• Use a Diamond drill bit for drilling into very hard tiles (porcelain) and glass
• Drill at low speed with medium pressure
• DO NOT set the drill on hammer action!
• Swap to a more appropriate type bit for the material behind the tile (masonry / concrete) or glass
• Water cooling will prevent glass from heating-up and cracking.
• Drill bits bit tends to run or wander on this kind smooth surface. Minimise this by drilling through pieces of masking tape stuck onto the glass or tile where the hole will be drilled