Ceramic and Porcelain Tile
Ceramic and Porcelain tile, used on walls, counters and floors, has changed considerably over the years. Ceramic tile was first developed with a heat-hardened vitrified glass finish on the top surface. The inside of the Ceramic tile was still relatively soft. Since the tile was easily scratched, manufacturers developed better manufacturing techniques to make the surface finish much harder. The newer Ceramic tile now has an extremely hard surface that wears very well and the inside of the tile is also relatively hard. While this is a distinct advantage from the stand point of wear, the newer Ceramic tile is often difficult to drill without a diamond drill bit.
Porcelain tile was originally developed as an alternative to Ceramic tile, for use in floor applications where usage and wear was more extreme. Porcelain tile is made with various mixtures of materials, normally including feldspar and quartz, which are two of the major components of natural Granite. The use of Porcelain floor tile was generally limited to commercial applications, but by the late 1980's, Porcelain tile use expanded more into residential construction.
In the 1990's, tile manufacturers began to expand their Porcelain tile product lines to include many different styles and many that closely resembled natural stones. Because of the natural stone look, Porcelain tile use on walls and counters became more popular. Finally, in the late 1990's tile manufacturer's developed new manufacturing techniques that made the Porcelain tile significantly harder. As with Ceramic tile, this was a major advancement resulting in reduced wear and very long life. However, many Porcelain tiles are now as hard as Granite and some are as hard as a low grade tool steel. The newer type of high-quality, "super-hard", "Class IV" and "Class V" Porcelain tiles are now almost impossible to drill with the older "spear point" carbide drill bits and generally can only be drilled with a diamond drill bit.
Lubrication
Water or coolant must always be used to cool and lubricate the tip. The lubrication reduces heat build-up, prolonging drill bit life and helps avoid heat fractures in the material. Water is most often used as the lubricant, since it works very well and has no cost. Oil based lubricants do not work well on diamond drill bits.
Good lubrication is critical. Minimal lubrication will keep the bit from burning up, but very good lubrication techniques will extend bit life by a factor of 5 or even 10.
When drilling in fiberglass, a diamond drill bit can be used dry or with a very small amount of water. When drilling in glass or ceramic, soft ceramic tile and porcelain, if properly lubricated, the dust from the cut should dissipate into the water. The drill bit contact with the surface should always be wet and the drill bit tip should never be hot. If the tip is ever more than just warm, it is generally an indication of too little lubrication (or possibly too much speed or pressure).
When drilling in hard, abrasive materials such as limestone, sandstone, hard ceramic and porcelain tiles, marble or granite, it is critical to have lots of lubrication. With these hard materials, it is common to drill under water or to have a small amount of water constantly running over the drill bit and bore hole. In either case, the "pumping" technique described below is needed to assure water reaches the very tip of the bit.
This discussion is presented only as a guide. It is almost impossible to have 'too much' lubrication and the only down side risk is the mess from water being thrown off by the bit. However, 'too little' lubrication will cause many problems.
