Definition:In accordance with ZF’s determinations, the case hardening depth CHD 610 (previously designated as EHT, refer to Sec. 4) relates to the limit hardness (abbreviated in German as GH) GH = 610 HV 1 (in deviation from DIN EN ISO 2639 with GH = 550 HV 1). The following ZF regulation applies for the limit hardness of sintered steels: GH = 500 HV 1 (in deviation from DIN EN ISO 4507 with GH = 550 HV 0.1).