Will not crosscut or undercut the thread the way a cutting die would. Do not use on hardened threads or to cut new threads. Made of high carbon alloy steel for a long tool life.
Archives
73214 Square Flute Screw Extractor Set, 1 – #6
Will Not Expand the Fastener Hole: Unlike spiral designs, these square extractors will not expand or distort the walls of the fastener hole during extraction—preserving the integrity of the work surface.