This page's designation, "K12 (HT)," marks it as the heat-treated (hardened and tempered) condition of the base "K12" designation covered elsewhere on this chart. As explained on that page, "K12" does not correspond to a designation we can confirm against the standard international references we check for every material here — AISI/SAE, ASTM, DIN/Werkstoffnummer, EN, JIS, AFNOR, or UNS. Since the base alloy identity is unconfirmed, we can't responsibly publish heat-treated hardness, composition, or machining data for this "HT" variant either — doing so would imply a level of certainty we don't have.

The legacy version of this page carried no chemistry, no hardness spec, and no cutting-speed data of its own. Rather than invent numbers for an alloy condition we can't positively identify, we're leaving this page as an honest placeholder alongside the base K12 page until the underlying alloy can be confirmed, for example from a mill certificate or supplier spec sheet.

If you're machining hardened material spec'd to you as "K12 (HT)," send FM Carbide the mill certificate or supplier data sheet — including the heat-treat condition and hardness — for your specific material lot, and we'll match you to the correct carbide grade and cutting parameters for the actual alloy in hand.