What are hole saws made of?

29th February 2020


What are hole saws made of?


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		Hole saws are typically made from tool steels such as carbon steel or high speed steel (HSS). They are also commonly made from bi-metals for increased hardness and durability.

		Carbon steel
		Carbon steel is a type of steel alloy with a minimum carbon content of 0.3% The properties of carbon steel depend on the amount of carbon it contains. You can find 3 types of carbon steel: low, medium and high. Many cutting tools like drill bits and hole saws are made from various types of high carbon steels.

		1. Low carbon steel – Contains up to 0.3% carbon. This improves ductility but has no effect on strength. Ductility is a measure of how much stress a material can take before it fractures.

		2. Medium carbon steel – Contains between 0.3 to 0.5% carbon. This is ideal for machining or forging and where surface hardness is desirable.

		3. High carbon steel – Contains more than 0.5% carbon. This becomes very hard and will withstand high shear and wear which makes it ideal for hole saws as they are frequently put under high levels of friction and wear.

		High speed steel
		High-speed steel (often referred to as HSS) is a sub-category of high carbon steel designed specifically for making drill bits and cutting tools. It is superior to other milder (less hard) steels because it can withstand much higher temperatures without losing its temper (hardness) and has a greater resistance to deformation and abrasion.

		These qualities make it an ideal substance from which to make cutting tools. High-speed steel gets its name because tools made from it can cut much faster than other tools whilst still retaining their sharp edges.

		Bi-metals
		Bi-metals are those which are made from two different and separate types of metal that have been joined together. Unlike alloys, which are a mixture of two or more metals, bi-metallic objects are made up of layers of different metals. The surface layer of bi-metals is typically stronger than an alloy of similar materials as it is this surface layer (usually on the hole saw teeth) that is used to cut through materials.

		The cutting teeth of a hole saw are often bi-metallic (given a layer of high speed steel or tungsten carbide). This increases their hardness and durability. Other hole saws (especially hole cutters) may be embedded with industrial diamonds which gives them excellent cutting ability and extra hardness.

		Tungsten carbide Tungsten carbide is an inorganic compound that contains equal amounts of tungsten and carbon atoms. Because of its hardness, tungsten carbide is often used to make industrial machinery, cutting tools, jewellery, and abrasives. It has twice the stiffness of steel and the hardness of ruby.

		Silicone carbide (carborundum) Silicone carbide (also known as carborundum) is a mass-produced compound made from mixing silicone and carbon. It is an extremely hard abrasive material that is often used to coat machining pieces like drill bits and cutting blades.

		Industrial diamonds When a mined diamond is not suitable for becoming a gemstone, it is often used for industrial applications instead. Industrial diamonds are valued for their hardness and thermal conductivity and many tools are embedded with diamonds to improve their hardness. Lots of industrial applications actually use synthetic diamonds instead of naturally occurring ones.

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