A porcelain drill bit is a specialty drill bit used by contractors and construction workers to drill holes in materials that are both hard and fragile, such as porcelain, glass, or marble. Porcelain drill bits come as either a spear-point carbide tip or a hollow-core diamond tip. They are designed to withstand higher temperatures caused by friction and usually have a lifespan of 10 to 100 holes, depending on the material being drilled.
A spear-point porcelain drill bit uses a harder metal tip to burrow into the material. These bits, which were originally used for harder surfaces, must be kept as cool as possible at the risk of the carbide tip separating from the drill bit. Spraying the bit with water is the simplest way of cooling it. This type of porcelain drill bit needs to be sharpened often.
A hollow, diamond-tip porcelain drill bit uses tiny diamonds to cut into the surface. This type of bit is more expensive but cuts more quickly and stays sharp for longer periods. It is also good for drilling larger holes.
Standard drill bits will wear down before they even scratch the surface of a porcelain tile. Porcelain tiles are made by compressing clay dust under extreme pressure, then firing the resulting tiles at very high temperatures. This process makes the tile not only much harder, but also denser and longer lasting than other ceramic tiles. Harder and more durable drill bits are needed to bore through this type of material.
When drilling porcelain tiles, it is best to use a variable speed drill fitted with a new porcelain drill bit. This allows for better control so neither the drill nor the bit will overheat. The hardness of porcelain tiles can make starting a hole difficult, even with the correct drill bit. To make it easier, it is recommended to place a piece of duct tape over the area to be drilled. Mark the duct tape where the hole is to be drilled and drill through the tape. This technique helps to alleviate any slipping that might occur as the drill bit tries to bite into the hard surface.
Experts say that one should never force a drill bit or apply extra pressure to cajole it into cutting a hole more quickly. This can cause the bit to overheat and wear out more quickly. Cooling off a hot drill bit by spraying it or dipping it in water can extend its life.