a long period of satisfactory service. However, tungsten carbide wheels have been proven to have a significantly longer life than steel wheels and offer greater and more reproducible penetration in scoring as well as easier opening of the scored glass. Cutting The cutter is then rolled firmly over the glass, producing a "score line" or "fissure," weakening the glass along this line. Pressure as light as 5 or 6 pounds, upon a 120 to 140 degree wheel on thin glass; Pressure as heavy as 20+ pounds, with a 154 to 160 degree wheel, on very thick glass. The well-scored pane is ready to be split. The glass may be further weakened by lightly tapping along the cut. The glass cutter in the photo has a ball on one end for tapping the glass. Running pliers may then be used to "run" or "open" to the split. Wheel diameter Glass cutters are manufactured with wheels of varying diameters. One of the most popular has a diameter of 5.5 mm ( in). The ratio between the arc of the wheel and the pressure applied with the tool has an important bearing on the degree of penetration. Average hand pressure with this size wheel often gives good results. For a duller wheel on soft glass a larger wheel (e.g., 6 mm ( in) will require no change in hand pressure. A smaller wheel (3 mm ( in)) is appropriate for cutting patterns and curves since a smaller wheel can follow curved lines without dragging. General purpose glass is mostly made by the float glass process and is obtainable in thicknesses from 1.5 to 25 mm ( to 1 in). Thin float glass tends to cut easily with a sharp cutter. Thicker glass such as 10 mm ( in) float glass is significantly more difficult to cut and break; glass with textured or patterned surfaces may demand specialized methods for scoring and opening the cuts. Large sheets Large sheets of glass are usually cut with a computer-assisted (CNC) semi-automatic glass cutting table. These sheets are then broken out by hand into the individual sheets of glass (also known as "lites" in the glass industry). See also Cutting Computer numerical control (CNC) Water jet cutter References Further reading Cut and install glass Glasschneider Test (in German) History (in French) History of glass cutters Glazier's tools Cutting tools Glass production