How to Cut Window Glass DIY

There are dozens of opinions on the correct way to cut glass. To understand how to do it properly, it is indispensable to understand that glass is not a solid; it is between a liquid and a solid. It performs like a solid when keeping out the weather, but acts like a liquid when cut. A few basic techniques can get beginners through most glass-cutting jobs.

Things You'll Need

• Oil
• Straightedge
• Glass cutter
• Permanent marker

Instructions

1. Cut standing up, not sitting down. Use the body, shoulders and arm to apply pressure. Do not use the wrist to apply pressure. A crucial step is to clean the glass surface. If it is not clean, it will not score properly and will not cut well.

2. Mark measurements directly onto the glass. A metal straightedge might slip on the glass. To prevent this, place masking tape on the back of the straightedge.

3. Hold the straightedge on the glass and apply a thin line of lightweight oil to the cutting line. An alternative is to dip the glass cutter into oil, which acts like a lubricant.

4. Hold the glass cutter with the notches facing downward. Let your index finger rest on the back of the cutter just below the teeth. Lay the cutter along the straightedge. Tip the cutter at a slight angle. Do not allow the cutter to lean to either side. If the cutter tilts, you will not be able to get a satisfactory score.

5. Make one continuous downward score in an even, sweeping motion. Make sure the cutter firmly drops off the edge. If scored properly, there will be a clicking sound. The cutter only scratches the surface; it does not cut the glass. Flakes of glass mean the cutter needs oil, or the pressure is too firm.

6. Break the glass as soon as possible after scoring, or it may not break cleanly. Scoring weakens the glass and focuses stress along a single path. Stress relief happens by breaking the glass in two. To make a break, put a dowel or a pencil under the score and press down on both sides.

Tips & Warnings

• Never correct a mistake by repeating a cut. Do not repeat scoring on the same line. Not only will the cut fail, it also can dull the cutter. Turn the glass onto the other side to rescore it. If the second scoring is unsuccessful, grind the jagged edges with a grinder.

References

• Ron Hazelton: How to Replace Broken Window Glass
• Mother Earth News: Cut Costs by Cutting Your Own Glass
• Austin Glass: The Secret of Cutting Glass
• Warm Glass: Glass Cutting Tips