Hole Placement

 How close to the edge of the glass can I drill a hole for hanging?

The rule in glazing large toughened glass walls is that the edge of the hole must be at least 1mm further away from the edge of the glass than the thickness of the glass. The reasoning behind this is the same as the one that says you can’t cut a strip equal or thinner than the thickness of the glass. A strip won’t break off cleanly because the strip is weaker, and it breaks off in pieces.

In the same way a hole closer to the edge of the glass than the thickness will be create a weakness and be subject to breaking. But if the edge of the hole is further away, the glass space has the same strength as the general thickness of the glass.

For example, a 3mm (0.0625”) hole in 6mm (0.25”) glass needs to have the hole edge at least 7mm (0.28”) from the edge of the glass. The centre of the 3mm hole is 1.5mm from its edge, so the centreline of the hole must be at least 8.5mm (0.33”) from the edge of the glass. If it is a 1mm (0.04”) hole in 3mm (0.0625”) glass the centre line needs to be 4mm plus 0.5, or 4.5mm (0.18”) minimum from the edge.

Of course, for heavy or structural glass you probably should double those calculations, just like civil engineers do.

For other tips on glass drilling see:

Keeping things wet
Using a drill press
Drilling with a Flushing Head
Avoiding chipping
Drilling holes with copper tube and grit
Drilling tools
Drilling glass without a drill press
Hole Placement
Drilling Speeds for diamond bits