cut through or across the cracks, would not stand the weather in a sound state, in any degree to be compared with that which is cut in the same direction with them. I have no hesitation in stating that one-half the quantity of lumber manufactured in this way, will cover, and keep tight and sound, the same number of buildings for a hundred years, that is now used and consumed in fifty years.
Add to this, the reduction of expense in transportation, and of labour in putting it on, and I think every one must be convinced that the lumber manufactured in this improved way is entitled to the preference.
"In manufacturing staves and heading, a great saving is made in the timber, particularly as to heading, of which at least double the quantity may be obtained by this mode of sawing to what can be procured in the old method of riving it; nor is the straight grained or good rift indispensable for the saw, as it is for the purpose of being rived. The heading, when sawed, is in the form it should be, before it is rounded and dowelled together, all the dressing required being merely to smooth off the outsides with a plane. Timber for staves ought to be straight, in order to truss, but may be manufactured so exact in size, as to require but little labour to fit them for setting up. Both articles are much lighter for transportation, being nearly divested of superfluous timber, and may be cut to any thickness required, for either pipes, hogsheads, or flour barrels."
Mr. Alexander Craig, of St. Bernard's, in the county of Mid-Lothian, obtained a patent, in 1831, for "certain improvements in machines or machinery for cutting timber into veneers or other useful forms." In one of these improvements, Mr. Craig employs a circular saw, which he makes to traverse the whole length of the veneer to be cut, while it revolves on its axis in the usual way. It is made to traverse by means of a crank, having a radius equal to half the length of the intended veneer, and a connecting-rod, of length sufficient to prevent too much obliquity of action. A uniform tension is preserved on the band which communicates motion to the saw while it approaches to, and recedes from, the source of motion, by carrying the band round a pulley stationed at a small distance beyond the greatest distance of the saw from its driving drum. Though we have mentioned but one saw, there are a series of them attached to the same frame, and put in motion by the same band, which is pressed down by an adjusting pulley between each pair of saws, that it may turn them with more certainty, by embracing a larger portion of the circumference of the riggers fixed on their axes.
The log of wood from which the veneer is to be cut is suspended between centres, similar to those of a turning-lathe, and made to rotate in contact with the saws, so that it may be cut into one continuous spiral veneer. It is evident, that to produce a uniform motion in that part of the log in contact with the saws, is necessary to its perfect action; and this the patentee has effected in a very ingenious manner: he puts into slow motion, by a species of gearing known by the name of the endless screw, a shaft, having on its extremity a metallic cylinder, with a surface roughed in a manner similar to the surface of a rasp; and this cylinder, being pressed against the circumference of the log, will cause it to revolve at the same speed, whatever be its diameter. The specification is concluded by a description of an arrangement by which the saws are made to cut beyond their centres in a stationary log. This is effected by attaching them on axes which do not project beyond the surfaces next the log. To the frame carrying these saws, a descending as well as an alternating motion is given; and the veneer being, by a guide-plate, made to fold back under the saws, it is clear that they will with facility cut to any required depth, without reference to their diameters.
See the article Veneer.
The sawing of stone, as our readers cannot fail to have noticed, is an extremely slow operation, and no improvement of importance has been effected in the process for many centuries; the ancient mode of causing a plate of iron stretched out in a frame, to reciprocate horizontally by the two hands of the sawyer, seated before it, is still generally practised. In dividing very soft stone, the saw itself acts with efficacy upon the stone, by means of its small rude teeth, or notches, which the sawyer makes in its edge by striking it with a coarse tool: but the chief utility of these notches is to collect and apply the particles of sharp sand that are carried by a small current of water down into the incision, and under the saw. In hard stone, almost the whole effect of cutting is produced by the attrition of the sand, aided by the pressure of the weight of the saw.
In 1825, a patent was taken out by Mr. James Tullock, for "improved machinery for sawing stone," in which, however, the same principle of cutting is still adhered to; but the general arrangements of his stone-sawing-mill are judicious for the application of power; we therefore annex a description, with an illustrative cut.
A block of stone is shown at a, supposed to be under the operation of a number of saws b, fixed parallel to each other in a frame. The ends of this frame are formed on the under side into inclined planes, which run upon two anti-friction rollers at c c; so that when motion is given to the saws, each end of the frame will be alternately lifted up, and allow the sand and water (supplied by a small cistern represented) to descend into the fissure. The anti-friction rollers are attached to two slides, placed in grooves, in the two upright posts d d, and are suspended by two chairs e e, wound round the barrels f f, on the shaft g: this shaft turns in the bearings shown, and carries a third barrel k and a large pulley h; to the latter is suspended a weight which partly counterbalances the weight of the saws and frame; and a chain, passing round the barrel k, is attached at the other end to a sliding piece, on a vibrating beam l. The gear represented on the right hand of the engraving is for giving motion to the saw-frame. The power of a first mover being applied to the toothed wheel to, it actuates the two smaller wheels n n, to the shafts of which are fixed cranks, which as they revolve give motion, by means of the connecting-rods o o, to the vibrating beam l, and the latter gives the alternating motion to the saw-frame b.
The several pulleys to which the frame is suspended admit of its regular descent, and with a uniform pressure. The weight of the saws should of course always predominate over the counterbalance, that they may act effectively upon the stone.
It appears from the specification, that the patentee applies this mechanism in the forming of grooves, mouldings, cornices, pilasters, etc, of marble and other stone, by means of properly-indented instruments, which are to traverse the face of the stone, suspended in a suitable frame. By suspending the saws or tools in the manner described, it is considered that a great advantage is gained, as they may thereby be kept in a perfectly horizontal line, so that the face of the stone may be acted upon uniformly in all its parts, and the hardest parts be reduced equally with the softest.