Diamond cup wheels are abrasive tools designed for grinding and shaping various materials, including glass. They are composed of a metal or resin-based disc that is coated with industrial-grade diamonds, which are the hardest known material on earth. The diamonds act as cutting edges to grind away the glass, producing a smooth and precise finish. Diamond cup wheels are available in different grit sizes, which refer to the size of the diamond particles embedded in the disc. Coarser grits are used for removing more material, while finer grits are used for polishing and achieving a smoother finish. When using a diamond cup wheel for glass, it is important to use water or a coolant to prevent overheating and cracking of the glass. Overall, diamond cup wheels are an efficient and effective tool for shaping and polishing glass, and they are commonly used in the glass industry for applications such as edging, beveling, and creating intricate designs on glass surfaces.