A carbide bit is a type of tool attachment made out of a specialized metal alloy. Carbide is properly called tungsten carbide and is a specific combination of those two materials. The actual definition of tool bit varies slightly, but it is always the specific part of a tool that contacts the worked material. A carbide bit is much harder than steel, but it is also more brittle. As a result, many larger bits are made of cemented carbide or steel with a brazed carbide tip.
Tungsten carbide is an equal mixture of tungsten and carbon. When the alloy is created, it is typically made as a fine gray powder. This powder is compressed into the desired shape using a modified die-casting process. After hardening into its new shape, this material is extremely hard and can withstand heat that would melt other metals.
In its common form, tungsten carbide is very brittle. While the metal itself is very hard, a carbide plate can break with even slight impacts. To offset this problem, tungsten carbide is often combined with metallic cobalt to create cemented carbide. During the formation process, cobalt liquefies at a much lower temperature than tungsten carbide. This allows the liquid metal to ‘soak in’ to the carbide, greatly increasing its strength.
The actual definition of a tool bit is a matter of some debate. In some circles, a bit is a non-rotary cutting tool like the blade on a lathe or the head on a shaping machine. In other places, it is any removable or exchangeable tool piece, such as the drill part of a handheld drill. Both definitions have one thing in common—the bit is the part that directly interacts with the worked material, and any changes to the material are done by the bit alone.
Manufacturers use a carbide bit when the material or manufacturing process requires high tolerances or precision. These bits are often used when a material is hard enough that a typical bit won’t work it properly, such as with hardened or carbon steel. Since that’s what a common bit is made of, it isn’t hard enough to work the material. Interaction between two pieces of the same material typically results in both parts being ruined.
Another common reason for a carbide bit is when the material being worked needs exposure to very high temperatures either before or during the process. Since a carbide bit can withstand greater temperatures than steel, it is often used in high-heat situations. This is also true when the friction created by the working process would create enough heat to melt a steel bit, such as in high-speed grinding.
By M. McGee