Giovanni Valle is a licensed architect and LEED-accredited professional and is certified by the National Council of Architectural Registration Boards (NCARB). He is the author and managing editor of various digital publications, including BuilderSpace, Your Own Architect, and Interiors Place.
Tempered glass, also known as safety glass, is engineered using thermal and chemical processes to give it added strength. The glass is compressed on the outside and also compacted in the center, so when it breaks, it shatters into tiny pieces to cause minimum damage. This is why tempered glass is known for both its strength and safety.
It is not possible to drill a hole in tempered glass. It would completely shatter as soon as the drill comes into contact with the glass. If you need a hole in the tempered glass, it needs to be done before the process of tempering.
Thin layers of tempered glass, for example, protectors for mobile phone screens, can be cut with industrial lasers. However, this can only be done industrially and not at home or in a local shop. Thicker and larger products of tempered glass are still drilled and cut for desired shape and design before the tempering process because, after the tempering, it is not possible.
Why You Can’t Drill a Hole in Tempered Glass
Tempered glass is manufactured in a way that, if it breaks, it will crumble into tiny granular pieces. It does not break like typical glass, which shatters into dangerous and sharp shards. This is why it is difficult to drill a hole into it because it is meant to be a safety glass that will not break easily, and if it does break, it will not have perilous concerns. It is engineered in this way to distribute the pressure throughout the piece.
This is when we see a tempered screen protector break. Web-like cracks appear throughout the screen, not just on the area where the damage was done. Tempered glass is durable and therefore used in everyday products which could cause harm if shattered, for example, car windows, shower cabins, glass doors and tables, some cookware and microwavable objects, and of course screen protectors.
Can You Cut Tempered Glass?
Tempered glass cannot be cut just like it can`t be drilled into. Some people have suggested cutting it with a wet porcelain tile saw or a diamond/carbide blade. These materials will not work on tempered glass. If you are able to cut your glass with these blades, then the glass you have is not tempered, and its authenticity is in question.
It is certain that once a glass is tempered, there is no way you can cut or drill into it without breaking it. It is not possible to work on tempered glass.
How to Tell if a Glass is Tempered?
It can be tricky, but tempered glass has many indications to prove its authentic material. There are several ways to check whether a glass is tempered or not. If none of these ways help to show whether the glass is tempered or not, then it is likely that the glass you are checking is not tempered.
Smooth Edges Are a Sign That the Glass is Tempered
Tempered glass has a smooth finish on the edges of the sheet. Rough edges mean that the glass is not tempered. The rough edges will look visibly uneven and also feel coarse on touch.
Marks Left During Production Can Provide Clues that it’s Tempered
Tempered glass might have a bend or warp in it. These imperfections are due to the heating process when tempering glass. Some impressions left, can be seen on tempered glass if viewed clearly and are a good sign that the glass you own is tempered.
A Logo, Stamp or Signature of the Manufacturer
Watermarks can usually be seen on the corner of tempered glass. It will contain the manufacturer`s name or markings. Sometimes it is not easy to locate these watermarks because of the thickness of the glass, but they can be seen if viewed carefully.
Viewing the Glass Wearing Polarized Sunglasses
Another good way to identify tempered glass is through polarized sunglasses. Looking at tempered glass wearing them will show patterns on the surface. The patterns will have dark lines that are there because of the compression of the glass during manufacturing.
If none of these tricks work for you and you are still confused about the glass, it is best to visit a glass shop or two to confirm the type of glass you`re about to work on.
Cutting and Drilling Tempered Glass After Annealing it
Annealing tempered glass means giving it a heat and chemical treatment that will reduce its hardness and make it more workable—basically converting the glass from tempered to ordinary.
Once it has become ordinary glass, it can be cut and drilled like one too. The tempered glass will not remain safe either, and if it breaks, it won`t shatter into tiny pieces; it will break into shards.
It is better to drill and cut ordinary glass into the desired shape. This is because of two reasons:
- Tempered glass is expensive, and converting it into ordinary glass will add a hefty cost on your pocket because it is done industrially and can`t be done at home.
- Giving glass a particular shape can be done on ordinary glass, so that should be bought in the first place to make those changes.
How to Drill a Hole in Other Forms of Glass
Even though tempered glass cannot be drilled or cut, other forms of glass can. Drilling a hole in glass requires a few careful steps. The equipment required is a drill and glass drill bits. Diamond drill bits can also be used and give a smoother finish. They also cause less breakage as compared to carbide drill bits. It is best if the drill you buy can change its speed. Once your drill is in place, you`re ready to go.
Take Proper Safety Measures Before Beginning to Work on the Glass
First and foremost is safety. Before working with drills or wet tile, saws make sure to wear safety gloves and glasses to protect from any cuts from shards or pieces of glasses reaching the eyes. Wearing a mask is also recommended since glass dust can be breathed in and prove hazardous for health.
It is important to note that drilling can incur heat production and burn the glass. Therefore, apply some moisture for coolness before starting the drilling process or place a wet cloth under the glass to keep it from heating up.
Set the Glass on a Stable Place Before Drilling
Before starting to drill, the glass you are working on needs to be placed on a stable place, and it is better if it is attached to something when placed on the work table (for example, cardboard or a rubber pad), so it does not slip when drilled.
Increase the Speed of the Drill Gradually
The drill being used should be first operated a slow speed to create a small dent in the glass where the hole is to be drilled. After that, you can remove the material (cardboard or rubber pad) that was used to stabilize the glass from underneath and then drill the hole at a faster speed, around 350rpm.
The best way to buy tempered glass is to purchase it in a shape or size that you are planning to change it into later instead of buying it with a mindset of working on it at home. It is engineered with the intention of safety and strength; therefore, it is not meant to be cut and drilled into.
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