Product Overview
An internal gear shaft (also known as an internal ring gear shaft) is a functional component with internal tooth structure machined into the shaft body. The internal teeth mesh with planetary gears or external gears to form an internal gear transmission. Internal meshing transmission offers advantages including compact structure, large transmission ratio, coaxial layout, and high load capacity from multiple simultaneous tooth engagements. It is widely used in planetary reducers, RV reducers, slewing bearings, and automotive transmissions where space is limited and high reduction ratios are required.
Yubao Transmission Technology employs CNC gear shaping to machine internal gear shafts, with internal gear module range 0.5–3.0mm, accuracy up to DIN Grades 5–7 (ISO 1328). We can process straight and helical internal gears (helix angle 0–20°), including straight, helical, and herringbone tooth forms. Post-shaping grinding or honing is available for precision requirements, achieving tooth surface roughness Ra≤0.8μm. Inner bore diameter and keyways are customizable, with internal gear-to-bore coaxiality ≤0.02mm, ensuring transmission accuracy after assembly.
Technical Parameters
Internal Gear Parameters
| Parameter |
Symbol |
Unit |
Value/Range |
Tolerance |
Notes |
| Internal Gear Module |
m |
mm |
0.5–3.0 |
— |
Standard module series |
| Internal Gear Teeth |
z |
— |
Customized |
— |
Determined by ratio and inner diameter |
| Internal Gear Pressure Angle |
α |
° |
15°–30° |
— |
Typically 20° (standard) |
| Internal Gear Face Width |
b |
mm |
Customized |
±0.05 |
Working face width |
| Internal Gear Type |
— |
— |
Straight/Helical/Herringbone |
— |
Selected per transmission need |
| Internal Gear Helix Angle |
β |
° |
0–20° |
±0.5° |
For helical internal gears |
| Internal Gear Accuracy |
— |
DIN/ISO |
7 |
— |
Achievable: DIN Grades 5–7 |
| Internal Gear Roughness |
Ra |
μm |
0.8 |
≤ |
After shaping/broaching |
Shaft Parameters & Materials
| Parameter |
Symbol |
Unit |
Value/Range |
Tolerance |
Notes |
| Outer Diameter |
D |
mm |
50–500 |
h6–h9 |
Shaft body outer diameter |
| Inner Bore Diameter |
d0 |
mm |
Customized |
H7–H9 |
Fit bore or bearing seat |
| Total Length |
L |
mm |
≤800 |
±0.05 |
Overall length |
| Gear-to-Bore Coaxiality |
— |
mm |
0.02 |
≤ |
Critical assembly parameter |
| Tooth Hardness |
HRC |
— |
58–62 |
— |
After carburizing/nitriding |
| Core Hardness |
HRC |
— |
30–45 |
— |
Toughness assurance |
| Material Grade |
— |
— |
20CrMnTi/42CrMo |
— |
Common alloy steels |
| Heat Treatment |
— |
— |
Carburizing/Nitriding/Tempering |
— |
Determined by application |
| Processing Method |
— |
— |
Shaping/Broaching/Hobbing |
— |
Optimal process per structure |
Machining Capabilities
| Process |
Equipment |
Range |
Accuracy Achieved |
| Gear Shaping |
Changji YKS5132 Shaper |
Module 0.5–8mm, OD ≤320mm |
DIN Grades 6–7 |
| Gear Broaching |
Broaching Machine (internal pull broach) |
High-volume internal gears |
DIN Grade 7, high efficiency |
| Internal Gear Grinding |
Internal Gear Grinder |
Module 0.5–3mm |
DIN Grade 5 |
| Honing |
Honing Machine |
Improved tooth surface quality |
Ra≤0.4μm |
| Heat Treatment |
Carburizing/Nitriding |
Case depth 0.3–1.2mm |
Surface HRC 58–62 |
| Gear Inspection |
Gleason 300GMS/Double Flank Tester |
Profile/Pitch/Runout |
100% verification |
Internal Gear Type Description
Straight Internal Gear
- Features: Simple processing, no axial force, suitable for general transmission
- Process: Shaping or broaching
- Applications: Planetary reducer internal ring gears, transmission reverse brake drums
Helical Internal Gear
- Features: Smooth transmission, low noise, must withstand axial force
- Process: Helical shaping (requires dedicated helical shaping cutters)
- Applications: Precision planetary reducers, quiet transmission applications
Herringbone Internal Gear
- Features: Left-right symmetrical double helix, self-balancing axial forces
- Process: Shaped in left/right halves or with dedicated integral tooling
- Applications: Heavy-duty high-power transmission (less common for shaft-type components)
Internal Meshing Design Guidelines
| Design Parameter |
Recommended Range |
Notes |
| Tooth Count Difference (Internal – External) |
≥12 |
Avoid interference, ensure proper meshing |
| Internal Gear Tip Diameter |
≥Module×(Teeth+2.5) |
Ensure tip strength |
| Wall Thickness (Root to Outer Diameter) |
≥3×Module |
Ensure minimal deformation under load |
| Shaping Cutter Teeth (Reference) |
Internal Gear Teeth/2+5 |
Affects machining efficiency and accuracy |
| Lubrication Method |
Splash/Oil Jet/Grease |
Internal meshing heat dissipation requires attention |
Product Features
- Ultra-Compact Structure: Internal meshing layout enables coaxial arrangement, minimizing radial dimensions
- Large Transmission Ratio: Single-stage internal meshing achieves ratios of 3–10, reducing transmission stages
- High Load Capacity: Multiple simultaneous tooth engagements (planetary transmission) with uniform load distribution
- Precision Guaranteed: Internal gear-to-bore coaxiality ≤0.02mm, high transmission accuracy after assembly
- Flexible Processing: Shaping, broaching, or hobbing options available for different volumes and accuracy requirements
Typical Applications
| Application Sector |
Specific Use |
Typical Parameters |
| Planetary Reducers |
Internal ring gear (stationary carrier type) |
Module 1.0–3.0mm, DIN Grade 6 |
| RV Reducers |
Pin gear housing/internal ring gear |
Module 0.5–1.5mm, DIN Grade 5 |
| Automotive Transmissions |
Brake drum internal gears/reverse idlers |
Module 1.5–3.0mm, mass production |
| Slewing Bearings |
Internal-tooth slewing rings |
Module 3–8mm, large diameter |
| Industrial Automation |
Harmonic reducer rigid flexspline |
Module 0.3–1.0mm, extreme precision |
