In the Iron Age, frame saws were developed holding the thin blades in tension. Saws were also made of bronze and later iron. As the saw developed, teeth were raked to cut only on the pull stroke and set with the teeth projecting only on one side, rather than in the modern fashion with an alternating set. Egyptian saws were at first serrated, hardened copper which cut on both pull and push strokes. Particularly useful are tomb wall illustrations of carpenters at work that show sizes and the use of different types. Models of saws have been found in many contexts throughout Egyptian history. Saws have been used for cutting a variety of materials, including humans ( death by sawing). 3471 dating to the reign of Djer in the 31st century BC.
In ancient Egypt, open (unframed) saws made of copper are documented as early as the Early Dynastic Period, circa 3,100–2,686 BC. Saws were at first serrated materials such as flint, obsidian, sea shells and shark teeth.
Web: a narrow saw blade held in a frame, worked either by hand or in a machine, sometimes with teeth on both edges. Toothed edge: the edge with the teeth (on some saws both edges are toothed). Usually abbreviated TPI, as in, "A blade consisting of 18TPI." (cf. Teeth per inch: An alternative measurement of the frequency of teeth on a saw blade. Teeth: sharp protrusions along the cutting side of the saw. The set of the blade's teeth can be adjusted with a tool called a saw set. A "flush-cutting saw" has no set on one side, so that the saw can be laid flat on a surface and cut along that surface without scratching it. For example, a rip saw has a tooth set that is similar to the angle used on a chisel, so that it rips or tears the material apart. The set may be different depending on the kind of cut the saw is intended to make. This allows the blade to move through the cut easily without binding (getting stuck). 
In most modern serrated saws, the teeth are set, so that the kerf (the width of the cut) will be wider than the blade itself.
Set: The degree to which the teeth are bent out sideways away from the blade, usually in both directions. Teeth designed to cut with the grain ( ripping) are generally steeper than teeth designed to cut across the grain ( crosscutting) Rake: The angle of the front face of the tooth relative to a line perpendicular to the length of the saw. Those with more teeth per inch at the toe are described as having incremental teeth, in order to make starting the saw cut easier. Some saws do not have the same number of teeth per inch throughout their entire length, but the vast majority do. There is always one more point per inch than there are teeth per inch (e.g., a saw with 14 points per inch will have 13 teeth per inch, and a saw with 10 points per inch will have 9 teeth per inch). It is taken by setting the tip (or point) of one tooth at the zero point on a ruler, and then counting the number of points between the zero mark and the one-inch mark, inclusive (that is, including both the point at the zero mark and any point that lines up precisely with the one-inch mark). Points per inch (25 mm): The most common measurement of the frequency of teeth on a saw blade. The kerf left behind by a laser beam can be changed based on the laser's power and type of material being cut. The kerf created by a given blade can be changed by adjusting the set of its teeth with a tool called a saw tooth setter. For example, a too-thin blade can cause excessive wobble, creating a wider-than-expected kerf. Although the term "kerf" is often used informally, to refer simply to the thickness of the saw blade, or to the width of the set, this can be misleading, because blades with the same thickness and set may create different kerfs. The kerf depends on several factors: the width of the saw blade the set of the blade's teeth the amount of wobble created during cutting and the amount of material pulled out of the sides of the cut. Kerf: The narrow channel left behind by the saw and (relatedly) the measure of its width. Gullet: The valley between the points of the teeth. Fleam: The angle of the faces of the teeth relative to a line perpendicular to the face of the saw. Back: the edge opposite the toothed edge. Abrasive saw: A saw that cuts with an abrasive disc or band, rather than a toothed blade. The kerf may be sometimes be wider than the set, depending on wobble and other factors. The term set describes how much the teeth protrude. The teeth protrude to the left and right, so that the saw cut (kerf) is wider than the blade width. Diagram showing the teeth of a saw blade when looking front-on.
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