" In manufacturing staves and heading, a great saving is made in the timber, particularly as to 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 smooths 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, ob tained 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 • crank, having a radius equal • to half the length of the intended veneer, and a of length suf ficient 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 circum ference of the riggers fixed on their axes. The log of wood from which the veneer is to be cut is 'impended between centres, similar to those of a turning lathe, and made to rotate in contact with the saws, so that it may be eat into one continuous spiral veneer. It is evident, that to produce an uniform imotion 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 : be puts into slow motion, by a species of gearing known by the name of the endless screw, s shaft, having on 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 seed, whatever be its diameter. The specification is concluded by a description of an arrangement by which the saws are made to eat beyond their centres, in a stationary log. This is Abated by attaching them co axes whieh 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 Vanes& The sawing of stone, as our readers cannot fail to have noticed, is an ex tremely slow operation, and no improvement of importance has been efibcted in the process for many centuries ; the ancient mode of causing a plate of iron stretched out in a frame, to reciprocate horisontally by the two bands 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 mans 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 inoision, and under the saw. In hard stone, abatis& the whole effect of cutting is produced by the attrition of the sand, aided by the pressen of the weight of the saw.
In 1825, a patent was taken out by Mr. James Tulloek, 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-sawinemill 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 el a number of saws 6, 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 e ; so that when motion is given to the saws, each end of the frame will be alternate) ,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 to d d, and are suspended by two chairs e e, wound round the barrels f , on the shaft g : this shaft turns in the bearings shown, and carries a thi barrel k and a large pulley h ; to the latter is suspended a weight which partly counter balances 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 I. The gearted on the right hand of the engraving is for giving motion to the The power of a first mover being applied to en.• toothed wheel so, it actuates the two smaller wheels n is, to the shafts of which are fixed crania', which es they melee give motion, by means of the connecting-rods o p, to the vibrating beam I, 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 an uniform pressure. The weight of the saws should of course always predominate over the counterbalance, that they may act effectively upon the stone.
It timers from the specificadon, that the patentee applies this mechanism in the forming of grooves, mouldings, cornices, pilasters, Ike. of marble and other stone, by means of properly-indented instruments, which are to traverse the face of the stone,ded in a suitable frame. By suspending the saws or tools in the 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.