Focusing on the design, manufacturing processes, heat treatment techniques, and key quality control points for all types of standard and non-standard gears.
| Parameter Item | Total Range |
| Module / Diametral Pitch (DP) | M1.5 ~ M25 / DP 1 ~ DP 24 |
| Accuracy Grade | GB/T 10095 Grades 4~8, up to Grade 4 |
| Max. Outer Diameter of Gear Ring | ≤ 1200 mm |
| Number of Teeth Range | Z20 ~ Z250 |
| Helix Angle Range | 5° ~ 25°, left-hand / right-hand customizable |
Helical internal gears, also known as helical internal cylindrical gears, are a widely used category of internal gearing solutions recognized for their superior transmission performance. Their teeth are uniformly machined along the inner circumference of the cylindrical body, with the tooth trace set at a constant helix angle relative to the gear axis. When paired with a mating helical external gear, they form an internal gear drive that transmits power and motion between two parallel shafts, with both shafts rotating in the same direction.
The core difference between helical and spur internal gears lies in their tooth trace geometry and meshing characteristics. For spur internal gears, the tooth trace runs perfectly parallel to the axis, meaning the entire tooth face engages and disengages at once — this leads to impact loads and noise during start-stop cycles. Helical internal gears, by contrast, feature a helical tooth form that engages and disengages gradually and progressively, resulting in smoother, more continuous power transmission.
In practice, helical internal gears are the preferred choice for heavy-duty, high-speed applications where smooth operation and low noise are required. They are the standard internal gear configuration used in planetary gear reducers, slewing drives, and precision gearboxes.
These gears feature a concave involute tooth profile that meshes with a mating helical external gear, delivering a constant transmission ratio with good tolerance for center distance deviations. The key distinction from spur internal gears is the helical tooth trace, which runs at a fixed helix angle relative to the gear axis — typically 15° to 25° as standard, with custom angles available on request.
Limited by the internal ring geometry, these gears are most commonly produced via helical slotting and skiving processes; high-precision variants require an additional internal gear grinding step. The standard pressure angle is 20°, though non-standard specifications such as 14.5° can also be accommodated. Note that helical teeth generate axial thrust during operation, so bearing selection and housing support structure must be specified to match this load.
In an internal gear arrangement, the smaller external pinion meshes tangentially inside the ring gear. The center distance between the two shafts equals the difference between their respective pitch circle radii, and both shafts rotate in the same direction.
Unlike spur gears — where the entire tooth face engages and disengages simultaneously, creating rigid impact loads — helical gear teeth enter and exit mesh gradually. Combined with the increased axial contact ratio introduced by the helix angle, this results in a significantly higher total contact ratio and more teeth sharing the load at any given time. Tooth surface contact stress is reduced accordingly, giving helical internal gears over 30% higher load capacity than equivalently sized spur internal gears.
The nested internal layout also compresses the overall drive footprint. With smooth meshing action and uniform tooth wear, this configuration is well suited for high-speed gearboxes operating with enclosed oil bath lubrication.
Precision-grade helical internal gear systems achieve a transmission efficiency of 97.5% to 98.5%. While this figure is slightly lower than equivalent-precision spur gear drives — due to additional friction caused by axial thrust — the overall performance under heavy-duty, high-speed operating conditions is superior.
Load distribution across multiple teeth reduces unit pressure on the tooth surface. When paired with high-precision lead crowning, the meshing contact pattern can be further refined, leading to steady, gradual wear over extended service life. Both torque density per unit volume and service life outperform comparable spur gear designs.
The axial thrust generated by the helical tooth form requires bearings with axial load capacity, making shaft and housing design slightly more complex and costly than spur gear alternatives. Machining processes and tooling also demand higher precision, and thin-walled large-diameter rings require tighter control over workholding distortion.
Even so, the advantages of high contact ratio, low impact loading and quiet operation are significant. Helical internal gears are the preferred choice for high-speed, heavy-duty applications where smooth, low-noise performance is critical. They are widely used as internal gear rings in precision planetary gear reducers, wind turbine slewing drives, industrial robot joints and similar systems.
For low-to-medium speed applications with steady loads where cost control is the priority, spur internal gears offer a more cost-effective solution.
| Parameter Item | Standard Mass Production(General Application) | High Precision Custom(Precision Transmission) |
| Core Dimensional Specifications | ||
| Module / Diametral Pitch (DP) | M1.5 ~ M25 / DP 1 ~ DP 24 | M2 ~ M16 / DP 2 ~ DP 16 |
| Number of Teeth Range | Z20 ~ Z250 | Z24 ~ Z180 |
| Max. Outer Diameter of Gear Ring | ≤ 1200 mm | ≤ 900 mm |
| Face Width Range | ≤ 300 mm | ≤ 250 mm |
| Internal Tip Diameter Range | φ30 mm ~ φ1100 mm | φ50 mm ~ φ800 mm |
| Secondary Machining | Internal bore spigot, dowel pin holes, lightening holes, oil grooves, and end face threaded holes available | One-setup machining for full process, strict guarantee of bore-to-gear concentricity, lead runout and face runout accuracy |
| Tooth Profile & Accuracy Specifications | ||
| Tooth Profile Standard | Involute internal tooth profile, metric / imperial dual standards supported | Involute internal tooth profile, non-standard profile and positive/negative profile shift customizable |
| Standard Pressure Angle | 20° (default), 14.5°/15° customizable | 20°, 14.5°/15°/22.5° and other non-standard angles customizable |
| Helix Angle Range | 8°~20° (standard for general use) | 5°~25° customizable, helix angle deviation strictly controlled |
| Hand of Helix | Left-hand / right-hand available on request | Left-hand / right-hand customizable, can be manufactured with matched external gear sets |
| Accuracy Grade | GB/T 10095 Grades 7~8Equivalent to AGMA 10~11 / ISO 7~8 | GB/T 10095 Grades 4~6, up to Grade 4Equivalent to AGMA 12~14 / ISO 4~6 |
| Profile Modification | Standard profile, basic tip relief available | Tip relief, lead crowning, helix modification and root fillet optimization available |
| Tooth Surface Roughness | Ra 3.2 ~ 6.3 μm | Ra 0.8 ~ 1.6 μm |
| Material & Heat Treatment Capabilities | ||
| Common Materials | 45# carbon steel, 40Cr alloy steel, QT700-2 ductile iron, HT300 gray cast iron | 42CrMo alloy steel, 20CrMnTi carburizing steel, 38CrMoAl nitriding steel, stainless steel (304/316), custom special alloy steel |
| Heat Treatment Process | Quenching & tempering, normalizing, high-frequency induction hardening | Carburizing & quenching, gas nitriding, through hardening, deep induction hardening; hardness controllable from 28 to 62 HRC |
| Note | The above covers the standard machining range for our helical internal gears (internal gear rings). Custom specifications, non-standard structures and profile shift designs are all available based on your drawings. For quotation, please provide module, number of teeth, helix angle, hand of helix, outer diameter of gear ring, internal tip diameter, material, accuracy grade and quantity. We will provide an accurate quotation within 12 hours. |
|
High-quality blanks are forged and normalized to eliminate internal stress and stabilize material structure.
Turning, milling and hobbing/shaping are applied to form the target tooth profile with strict accuracy control.
Carburizing quenching or tempering processes to improve tooth surface hardness and core toughness.
Grinding of tooth flanks, bores and datum faces to correct deformation and enhance meshing precision.
Full-dimensional verification by gear measuring center and CMM to qualify products before release.
Professional anti-rust and protective packaging to keep products intact during storage and transit.
High-precision gear grinding delivers tooth surface roughness as low as Ra 0.4, with tight meshing, low vibration and noise for smoother equipment operation.
Premium materials matched with precise heat treatment ensure wear-resistant tooth surfaces and impact-resistant core, cutting maintenance and replacement costs.
Custom solutions for high-speed heavy load, corrosion resistance and food-grade scenarios, eliminating trial-and-error costs in product selection.
Scaled production supports tiered pricing for bulk orders with consistent quality; full-process control guarantees stable lead time and complete after-sales support.
Representative grades: 45# steel
This material delivers balanced mechanical properties, good machinability and excellent cost efficiency. Tooth surface hardness can be enhanced through high-frequency induction hardening, though quenching distortion on internal tooth flanks is inherently difficult to control — and the helical tooth geometry makes lead accuracy deviations more likely. With limited hardenability, it is best suited for standard internal gear rings in small to medium modules, used in medium- and low-speed light-duty scenarios.
Representative grades: 42CrMo, 20CrMnTi, 20CrMnMo
These steels have far superior hardenability than carbon grades, with controllable ring distortion after heat treatment and strong retention of lead accuracy. They achieve an optimal combination of high tooth surface hardness for wear resistance and high core toughness for impact loading, making them the primary material choice for high-precision helical internal gear rings. They perform well in high-speed, high-precision applications, but carry higher material and processing costs and longer production lead times.
Representative grades: 304, 316 stainless steel
Stainless steels provide excellent corrosion and rust resistance to meet clean production requirements. Their strength and wear resistance are lower than alloy structural steels, and the machining of helical tooth forms involves higher difficulty and precision control costs. They are suitable for light-duty, low-speed internal gear rings in humid and corrosive environments, with limited load capacity and a higher overall cost.
Representative grades: typical grade: tin bronze
Copper alloys feature outstanding anti-friction and noise-damping performance, along with corrosion resistance and non-magnetic properties. Dimensional precision is readily achievable for small-format helical gears, but overall strength is significantly lower than steel. They are applied in very small module, light-duty, low-speed precision scenarios to meet requirements for quiet operation, non-magnetic performance and high-cycle light-load transmission.
Glass-fiber reinforced PA, POM, PEEK, etc.
These materials offer excellent self-lubricating properties, very low operating noise, and the advantages of corrosion resistance and light weight. Their strength, temperature resistance and load capacity are limited, making them ideal for small, light-duty low-speed internal gear rings used in office equipment, food packaging machinery and other applications requiring quiet, clean operation.
Representative grades: QT450, QT600
Ductile iron boasts excellent castability and low cost, with better vibration and noise damping performance than steel. The smooth meshing action of helical teeth partially offsets its weakness in impact resistance, but tooth surface fatigue wear still occurs under high-speed operating conditions. It is suited for large-diameter, low-speed, steady-load large internal gear rings in open or semi-open designs.
Helical internal gear rings serve as the core stationary component in high-precision planetary gear reducers, working with sun gears and planet gears to deliver high-reduction-ratio power transmission. Compared with spur gear designs, they engage without rigid impact, delivering smoother running, lower noise at high speeds and higher torque density per unit volume, making them the standard choice for servo gearmotors and high-speed heavy-duty gearboxes.
Helical internal gear rings are widely used in the electric drive reducers and hybrid transmissions of new energy vehicles. Their nested configuration reduces the overall footprint of the powertrain while accommodating the high operating speeds of electric motors, delivering smooth power transfer with low noise. High-precision helical internal gear rings are also specified for the precision slewing mechanisms of high-end construction equipment, balancing heavy load capacity with smooth rotation to minimize impact and vibration during operation.
High-precision helical designs are the standard for the internal gear rings at the heart of precision servo planetary reducers and precision slewing drives. They offer high transmission accuracy, low backlash, and impact-free, quiet operation during high-speed start-stop cycles, enabling high-torque precision speed reduction in compact spaces. They are widely used in industrial robot joints, precision rotary tables and high-end automated indexing mechanisms — applications with strict requirements for accuracy, smoothness and quiet operation.
Helical internal gear rings are critical transmission components in the high-speed stages of wind turbine gearboxes, the precision slewing drives of photovoltaic tracking mounts and solar tracking systems. Compared with spur gear alternatives, they handle higher operating speeds with lower vibration and better long-term running smoothness. Their annular design can be integrated with support bearings as a single assembly, extending tooth flank fatigue life under reciprocating slewing conditions and effectively reducing equipment operation and maintenance costs.
High-precision alloy steel helical internal gear rings are widely used in the planetary spindle drives of high-end machine tools, the main drive reduction gearboxes of precision rolling mills and the high-speed lifting mechanisms of metallurgical equipment. The multi-tooth meshing characteristic delivers higher load capacity, with far less impact and vibration at high speeds than spur gear configurations. They can withstand continuous high-speed, high-torque operation, meeting the demanding requirements of high-end equipment for transmission smoothness and reliability.
High-strength carburized and quenched helical internal gear rings are commonly specified for the high-speed enclosed reduction systems of large mine hoists and heavy lifting and hoisting equipment. Compared with spur internal gearing, they offer better impact and overload resistance, with more uniform tooth flank wear at high operating speeds. The fully enclosed design seals out dust and contaminants, making them well suited to the heavy-duty, high-speed and harsh operating conditions found in mining applications.
Inner VCI vacuum anti-rust process fully seals tooth flanks and critical machined surfaces, effectively resisting salt spray and moisture during ocean and air freight to keep precision gears corrosion-free throughout long-distance transit.
We select cost-effective logistics channels with stable transit time and controlled costs. Full logistics tracking is available with real-time status updates to ensure reliable and punctual delivery.
All products are covered by a 1-year warranty. Quality defects caused by non-human factors are fully guaranteed, removing your procurement concerns.
Our professional technical and after-sales team is always available to respond quickly to inquiries and after-sales needs, and efficiently resolve issues during installation and operation.
We support full-parameter OEM/ODM customization based on 2D/3D drawings or physical samples, including module, tooth profile, material and heat treatment specifications. You only need to provide core gear parameters, detailed drawings or physical samples to start the customization process.
You can send physical samples to us via international courier. Upon receipt, we will complete full-dimensional measurement and parameter verification, then arrange sample production after confirming the solution, ensuring the finished product fully matches the original in installation dimensions and transmission performance.
Prototype orders usually ship within 15–25 days, subject to heat treatment and grinding scheduling. Lead time for bulk orders will be confirmed after process finalization, with stable and well-managed production schedules.
We adopt a tiered pricing policy — the larger the order quantity, the more favorable the unit price. All orders follow the same production and quality inspection standards with strict accuracy control. Quality will never be compromised for larger order volumes.
We can include dimensional inspection reports, hardness test records and material certificates with each shipment. For high-precision key projects, professional inspection data from CMM and gear measuring centers is also available.
All products come with a 1-year warranty covering material defects and manufacturing quality issues under normal use. We also have a professional technical team to provide full-process consultation and selection support.
Spur gears feature a simple structure and no axial load, ideal for medium-low speed general transmission with higher cost-effectiveness. Helical gears run smoother with lower noise and higher load capacity, suitable for high-speed heavy-duty applications. We can recommend the optimal solution based on your actual requirements.
+86 184 3796 0706 
info@destinytrans.com 
