Drill bit

Drill bits are the cutters of drill tools. Bits are interchangeable, meaning that they can be removed from the end of the drill, either to replace a worn part or to change the size of the part.

Materials for Bit Construction

Many different materials are used for or on drill bits, depending on the required application.

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Steel

Soft steel bits are used only in wood, as they do not hold an edge well, and require frequent sharpening. Working with hardwoods can cause a noticeable reduction in lifespan. They are, however, inexpensive.

Related Topics:
Steel - Hardwood

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Carbon steel

Carbon steel bits are made from high carbon steel and are an improvement on plain steel due to the hardening and tempering capabilities of the material. These bits can be used on wood or metal, however they have a low tolerance to excessive heat which causes them to lose their temper, resulting in a soft cutting edge.

Related Topics:
Carbon steel - Hardening and tempering - Temper

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High-speed steel

High speed steel is a form of tool steel where the bits are much more resistant to the effect of heat. They can be used to drill in metal, hardwood, and most other materials at greater cutting speeds than carbon steel bits and have largely replaced them in commercial applications.

Related Topics:
High speed steel - Tool steel

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Cobalt steel

Cobalt steel alloys are very hard, and are used to drill stainless steel and other hard materials. In addition, the cobalt alloys dissipate heat very efficiently, and help keep the cutting edge cool.

Related Topics:
Cobalt - Alloy

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Tungsten carbide

Tungsten carbide is extremely hard, and can drill in virtually all materials while holding an edge longer than other bits. However, due to its high cost and brittleness, it is usually only used in small chips brazed onto the cutting edges of the bit. A few bits, however, are solid carbide, most notably PCB through-hole bits.

Related Topics:
Tungsten carbide - Brazed - PCB

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Titanium nitride coating

Titanium nitride is a very hard ceramic material, and when used to coat a high-speed steel bit (usually twist bits), can extended the cutting life by three or more times. A titanium nitride bit can not properly be sharpened, as the new edge will not have the coating, and will not have any of the benefits the coating provided.

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Diamond powder coating

Diamond powder is used as an abrasive, most often for cutting tile, stone, and other very hard materials. Large amounts of heat is generated, and diamond coated bits often have to be water cooled to prevent damage to the bit or the workpiece.

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Stainless Steel

Stainless steel is rarely used for drill bits, as it does not hold an edge well. However, they are much less brittle than other materials, and are used where a normal drill bit might be prone to breaking, and a shorter-lived but flexible bit is considered a better compromise.

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