Case & Induction Hardening, Eddy Current Testing & Gaging - Cleveland, Ohio - Euclid Heat Treating Company Euclid Heat Treating Company,Cleveland,Ohio,heat treating services,case hardening,induction hardening,eddy current testing,gaging. Since 1945, Euclid Heat Treating Company has offered heat treating services including case hardening, induction hardening, eddy current testing, and gaging.