What is an Internal Gear?
An internal gear features teeth machined on the inner surface of a ring, meshing with external pinions or planet gears to form compact, high-ratio transmission systems. Yantong Tech manufactures internal gears with controlled tooth form, consistent case depth, and verified contact patterns, ensuring smooth power transfer and extended service life in planetary gearboxes, wind turbine drives, and heavy industrial rotating equipment.
- Precision tooth shaping and profile grinding achieve DIN 6–9 accuracy for stable meshing and low vibration
- Carburizing or nitriding heat treatment provides HRC 58–62 surface hardness and predictable fatigue resistance
- Full dimensional and tooth profile inspection data archived by batch for traceability and quality assurance
- Custom bore tolerances (IT6–IT8) and mounting interfaces designed to match planetary carrier assemblies
Core Characteristics and Performance Advantages
Engineering features that enable compact design, reliable load transmission, and predictable service life
Controlled Tooth Accuracy
Gear shaping and grinding processes maintain involute profile, lead, and pitch consistency to DIN 6–9, reducing backlash variation and ensuring uniform load distribution across all planet gears.
Verified Surface Integrity
Carburizing depth and surface hardness (HRC 58–62) validated per specification; magnetic particle testing available for critical applications to confirm freedom from grinding cracks or heat treatment defects.
Flexible Design Adaptation
Module range m0.5–m12, outer diameter 50–800 mm, and tooth count 20–400 accommodate diverse planetary configurations; bore tolerance and keyway dimensions matched to carrier design requirements.
Technical Specifications and Manufacturing Range
Comprehensive parameter overview for engineering evaluation and design integration
| Item | Specification Range | Remarks |
|---|---|---|
| Outer Diameter | 50 mm – 800 mm | Custom sizes per customer drawing |
| Module | m0.5 – m12 | Spur or helical teeth available |
| Number of Teeth | 20 – 400 | Adjustable per planetary carrier design |
| Bore Tolerance | IT6 – IT8 | Customized per assembly requirements |
| Tooth Accuracy | DIN 6 – DIN 9 | Inspection report available |
| Materials | 20CrMnTi / 42CrMo / SCM415 / C45 | Material composition customizable |
| Heat Treatment | Carburizing / Nitriding / Induction Hardening | Enhances wear resistance and fatigue life |
| Surface Hardness | HRC 58–62 (Carburized) HRC 50–55 (Nitrided) |
Dependent on material and process |
| Surface Roughness | Ra 0.4 – 1.6 μm | Achieved after grinding or honing |
| Inspection | CMM / Gear Measuring Center / Profile Projector | Inspection reports provided |
Custom Manufacturing Capability for Internal Gears
Four core competencies supporting OEM planetary systems, heavy-duty drives, and precision automation assemblies
Design & Engineering Capability
Gear geometry calculation, module and tooth number optimization, profile modification analysis, and reverse engineering from samples or worn parts for OEM replacement.
Precision Machining
CNC gear shaping for internal teeth, finish grinding for high-accuracy profiles, and profile inspection on gear measurement centers to ensure dimensional stability across batches.
Material & Heat Treatment Options
Standard alloy steels (20CrMnTi, 42CrMo, SCM415) with carburizing or nitriding; case depth and hardness validated per drawing; material traceability reports provided with shipment.
Testing & Technical Support
Full dimensional and tooth profile data archived; CMM and gear measurement center reports; remote technical consultation for assembly guidance and performance feedback.
Manufacturing Process: From Raw Material to Verified Internal Gear
Six controlled stages ensuring dimensional consistency, surface integrity, and full traceability
Raw Material Preparation
Incoming steel (20CrMnTi, 42CrMo, or customer-specified grade) validated with mill certificates; chemical composition and initial hardness verified before release to machining. Material lot numbers recorded for batch traceability.
Turning & Rough Machining
CNC turning establishes outer diameter, bore, and mounting surfaces to near-final dimensions. First-piece inspection confirms toolpath accuracy before batch production, ensuring dimensional consistency across all parts in the lot.
Gear Shaping / Gear Hobbing (Internal Teeth Cutting)
CNC gear shaping cutter machines internal teeth per involute profile; module, pressure angle, and helix angle controlled to drawing specification. In-process checks monitor tooth thickness and profile form.
Heat Treatment (Carburizing or Nitriding)
Parts undergo carburizing (gas or vacuum) to achieve HRC 58–62 surface hardness with specified case depth, or nitriding for HRC 50–55. Heat treatment cycles documented; hardness and case depth verified on test coupons and production samples.
Finish Grinding & Deburring
CNC internal gear grinding (for precision grades) corrects distortion from heat treatment and achieves final tooth profile accuracy (DIN 6–7). Bore and mounting faces ground or honed to final tolerance; edges deburred to prevent assembly damage.
Final Inspection & Documentation
Gear measurement center records involute profile, lead, pitch, and runout data; CMM verifies bore and mounting dimensions; surface hardness and case depth measured. Inspection certificate, material traceability, and heat treatment report prepared for shipment.
Quality Control and Inspection System
Five-stage verification protocol ensuring batch consistency and full traceability from material to shipment
Raw Material Verification
Mill certificates validated against order specification; chemical composition spot-checked via spectrometer; hardness measured to confirm annealing condition. Material accepted only when documentation and test results meet requirements.
Machining Accuracy Check
First-piece inspection after each setup confirms dimensional compliance; in-process sampling monitors bore diameter, outer diameter, tooth thickness, and profile form. Statistical process control (SPC) applied to critical dimensions for high-volume runs.
Tooth Profile & Lead Inspection
Gear measurement center captures involute profile deviation, helix deviation, pitch variation, and total composite error. Data compared to ISO 1328 or customer-specified tolerance class; out-of-tolerance parts segregated and corrected or scrapped.
Hardness & Surface Treatment Test
Surface hardness (Rockwell C scale) measured at multiple locations; case depth verified via microhardness traverse on sectioned samples or non-destructive eddy current testing. Heat treatment report includes furnace cycle data and test results for traceability.
Final 100% Inspection
Every internal gear subjected to visual inspection for grinding burns, surface defects, and edge quality; dimensional spot-checks confirm bore tolerance and mounting face runout. Magnetic particle or ultrasonic testing available for critical applications. Full inspection data archived by batch number.
Applications and Industry Integration
Internal gears delivering compact design, high reduction ratios, and reliable load transmission across six core sectors
Certifications and Quality Standards
Recognized quality systems and compliance documentation supporting international procurement requirements
ISO 9001:2015
IATF 16949 Methods
Material Traceability (EN 10204 3.1)
RoHS / REACH Compliance
Material Selection and Heat Treatment Process
Material composition and heat treatment directly determine internal gear durability, load capacity, and service life. Yantong Tech applies controlled carburizing, nitriding, or induction hardening to achieve specified surface hardness and case depth, with full process documentation for quality assurance.
Material Options
20CrMnTi, 42CrMo, 18CrNiMo7-6, SCM415, or customer-specified alloy steel; mill certificates (EN 10204 3.1) provided with chemical composition and mechanical properties verification.
Carburizing
Gas or vacuum carburizing to HRC 58–62 surface hardness with effective case depth 0.8–2.0 mm per drawing; microstructure validated via metallographic examination to confirm uniform carbide distribution.
Nitriding
Plasma or gas nitriding to HRC 50–55 for improved fatigue resistance and minimal distortion; particularly suited for large-diameter internal gears where grinding capacity is limited.
Induction Hardening
Selective hardening of tooth flanks for applications requiring core toughness with surface wear resistance; induction pattern and hardness profile documented by batch.
Traceability
Heat treatment cycle data, hardness test results, and case depth measurements archived by batch number; material and process reports available for customer quality audits and regulatory compliance.
Design and Engineering Collaboration
Manufacturing engineers supporting gear geometry optimization, tolerance analysis, and reverse engineering for OEM replacement
- Gear geometry calculation and module/tooth number optimization based on load requirements, speed range, and available envelope constraints
- CAD/CAM-based profile design and tolerance control; profile modification analysis for noise reduction and load distribution improvement
- Reverse engineering from samples or worn parts for OEM replacement; dimensional measurement, material identification, and heat treatment replication with manufacturability recommendations
- Technical drawing verification and export documentation support; dimensional clarification and tolerance stack-up analysis to ensure assembly fit and function
What Our Clients Say
Trusted by planetary gearbox manufacturers and heavy equipment OEMs across three continents
We needed internal gears with tight bore tolerance and verified tooth contact for our wind turbine yaw drives. Yantong Tech provided full inspection data, held dimensions consistently across five batches, and responded quickly to our technical questions. That reliability is what we need for long-term cooperation.
Our planetary gearbox design required custom internal gears with modified profile for load sharing. Yantong's engineering team understood our contact pattern requirements and delivered parts that met DIN 7 accuracy with full gear measurement reports. Lead time was competitive and communication was clear throughout.
We replaced worn internal gears in our material handling equipment with reverse-engineered parts from Yantong Tech. They measured our samples, identified the material, and matched the heat treatment. The replacement gears fit perfectly and have been running without issue for over a year. Honest service and good quality.
Why Engineers and Procurement Teams Choose Yantong Tech for Internal Gears
Four core competencies supporting planetary system reliability, predictable delivery, and long-term partnership
Proven Manufacturing Capability
96-person team with dedicated gear machining, heat treatment validation, and gear measurement facilities; module range m0.5–m12, outer diameter up to 800 mm, DIN 6–9 accuracy achievable through controlled process.
Full Traceability & Documentation
Material certificates (EN 10204 3.1), heat treatment cycle reports, gear measurement data, and NDT results archived by batch; ISO 9001 quality system with documented corrective action and continuous improvement process.
Engineering-Focused Communication
Manufacturing engineers with gear design background engage directly with customer technical teams; drawing clarification, tolerance analysis, and manufacturability feedback provided before quotation to avoid misunderstanding.
Realistic Pricing & Delivery
Quotations based on actual drawing complexity, material specification, and heat treatment requirements; lead time commitments honored through rolling safety stock for standard parts and milestone tracking for custom orders.
Packaging and Export Logistics
Three-stage protection protocol ensuring gear integrity from factory to your receiving dock
Corrosion Prevention & Sealed Protection
Surfaces are treated with rust-inhibiting oil or VCI protection depending on transit duration and climate, and each gear is sealed in PE bags with desiccant to control humidity from factory loading to overseas delivery.
Tooth Edge Protection & Anti-Impact Support
Large gears are positioned on rigid pallets or supports that bear the weight, while tooth edges are wrapped or cushioned to avoid contact damage during loading and transport. Wrapping also helps reduce dust and moisture exposure before crating.
Reinforced Crating & Export-Ready Loading
Gears are secured in reinforced plywood crates with proper corner strength and lifting points, and crate dimensions are planned for safe forklift engagement and container loading according to destination requirements.
Frequently Asked Questions About Worm Gears
Quick answers to common technical and commercial inquiries
Technical Questions
Commercial Questions
How to Start Cooperation with Yantong Tech
A transparent seven-step process from inquiry to ongoing technical support
Send Your Drawing / Specification
Submit technical drawings (PDF, DWG, STEP) or samples via email. Include specifications for material, heat treatment, accuracy grade, and any special requirements. Our engineering team reviews for manufacturability within 24 hours.
Initial Contact
Drawing review and feasibility confirmation
Technical Clarification
Engineering dialogue and tolerance verification
Technical Review & Proposal
Our manufacturing engineers discuss drawing details, clarify tolerances, and recommend process approach (shaping vs. grinding, heat treatment method). Any manufacturability concerns or improvement suggestions communicated before quotation.
Quotation & Lead Time Confirmation
Detailed quotation provided with breakdown of material, machining, heat treatment, and inspection costs. Lead time estimated based on current production schedule. Payment terms and shipping arrangements confirmed.
Commercial Agreement
Transparent pricing and delivery commitment
Manufacturing Phase
Process control and milestone tracking
Production & Machining
Manufacturing executed per documented process plan. First-piece inspection, in-process checks, and heat treatment validation performed at each stage. Production milestones updated for customer visibility on lead time status.
Inspection & Quality Documentation
Final 100% inspection including gear measurement, dimensional verification, hardness testing, and visual examination. Inspection certificates, material traceability, and heat treatment reports compiled for customer approval before shipment.
Quality Assurance
Full documentation and traceability package
Logistics & Delivery
Protected packaging and export documentation
Packaging & Shipping
Gears packed per export standards (anti-rust coating, foam protection, plywood crates with steel reinforcement). Export documentation prepared for customs clearance. Tracking information provided upon shipment dispatch.
Technical Consultation & After-sales Follow-up
Remote technical support available for assembly guidance, installation questions, and performance feedback. Quality issues addressed through root cause analysis and corrective action. Long-term partnership built on continuous improvement and mutual trust.
Ongoing Support
Technical consultation and continuous improvement
Ready to Source High-Quality Internal Gears?
Send your drawing and receive an engineering reply within 24 hours — no obligation, just transparent technical dialogue.
- Precision manufacturing: Module m0.5–m12, OD up to 800 mm, DIN 6–9 accuracy
- Controlled heat treatment: Carburizing, nitriding, or induction hardening with full process documentation
- Complete traceability: Material certificates, gear measurement data, and heat treatment reports by batch
- Engineering support: Reverse engineering, profile modification analysis, and tolerance optimization
- ISO 9001 certified with IATF 16949 methods for automotive-level quality assurance