Things You'll Need
1/4 inch dowel
T-square or other straight edge
While cutting window glass is not difficult, it does take practice. Many people make the mistake of trying to scratch too deeply into the glass, or running the glass cutter over the same line multiple times. As for tools, there are two types of glass cutters on the market--a simple steel wheel and a diamond-chip-coated cutter. Either type will work, although many novice glass cutters find that the diamond cutter is slightly easier to use. The trick to cutting glass is to put just the right amount of pressure on the cutting wheel and to pull the cutting wheel across the glass smoothly and at an even speed. The success of the actual breaking of a scored piece of window glass depends on the quality of the scratch you have made as well as the size of the glass. With a little practice almost anyone can cut like a pro.
Lay your glass sheet on a smooth, clean, level surface.
Dip the tip of your glass cutter into kerosene for a smoother cut.
Lay your T-square to the straight edge where you want your cut made. Hold the straight edge firmly to the glass.
Grasp your glass cutter as if you were holding a pencil. Angle the cutter just slightly so the cutting wheel touches the glass where you wish to make your cut. Start at the very edge of the glass and draw your cutter all the way across to the other edge of the glass with a moderate amount of pressure in one smooth, even motion. There should be just a slight scraping sound as the cutter scores the glass.
Place the 1/4 inch dowel under the glass, directly under the scored line.
Wearing your eye protection and gloves, apply a sharp downward thrust to the glass on either side of the dowel. The glass should snap cleanly along the score. Use caution as the edges of the glass can be very sharp.
Rub your whetstone lightly along the cut edges of the glass. Round the sharp cut edges slightly to increase the strength of the glass as well as to make it safer to hold.
Do not press too hard when making your cut. If you hear a crackling grinding noise when cutting, you are probably putting too much pressure on your cutter.
Always wear eye protection and gloves especially when actually snapping the glass.