Norseman NOR-47462 - Drill 1/16 - 1/2 29 Pc Cryogenic Drill Bit SetNorseman 190 CN CN Tech Cryogenic Drill Bit Set, 135 Split Point, Jobber Length, 1 16" to 1 2" by 64ths Cryogenic treatment creates a more uniform "grain" structure by transforming retained austenite into martensite. Modifies the carbon microstructure through precipitation of carbides increasing resistance to wear. Nitride process diffuses nitrogen into the surface to create a case hardening resulting in superior tool life and exceptional corrosion