A saw is a tool that has a strong blade, wire, or chain. It has a hard, toothed edge used to cut materials. There are many names for toothed and abrasive saws.

Saws first had notched edges made from early materials. When people learned to use iron, it became the most commonly used material for all types of saw blades. There are many kinds of hand saws and power saws, as well as different kinds of blades and cutting methods.

Description

A saw is a tool made up of a strong blade, wire, or chain with hard teeth. Saws are used to cut through materials, such as wood, and sometimes metal or stone.

Terminology

Saws are described using several terms. The thin space left behind by a saw, and the measure of its width, is called the kerf. This term also refers to the material that turns into sawdust during cutting. The kerf affects measurements when cutting. For example, if an 8-foot (2.4 meter) piece of wood is cut into 1-foot (30 cm) sections, and each cut has a kerf of 1/8 inch (3 mm), the result will be seven full sections and one section that is 7/8 inch (21 mm) shorter than 1 foot. The kerf depends on factors such as the width of the saw blade, the set of the blade's teeth, the amount of wobble during cutting, and how much material is pulled out of the sides of the cut. While the term "kerf" is sometimes used to describe only the blade's thickness or the set of the teeth, this can be misleading. Blades with the same thickness and set may create different kerfs. For example, a blade that is too thin may cause more wobble, leading to a wider kerf. The kerf of a blade can be changed by adjusting the set of its teeth using a tool called a saw tooth setter. The kerf from a laser beam can also change based on the laser's power and the material being cut.

A toothed saw has a hard, toothed edge. The cut is made by placing the toothed edge against the material and moving it back and forth or continuously forward. This force may be applied by hand or powered by steam, water, electricity, or other power sources.

The most common way to measure the spacing of teeth on a saw blade is "points per inch" (25 mm). This is done by placing the tip of one tooth at the zero point on a ruler and counting how many tips fit between the zero and one-inch marks, including both ends. There is always one more point per inch than there are teeth per inch (e.g., a saw with 14 points per inch has 13 teeth per inch, and a saw with 10 points per inch has 9 teeth per inch). Most saws have the same number of teeth per inch along their entire length, though some have more teeth near the end closest to the handle, called incremental teeth, to make starting a cut easier.

Another way to measure tooth spacing is "teeth per inch," often written as TPI (e.g., "18TPI").

"Set" refers to how far the teeth are bent sideways away from the blade. Modern serrated saws have teeth set in both directions so the kerf (the width of the cut) is wider than the blade itself. This allows the blade to move through the cut without getting stuck. The set of the teeth may vary depending on the type of cut the saw is designed for. For example, a ripsaw has teeth set at an angle similar to a chisel to tear material apart. A "flush-cutting saw" has no set on one side, allowing it to cut along a surface without scratching it. The set of the teeth can be adjusted using a tool called a saw set.

Key parts of a saw include:
– Back: The edge opposite the toothed edge.
– Fleam: The angle of the teeth's faces relative to a line perpendicular to the saw.
– Gullet: The space between the tips of the teeth.
– Heel: The end closest to the handle.
– Rake: The angle of the front face of a tooth relative to a line perpendicular to the saw's length. Teeth for cutting with the grain (ripping) are steeper than those for cutting across the grain (crosscutting).
– Teeth: Sharp, pointed parts along the cutting edge.
– Toe: The end farthest from the handle.
– Toothed edge: The edge with the teeth (some saws have teeth on both edges).
– Web: A narrow blade held in a frame, used by hand or in machines, sometimes with teeth on both edges.

An abrasive saw has a powered circular blade designed to cut through metal or ceramic.

History

Saws were first made from materials like flint, obsidian, sea shells, and shark teeth, which had sharp, jagged edges.

Serrated tools used for cutting wood were found in Pech-de-l'Azé cave IV in France. These tools are from 90,000 to 30,000 years before the common era (BCE).

In ancient Egypt, open (unframed) pull saws made of copper were used as early as the Early Dynastic Period, around 3,100–2,686 BCE. Many copper saws were discovered in tomb No. 3471, which dates to the reign of Djer in the 31st century BCE. Saws were used to cut many materials, including humans (death by sawing). Models of saws were used in many ways throughout Egyptian history. Tomb wall drawings show carpenters using saws, which helps explain their sizes and purposes. Early Egyptian saws had serrated, hardened copper teeth that could cut during both pulling and pushing motions. Later, teeth were shaped to cut only during the pull stroke and were set to extend only on one side, unlike modern saws that have teeth alternating on both sides. Saws were also made of bronze and later iron. During the Iron Age, frame saws were developed to hold thin blades tightly. The earliest known sawmill was the Roman Hierapolis sawmill from the third century AD, used for cutting stone.

According to Chinese legend, Lu Ban invented the saw. In Greek mythology, as described by Ovid, Talos, the nephew of Daedalus, invented the saw. Archaeological evidence shows that saws existed in prehistoric times and likely 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."

After humans learned to use iron, it became the main material for saw blades. Some cultures learned to harden the surface of iron ("case hardening" or "steeling"), which helped blades last longer and stay sharp.

Steel, made from iron with some carbon and hardened by cooling hot steel in water, was used as early as 1200 BCE. By the end of the 17th century, steel production in Europe focused on Germany (the Bergisches Land), London, and the Midlands of England. Most blades were made of steel (iron mixed with carbon and reshaped using different methods). In the mid-18th century, a better type of steel called "crucible cast" was made in Sheffield, England. This steel was preferred because it was hard, flexible, and could be polished finely. A small saw industry remained in London and Birmingham, but by the 1820s, production grew rapidly and focused mainly on Sheffield, which became the largest center for saw making, with over 50% of the country's saw makers. The US industry later surpassed it due to better machines, marketing, a large market, and high taxes on imported goods. Germany and France also had highly productive saw industries.

Early European saws were made by heating a sheet of iron or steel and flattening it with many people hammering it on an anvil. After cooling, teeth were punched out one by one with a tool called a die, with sizes depending on the saw's size. Teeth were sharpened with a triangular file and set using a hammer or tool. By the mid-18th century, rolling metal became common, with power from water and later steam engines. The industry gradually used machines for all steps, including grinding the saw plate "thin to the back" by a small amount, which helped the saw move through the cut without getting stuck. Using steel required hardening and tempering the blade, shaping it flat, hammering it by hand to make it flexible, and polishing it.

Most hand saws today are made without human help, with steel plates already rolled to the right thickness and tensioned before being cut into shape by lasers. Teeth are shaped and sharpened by grinding and then hardened with heat to prevent them from needing sharpening again. Some high-quality saws still require hand finishing by a few specialists who make designs from the 19th century.

A pit saw was a two-person ripsaw. In early colonial North America, it was a key tool in shipyards and other industries where water-powered sawmills were not available. It was called a "pit saw" because it was usually used over a saw pit, either at ground level or on supports above the ground where logs were cut into boards. A pit saw was a strong steel blade with large, sharp teeth, about eight to ten feet long, with handles on both ends or attached to a frame. It was also called a "whipsaw" and required two to four people to operate. One person, the "pit-man," worked inside the pit, while another, the "top-man," worked outside. They worked together to cut, guide the saw, and raise it. Pit-saw workers were among the highest-paid laborers in early colonial North America.

Types of saws

Hand saws usually have thick blades to stay stiff enough to cut through materials. (The pull stroke also reduces the need for stiffness.) Thin-bladed handsaws are made stiff by being held tight in a frame or by having a folded strip of steel (formerly iron) or brass on the back (which is why they are called "back saws"). Some examples of hand saws are:

• Artillery saw, Chain saw, Portable link saw: A flexible chain saw up to 122 cm (four feet) long, used by the military to clear tree branches for gun sighting.
• Butcher's saw: Used for cutting bone; many designs exist, including a large one for two people, called a "beef-splitter" in the U.S. Most are frame saws, some are back saws.
• Crosscut saw: Cuts wood across the grain.
• Docking saw: A large, heavy saw with a strong metal handle, used for rough work.
• Farmer's/Miner's saw: A strong saw with coarse teeth.
• Felloe saw: The narrowest-bladed type of pit saw, up to 213 cm (seven feet) long, used to cut curved parts of cart wheels. A slightly wider version, called a "stave saw," cuts wooden cask parts.
• Floorboard/flooring saw: A small saw, usually without a back, used by carpenters to cut floorboards without damaging nearby boards.
• Grafting/grafter/table saw: A hand saw with a narrow blade from 15 to 76 cm (six to 30 inches) long. The origin of the names is unclear.
• Ice saw: Either a pit saw without a bottom tiller or a large handsaw with very coarse teeth, used to cut ice for storage or transport.
• Japanese saw or pull saw: A thin-bladed saw that cuts on the pull stroke, with teeth different from European or American designs.
• Keyhole saw or compass saw: A narrow-bladed saw, sharply tapered to the back, used to cut round shapes. One end is fixed in a handle.
• Musical saw: A hand saw, sometimes with filed-off teeth, used as a musical instrument.
• Nest of saws: Three or four interchangeable blades attached to a handle with screws or quick-release nuts.
• One-man cross cut saw: A coarse-toothed saw from 76 to 152 cm (30 to 60 inches) long, used for rough or green timber. A second handle can be added for a second person.
• Pad saw: A short, narrow blade held in a wooden or metal handle (the pad).
• Panel saw: A lighter handsaw, usually under 61 cm (24 inches) long, with finer teeth.
• Plywood saw: A fine-toothed saw to reduce tearing when cutting plywood.
• Polesaw: A saw blade attached to a long handle.
• Pruning saw: A common type has a 30-71 cm (12-28 inch) blade, with teeth on both edges, one pattern coarser than the other.
• Ripsaw: Cuts wood along the grain.
• Rule saw or combination saw: A handsaw with a measuring scale along the back and a handle at a 90° angle to the scale.
• Salt saw: A short hand saw with a non-corroding zinc or copper blade, used to cut blocks of salt.
• Turkish saw or monkey saw: A small saw with a straight blade, designed to cut on the pull stroke.
• Two-man saw: A general term for a large crosscut or ripsaw used for cutting large logs or trees.
• Veneer saw: A two-edged saw with fine teeth for cutting thin wood layers.
• Wire saw: A toothed cable or wire wrapped around material and pulled back and forth.

Back saws, which have thin blades supported by steel or brass to stay stiff, are a type of hand saw. They are called by different names based on blade length; "tenon saw" is a common name for all sizes of woodworking back saws. Examples include:

• Bead saw/gent's saw/jeweller's saw: A small back saw with a turned wooden handle.
• Blitz saw: A small back saw with a hook at the toe for the non-dominant hand.
• Carcase saw: A term used until the 20th century for back saws with 10–14 in (25–36 cm) long blades.
• Dovetail saw: A back saw with a 6–10 in (15–25 cm) blade, used for detailed cabinet joints.
• Electrician's saw: A very small back saw used in the early 20th century for cutting wooden wiring casings.
• Flush-cutting saw/offset saw: A back saw with a flat side and an offset handle, used to cut flush with a surface.
• Mitre saw: A saw with an 18–34 in (46–86 cm) blade, held in an adjustable frame for accurate cuts.
• Sash saw: A back saw with a 14–16 in (36–41 cm) blade.

A group of saws that can cut various materials, in different sizes, with wooden or metal frames. Examples include:

• Bow saw, turning saw, or buck saw: A narrow blade held tight in a frame; the blade can rotate and may have teeth on both edges. Used by European woodworkers before machines.
• Coping saw: A narrow blade in a metal frame, rotated for cutting wood patterns.
• Felloe saw: A pit saw with a narrow blade for cutting cart wheel parts.
• Fretsaw: A narrow blade in a deep metal frame, used for intricate wood patterns.
• Girder saw: A large hack saw with a deep frame.
• Hacksaw/bow saw for iron: A fine-toothed blade in a frame for cutting metal.
• Pit saw/sash saw/whip saw: Large wooden-framed saws for cutting timber into lumber, with blades up to 305 cm (10 feet) long.
• Stave saw: A narrow blade pit saw for cutting wooden cask parts.
• Surgeon's/surgical saw/bone cutter: Used for cutting bone during surgery; some have frames, others have open blades.

• Circular saw: A saw with a spinning circular blade. Sizes vary, from large mill saws to handheld models that cut wood, stone, brick, and plastic.
• Table saw:

Types of blades and blade cuts

Many blade teeth are made from either tool steel or carbide. Carbide is harder and keeps a sharp edge for a longer time.

Uses

• Saws are often used to cut hard materials. They are frequently used in forestry, construction, demolition, medicine, and hunting.
• Musical saws are used as instruments to create music.
• Chainsaw carving is a popular modern art form. Special tools have been created for this purpose.
• The production of lumber, which is squared wood used in construction, begins with cutting trees and moving the logs to a sawmill. Plainsawing: Lumber used in buildings is usually plainsawn (also called flatsawn), a method that divides the log to produce the most wood and is the most cost-effective. Quarter sawing: This method creates edge-grain or vertical grain lumber, where the growth rings of the tree are more straight and perpendicular to the wider sides of the wood pieces.