A Machining Process for Metal Mirror Surfaces.

This invention pertains to a method for producing high quality metal mirror surfaces. In particular, this method pertains to hardened metal surfaces suitable for high energy laser mirrors. Hardened metal surfaces from materials such as copper, silver, gold, aluminum and alloys of these metals can be made by two distinctly different precision diamond machining processes. In the first method, an optically machined surface is prepared initially using customary tool top rake angles in the 5 to -5 deg. range. This surface is then cold worked using a very large negative rake angle in the range of -30 deg. Upon completion of the machining at this very large negative rake angle, the surface is remachined using a less negative rake angle in the range of -5 to 5 deg. Alternately, the surface can be produced in one step, using an intermediate negative rake angle, -15 deg to -20 deg which produces a large degree of cold work, but also prepares a very high quality optically finished surface at the same time. An object of the present invention is to produce optically finished, hardened metal surfaces which have spatial uniformity in the degree of hardening and surface finish, and are thus suitable for high energy laser mirrors in that the damage threshold is uniformly high.