* See Gregory's Mechanics, 1807, Vol. II, page 328, plate 26.

8. Sawing or cross-cutting the ends of pieces, either square or bevilled; or those in which the angular variations are in the horizontal plane. - The saw-bench is not much employed in cross-cutting the ends of long timber for the general purposes of carpentry; but short pieces are sometimes guided to the saw, as in the small machines, by the intervention of either a wooden square or bevil, the one edge of which rests against the parallel rule, the other thrusts forward the work. In cutting the square scantling for wood pavement into oblique prisms, a wooden slide is sometimes added to the saw-bench, with a trough exactly at the required angle, and in this case, as well as the last, the parallel rule serves as the guide for the length of the blocks.

The Metropolitan Wood-Paving Company employ for this purpose, an iron machine which has a slide running in V bearings or angular grooves, planed in the bed of the machine and parallel with the saw: the cast-iron slide is constructed to serve as the inclined trough to receive the squared wood, and has an adjustable stop to determine the length of the blocks.*

The three following diagrams are intended to show the principles of different circular saw machines for cross-cutting; the wood is shaded in each of the examples, and the arrows denote the movements for following up the cuts of the revolving saws.

In cross-cutting the round logs of lignum vitae for the sheaves of ship blocks, Messrs. Esdailes use a wooden saw-bench, the sliding platform of which is inclined, and has at its lower end a perpendicular rail, as in fig. 787. The log of wood is laid in the nook, and the entire platform is then thrust by the hands past the saw, which revolves on a fixed axis as usual, and thus the log is sliced into pieces, their thickness being determined by a wooden stop; but it is necessary, in this machine, that the saw should have rather more than twice the diameter of the log.

In the block machinery at Portsmouth, a somewhat elaborate machine is used for the same purpose, which is so constructed that the saw s, need only be large enough to penetrate to the center of the log, as explained in fig. 788. A short log of lignum vitae is mounted on a kind of lathe mandrel; the saw spindle is then traversed sideways until the teeth cut to the center of the wood, and the mandrel is afterwards rotated once on its axis by a wheel and pinion, to extend the cut around the log. One slice having been removed, the saw is withdrawn sideways to the dotted position s', and the mandrel and wood are set forward through the collars, as much as the thickness of the sheave, by a screw at the back of the mandrel, preparatory to the next slice being removed.

* The angle specified in the Count de Liles's Patent is 63o 26' 6", every block is afterwards chamfered on three edges, grooved on the face, and drilled with four holes for the dowels, in appropriate machines, nearly the whole of which are constructed in iron and driven by two steam-engines, each of twelve horses' power. The thirteen various machines, are managed by sixteen men and fifteen boys, and in one week of seventy-two working hours, produce on the average 30,000 blocks, or 800 square yards of paving.

Less Common Or Specific Applications Of Circular S 200203

Another cross-cutting machine, after the manner of fig. 789, and also contrived with a view of using a saw for work of nearly its own diameter, is used at Portsmouth, for cross-cutting the butts of round elm timber, into short pieces used for the wooden shells of the blocks. In this latter case, the timber is fixed horizontally and immoveably, and the saw is carried in one plane, first down the one side of the timber and then the other. To accomplish this, the saw spindle is mounted at the end of a double swing frame, near the centers of which are placed guide pulleys, for the strap that connects the saw with the steam-engine. The parts of the wooden swing frame, are double and strongly braced with iron bars, and the angular movements of the frame are governed by racks and pinions, but the various details are altogether omitted in the diagram.*

9. Sawing bevilled edges and prismatic pieces; or those works in which the angular variations are in the vertical plane. - The most

* The two machines, figs. 788 and 789, were invented by Mr. (now Sir M. I.) Brunel, and are fully described and figured in Rees's Cyclopaedia, article "Machinery for Manufacturing Ships' Blocks;" and also in Encycl. Metrop., part Manufactures, articles 533 and 535.

Eastman's saw machine for weather boards. 797 simple and usual method of accomplishing this class of work, is by the employment of oblique supplementary beds, as explained in fig. 748, page 768; the hexagonal blocks for wood paving hare been cut on the common saw-bench, precisely in the mode there described for small hexagonal and other prisms: indeed, the whole of the remarks already given on bevilled or prismatic works, are applicable alike to the small saw machines and the full-sized saw-benches.

In the sawing machine invented by Mr. Robert Eastman, of America, for cutting feather-edged or weather-boards, etc, (as in fig. 790,) the round log of timber is held horizontally, between centers inserted in the end of a long rectangular frame or carriage, which has rollers that run on fixed bars or rails. The round timber is placed above the revolving saw, which makes a vertical and radial incision into the timber; the slide then runs quickly back, and the wood is afterwards shifted on its axis for a new cut, by means of a dividing plate and appropriate mechanism. The machine is automatic, or self-acting, so that, the primary adjustments having been first made, the entire tree is cut into radial feather-edged boards without further attention. The rough exterior edges of the board are also cut away by sappers, or chisels c, screwed near the center of the saw-plate, which cut away the sap or waste wood, and reduce the tree to the cylindrical form; sometimes, if the tree is large, two series of radial boards are cut.