[THE_MASK]

Glass cutting isnt easy . I did it for over 20 years . You will need a new glass cutter . You can sharpen old ones but you need a slate stone and its impossible to do if you dont know what you are doing . Ok , so you have a new cutter . You also need a straight edge , something like a thin piece of wood say no more than 6mm thick and about 2 inches wide . Some oil , any type will do . Be careful you dont get toughened glass because if you score that it will explode . Laminated glass like whats in shower doors is no good either . Lay the glass down on a blanket on a table . Warning dont ever carry glass flat . Placing on a table etc you should be holding vertically one hand on top and one on bottom . Rest the glass on the edge of the table and slowly tip it onto the table keeping the glass resting on the edge of the table at all times . Put a blanket on a table and put the glass on the blanket .
glass cutting.
The glass cutter wheel has to be perfect . In other words if you go over a cut you just did with the wheel then its destroyed . So what you do is start at the top of the pane and in one smooth stroke with even pressure cut down the length of the glass . Clean the glass where you will be cutting and dip the end of the cutter in some oil (engine oil etc) so you have a nice wet cut . Never cut dry . Get someone to press down on the wooden straight edge at the top and press down the wooden straight edge at the bottom with your left hand . You dont want the straight edge to move but not too much pressure .
Holding the cutter
Hold it exactly like a pencil . Except have the shaft of the cutter in between the index and middle finger .
You just want enough pressure to score the glass . You are not trying to cut thru the glass , just scoring the surface .
Mark the cut with a marker pen and allow 2mm for the width of the cutter . In other words move the straight edge 2mm to the left of the mark to allow for the cutter width .
Once its scored
Lift the edge of the glass up and place the straight edge under the cut . Put some gloves on and slightly press down on the glass . It should just snap .

I never told you this bit
Do this at your own risk
Cleaning the edges
Put on safety goggles . Get out your 4 inch angle grinder and rub some oil into the grinding wheel surface . Put some gloves on and just ever so lightly feather the wheel along the sharp glass edge on an angle . You just want to take off the sharp edge . You want to be touching the edge that softly that you are only just sure you touched it . Never run your finger along the edge of glass length ways to check . I have seen people do this . Ouch .