SAW

A saw is a tool consisting of a tough blade, wire, or chain with a hard toothed edge. It is used to cut through material, most often wood. The cut is made by placing the toothed edge against the material and moving it forcefully forth and less forcefully back or continuously forward. This force may be applied by hand, or powered by steam, water, electricity or other power source. An abrasive saw has a powered circular blade designed to cut through metal.

Saw

A crosscut hand saw about 620 mm (24 inches) long
Classification	Cutting
Types	Hand saw Back saw Bow saw Circular saw Reciprocating saw Bandsaw
Related	Milling cutter

Terminology

Diagram showing the teeth of a saw blade when looking front-on. The teeth protrude to the left and right, so that the saw cut (kerf) is wider than the blade width. The term set describes how much the teeth protrude. The kerf may be sometimes be wider than the set, depending on wobble and other factors.

• Heel: The end closest to the handle.
• Toe: The end farthest from the handle.
• Front: The side with the teeth (the "bottom edge").
• Back: The side opposite the front (the "top edge").
• Teeth: Small, sharp protrusions along the cutting side of the saw.
• 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.
• Rake: The angle of the front face of the tooth relative to a line perpendicular to the length of the saw. Teeth designed to cut with the grain (ripping) are generally steeper than teeth designed to cut across the grain (crosscutting)

• Points per inch (25 mm); The most common measurement of the frequency of teeth on a saw blade. 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). 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). Some saws do not have the same number of teeth per inch throughout their entire length, but the vast majority do. Those with more teeth per inch at the toe are described as having incremental teeth, in order to make starting the saw cut easier.
• Teeth per inch: An alternative measurement of the frequency of teeth on a saw blade. Usually abbreviated TPI, as in, "A blade consisting of 18TPI." [Compare points per inch.]
• Kerf: The width of a saw cut, which 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. 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. For example, a too-thin blade can cause excessive wobble, creating a wider-than-expected kerf. 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.
• Set: The degree to which the teeth are bent out sideways away from the blade, usually in both directions. 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. This allows the blade to move through the cut easily without binding (getting stuck). The set may be different depending on the kind of cut the saw is intended to make. 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. 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. The set of the blade's teeth can be adjusted with a tool called a saw tooth setter.
• Abrasive saw: A saw that cuts with an abrasive disc or band, rather than a serrated blade

History

Saws were at first serrated materials such as flint, obsidian, sea shells and shark teeth.

Roman sawblades from Vindonissa approx. 3rd to 5th century AD

In ancient Egypt, open (unframed) saws made of copper are documented as early as the Early Dynastic Period, circa 3,100–2,686 BC. Examples of saws used for cutting both wood and stone and as a tool for execution of people and models of saws have been found in many contexts throughout Egyptian history. Particularly useful are tomb wall illustrations of carpenters at work that show sizes and the use of different types. Egyptian saws were at first serrated, hardened copper which cut on both pull and push strokes. 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. Saws were also made of bronze and later iron. In the Iron Age, frame saws were developed holding the thin blades in tension. The earliest known sawmill is the Roman Hierapolis sawmill from the third century AD and was for sawing stone.

According to Chinese legend, the saw was invented by Lu Ban. In Greek mythology,  as recounted by Ovid, Talos, the nephew of Daedalus, invented the saw. In archeological reality, saws date back to prehistory and most probably evolved from Neolithic stone or bone tools. "[T]he identities of the axe, adz,  chisel and saw were clearly established more than 4,000 years ago."

Bronze-age saw blade from Akrotiri, late Cycladic period c. 17th century BC.

Manufacture of saws by hands

Until at least the mid-19th century, saws were made laboriously by hand. The teeth were filed out individually, then "set" by striking alternate teeth with a hammer against a "stake" or small anvil. Due to risk of breaking teeth, beginners were given saw set pliers which set even more slowly.

Pit saws

A pit saw was a two-man rip saw. In parts of early colonial North America, it was one of the principal tools used in shipyards and other industries where water-powered sawmills were not available. It was so-named because it was typically operated over a saw pit, either at ground level or on trestles across which logs that were to be cut into boards. The pit saw was "a strong steel cutting-plate, of great breadth, with large teeth, highly polished and thoroughly wrought, some eight or ten feet in length" with either a handle on each end or a frame saw. A pit-saw was also sometimes known as a whipsaw. It took 2-4 people to operate. A "pit-man" stood in the pit, a "top-man" stood outside the pit, and they worked together to make cuts, guide the saw, and raise it. Pit-saw workers were among the most highly paid laborers in early colonial North America.

Types of saws
Hand saws

Rip sawing circa 1425 with a frame or sash saw on trestles rather than over a saw pit.

Hand saws typically have a relatively thick blade to make them stiff enough to cut through material. (The pull stroke also reduces the amount of stiffness required.) Thin-bladed handsaws are made stiff enough either by holding them in tension in a frame, or by backing them with steel or brass (on account of which the latter are called "back saws.") Some examples of hand saws are:

• Bow saw or Buck saw; a crosscut saw with the thin blade held in tension in a frame;
• Coping saw: for cutting wood patterns;
• Crosscut saw;  for cutting wood perpendicular to the grain;
• Dovetail saw: for cutting intricate joints, mainly found in drawers;
• Frame saw or "sash saw": In general any saw with a thin blade held in tension by a frame, this term often specifically means the rip saw also called a whipsaw.
• Fret saw: for cutting intricate wood patterns;
• Hacksaw: a fine-toothed tempered blade under tension, for cutting metal, bone, and other hard materials;
• Japanese saw or pull saw: a thin-bladed saw that cuts on the pull stroke;
• Pad saw or "keyhole saw" or "jab saw": a narrow-bladed saw;
• Plywood saw: a fine-toothed saw (to reduce tearing), for cutting plywood;
• Rip saw: for cutting wood along the grain;
• Turning saw:  a frame saw with a narrow blade used for cutting curves, larger than a coping saw.
• Two-man saw: a general term for a large crosscut saw or rip saw for cutting large logs or trees;
• Veneer saw: a two-edged saw with fine teeth for cutting veneer;
• Whipsaw or pit saw: a kind of rip saw for cutting logs into lumber;
• Wire saw: a toothed or coarse cable or wire wrapped around the material and pulled back and forth.

Back sawsEdit

Main articles: Backsaw and Japanese saw

"Back saws," so called because they have a thinner blade backed with steel or brass to maintain rigidity, are a subset of hand saws. Back saws have different names depending on the length of the blade. Some examples are:

• Miter saw: for making accurate crosscuts and miters in a workplace
• Tenon saw or "dovetail saw" or "sash saw": for doing precision cutting in woodworking.

Mechanically powered saws
Circular blades saws

Circular wood-cutting saw at Maine State Museum in the capital city of Augusta, Maine

• Circular saw: a saw with a circular blade which spins. Circular saws can be large for use in a mill or hand held up to 24" blades and different designs cut almost any kind of material including wood, stone, brick, plastic, etc.
• Table saw: a saw with a circular blade rising through a slot in a table. If it has a direct-drive blade small enough to set on a workbench, it is called a "workbench" or "jobsite" saw. If set on steel legs, it is called a "contractor's saw." A heavier, more precise and powerful version, driven by several belts, with an enclosed base stand, is called a "cabinet saw." A newer version, combining the lighter-weight mechanism of a contractor's saw with the enclosed base stand of a cabinet saw, is called a "hybrid saw."
• Radial arm saw: a versatile machine, mainly for cross-cutting. The blade is pulled on a guide arm through a piece of wood that is held stationary on the saw's table.
• Rotary saw or "spiral-cut saw" or "RotoZip": for making accurate cuts, without using a pilot hole, in wallboard, plywood, and other thin materials.
• Electric miter saw or "chop saw," or "cut-off saw" or "power miter box": for making accurate cross cuts and miter cuts. The basic version has a circular blade fixed at a 90° angle to the vertical. A "compound miter saw" has a blade that can be adjusted to other angles. A "sliding compound miter saw" has a blade that can be pulled through the work, in an action similar to that of a radial-arm saw, which provides more capacity for cutting wider workpieces.
• Concrete saw;  (usually powered by an internal combustion engine and fitted with a Diamond Blade) for cutting concrete or asphalt pavement.
• Pendulum saw or "swing saw" a saw hung on a swinging arm, for the rough cross cutting of wood in a sawmill and for cutting ice out of a frozen river.
• Abrasive saw; a circular or reciprocating saw-like tool with an abrasive disc rather than a toothed blade, commonly used for cutting very hard materials. As it does not have regularly shaped edges the abrasive saw is not a saw in technical terms.
• Hole saw:  ring-shaped saw to attach to a power drill, used for cutting a circular hole in material.

This particular circular saw, which cut wood into segments to fit a wood-burning kitchen stove, is displayed at the Cole Land Transportation Museum in Bangor, Maine.

Reciprocating Blade Saw

• Jigsaw or "saber saw" (US): narrow-bladed saw, for cutting irregular shapes. (Also an old term for what is now more commonly called a "scroll saw.")
• Reciprocating saw or "sabre saw" (UK and Australia): a saw with an "in-and-out" or "up-and-down" action similar to a jigsaw, but larger and more powerful, and using a longer stroke with the blade parallel to the barrel. Hand-held versions, sometimes powered by compressed air, are for demolition work or for cutting pipe.
• Scroll saw: for making intricate curved cuts ("scrolls").
• Dragsaw: for bucking logs (used before the invention of the chainsaw).
• Frame saw or sash saw: A thin bladed rip-saw held in tension by a frame used both manually and in sawmills. Some whipsaws are frame saws and some have a heavy blade which does not need a frame called a mulay or muley saw.
• Sternal saw:  for cutting through a patient's sternum during surgery.
• Ice saw: for ice cutting. Looks like a mulay saw but sharpened as a cross-cut saw.

Continuous bandEdit

• Band saw: a ripsaw on a motor-driven continuous band. Portable sawmills are typically band saw mills.

ChainsawsEdit

• Chainsaw:  an engine-driven saw with teeth on a chain normally used as a cross-cut saw.
• Chainsaw mill: a chainsaw with a special saw chain and guide system for use as a rip-saw

Types of blades or blades cuts

Most blade teeth are made either of tool steel or carbide. Carbide is harder and holds a sharp edge much longer.

Band saw blade

A long band welded into a circle, with teeth on one side. Compared to a circular-saw blade, it produces less waste because it is thinner, dissipates heat better because it is longer (so there is more blade to do the cutting, and is usually run at a slower speed.

Crosscut

In woodworking, a cut made at (or close to) a right angle to the direction of the wood grain of the workpiece. A crosscut saw is used to make this type of cut.

Rip cut

In woodworking, a cut made parallel to the direction of the grain of the workpiece. A rip saw is used to make this type of cut.

Plytooth blade

A circular saw blade with many small teeth, designed for cutting plywood with minimal splintering.

Dado blade

A special type of circular saw blade used for making wide-grooved cuts in wood so that the edge of another piece of wood will fit into the groove to make a joint. Some dado blades can be adjusted to make different-width grooves. A "stacked" dado blade, consisting of chipper blades between two dado blades, can make different-width grooves by adding or removing chipper blades. An "adjustable" dado blade has a movable locking cam mechanism to adjust the degree to which the blade wobbles sideways, allowing continuously variable groove widths from the lower to upper design limits of the dado.

Strobe saw blade

A circular saw blade with special rakers/cutters to easily saw through green or uncured wood that tends to jam other kinds of saw blades.

Materials used for saws

There are several materials used in saws, with each of its own specifications.

Brass

Mostly used in back saws, because of its low price and its flow characteristics, which make it relatively easy to cast. Brass contributes to the rigidity that is needed in back saws, which require less force to operate than other kinds of saws because of the pulling motion involved.

Steel

Used in almost every existing kind of saw. Because steel is cheap, easy to shape, and very strong, it has the right properties for most kind of saws.

Diamond

Fixed onto the saw blade's base to form diamond saw blades. As diamond is a superhard material, diamond saw blades can be used to cut hard brittle or abrasive materials, for example, stone, concrete, asphalt, bricks, ceramics, glass, semiconductor and gem stone. There are many methods used to fix the diamonds onto the blades' base and there are various kinds of diamond saw blades for different purposes. High speed steel (HSS): The whole saw blade is made of High Speed Steel (HSS). HSS saw blades are mainly used to cut steel, copper, aluminum and other metal materials. If high-strength steels (e.g., stainless steel) are to be cut, the blades made of cobalt HSS (e.g. M35, M42) should be used.

Tungsten carbide

Normally, there are two ways to use tungsten carbide to make saw blades:

1. Carbide-tipped saw blades: The saw blade's teeth are tipped (via welding) with small pieces of sharp tungsten carbide block. This type of blade is also called TCT (Tungsten Carbide-Tipped) saw blade. Carbide-tipped saw blades are widely used to cut wood, plywood, laminated board, plastic, grass, aluminum and some other metals.
2. Solid-carbide saw blades: The whole saw blade is made of tungsten carbide. Comparing with HSS saw blades, solid-carbide saw blades have higher hardness under high temperatures, and are more durable, but they also have a lower toughness.

Uses

A man recording the sound of a saw for sound effect purposes in the 1930s

• Saws are commonly used for cutting hard materials. They are used extensively in forestry, construction, demolition, medicine, and hunting.
• Musical saws are used as instruments to make music.
• Chainsaw carving, is a flourishing modern art form. Special saws have been developed for the purpose.
• The production of lumber, lengths of squared wood for use in construction, begins with the felling of trees and the transportation of the logs to a sawmill.

Plainsawing: Lumber that will be used in structures is typically plainsawn (also called flatsawn), a method of dividing the log that produces the maximum yield of useful pieces and therefore the greatest economy.

Quarter sawing: This sawing method produces edge-grain or vertical grain lumber, in which annual growth rings run more consistently perpendicular to the pieces' wider faces.

References

1. ^ Barley, Simon "British Saws and Saw Makers from c1660, 2014
2. ^ ^a b P. d'A. Jones and E. N. Simons, "Story of the Saw" Spear and Jackson Limited 1760-1960.
3. ^ Walter B. Emery Excavations at Saqqara, The Tomb of Hemaka and Hor-Aha, Cairo, Government Press, Bulâq, 1938 (2 vols)
4. ^ Lu Ban and The Invention of the Saw, History Anecdote at Cultural China website
5. ^ Ovid Metamorphoses Bk VIII:236-259: The death of Talos, A. S. Kline translation, Electronic Text Center at University of Virginia Library
6. ^ Richard S. Hartenberg, Joseph A. McGeough Neolithic Hand Tools at Encyclopaedia Britannica Online
7. ^ Tomlinson, C., ed. (1866). Tomlinson's Cyclopaedia of Useful Arts. London: Virtue & Co.Vol II, page 478.
8. ^ Charles W. Upham Salem Witchcraft with an account of Salem Village and a History of Opinions on Witchcraft and Kindred Subjects. Frederick Unger, New York, 1978 (Reprint), 2 vols., vol. 1, p 191
9. ^ Glossary of Tools at (American) Pilgrim Hall Museum website
10. ^ Massingham, H. J., and Thomas Hennell. Country relics; an account of some old tools and properties once belonging to English craftsmen and husbandmen saved from destruction and now described with their users and their stories. Cambridge, Eng.: University Press, 1939.reprint 2011 ISBN 9781107600706 books.google.com/books?id=6_auYCccqoQC&pg

Further Reading

• Naylor, Andrew. A review of wood machining literature with a special focus on sawing. BioRes, April 2013
• The Saw in History. Philadelphia: Henry Disston & Sons. 1915. Retrieved September 15,2015.

- Wikipedia