Most marble tile installations rely on a tile wet saw or an angle grinder to make cuts in the stone. However, for circular cuts made to fit around pipes and other appliance fittings you need to use a drill to cut through the stone. The type of drill bit you use depends on the type of marble you are dealing with, as marbles vary in thickness and hardness.
Diamond Tipped Bit
Similar to normal drill bits used to drill through wood and metals, a diamond tipped bit utilizes the same combination of spiral channels to remove the excess debris. The only difference is that the bit is tipped with chunks of diamonds. Diamond bits are superior to carbide bits and are reserved for the hardest, polished types of marble tiles, and they come in a variety of sizes.
Carbide Tipped Bit
Carbide tipped bits are similar to diamond bits except they use carbide on the drilling tip of the bit. They can be used with all but the hardest types of marbles and come in a variety of sizes. Different channel types are also sold depending on your personal preference, such as dual channel bits or single channel bits, with the channels removing the debris as you drill through the stone.
Hole bits or core bits are specially designed drill bits that are tipped with either diamond or carbide. Rather than relying on channel action like normal bits, core bits have a central pilot bit that holds the bit in place while the outer sections of the bit cuts a hole through stone. Core bits are reserved for larger holes above 1/2-inch in most cases, with a variety of sizes available. They can be used with all types of marble tiles.
Spade bits for stone can only be used with soft types of marble, such as tumbled marble. They are exactly like spade bits for wood except that they are tipped in diamond or carbide. Since the spade bit is weaker than a traditional drill bit, it cannot be used with the harder types of stone as the spade section of the bit is likely to bend under the pressure.