How to Cut a Sheet of Glass
All it takes is a straight edge, a glass cutter, a flat work surface, and a few simple steps to get clean cuts every time.
Whether you’re repairing a broken window pane or building a new window from scratch, you’ll need a piece of glass that’s just the right size. All you need are a few basic tools and supplies to do the job yourself. As easy as the job is, you might want to wear gloves, and you will definitely want to take your time to avoid cutting yourself or breaking the glass.
Here’s what you will need:
• Tape measure or other measuring tool
• Permanent marker, wax pencil, or other marking tool
• Flat, clean work surface (cardboard, foam core, etc.)
• Rags or paper towels
• Glass cleaner
• Straight edge
• Glass cutter
• Oil or kerosene, for lubricating cutter
Here’s how to cut glass:
1. Place the glass on piece of cardboard, foam core, or any other surface that is flat, clean, and not too hard.
2. Clean the glass where you want to make the cut with a rag or paper towel and some glass cleaner.
3. Use a permanent marker to make marks for the cutline on both ends of the sheet of glass to match your measurements.
4. Lay a ruler or other straight edge on the glass so that the glass cutter lines up with the marks when placed next to the straight edge. The straight edge should be thick enough so the glass cutter’s wheel won’t accidentally ride over it, but not so thick that it interferes with the handle.
5. Before scoring the glass, oil the cutter’s wheel to lubricate the tool and extend its life.
6. Start by resting the wheel of the cutter just off of the glass on the far side of the sheet, then draw it toward you while applying consistent, downward pressure as you pull the cutter across the surface. This motion should make a single score line, and the process should sound a bit like tearing paper and look like a small scratch.
7. To finish the cut, place a pencil or small dowel directly under the scored line near the edge, and press down on both sides with increasing pressure until the glass snaps along the score line.
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Having been a glazier in the past, here are a few additional points for those wanting to work with glass:
1. Purchase a good glass cutter from a glass & mirror retailer - big box store options are limited. I always preferred a wood handle cutter...
2. Rather than dip the cutter wheel in the lubricant, I always has a nylon 1/2" paint brush in a coffee can with lubricant and applied it along the full length of the cut against the straight edge. This cleared the path of debris and kept the cutting wheel sharp for a longer time.
3. Scoring glass is by feel and sound - you can feel the wheel score and hear it as well. If it skips, you will know. Do not double score a cut - review the cut, rescore only the missed section, and then snap the cut over the edge of the table, lining the score up parallel to the edge. Lift it, then drop it down with your hand ready to grab the piece that will snap off. If you attempt to peel a skipped cut, it will usually run off and produce a nasty flare.
4. Thinner glass (1/16" - single strength or 1/8" double strength) requires a sharper wheel and less pressure. Practice on a side piece - you will get the feel. Too much pressure causes little fissure flakes to pop off the surface of the glass - more than likely resulting in a break that will run away from the score line.
May I also add that I keep my glass cutter in a pill container that has a round hole cut in its top. Inside the pill container I keep a small rag soaked with mineral oil. I slip the wood handle of the glass cutter through the round hole and then put the top on the pill container. The working end of the glass cutter is now contained in the pill container and its blade and axle won't rust or be damaged.
Actually I've never cut glass, but my father gave me his spare and set me up with this system many years ago.