Patent ID: 7814633

Claim:
A method for producing a centralizer, the method comprising the steps of: providing a length of metal tubular work piece, the work piece having a longitudinal axis, a sidewall and a central opening, inside a confining surface comprised of first and second mold elements, each of the mold elements having a cylindrical sidewall, inner and outer ends, a slot extending from its inner end, the mold elements having their inner ends in abutment such that the slots mate at the inner ends to a configuration of a side wall centralizer rib, the mold elements being supported within a housing assembly substantially against expansion radially outward from their position about the tubular work piece; inserting a mandrel having a cylindrical exterior into the tubular work piece and sealing between an outer diameter portion of the mandrel and an inner diameter portion of the tubular work piece to define a sealed annular space between the mandrel and the tubular work piece; applying sufficient fluid pressure to the annular space to force the tubular sidewall radially outward against the confining surface and into the mold cavities to plastically deform the side wall to form centralizer ribs on the side wall; removing the tubular work piece from the confining surface; wherein the confining surface further comprises: a cylindrical bell having a tapered bore therein with a larger inner diameter at one end of the bell than at another end of the bell; a collet having a tapered outer surface that mates with the inner diameter of the bore, the mold elements being located within the collet; and removing the tubular work piece from the confining surface comprises: moving the collet axially relative to the bell; then removing the tubular work piece along with the mold elements from the collet.