Crucible Rex 121 Knife Steel
Composition Analysis Graph, Equivalents And Overview

Rex 121(Crucible) - Developed in 1998. CPM REX 121 is a high vanadium cobalt high speed tool steel designed to offer a combination of the highest wear resistance, attainable hardness, and red hardness available in a high speed steel. As far as hardness is concerned, it is truly a champion, capable of reaching 70-72HRC. For the record, officially, Rockwell C scale maxes out at 70. Extremely high wear resistance as well. Difficult to grind and consequently, difficult to sharpen too. Frankly, sharpening this alloy is borderline nightmare even at 68HRC, and it will be exponentially harder at higher hardness. I've killed ceramic belts on the grinder trying to thin down the edge on Rex 121 knife, and even 120 grit DMT wasn't much of a success. With that much alloying elements in it, carbides are abundant, and some of them are not very small either. In the end, it works better with coarse edge, and I am not sure how many people would have a patience to sharpen 100K edge on that thing anyway.

Manufacturing Technology - CPM

Country - United States(US)

Known Aliases:
Crucible - CPM Rex 121