Custom Metal Spur Gear

Step 1: Material Selection & Cutting
For heavy-duty applications, we often select 20CrMnTi (DIN 20MnCr5 / AISI 8620) alloy case-hardening steel. For better grain flow and impact toughness, the blank is preferably produced by precision forging, followed by isothermal normalizing to refine the microstructure and ensure uniform machinability. After forging, ultrasonic flaw detection is performed on the raw material to verify the absence of internal defects.

Step 2: Blank Preparation (Precision CNC Turning)
The metal blank is loaded into our high‑rigidity CNC turning center. We precisely turn the outer diameter (OD), inner bore, and both end faces. Engineering detail: The bore and end faces are machined to extremely tight tolerances (H6) as they serve as the crucial datum (reference points) for the subsequent gear-cutting operations to ensure perfect concentricity.

Step 3: Gear Teeth Cutting (Hobbing / Skiving)
We use the Ningjiang YK3610Ⅳ CNC Hobber for high-efficiency external teeth generation, or the Kashifuji KPS30 Gear Skiving Machine for internal/clearance-restricted gears. During this rough/semi-finish cutting phase, our engineers purposefully leave a precise machining allowance (0.1mm - 0.15mm) on the tooth flanks to prepare for post-heat treatment finishing.

Step 4: Heat Treatment (Carburizing & Quenching)
The semi‑finished gears undergo a complete carburizing and hardening cycle: carburizing → high‑temperature tempering (to eliminate network carbides) → quenching → low‑temperature tempering. With precise carbon‑potential control, the surface layer achieves a hardness of HRC 58–62 for excellent wear resistance, while the core retains a tough, low‑carbon tempered martensite structure to effectively absorb shock loads during transmission.

Step 5: Hard Skiving / Finishing (Reaching ISO 6)
Heat treatment inevitably causes micro‑distortion. To correct this and reach the required precision, we adopt a tiered finishing strategy:

Efficient approach (Hard Skiving): Using the advanced hard‑skiving capability of our Kashifuji KPS30, we efficiently remove the distorted layer. This process typically achieves DIN 7 accuracy stably, and with optimized tooling and parameters, it can approach DIN 6.
Precision‑assured approach (Grinding): For gears that must strictly and consistently meet ISO 6 / DIN 6 or higher stability, we apply precision form grinding (e.g., on Kapp or Reishauer grinders) after hard skiving. This step ensures that tooth profile, lead, and pitch errors are reliably locked within ISO 6 tolerances, fully eliminating heat‑treatment distortion.

Step 6: Comprehensive CMM & Gear Inspection
No custom gear leaves our facility without verification. The finished gear is inspected in our metrology lab using a Gear Measuring Center and ZEISS CMM to ensure the tooth profile, lead, and runout conform strictly to the customer's 2D/3D drawings.