Shaft

Features & Benefits

• High-strength shaft materials for torsion & bending
  Transmission shafts experience combined torsional and bending stresses from transmitted torque and gear or chain forces. DD Gear typically uses alloy steels such as 42CrMo4 / AISI 4140 / 40Cr and carburizing grades like 20CrMo, which are commonly selected for heavily loaded shafts and gears due to their high strength and good response to heat treatment.

• Tailored heat treatment for core toughness & surface hardness
  Through-hardening (quench & temper), localized induction hardening, carburizing or nitriding can be applied where needed: tough cores for bending, hardened surfaces at bearing seats, splines and gear teeth for wear and fatigue resistance.

• Precision fits and runout control
  Bearing journals, seal diameters and coupling seats are machined to tolerance classes derived from ISO 286 shaft fits to achieve the required clearances or interference fits for bearings and couplings. This helps maintain low vibration, controlled bearing preload and consistent alignment with mating gears.

• Integrated gear-shaft solutions
  For many applications, DD Gear manufactures gear shafts with integral spur or helical gears. Integrating the gear and shaft can reduce interfaces, improve concentricity and runout, and simplify assembly compared with separate parts.

• Small-module precision for compact drives
  Combining shaft machining and small-module gear grinding capabilities, DD Gear supports compact EV reduction drives, robot joints and AGV axles where space is tight but accuracy and durability requirements are high.

• Prototype to series production
  We support early-stage designs with small prototype batches (including alternative materials or heat treatments), then stabilize the process for series production with defined control plans and traceability.

Technical Specifications

Final values will be defined according to your drawings and performance requirements.

Applications

Transmission and gear shafts from DD Gear can be found in a wide range of driveline and machinery applications:

• EV drive units & e-axles – Motor shafts, intermediate shafts and output shafts connecting e-motors, reduction gears and differential units.

• Truck & bus gearboxes – Input shafts, main shafts and countershafts carrying multiple gears, designed for high torque and long service life.

• Agricultural and construction machinery – PTO shafts, gearbox shafts and axles in tractors, harvesters, wheel loaders and other off-highway equipment.

• Industrial gearboxes & gearmotors – Parallel-shaft and right-angle gear units for conveyors, mixers, pumps and compressors.

• Robotics & AGVs – Compact shafts and gear shafts for robot joints, wheel drives and lifting mechanisms in AGVs and automated systems.

• Machine tools & equipment – Spindle-like shafts and precision support shafts in CNC equipment, packaging lines and textile machines.

Gear Manufacturing Process

Every custom shaft is produced under a controlled gear manufacturing route designed for precision and durability. A typical process flow is:

1. Forging or bar cutting of shaft blanks

2. Lathe machining of shaft diameters and reference surfaces

3. Hobbing or shaping of gear teeth

4. Drilling, milling, and other CNC machining operations

5. Heat treatment (such as carburizing, quenching, tempering, nitriding)

6. Shot blasting and stress relief as required

7. Finish machining and grinding of journals and critical surfaces

8. Gear grinding (profile or worm grinding) where accuracy demands it

9. Cleaning and rust prevention treatment

10. Final inspection and packaging for shipment

Precision Gear Customization Process

DD Gear follows a clear, eight-step customization process:

Step 1 – Requirement Collection
Customers provide design requirements, 2D drawings, 3D models, or physical samples, together with basic duty cycle information (torque, speed, life, installation).

Step 2 – Drawing Design & Optimization
Based on the provided drawings or samples, DD Gear prepares or optimizes detailed manufacturing drawings and shares them with the customer for confirmation.

Step 3 – Quotation
After the drawings and technical points are confirmed, we issue a precise quotation covering tooling, piece price, lead time, and quality requirements.

Step 4 – Tooling & Fixture Preparation
Once the price is confirmed, we arrange tooling and fixture production. Any tooling cost is agreed with the customer in advance and can be offset or refunded after mass orders, according to the commercial agreement.

Step 5 – First Sample Approval
After tooling and fixtures are ready, we manufacture the first sample batch—typically within about 30 days—and ship it to the customer for testing.The customer inspects and validates the samples in their gearbox or test bench and provides feedback on dimensions, performance, and any required adjustments.

Step 6 – Mass Production
When the sample is approved, we start mass production according to the agreed production plan and quality standards.

Step 7 – Finished Product Inspection
After production, we inspect hardness, dimensions, runout, tooth accuracy, and other critical characteristics to ensure full compliance with the drawing and standards.

Step 8 – Shipping Arrangement
Once inspection is passed and shipment is approved by the customer, we arrange booking, packaging, and delivery to the specified destination.

Quality Assurance & Inspection

DD Gear applies the same quality philosophy to all precision gears:

• Quality management systems based on ISO 9001 and IATF 16949

• Process control from incoming material to final inspection, including:

  • Material certification and chemical composition checks

  • Hardness and case depth verification after heat treatment

  • Gear measurement for profile, lead, pitch, and runout

  • Surface roughness testing on gear flanks and journals

  • Dimensional inspection with calibrated gauges and CMMs

• Traceability for each batch with inspection records and reports

• Optional documentation such as PPAP/FAIR packs on request

Packaging

Usage & Installation Notes

• Ensure proper alignment and support between bearings to avoid excessive bending deflection, which can accelerate fatigue and increase vibration.

• Follow the specified fits for bearing and coupling seats; forcing parts onto incorrect fits can damage surfaces or alter preload.

• Avoid sharp damage or nicks on fillets, keyways and splines; these can act as stress raisers and reduce fatigue life.

• Use the recommended lubricant type and viscosity in bearings and gear meshes; poor lubrication can increase temperature and shorten shaft and bearing life.

• During maintenance, monitor noise, vibration and bearing temperature; unusual changes can indicate misalignment, imbalance or shaft damage that should be investigated before failure.

Company Strength – DD Gear

• Specialized in small module, high-precision gears and shafts for EVs, humanoid robots, AGVs, and intelligent automation.

• Integrated manufacturing from forging and machining to heat treatment and gear grinding.

• Quality systems aligned with automotive standards, with experience supporting OEM and Tier 1 projects.

• Engineering support covering concept feasibility, DFM reviews, and failure analysis feedback.

• Global export capability with experience serving customers in multiple countries.

Q1: What information do you need for a shaft or gear-shaft quotation?
We normally need 2D drawings (PDF) and preferably 3D models; shaft type (solid/hollow, gear shaft or plain); material and heat treatment; torque and speed range; support arrangement (bearing positions and loads); life targets; and expected annual volume.

Q2: Can you help optimize the shaft design for fatigue and deflection?
Yes. Shaft design is driven by torque, bending moments, stress concentrations and deflection / critical speed considerations. Based on your constraints, we can review fillet radii, step transitions, gear and bearing positions and material/heat-treatment choices and provide manufacturability and durability feedback.

Q3: Do you supply shafts with integral gears and splines?
Yes. DD Gear frequently produces gear shafts with integrated spur or helical gears and spline shafts. This reduces assembly steps and can improve runout and alignment versus separate gear and shaft parts.

Q4: How are fits and tolerances defined on shaft journals?
Fits between shafts and bearings or hubs are usually based on ISO 286 tolerance grades and fit types (e.g., clearance, transition or interference fits). We agree specific tolerance classes with you for each journal according to function and assembly method.

Q5: What maximum size of shaft can you handle?
Typical length and diameter limits depend on machine envelope and process route. We will confirm feasible max dimensions when we review your drawings and volumes.