Circular saw blades are generally made from a type of steel called high-carbon steel. High-carbon steel is an alloy containing between 0.3%-1.5% carbon and small amounts of manganese, silicon, phosphorus, sulphur and other impurities such as titanium and chromium (with the last two only added in small quantities for hardenability, corrosion resistance and strength).
High-carbon steel is a popular alloy for many reasons. It has a high hardness and abrasion resistance of 750 HV10, which means it can withstand wear quickly and easily under normal working conditions. Its hard surface makes it easier to cut materials with a circular saw blade. The alloy also has a low ductility which means it can bend without fracturing, making it a good candidate for thin circular saw blades with a large radius. Finally, its low toughness makes it break more easily in brittle situations such as when impacted from the side by a hard surface after cutting through something soft.
For these reasons, high-carbon steel is among the most common alloys used to make circular saw blades for construction, woodworking, and other heavy-duty carpentry jobs.
Circular saw blades are typically 6 inches (150 mm) in diameter with 6-12 teeth per inch on the periphery. Blades for larger tools may be up to several feet in diameter.
Steel has a very high ultimate tensile strength and good abrasion resistance, which makes it a practical and economical choice for saw blades. The use of steel has allowed special purpose cutting tools to be developed with steel teeth (or inserts) allowing the blade to function as a router bit or jigsaw blade.
Types of steel
There are many types of steel but high alloy steels and low alloy steels are common choices. High alloys, such as tool steel grades like A2 (air-hardened), D2 (oil tempered), and W1 (water-hardened), provide some significant advantages over plain carbon or low alloy steels: they attain their hardness through heat treating and have greater resistance to abrasion and chipping.
Tool steels are alloyed with a variety of elements, but often contain high concentrations of tungsten (W), vanadium (V), or both. These additions enhance the steel’s properties for use as cutting tools by increasing hardness and imparting dimensional stability, as well as resistance to wear and corrosion.
As a general rule, as the percentage of tungsten or vanadium increases, the alloy becomes less soft and tougher. These alloys also have increased hot hardness and reduced thermal conductivity compared with other non-tool steels. This means that blades made from these materials retain their hardness at high temperatures, which helps to keep the blade from being caused to wander, or “wander”, during cutting.
Steel does corrode but has excellent corrosion resistance compared with other materials. It is resistant to attack by most acids and can be left in contact with water without undue rusting. However, steel will corrode over time when exposed to air, especially if it is not treated with a coating.
Steel has low ductility and cannot be bent back on itself repeatedly without fracturing. Some steel alloys are susceptible to stress corrosion cracking, which can make the blade extremely brittle; this is particularly true for lower alloy (carbon) steels or high-speed tool steels.
The disadvantage of steel blades
The major disadvantage of steel blades is that they become dull when they contact the material they are cutting. Because the steel blade must cut through the material it is pressed against, and because that material has a certain degree of moisture or “tackiness”, the blade will become dulled with repeated use.
Nevertheless, this drawback can be minimised by allowing a saw blade to cool between successive cuts and by periodically cleaning the blade with a wire brush or a grinding stone.
Different types of grades
Tool steel blades are available in a variety of grades and manufacturers provide information as to the intended use.
Industrial tool steels have a special quenching process that makes them particularly hard, but also brittle, so they can shatter rather than bend if dropped on a concrete floor. They are often used for specific industrial applications like cutting metal.
Carbon steel blades are harder than high alloy steels, but they dull quickly and require frequent sharpening.
Manufacturers typically indicate the type of carbon steel alloy used, typically medium-carbon or high-carbon steel.
The higher the carbon content, the larger (and thus harder) the carbides, and the higher the wear resistance.
Abrasion resistance is about the same for all carbon steels; however, toughness will vary depending on alloy content. Medium-carbon steel is tougher than high-carbon steel with similar composition and hardness (i.e., medium carbon has more alloy and less carbon than high carbon).
Carbon steel blades are typically used for saws that cut wood, nonferrous metals and cast iron. Carbon steel blades can be found as thin as 0.020″ (0.5 mm) to as thick as 0.125″ (3 mm).
Lower alloy steels are used for circular saw blades that are designed to cut steel, masonry or granite. They are harder than carbon steel blades but not as tough.
Lower alloy steels contain 0.1-0.25% manganese (Mn), 0.5-1% chromium (Cr) and up to 1% silicon (Si).
Non-alloy carbon steels are mainly used for cutting wood or green material (wood with moisture). They have a high ash content and poor edge quality
Non-alloy carbon steel blades are typically identified with a -C or W suffix.
Alloy steel blades are used for cutting cured concrete, brick, block, and stone. They have significantly lower ash content than non-alloy carbon blades and generally better edge quality. Alloys will vary depending on the manufacturer’s intended use of the blade; some manufacturers offer specific types to improve edge quality, abrasion resistance, or corrosion resistance. Alloy blades are typically identified by a -B, -SK or -SIC suffix.
The blades are the next important companion to your circular saw. But as you can see, there are a lot of factors that go into the making of a saw blade so hopefully, we managed to shed some light on the type of steel that’s being used.