1904 Feb. 51/1 The usual method [for producing sorbite in steel] has been to reheat and oil-harden.
1999 Re: Does Anyone sharpen Jack Hammer Bits? in alt.crafts.blacksmithing (Usenet newsgroup) 18 Dec. Although it is possible to oil harden water hardening steel it is not advisable to attempt to water harden steels that are specifically made for oil hardening.