Step 4 of 8
45%
Writing the spec — what goes on the print
An annotated nitriding callout template a competent vendor can hit and an incompetent one will refuse, with the eight elements that turn a wish into a spec.
Step 4 of 8Case depth and definition
Case depth without a definition is ambiguous by a factor of two. DIN 50190-3 NHD (nitriding hardness depth) is the depth at which microhardness equals core hardness + 50 HV. SAE-style effective case depth is the depth to a fixed absolute hardness, often HV 400. On the same part, the two numbers can differ by 2× depending on how steeply the hardness traverse drops. Pin down the standard, the threshold, and the units. ISO 18203:2016 is the current international standard for the measurement; DIN 50190-3 is the European national standard most European vendors will cite by default.
Effective case depth 0.30-0.40 mm per DIN 50190-3 NHD (core hardness + 50 HV).
Quick check
The print reads "case depth 0.40 mm minimum." Two vendors quote: one to NHD per DIN 50190-3, one to ECD = HV 400 per AMS 2759/10. Why is the print broken, and what definition wins for an H13 die with HV 500 core?