"Walker" gives you options the holes drilling capabilities starting at 1/4 inch. The two-sided hole drilling equipment offers precision accuracy. 

Maximum Number of Holes 

The maximum number of holes allowed in any lite of glass is ten (10).

Guideline for Holes Dimension 

Minimum Size: Circular holes must have a diameter at least 1/16" greater than the thickness of the glass, with 1/4" (6mm) being the smallest hole allowed.

Maximum Size: The maximum size of a hole can not be more than 1/3 the narrowest dimension of the glass. 

For holes that have a straight edge, or are non-circular, fillets are required in the corners. A fillet is a rounded corner from which the straight edge emerges. The radius of the fillet must be equal to or greater than the thickness of the glass, but not less than 1/2".

Guideline for Minimum Glass Width with Holes 

The minimum width of glass containing holes that can be satisfactorily tempered is an 8" width. All other requirements of hole location, spacing of holes, and dimensions of holes must also be met.

Guidelines for Hole Spacing 

The distance from any edge of glass to the nearest point on the rim of the hole (x) must be at least 6mm (1/4") or 2 times the thickness of the glass, whichever is greater. 

The distance between holes must be 10mm (3/8") or two (2) times the thickness of the glass, whichever is greater.

Guideline for Holes Placement Near the Glass Corners 

Holes near corners must be located so that the nearest edge of the hole is at least 6.5 times the thickness of the glass from the tip of the corner when the corner is 90° or more.