*These are the maximum hardness values recommended by East~Lind Heat Treat, Inc. for use with general tool & die steels. Though most of these steels are capable of attaining a slightly higher hardness, these numbers represent good, safe, practical maximum hardness values for use in many tool & die steel applications. They are a good rule of thumb; however, they are not exact or concrete figures due to the many variables that may influence the maximum hardness desired for a steel part. These numbers maybe adjusted up or down, depending on the part's application, configuration (design) and/or mass (cross-sectional thickness).