1.SUS420,Hardness HRC52-63 degree for buyer's choice 2.blade ... workmanship. We have overcome the technical problem of anti-rust, hardness and tenability, sharpness with low noise, clean,shine,free ... rang from No. 5 to No. 42 and hubbed or unhubbed either and the hardness is kept at HRC45-62 degree ... core of pepper grider and coffee grinder, and the hardness is HRC 44-60 degree for the buyer's choice ...