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HOW TO CUT GLASS

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Actually one seldom “cuts” glass as such. Glass is scored on one side with a glass cutter and then broken on the score line.

Tools required:
Glass cutter
Measuring tape or rule
Wooden straight edge or T-square
Paintbrush
Glass pliers (nice but not essential)
also

Turpentine

Always place glass on a level, smooth and preferably resilient surface, like a table top with a piece of carpeting on it. To mark the glass for breaking make a small mark with your glass cutter 3 mm from the score line to allow for the thickness of the glass cutter. Use a wooden straight edge of at least 6 mm thickness as this is kinder to the glass and to the glass cutter. Do not use a steel rule as these are too thin and you will have to run the wheel or diamond directly next to it, which damages the cutter wheel or diamond, and can cause “skips”. Place the side of the straight edge on the marks. With a small paint brush put a light coat of turpentine along the straight edge to lubricate the cut and make breaking easier. Maintaining a steady pressure run the glass cutter along the straight edge at an angle of about 60° which will keep the foot of the cutter parallel to the glass. You cannot redo a score so take it easy and make sure that you do not skip. Do not stop and start a score by lifting the cutter blade from the glass and never score over the measuring marks as this can cause the break to “jump” off in any direction.

Always start the break at the end of the score mark. Lift glass of 1 mm to 3 mm thickness by placing your bent forefinger under the glass and your thumbs as close as possible next to the score mark on both sides of the score and “opening” the crack like a book to break it. For thicker glass you may have to start the break by tapping gently under the score mark with a glass cutter head or a light hammer. If you are breaking really thick glass, put the glass cutter handle or, if it is a long break, the straight edge under one side of the score mark. A smart rap with the fist on the other side of the glass while holding down the supported side will break the glass cleanly.

If the offcut is too small to hold between thumb and forefinger use the glass cutter to break it off. Glass cutters have notches in the head for the different thicknesses of glass. Select the correct notch and slip it over the glass about 1 mm from the score. Gentle sideways pressure on the handle will break the glass cleanly. If the glass does not break cleanly small pieces can be removed with glass pliers, gas pliers or combination pliers.

Score mirror on the clear side.

Score obscure glass on the smoothest side.

Only specialists can cut “Shatterprufe” and “SafetyGlass”.

Score laminated glass on one side and tap the score to break the glass and bend slightly open. Pour a small amount of methylated spirits in the crack and set alight to burn away the plastic lamination. Carefully turn the glass over and score exactly over the previous line and break the glass.

To cut a circle or an irregular shape:

For a perfect circle you will need a circle cutter. This is a long brass bar with an adjustable cutter at one end and a powerful suction cup at the other. If you have a wooden template with a diameter 6 mm smaller than the required circle or shape and at least 6 mm thick you can use that to score around. Any other shape can also be cut freehand as long as you make sure that the two ends of the score meet exactly.

Tap the glass under the score all around to break the glass.

From the outer edge of the shape make scores to the nearest edge of the glass and tap these from below beginning at the end of the score. As the glass breaks the pieces will fall away. You can lightly polish the edges with a piece of 80 grit emery cloth. For a deep polish you will need a special machine.

To cut a hole in glass follow the same procedure as above but score from the break towards the centre of the shape. Don’t be shy of making lots and lots of score marks, especially near the centre. The more the merrier! Patiently start tapping out glass from the centre of the shape. It is absolutely essential that the shape is broken into the glass before the removing score marks are made. This will prevent the removing scores running over onto the surrounding glass causing it to crack.

To make a square hole in glass you will have to drill a hole with a special glass bit at each corner of the required hole. Make a little well of putty around the place where each hole has to drilled and fill this with mineral turpentine. Holes can be drilled in glass with a hand held electric drill but a steady hand is needed and a lot of patience. Join the holes with score marks and tap the glass out.



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