Helical impact bit for drilling stone with narrow guide lips
AssigneeGuex and Fils S.A.
InventorRaymond Guex
Life of this patent
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Abstract
The bit for drilling stone for use in a hammer drill or an electric hammer comprises a body defining recesses which, in axial section, have a profile at least approximately in the form of an arc of a circle with a radius of between approximately 8 mm and 15 mm. The ratio of the surface area of guide lips each located between two of the recesses in the body of the bit and of the outer cylindrical surface defined by the bit is less than 5%, and preferably of the order of 1 to 2%. The diameter of a tip of the bit, which is provided with a plate of hard metal is equal to the diameter of said cylindrical surface in the vicinity of the plate.
Claims5
A bit for drilling stone for use in a hammer drill or an electric hammer, comprising a tip having a diameter with a value within the range of 5 to 12 mm, a plate of hard metal provided at the tip of the bit, a cylindrical body defining two helical recesses for the evacuation of waste material produced during drilling, said helical recesses defining an angle of less than 35.degree. to the longitudinal axis of the bit, the body in axial section defining said recesses such that all of the latter have like profiles at least approximately in the form of an arc of a circle with a radius having a value within the range of 8 mm to 15 mm according to the diameter of said cylindrical body, a core defined by said recesses and two guide lips forming a part of said cylindrical body and located between said two recesses, said guide lips defining a surface area which forms a part of the outer cylindrical surface defined by said body, the ratio of the cylindrical surface area of said lips to the total cylindrical surface of said cylindrical body being less than 5%, and the ratio between the minimum diameter of said core and the diameter of said outer cylindrical surface having a value within the range of 0.6 to 0.65.
Dependencies are inferred from the claim text.