Abstract: A method and apparatus for controlling glass drilling in which the starting position for the drill bit is calibrated prior to drilling. The drill bit is initially spaced close to the surface to be drilled and the rotating bit is slowly advanced toward the surface while a cooling fluid is discharged through an axial passage through the bit. Contact between the bit and the surface is determined by sensing either an increase in the fluid back pressure or a decrease in the fluid flow rate. The determined bit position is stored and used as a starting position when subsequently drilling holes. The starting position may be modified for subsequent workpieces to compensate for bit wear.

Abstract: An improved structure for supporting and positioning a planar glass workpiece within a glass grinding apparatus is disclosed. Three radially extending carriage assemblies are provided between a lower pan and an upper supporting platform. Each of the carriage assemblies extends radially outwardly from a central drive shaft connected to the supporting platform to the periphery of the lower pan. The radial inner ends of the carriage assemblies are rotatably supported about the drive shaft, while the radial outer ends are carried on respective motor assemblies connected to a gear formed on a lower pan. Energization of the motor assemblies causes the associated carriage assemblies to pivot relative to the lower pan. Each of the carriage assemblies also carries a locator cylinder assembly thereon. The locator cylinder assemblies are movable radially inwardly and outwardly throughout the length of the corresponding carriage assemblies by means of the associated motor assemblies.