Semi-Automatic Button Bit Grinder BTON 500 semiautomatic button bit grinder have quickly established themselves as dependable and versatile machines, credited by the professionals and CE approved. Our Air Grinders require a clean and dry air supply of a minimum 80 psi and 29 cfm passing through an in-line oiler to supply lubrication to the grinder. Also, a supply of water from a mains supply or a sump is required to act as a coolant During the grinding process.