Whilst the saw is in the act of cutting, the principal attendant applies a soft deal freeing-stick, on the right and left of the blade beneath the timber, in order to clear the sawdust out of the teeth. The speed at which the table is fed is easily adjusted, by the selection of an appropriate groove of the cone pulley on the main shaft, which communicates with the driving pinion beneath the floor; and this adjustment of the feed is jointly dependent on the condition of the saw as to sharpness, and the general quality, hardness, and size of the wood.

The veneer-saw may be used for logs of wood measuring as much as 24 feet in length and 5 1/2 feet in breadth, but which sizes are rarely or never met with in the same log. It may be added, that the number of veneers cut out of each solid inch of wood, varies with the width and the intended purpose of the veneers; but that on the average -

When the width of the wood is

6

12

18

24

30

36

48

60

inches,

Each inch of wood is cut into

15

14

13

12

11

10

9

8

veneers

and, as about one-third of the wood is wasted in sawdust, the respective veneers are about two-thirds the 15th, 14th, etc. of an inch in thickness.

The veneer-saw is also applied to cutting cedar wood for making pencils; bead stuff, or thin wood for making the headings in cabinet work; quarter stuff, or wood 1/4 inch thick; and occasionally also to wood nearly 1/2 inch thick; and this may be considered the point of meeting, between the veneer-saw and the upright frame-saw, page 742, in which ten or a dozen saw-blades are occasionally used for deals. But the veneer-saw works with greater accuracy, and is almost always used for such thin boards of mahogany as are not cut by hand at the saw-pit.

For sawing thin boards, the segments should be nearly new or very wide, in order that the angle made by the removed board may be slight. But as the board in riding over the guide, (page 810,) near the edge of the saw, is nevertheless somewhat strained open, it becomes needful to apply a contrivance called a guard, to prevent the thin board from being at all split off, instead of being entirely separated by the saw. This is accomplished by a curvilinear arm, equal in size and form to the feather-edged guide which lies against the hardened saw-plates, but the guard is very much thicker and stronger, and is covered with a thin plate of brass.

It will be further perceived in the perspective figure, page 812, that the guard is attached to a column, and is represented turned back, or out of work, which is the case whilst veneers are being cut; but in sawing boards, the guard is placed parallel with the edge of the saw, just external to its teeth, (as dotted,) and is adjusted by set-screws to rest in hard contact with the face of the wood which is sliding past it, the removed board is consequently held securely unto within half an inch of the saw teeth, or the line of separation, as shown by the diagram, fig. 803.

In sharpening the veneer-saw, the workman first applies a lump of grindstone very cautiously upon a proper support, against the edge of the teeth as the saw revolves, so as to reduce the few points extending beyond the circle. The saw having been stopped, he then stands on a stage and rests his left arm, which is guarded by a wooden board, or leather shield, upon the teeth of the saw, whilst he manages the triangular saw-file with both hands. The saw teeth are afterwards set by a hammer and a small flat stake held in the left hand. The necessity for the recurrence to sharpening and setting depends much on the hardness of the wood, but it is commonly needed several times each day that the saw is in constant work. When the edge becomes too thick and wasteful, it is ground by means of revolving laps of lead or iron fed with emery, one lap on the face, another on the back of the saw; the laps are placed one below the other, to prevent their faces touching, and are kept in rapid motion, whilst the saw traverses between them, as in cutting, so that all parts of the circumference, of this most stupendous and accurate of saws, may be ground alike.*

Notwithstanding the very considerable length to which the chapter on saws has been extended, the subject may be considered as very far from exhausted. Thus the great majority of the applications of the saw hitherto noticed have been for manufactures in wood, but toothed saws are also employed for many other purposes, and different materials, some few of which will be glanced at by way of conclusion.

Both reciprocating and circular saws are occasionally employed in cutting off piles beneath the surface of water, when to draw them (by the aid of the hydrostatic press,) would endanger the safety of the foundations. Two methods of thus using rectilinear saws have been described, to which the reader is referred.†

The circular saw, when used for piles, is commonly placed at the bottom of a long vertical shaft, the top of which is driven by a winch, through the medium of a pair of mitre-wheels. The shaft is attached to a swing-frame, like a gate, or to a traversing platform, connected with such of the piles as may with safety be ultimately drawn up; in every case the erection of machinery for sawing piles is troublesome, and the process tedious.

In the American steam pile-driving machine, intended principally for constructing the foundations of railways, two piles are driven at the same time, in the respective track. After which, they are sawn off by a circular saw four feet in diameter, the spindle of which is mounted on the end of a strong horizontal frame, moving on a joint, so as to cut first the one pile and then the other. Notwithstanding the irregularities of the ground, the piles may be cut either to a dead level or to any particular inclination.*

* The author is greatly indebted to Messrs. Esdaile and Margrave, of the City Saw-Mills, for the free access they permitted him to their establishment, which contains eleven veneer-saws, from 17 ft. 6 in. to 5 feet diameter, and also nearly every kind of machine-saw and shaping-engine for wood that is extensively used.

Many of the practical details, on sawing ivory veneers, were derived from the experience of Mr. Donald Stewart.

† See Encycl Metro. Part Mechanics, article 536; also, Civil Eng. and Arch. Journal, 1843, vol vi, page 439.

Circular saws are used in cutting sheets of slate into rectangular pieces, many of which are afterwards planed by machinery (vol. i. page 165). Slate is also grooved with thick circular saws, for making a particular kind of roofing, the joints for cisterns, and other works; and more frequently two thinner saws are used, and the intermediate substance is chiselled or tooled out. Rectilinear toothed-saws, driven both by hand and machinery, are likewise used for blocks of slate and soft building stone.

A saw machine is used at the Butterley Iron Works, Derbyshire, in cutting off the ends of railway bars whilst red hot; in fact, the moment they leave the rollers. The two saws are exactly like those for wood, of three feet diameter, with flanges of two feet, they travel at upwards of 1000 revolutions per minute, and their lower edges, dip into water. The bar is brought up to the saws by machinery, and both ends are cut off simultaneously, in twelve to fifteen seconds, to the precise length required.†

If the customary applications of the saw machine to works in metal had been touched upon in this chapter, they would almost inevitably have trenched upon the fifth volume; as it would have been difficult, to avoid proceeding from the circular saw, used simply for dividing works, to circular cutters with plain edges, used in cutting grooves, and to cutters with curvilinear or figured edges, used for the teeth of wheels, and various other analogous works, subjects that are for the present held in reserve.

By analogy, it might also have been shown, that in some of the various apparatus employed in ornamental turning, revolving cutters of all kinds, with plain or figured edges, are likewise used. But in reference to these, it will be explained in the fourth volume, that the many teeth of the circular saw, or figured cutter, dwindle down to a single radial tooth; and that the solitary cutting edge makes up for its apparent deficiency, by the extreme rapidity with which it is in general driven.

• Civil Eng. and Arch. Journal, vol. v., page 1. † Trans. Inst. Civil Engineers, vol. iii., p. 197.