Precision starter ring gears cut and hobbed for engine flywheels, flexplates and industrial drives. We control tooth geometry, runout and case depth from the first blank to the final inspection report.
Most ring gear failures trace back to one of these four issues.
Hardening moves the pitch diameter and distorts the ring. A 300 mm ring that grows 0.15 mm at the pitch line will not mesh cleanly with the pinion, and the whole batch goes to scrap. We rough machine oversize, harden, then finish grind the bore and teeth back to print.
A burr on the lead chamfer, or a chamfer cut to the wrong angle, makes the pinion skip instead of sliding into mesh. Drivers hear it as a screech every cold start. Controlled chamfering plus deburring removes that risk before the ring leaves the cell.
Ring gears are welded or shrunk onto a flywheel. If the ring itself carries 0.2 mm of radial runout, the assembled flywheel inherits it and the transmission input bearing pays for it. We hold runout at the ring so assembly stays predictable.
Case depth and core hardness decide tooth life. Without per-lot hardness and case-depth records, a field failure gives you nothing to investigate. Every hardened lot we ship carries its own inspection data on request.
One process route, from bar stock to a hardened, inspected ring.
Steel bar is rolled into coils and cut along the centerline into individual blanks. Each blank is welded into a closed ring, left oversized so the weld seam and the ring joint can be cleaned up in a later pass. Welded construction keeps material waste low on large diameters where a solid billet would be expensive and slow to source.
Teeth are cut by hobbing on the same setup that establishes the bore and the mounting face. Cutting teeth and datum surfaces in one fixturing keeps pitch diameter concentric with the bore. For rings above 300 mm, we check cumulative pitch and total composite error before the part moves to heat treat.
Tooth flanks take the wear, so the case does too. We harden the tooth band to a controlled depth, then temper to relieve stress. The bore and mounting face are finish ground afterward, which brings back the dimensions that heat treat moved. That sequence is what lets a hardened ring still hold ±0.005 mm on critical features.
Chamfering comes after hardening. A lead chamfer that is too sharp chips the pinion; too blunt and the pinion will not slide in. We cut the chamfer to the angle on the drawing, deburr every tooth edge, then clean and dry the ring. Final inspection covers tooth profile, runout, hardness and case depth before anything is packed.
Pick the grade by load, corrosion exposure and volume.
| Material | Typical Use | Notes |
|---|---|---|
| 1045 carbon steel | Automotive flywheel rings | Good core toughness, low cost |
| 4140 alloy steel | High-torque and diesel engines | Better hardenability, deeper case |
| 4340 alloy steel | Heavy industrial drives | For shock loads and large diameters |
| 17-4PH stainless | Marine and wet environments | Corrosion resistance plus strength |
Gear cutting, machining and finishing under one roof.
Simultaneous 5-axis work for complex ring profiles, bolt patterns and angled features on flywheel assemblies.
Bore, face and register turning, plus milled slots and mounting holes on the same part.
Spur, helical, ring and pinion, flywheel and flexplate gear sets across common modules and pitches.
Case and induction hardening with tempering, plus hardness and case-depth verification.
Black oxide, plating, bead blasting and tumbling to control corrosion and appearance.
Single-piece rings for fit checks and dyno builds before tooling is committed to a production run.
What we quote against, and what we check.
| Parameter | Range | Verification |
|---|---|---|
| Outside diameter | Up to 4,000 mm | CMM and bore gauge |
| Tolerance | ±0.005 mm | Dimensional report on request |
| Tooth finish | Ra 0.8–1.6 μm | Profilometer check |
| Runout | Held at the ring | Dial indicator before assembly |
| Case depth | Per drawing, lot specific | Hardness and case records |
| Inspection | 100% before shipment | Raw material to final check |
Numbers we can back up, not adjectives.
Founded in 2011, three wholly-owned plants, 7,600 m² of production space and 150 technicians.
±0.005 mm, or ±0.0002 in, on critical bore and face features after hardening.
127 high-precision CNC machines, including 16 simultaneous 5-axis centers and 16 mill-turn centers.
Quotation and free DFM analysis back within 12 hours; production can start in 24 hours.
From one prototype ring to 10,000+ part runs on the same process route and the same inspection standard.
ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022.
Flywheel and flexplate ring gears held to IATF 16949 process control.
Larger diameters for starter drives on heavy equipment and generators.
Ring and pinion sets for drive units where weight and runout both matter.
Small-diameter rings for actuator and indexing drives, produced from one piece upward.
They are usually the same part. The ring gear is the toothed rim that the starter pinion engages; it is mounted on the flywheel or flexplate, so the two names describe the same component from different directions.
If you are sourcing one, send the assembly drawing rather than the ring drawing alone. Bore, register and mounting method determine how the ring has to be machined.
For large diameters we roll bar stock into coils, cut blanks along the centerline and weld them closed. That keeps material cost and lead time down compared with hogging a solid billet.
For small rings, or where a weld seam is not acceptable, we machine from solid. The drawing and the load case decide which route we quote.
We rough machine oversize, harden the tooth band, then finish grind the bore and mounting face. The material moves during heat treat, and the grinding pass takes that movement out instead of trying to prevent it.
Hardness and case depth are checked per lot. If a ring still falls outside print after grinding, it does not ship.
Ra 0.8–1.6 μm is our standard high-finish band on tooth flanks. Ra 0.2–0.8 μm is available where the application calls for it, and as-machined Ra 1.6–3.2 μm is fine for non-critical surfaces.
Surface finish and case depth interact. Tell us which one drives the design so we set the process route accordingly.
Yes. Send the sample or a full set of measurements: outside diameter, tooth count, module or diametral pitch, pressure angle, bore, register and chamfer angle.
We measure the sample, build the model and quote against it. If any dimension is ambiguous, we flag it in the DFM analysis rather than guessing.
There is no minimum order quantity. One prototype ring and a 10,000-piece run go through the same process route and the same inspection standard.
Prototype rings typically ship in 3–5 days once the drawing is released. Volume scheduling is quoted per project.
Uploads are secure and confidential, and we sign an NDA on request before drawings change hands.
Our quality system includes ISO 27001:2022, which covers information security as well as production control.
A 2D drawing with tolerances, or a 3D model plus critical dimensions. Material, quantity, hardening requirement and any surface finish spec help us quote accurately the first time.
Quotation and free DFM analysis come back within 12 hours.
Quote and free DFM analysis within 12 hours. One prototype or 10,000, same process and same inspection.
12-hour quote100% inspectionNo minimum order quantityNDA on request
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Upload your 3D model or 2D drawing and get a quotation with a free DFM analysis. Maximum processing size 4,000 mm.
CNC Metals 13 grades
CNC Plastics 10 grades
Machines & processes 12 options
Surface & post-processing 10 options
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