Holes can be drilled in all thicknesses of glass but must be processed in toughened and heat strengthened before furnacing. Holes are generally as drilled unless processed for toughening.
Holes can be countersunk in toughened glass before toughening for accommodating mechanical fixings. Standard bush is held at toughening lines for sizing purposes.

Drill Sizes Stocked at Toughening Lines

The available holes are :
5mm, 6mm, 6.5mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 25mm, 26mm, 28mm, 30mm, 34mm, 35mm, 40mm, 42mm, 45mm, 50mm, 58mm, 60mm, 66mm, 70mm, 75mm,
80mm max drill size.
Finger pull/thimble hole size = 21mm.
Plunger lock hole size = 19mm.