Can you drill toughened glass?

Whether you're making home improvements or fitting a shopfront, toughened glassmakes for a robust, energy-efficient and versatile option.
But because of the way it's manufactured, it shatters when put under too much pressure. This makes it safe – but it also means you shouldn't drill it.
Instead, a standard sheet of glass must be drilled (or otherwise cut into) before it's put in the furnace for toughening.

Why does toughened glass shatter when drilled?

Toughened glass is a unique kind of glass made by heating an ordinary sheet of glass to a high temperature and then cooling it rapidly with blasts of cold air.
This process excites the molecules in a way that makes the glass shatter into tiny pebble-like pieces when it breaks. This contrasts it with standard annealed or float glass, which breaks into harmful, jagged shards.

What if I want a hole in a pane of toughened glass?

 If you want a hole in a pane of toughened glass, it needs to be drilled into a piece of annealed glass and then put into the furnace.
Whatever project you're working on, you should communicate with the glass supplier to make sure you're getting the right materials for the job. The alternative is a lot of broken glass!

How do you know if a piece of glass has been toughened?

Toughened glass and annealed glass look very similar to the untrained eye. There are, however, a few ways you can tell the difference.

The manufacturing process gives toughened glass smooth, rounded edges. It's important to note, however, that annealed glass can be processed to have smooth, rounded edges, too.
Toughened glass will often bear an etched or sandblasted stamp. This will tell you the manufacturer and product details.
Finally, you can view the glass through polarised sunglasses. If it's toughened, you should see a distorted pattern along the glass.

Misconceptions about drilling toughened glass

You may have seen tutorials online purporting to give you tips on drilling toughened glass safely. The following claims should be taken with a pinch of salt:

Myth 1: "You can drill through toughened glass successfully with diamond-tipped or carbide drill bits"

It's true this will cut through the glass more effectively. However, the glass will still shatter.

Myth 2: "Using oil or water as a lubricant and coolant will stop the glass from shattering"

This is incorrect. Lubricants and coolants will lubricate and cool. They won't stop a piece of toughened glass from shattering.

Myth 3: "Drilling slowly and applying less pressure will stop the glass from shattering"

 This is also incorrect. The molecular composition of toughened glass is such that  any amount of pressure can cause it to shatter – even the smallest amount.
ToughGlaze is a UK glass processor with more than 30 years of experience. We provide fully compliant,custom-cut toughened glass that can be shaped and drilled to your exact specification. Please get in touch to request a quick, competitive quote.