High pressure gas drilling

Abstract

High pressure gas cutting process useful for drilling large numbers of holes in large surface area workpieces such as air frame components and the like. The procedure utilizes a cutting tool which has an internal fluid passageway extending through the shank portion thereof and terminating in at least one discharge port adjacent a cutting edge of the tool. As the cutting tool is rotated and advanced into the workpiece in the course of the cutting operation, a high pressure gas is supplied into the cutting tool passageway under an applied pressure of at least 500 psia. The gas, which may be an inert gas such as nitrogen, is discharged from the cutting port into the tool with an expansive cooling effect. The gas then flows outwardly through the hole and exits the hole with sufficient velocity to entrain and remove the drill cuttings from the hole. A liquid lubricant can be employed to prolong the life of the cutting tool. The lubricant is present in such small portions as to avoid the buildup of an identifiable liquid phase within the hole. The cutting tool is operated at a cutting speed of at least 2,000 rpm and a penetration rate of no more than 1 mil per revolution of the tool.

Dependencies are inferred from the claim text.