Abstract: A casing mill for milling pipe cemented in an oil well comprises a body with a plurality of fixed milling blades having a diameter corresponding to the outside diameter of the pipe to be milled, and a second plurality of movable blades movable between a retracted position smaller than the inside diameter of the pipe to be milled, and an extended diameter corresponding to the outside diameter of a pipe coupling between adjacent sections of pipe. Means are provided for selectively moving the blades between the retracted and extended positions in response to drilling fluid flow. A stabilizer keeps the casing mill centered in the pipe to be milled. In this way, one can mill both the pipe and coupling in the vicinity of a coupling and mill only pipe between the vicinities of adjacent couplings.

Abstract: A casing mill is set forth having a cylindrical body with one end adapted to be attached to a drill string and at the other end pilot vanes to guide the mill with respect to the casing. A plurality of blades project outwardly from the body to present a cutting edge for milling of the casing upon rotation of the mill. Polygonal tungsten carbide cutting elements are secured across a forward surface of each blade in a tesselating fashion, each element tilted in the direction of rotation of between 10-20 degrees. To mount the elements, the blade forward surface may include an inclined stairstep arrangement or inclined slots. Each element is brazed or bonded by a suitable organic adhesive to the forward surface.