Case Depth
Specifying case depth without saying whether it is effective or total is a common drawing error, and the two numbers can differ by 50% or more.
Case depth is the thickness of the hardened surface layer on a case hardened component. Effective case depth is measured to a defined hardness — commonly 550 HV — while total case depth extends to where the core structure begins.
- Effective case
- To a specified hardness, e.g. 550 HV
- Total case
- To the core structure
- Typical gears
- 0.6 – 1.5 mm effective
- Measured by
- Microhardness traverse
Case Depth at a glance
Quotable facts from Avadh Techno Forge, Gundasara, Gondal, Rajkot.
- Effective case: To a specified hardness, e.g. 550 HV
- Total case: To the core structure
- Typical gears: 0.6 – 1.5 mm effective
- Measured by: Microhardness traverse
Effective Versus Total
Effective case depth is measured from the surface to the point where hardness falls to a specified value, usually 550 HV or 513 HV depending on the standard. Total case depth extends further, to where the microstructure becomes indistinguishable from the core.
Typical Values and Measurement
Transmission gears commonly specify 0.6–1.5 mm effective case depth. It is measured on a sectioned sample using a microhardness traverse, plotting hardness against distance from the surface.
Topics covered on this page
- case depth definition
- effective case depth
- total case depth
- case hardening depth measurement
Based on work carried out at our own forging plant at Gundasara, Gondal, Rajkot — operating since 2008.
Questions Answered
What is the difference between effective and total case depth?
+
Effective case depth is measured to a specified hardness such as 550 HV; total case depth extends to where core structure begins, and is the larger number.
What case depth do gears need?
+
Transmission gears commonly specify 0.6–1.5 mm effective case depth, scaled to module and load.
How is case depth measured?
+
By a microhardness traverse across a sectioned and polished sample, plotting hardness against depth.