In most cases, any glass you need will be cut by the glass merchant, with you just supplying the measurements. However, there may be times when you need to cut class yourself and it is important you know how to cut it correctly.
The first thing you need to get is a glass cutter. You can buy diamond tipped glass cutters, but for most DIY jobs a simple cutter with a small steel wheel will be fine (and much cheaper). You can buy glass cutters from most hardware and diy stores. If you have never cut glass before, it is worth practicing on a scrap piece if possible. Make your mistakes on the scrap piece and you should have more confidence cutting the section of glass you need. Make sure you are wearing gloves at all times when handling the glass.
Lay the glass on a firm, flat surface which has been covered by an old sheet or blanket. If you are cutting patterned glass, the patterned side faces downwards and the cut is made to the smooth side. Ideally, you should clean the area you are cutting with methylated spirit to remove any dirt or grease. You should also dip the wheel of the glass cutter in thin oil or paraffin to lubricate it.
Measure and mark where you need to cut and lay a straight-edge along the mark. Hold this down firmly and grip the cutter between your middle and forefinger. Draw the cutter smoothly along the straight-edge in one continuous stroke, applying firm, even pressure. Slide the glass out over the edge of the table or bench where you are working and tap the underside of the scored line with the cutter. This helps to initiate the cut.
Now hold the glass on either side of the scored line and snap it in two. If you are not confident enough to do that, with the glass on the flat surface, place a pencil under the scored line and apply even pressure on both sides to snap it.
Cutting Thin Strips
If you need to cut thin strips from the edge of a pane of glass (if, for example, your frame is not quite square), you can do this using normal pliers. Mark and score the glass as normal and then “nibble” at the thin piece that needs cutting away with the pliers. It is best to lay the glass down on a flat surface covered in a sheet, with the piece to be cut hanging slightly over the edge.
Cutting a Circle
There are some situations where you might need to cut a circle out of a pane of glass (to fit an extractor, etc). To do this, you will need to buy a Beam Compass Glass Cutter. This has a suction cup and a pivot which allows you to score a perfect circle.
Place the suction cup in the centre of where you want your circle to be and adjust the cutting arm until you have the circumference you need. Press one finger down on the pivot to stop it moving and then move the cutting arm around in a smooth motion to score your circle. Before moving the suction cup, move the cutting blade in by about 1cm and score a second, smaller circle.
Remove the Beam Compass Cutter and score several straight lines across the inner circle (dividing it up into squares). Now make small radial cuts in the outer rim of the circle. Tap the centre of the scored area from underneath and then gently knock out the glass from the inner circle. Once this is removed, start to break away the outer rim, using pliers to nibble the edge if required.