SCALLOPED GUN BODY WITH IMPROVED TOLERANCES FOR UNDERGROUND WELL PERFORATING, AND PROCESS OF MANUFACTURING THE SAME

摘要

Scallops are cut into a tubular gun body for use in underground jet perforation by measuring with a sonic or like probe the wall thickness of the tubular gun body at the location or locations where the scallops are to be machined on the exterior of the gun body. The measured wall thickness is inputted into a central processor which also has input of data defining the desired thickness of the web to remain in the tubular gun body after scalloping. The computer utilizes an algorithm to calculate how much metal needs to be removed by a machine tool from the tubular wall to obtain the desired web thickness. In the step of actually cutting the scallop the cutter of the machine tool, directed by the computer through robotic machinery, "senses" the zero point, that is the beginning of the wall, by sensing a surge in current load (amperage) as the cutter touches the wall and begins removing metal from it. The sensed zero point is inputted into the central processor which thereafter directs the cutter to remove the calculated thickness of metal from the wall. The web that remains after the scallop has been cut has dimensions with tolerance on the basis of the accuracy of the measuring and cutting process and not on the basis of the manufacturing tolerance of the tubular gun body. Web dimensions having tolerance limits of approximately +/- 0.20 inches or less, preferably approximately +/- 0.005 inches or less, are attained in this manner even with gun bodies that have been made by hot finished manufacturing process.