Saws: History, development, action, classification and comparison

The literature of the saw considered as a tool is very meager, although there are a few not altogether impartial treatises on woodworking machinery, by leading manufacturers and others. Since Holzappfel, in 1846, there has been nothing of importance written on the subject. But in this work, and at that date, the band saw is dismissed with a few lines; the mulay was uninvented, or unknown; inserted tooth circular saws not dreamed of; the M-tooth shown as a curiosity, and the dimensions and working capacity of the circular and other saws, correct as they were for that date, would make the present reader smile. Saws are now much thinner, have better teeth, are of better steel, and run at double the speeds there laid down. Mr. Joshua Rose, in a lengthy article in the Polytechnic Review, Dec. 1876, went quite thoroughly into the action of certain kinds of saw teeth; and his intelligent articles on straightening plates were the first accurate and complete published matter on that subject. From these sources the author has drawn liberally and in some cases literally.

The writer has tried to be thorough and impartial. Naturally his personal knowledge of some makes of saws (notably in the lines of cross-cuts, hand-saws and circulars) is greater than others; some makers and users were much more liberal and detailed in giving data than others, and if their saws receive greater prominence than the others, it is not the writer's fault nor intention, and can be remedied in case a second edition be called for. There are many cases in which information was refused after repeated requests.

The collection of material for such a work is at once amusing and annoying. The most contradictory opinions and most impossible data are met with. In the matter of horse power, as engineers differ so largely as to the rating of boilers and engines, it is not remarkable that steam users should differ or err in their calculations. It is not common to apply dynamometers to sawing machinery; and as this book is not on sawing machinery, and as the power required differs so with the condition of the lumber and the form and sharpness of the saw teeth, etc., we may let that go for a time, and say to users of machines, “A little too much belt power is about enough.”

Unless specially stated otherwise, the figures and statements in this work refer to American practice.

Some engravings and information arrived too late for use here, but will be used and duly acknowledged should another edition be called for.

The saw is one of the most ancient, useful and familiar of tools. The generic term applied to a serrated dividing tool is generally understood as applying to a saw for wood, although the implement is used also for bone, stone, metal, ice, etc. (There is also a familiar limitation to a reciprocating hand tool). The ancient Egyptians, far back in the silent centuries, knew and used this tool, the material being bronze, hardened by an art now lost. The Greeks, masters of many and far-sailing wooden ships for war and exploration, deified the inventor, who comes down to us as Talus or Perdrix. The original saw was, doubtless, a flat notched or jagged piece of metal like a nicked knife blade, having no special form of teeth, but used with a straight reciprocating stroke, and for either ripping or cross cutting. It cut on both strokes. The saws of the stone age had flakes of flint imbedded in a wooden blade and held by means of bitumen. The Mexicans used obsidian for saw teeth. The South Sea Islanders employ sharks' teeth, and the Caribs use notched shells.

The saw is mostly used for converting wood and other materials from original forms, and naturally precedes the plane and other tools, although it follows the ax. It does its work with considerable speed and accuracy. In some elaborate and highly ornamental arts it is nearly the only tool used.

The importance of scientific and economical timber-cutting may be conceded when it is asserted that the annual value of the wood, lumber and timber crop of America is a billion dollars ($1,000,000,000), or four times that of our wheat crop. The immense waste in cutting timber, with the millions of axes now in use, is almost incredible. The tough and knotty timber and chips now wasted in cutting cord wood might be saved by cross cutting with saws into short blocks, say one foot long, making good stove wood.

It is computed that the saving of timber and time by the scientific use of saws would equal the interest of the United States public debt; to say nothing of lightening the toil of millions of farmers.

As we now know the saw it is either RECIPROCATING or CONTINUOUS in action; the first class having a flat blade and practically straight edge and making a plane cut ; and the latter being either

(1) a circular rotating disk, cutting in a plane and at a right angle to its axis;

(2) cylindrical, or barrel-shaped, with a convex edge, cutting parallel to its axis; or

(3) a continuous ribbon or band, running on two pulleys and making a plane or curved cut, with a straight edge, parallel to their axes of rotation.

There is a fourth class, or spiral saw, composed of segments clamped between plates, and cutting a dovetail joint (Armstrong's patent). The entering segments cut like a circular saw ; subsequent segments are flanged at first slightly, and gradually more and more ; these later segments have the cut of a cylinder saw. As the flange wears away by filing, the segments are moved on towards the unflanged end of the spiral.

Between the Reciprocating Rectilinear and the Continuous-acting Curvilinear saws may be -classed the Chain Saw; its many varieties having either one or two axes, at right angles to the plane of cut ; cutting with either a concave, a convex, or a straight edge, and either reciprocating or continuous in action.