A jig device holding a work piece is used with a milling machine that cuts from the work piece a prosthesis having a surface essentially free of defects. The jig device is inserted repeatedly into the machine in the same predetermined location, even upon inverting the jig device. This maintains the spatial relationship between the jig device and milling so, at start up, they are always in the same exact spatial relationship. The milling machine partially cuts through a first side of the work piece to form in the work piece a cavity having a surface part corresponding to at least a portion of the prosthesis being made. The jig device is then removed from the machine, inverted and reinserted into the machine at the same predetermined location. A support material is placed in the cavity prior to reinserting the jig device. Upon reinserting the jig device, the machine precisely cuts through an opposed side of the work piece to form within the work piece a prosthesis having a surface essentially free of defects. The prosthesis is supported within the work piece by the support material. The prosthesis and support material are separated to complete our method.