DIN 6 Ground Gears for a Gearbox Maker: How ≤0.012 mm Cumulative Pitch Deviation Was Delivered
Overview
In 2026, Geyon Transmission supplied DIN 6 ground helical gears to a gearbox manufacturer in East China. Module m=3, 23 teeth, 20CrMnTi carburized and quenched: surface hardness 58–62 HRC, effective case depth 0.8–1.2 mm, tooth flank roughness Ra≤0.8 μm. Full-size inspection measured cumulative pitch deviation ≤0.012 mm and helix deviation ≤0.009 mm. The first article passed complete inspection, every batch passed spot inspection, and the client confirmed volume supply. Lead time from order to shipment: 45 days. Here is how this order was planned and executed.
Background
The client builds helical gear reducers for automation line integrators, with part of the output exported to Europe. In a reducer, the gears decide noise and service life, and they are also the part most likely to cause trouble in batch production.
The client’s previous gears were delivered at DIN 7–8, hobbed and heat-treated — the standard configuration for general-purpose gearboxes, and the DIN standard lists hobbing plus heat treatment as the typical process for that grade range. The problems showed up in batches: some reducers ran quietly, others hummed. Assembly workers had to match and re-fit gear pairs by hand, which created rework. European customers also raised noise consistency issues on export batches.
Challenges
- Precision ceiling: Hobbed and heat-treated in one pass, the gears had no way back once 20CrMnTi carburizing distortion moved the tooth profile and helix.
- Noise and rework: Larger helix deviation meant visible meshing impact, inconsistent gearbox noise, and assembly that depended on hand fitting.
- Export paperwork: European customers required full-size inspection reports for tooth profile, helix, and pitch with every batch — the previous supplier could not provide them.
- Tight schedule: Production planning was fixed; the gear supply had to arrive within 45 days and pass first-article validation.
Solution
After receiving the drawings, Geyon did three things before quoting: checked the gear parameters, confirmed the heat treatment route, and agreed on the inspection items and report format. Then the order was executed as follows:
| Item | Solution |
|---|---|
| Gear parameters | Module m=3, teeth z=23, pressure angle α=20°, profile shift x=0, face width b=40 mm, bore φ25H7 |
| Accuracy grade | DIN 6 (DIN 3962), tooth flank roughness Ra≤0.8 μm |
| Material & heat treatment | 20CrMnTi, carburized and quenched, effective case depth 0.8–1.2 mm, surface hardness 58–62 HRC, core 30–42 HRC |
| Process route | Hob with 0.2–0.3 mm grinding allowance → carburize & quench → generate grinding |
| Inspection & delivery | Full-size inspection reports for profile/helix/pitch with shipment; first-article full inspection, batch spot inspection |
| Packaging | Rust-preventive paper + vacuum bag + wooden case, meeting EU export requirements |
Why grinding cannot be skipped: carburizing and quenching always cause distortion, and the hobbed flank loses its accuracy at that point. Grinding is the step that actually produces DIN 6. That is the core difference between the old route and this one. Geyon’s cylindrical gear line covers modules 1–12 and 18–200 teeth, with batch precision at GB 4–5 and grinding capability rated to DIN 3 — the processes used in this order are within normal production range.
Results
Source: full-size inspection records for the 200-piece batch and the client’s assembly acceptance feedback (2026)
| Item | Measured / delivered |
|---|---|
| Accuracy grade | DIN 6 (DIN 3962), achieved by grinding |
| Cumulative pitch deviation Fp | ≤0.012 mm |
| Helix deviation Fβ | ≤0.009 mm |
| Tooth flank roughness | Ra≤0.8 μm |
| Surface hardness | 58–62 HRC |
| Effective case depth | 0.8–1.2 mm |
| Transmission efficiency (cylindrical pair) | 98–99% |
| Lead time | 45 days (order to shipment) |
| Inspection result | First article fully passed; every batch passed spot inspection; client confirmed volume supply |
Client acceptance feedback: all dimensional tolerances met, cumulative pitch deviation ≤0.012 mm, helix deviation ≤0.009 mm, first article passed complete inspection, all batches passed spot inspection, volume supply confirmed. The client has since listed Geyon as an approved supplier and frozen these parameters into the drawings of its main product lines.
What Worked in This Order
- Precision and material fixed up front: DIN 6, 20CrMnTi, 0.8–1.2 mm case depth, 58–62 HRC — all written into the inspection items, leaving no gray areas.
- Reports shipped with the goods: full-size profile/helix/pitch reports traveled with each batch, which simplified both client acceptance and export customs.
- Enough grinding allowance: hobbing left 0.2–0.3 mm, so grinding had material to work with after heat treatment distortion — no scrapped parts, no re-cutting.
Conclusion & Call to Action
The quality of a gearbox largely rests on the gears. Accuracy grade, material and heat treatment, and inspection reports — when all three are in place, assembly is straightforward and export audits pass without drama.
If your reducers or gearboxes are fighting noise, rework, or export acceptance:
👉 Contact the Geyon Transmission engineering team → get an assessment of accuracy grade and process route 👉 Browse high-precision gear product lines → cylindrical gears · bevel gears · worm gears · custom parts 👉 Submit gear parameters and drawings → get an initial proposal and quote 👉 Understand DIN/ISO accuracy grades → pick the right grade without overspending
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