Product Overview
A twin gear is a composite transmission component featuring two gears with different parameters machined on the same disk body, sharing a common axis of rotation. This design enables two-speed transmission, dual-output drive, or special ratio combinations. Compared to manufacturing two separate gears and assembling them, the integrated twin gear design eliminates accumulated assembly errors between gears, ensuring extremely high coaxiality and phase accuracy between the two gears, significantly improving overall transmission system precision and reliability. Widely used in transmission shift mechanisms, multi-speed reducers, differentials, and precision indexing mechanisms requiring exact ratio relationships.
Yubao Transmission Technology employs forged blanks + CNC turning + gear hobbing/shaping processes to produce twin gears with different modules and tooth counts. Coaxiality between Gear 1 and Gear 2 ≤0.01mm, phase accuracy ±5′ (±2′ achievable on request), and inter-gear spacing tolerance ±0.03mm. Available in integral and assembled configurations to suit different sizes and volumes. Heat treatment uses controlled-atmosphere carburizing to ensure uniform hardness across both gear sections.
Technical Parameters
Gear 1 Parameters
| Parameter |
Symbol |
Unit |
Value/Range |
Tolerance |
Notes |
| Gear 1 Teeth |
z1 |
— |
Customized |
— |
Typically more teeth (larger gear) |
| Gear 1 Module |
m1 |
mm |
Customized |
— |
May differ from Gear 2 |
| Gear 1 Pressure Angle |
α1 |
° |
15°–30° |
— |
Typically 20° |
| Gear 1 Face Width |
b1 |
mm |
Customized |
±0.05 |
Working face width |
| Gear 1 Accuracy |
— |
DIN/ISO |
Grades 5–6 |
— |
Per application requirements |
Gear 2 Parameters
| Parameter |
Symbol |
Unit |
Value/Range |
Tolerance |
Notes |
| Gear 2 Teeth |
z2 |
— |
Customized |
— |
Typically fewer teeth (smaller gear) |
| Gear 2 Module |
m2 |
mm |
Customized |
— |
May differ from Gear 1 |
| Gear 2 Pressure Angle |
α2 |
° |
15°–30° |
— |
Typically same as Gear 1 |
| Gear 2 Face Width |
b2 |
mm |
Customized |
±0.05 |
Working face width |
| Gear 2 Accuracy |
— |
DIN/ISO |
Grades 5–6 |
— |
Same as or one grade below Gear 1 |
Structural Relationship Parameters
| Parameter |
Symbol |
Unit |
Value/Range |
Tolerance |
Notes |
| Inter-Gear Spacing |
c |
mm |
Customized |
±0.03 |
Distance between two gear sections |
| Phase Accuracy |
— |
° |
±5′ |
± |
Critical parameter, high precision ±2′ |
| Gear 1-to-Gear 2 Coaxiality |
— |
mm |
0.01 |
≤ |
Critical assembly parameter |
| Connection Type |
— |
— |
Integral/Assembled |
— |
Integral offers best rigidity |
| Max Outer Diameter |
Da |
mm |
50–400 |
— |
Maximum tip diameter |
| Bore Diameter |
d |
mm |
Customized |
H7 |
Fit bore |
| Total Thickness |
H |
mm |
Customized |
±0.05 |
Including inter-gear spacing |
Materials & Heat Treatment
| Parameter |
Symbol |
Unit |
Value/Range |
Tolerance |
Notes |
| Tooth Hardness |
HRC |
— |
58–62 |
— |
Uniform hardness on both gears |
| Core Hardness |
HRC |
— |
30–45 |
— |
Toughness assurance |
| Material Grade |
— |
— |
Customized |
— |
Common: 20CrMnTi, 16MnCr5, 42CrMo |
| Heat Treatment |
— |
— |
Carburizing + Tempering |
— |
Both gears hardened simultaneously |
Machining Capabilities
| Process |
Equipment |
Range |
Accuracy Achieved |
| Blank Forming |
Forging/Round Bar Cutting |
φ50–400mm |
Proper fiber flow |
| CNC Turning |
HEADMAN/DOOSAN Lathe |
Multi-step integrated machining |
Inter-gear spacing ±0.03mm |
| Gear Hobbing |
Ningjiang YK3610V etc. |
Gear 1 + Gear 2 separate hobbing |
DIN Grades 6–7 |
| Gear Shaping |
Changji YKS5132 |
Internal gears or special structures |
Module 0.5–8mm |
| Gear Grinding |
Qinchuan YKZ7230 |
High precision requirements |
DIN Grades 4–6 |
| Phase Inspection |
CMM/Dedicated Phase Fixture |
Relative tooth slot position |
±5′ (achievable ±2′) |
| Heat Treatment |
Controlled Atmosphere Carburizing |
Uniform hardening of both gears |
HRC 58–62 |
Structural Types
Integral Twin Gear
- Features: Two gears and hub forged/machined as one piece, maximum rigidity
- Advantages: Highest coaxiality, no connection loosening risk
- Limitations: Large blank size, higher machining difficulty, lower material utilization
- Applications: Medium-high volume, high precision, high reliability requirements
Assembled Twin Gear
- Features: Two gears machined separately then assembled via shrink fit/key/spline connection
- Advantages: Each gear can be individually optimized, higher material utilization
- Note: Accumulated assembly errors must be controlled, phase accuracy slightly below integral type
- Applications: Large diameters, low volumes, or significantly different gear parameters
Product Features
- Extremely High Coaxiality: Two gears coaxiality ≤0.01mm, eliminating assembly errors
- Precise Phase: Phase accuracy ±5′, meeting synchronous transmission and shifting requirements
- Compact Structure: Integrated design minimizes axial dimensions
- Exact Ratio: Two gears on one component, ratio guaranteed by machining, unaffected by assembly
- Excellent Rigidity: Integral structure with no connection clearance, high torsional rigidity
Typical Applications
| Application Sector |
Specific Use |
Design Features |
| Automotive Transmissions |
Shift gear sets |
Different tooth count combinations for multiple ratios |
| Machine Tools |
Headstock change gears |
Integral type, high phase accuracy |
| Reducers |
Dual-stage intermediate gear |
Gear 1 (large) + Gear 2 (small) combination |
| Differentials |
Planetary gear mechanisms |
Two-stage planetary transmission |
| Precision Indexing |
Precision indexing mechanisms |
Phase accuracy ±2′, high-precision positioning |
