The effect of glass thickness on cutting
Most of the thicker glass being used today is produced by the "float" method. In this process the glass travels horizontally from the furnace, through a molten tin bath, through annealing lehrs, then continues on rollers where it is inspected, scored and broken into the sizes required. The thickness generally dictates how fast the ribbon of glass moves. The thicker the glass, the slower it is processed and the more effective the annealing. This applies to thicker art glass too.
The key to subsequent cutting is the annealing cycle. Thicker glass tends to have less compression at the surface and tension in the interior. As a result, the glass cutting wheel encounters less resistance to producing a fissure with the shearing forces. However, this means the glass surface will chip more readily. Therefore, a larger wheel angle is required to prevent chipping. It is also common practice to use a larger diameter wheel and larger angle so the fissure can be driven deeper without chipping.
Prepared from information provided by the Fletcher-Terry company.