Abstract: An abrasivejet drilling system is disclosed for drilling small diameter holes in fragile materials of the type which tend to crack when impacted by such jets. The system employs a drilling jet formed from a high pressure liquid whose pressurization varies with time during the drilling process. To avoid damage to fragile materials, angular holes are drilled by initially penetrating the surface of the fragile workpiece perpendicular to the workpiece's surface and thereafter pivoting the jet to the correct angle. The jet dwell in the drilled hole for a predetermined time to modify the hole geometry is monitored by detecting the change in sound level when the jet drills completely through the workpiece.