GB810543A - Improvements in or relating to the drilling of metals - Google Patents

Abstract

810,543. Drills. NATIONAL RESEARCH DEVELOPMENT CORPORATION. July 6, 1955 [April 6, 1954], No. 10023/54. Class 83 (3). A drill comprises a longitudinal duct 2 in the shank 1, through which a refrigerating medium, e.g. carbon dioxide, or a refrigerated medium, which may be in the form of a mist, is fed to the vicinity of the cutting- edges of the drill. The duct 2, in the nature of a capillary tube, may be formed by drawing or extruding a thick-walled tube until the bore is of the required diameter, or by lining the shank with a capillary tube. A coaxial duct 6, in the tip 5 of a cermet or of hard metal, may have a smaller diameter than duct 2, and can be formed in the moulding of the tip or by drilling, e.g. by ultrasonic vibrations. The diameter of the shank may be the same as, or less than, that of the tip, or it may be less than that of the tip except at the part adjacent the tip. One or more ducts 7 may discharge the coolant to the rear of the cutting-edges of the tip. The coolant may be supplied to a chamber 10 of sufficient length to allow the drill to be fed without exposing the entrance passage 9 to the duct 2, or the end of the shank may project into a coolant chamber. An insert 13, Fig. 2, may be used having a ridged, dovetailed or rounded portion to engage the shank. The Provisional Specification refers to a diameter of from 0.001 to 0.02 inch for the capillary duct.