CNC Turning · Multi-Process
Controlling Concentricity Through Carburizing and Gear Shaping on 20MnCr5 Steel
A 20MnCr5 drawing combined an HRC 58–62 surface-hardness requirement with 0.02 mm concentricity — two requirements that have to be planned together around carburizing distortion.
At a Glance
- Material
- 20MnCr5 alloy steel
- Surface hardness requirement
- HRC 58–62
- Case depth requirement
- 0.4–0.6 mm
- Concentricity requirement
- 0.02 mm
- Gear feature position requirement
- 0.05 mm
From the Production Drawing
The Requirement, in the Engineer's Own Notes
An excerpt from the production drawing, showing the sectioned profile, the ⌀0.02 concentricity callout on the splined bore and the ⌀0.05 positional callout tying the external spline to the internal one, plus the case-hardening note that drove the process decisions above. Drawing number, customer application, and personnel identifiers have been removed.
01
The Challenge
The part required a carburized surface hardness of HRC 58–62 with a 0.4–0.6 mm case depth, while simultaneously holding 0.02 mm concentricity and keeping the positional relationship between the external and internal gear features within 0.05 mm. Carburizing and quenching distort a part enough, on their own, to threaten concentricity at that level — the two requirements had to be engineered together, not treated as separate steps.
02
OUJI's Approach
OUJI combined carburizing, gear shaping, and CNC turning into one controlled sequence rather than running each process independently. Machining was divided into staged operations specifically to limit how much heat-treatment distortion could accumulate, and finish-machining allowance was reserved after heat treatment to recover concentricity and correct the gear-feature relationship to spec.
03
The Result
OUJI's production confirmation reports that the specified requirements were met. The public evidence set, however, contains the redacted drawing rather than the final hardness, case-depth and dimensional inspection reports. This page therefore presents the values as project requirements and the staged route as the documented engineering response; it does not treat the drawing alone as independent proof of final results.
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