EASY TO USE Center pilot tips are for wood, metal, etc. Here's how you can keep the drill bit on target: a- You can make your own guide out of plywood - plastic or even cardboard. Just hold the bit in place until it makes the initial marks. b- It is possible to start drilling at an angle, with the edge of the drill bit forming a C-shaped groove and then bringing the drill bit vertically. c- You can manually guide the tip with a damp sponge.Package included: 1*diamond drill bit setDescription: Applicable industry: suitable for processing stone, tile, ceramic, glass and granite, etc. Silver color Quantity: 15pcs Feature: The electroplated diamond coating will wear if the tool overheats. Never let the drill bit dry out. Here's how to use water to cool the tool: a- You can build a mini water dam around the hole with plumber's grout. b- You can choose to spray water on the tip. c- Or you can use running water to cool the tip.Note: Start your hole diagonally, make a round track then keep the drill straight. Drilling pressure and increased use of water lubrication will significantly extend the life of the drill. Speed Kills: Reduced drilling speeds, low drilling pressure and increased use of water lubrication will significantly extend the life of the drill. Warnings: Do not use on concrete or for depths greater than approximately 1/2"; water is required when drilling for lubrication.