Behind the Luster, the Hard Side of Diamonds

When you want to drill holes into the glass without making the entire sheet crack, there are two kinds of drill bits that can do the job: a tungsten carbide and the harder diamond-tipped bit. As diamond is among the hardest minerals on Earth, many workshops choose to work with diamond-tipped bits, especially in precision glass cutting and drilling. With a Knoop hardness rating of 7,000, it's 3.5 times harder than tungsten carbide and can cut through glass, which falls between 400 and 550 in the hardness scale, with relative ease.

One material cutting into another material is a testament to the former's hardness. This is because the first material can resist changes in shape better than the second, which cuts or breaks under the first, when force is applied. However, experts say the cutting ability of diamond depends on how you use it. Using the edge or girdle of a diamond, for instance, may put stress on the diamond. It's one of a few instances where the glass actually wins over the diamond.

Fortunately, you don't have to worry about that with drill bits because the diamonds used here aren't the jewelry quality ones, but rather the ones meant for industrial use. Cutting glass with the tip on the surface ensures the longevity of the bit. No wonder diamond-tipped drill bits are very common in workshops.