A method and apparatus for installing a metal annular seal (54) between the outer rough surface of a casing member (11) which has had a portion thereof cut away with a remaining portion projecting upwardly from the upper end of a casing head (12). A slip installation tool (18) mounted on the upper end of the casing head (12) carries a slip assembly which includes segmented slips (40), a bushing (22), and a cam member (42). The slip installation tool (18) secures the slips (40) about the outer rough surface of the casing (11) with bushing (22) acting as a supporting base or foundation to oppose the forces from the camming action because of support from lock down screws (24). After mounting of the slip assembly about the casing (11), the installation tool (18) is removed, and the metal seal (54) is mounted over the extending end of the casing (11) and deformed into metal-to-metal sealing relation between casing (11) and tubing head (50).