A glass cutter is a tool which is designed to score glass, making it easy to snap the glass into pieces of a desired shape and size. There are a number of different styles of glass cutter available, from simple hand tools to glass cutting machines, but each style works in essentially the same way. Most hardware and craft stores carry glass cutters, along with other tools which may be useful when working with glass.
It is extremely difficult to literally cut through glass without causing the glass to split and break, creating a mess and a pile of potentially dangerous shards. Instead, people who work with glass score it, creating a line of weakness along the glass which can be exploited by gently bending the glass against the score, encouraging it to snap along the scored line. When done properly, the glass will break cleanly along the score, and then the edge can be sanded to make it less sharp.
A basic hand-held glass cutter includes several parts. On one end, an extremely sharp steel disc is designed to rotate as the cutter is dragged along the surface of a piece of glass. On the other end, a weighted ball can be used to gently tap the glass, encouraging it to break off. A series of notches along the side of the glass cutter can also be used to break off the piece of glass, as they are designed so that the glass can be slid into them, allowing the operator to use the glass cutter as a lever.
Using a glass cutter is fairly easy, but it does require some practice. Lubrication such as oil must be used, and the glass cutter cannot be applied with too much pressure, or it will cause the glass to crack. A ruler or guide should be used to keep the score straight and even. It is a good idea to wear gloves and goggles to protect the hands and eyes, and to move slowly as the glass is scored and snapped. Various tools like vises and pliers may be used to hold the glass in place while it is snapped, distancing the potentially sharp glass from the person cutting it.
Industrial glass cutters come with their own cooling and lubricating systems, which typically use water. Depending on the machine, the user either runs the machine along the piece of glass, or runs glass along the machine, like using a table saw. In both cases, it is still important to move slowly and deliberately to avoid injury or damage.