Custom Spiral Bevel Gear Shaft for Mechanical Transmission

This custom spiral bevel gear shaft is made from 20CrMnTi alloy steel for a mechanical transmission application. Unlike a separate gear assembled onto a shaft, the gear teeth and shaft are produced as one component, so the tooth geometry, bearing journals and shaft reference surfaces all need to work around the same rotational axis.
The part is manufactured to the customer's engineering drawings and undergoes carburizing and hardening after the main machining and gear-cutting operations. Finished components are exported to Italy, typically in repeat batches of around 300 pieces.
YS Precision provides custom spiral bevel gear manufacturing and gear shaft machining, covering shaft machining, gear cutting, heat treatment, required finishing and final inspection.
 

Product Specifications

When the Gear and Shaft Are One Component

The integrated structure is the most important feature of this part.
The spiral bevel teeth engage with the mating gear and transfer motion through the transmission. At the same time, the shaft journals locate the component in bearings, while shoulders and reference surfaces establish its position in the assembly.
These features cannot always be treated independently.
If the drawing specifies gear-to-shaft runout or concentricity, accurate tooth geometry alone is not enough. The gear must also remain correctly positioned relative to the shaft reference axis.
This relationship between gear teeth, shaft journals and rotational center influences how the component is machined, heat treated and inspected.
 

Gear Geometry Comes from the Customer's Design

This is a non-standard transmission part rather than a catalog gear.
Its tooth geometry and shaft dimensions are manufactured from the customer's 2D drawing and 3D CAD data where available. Gear specifications can include:
Module · Tooth Count · Pressure Angle · Spiral Angle · Gear Accuracy
The same technical documentation defines shaft diameters, bearing journals, shoulders and critical tolerances.
Producing the component this way allows the custom spiral bevel gear to match the customer's mating gear, bearing positions and existing transmission layout.
For production, critical gear data is taken from the engineering specification rather than estimated from an existing sample or outside diameter.
 

20CrMnTi and Carburizing for Transmission Gears

20CrMnTi is widely used for transmission gears that require a hard, wear-resistant working surface.
For this gear shaft, the component is carburized and hardened after the main machining operations. The process develops the specified hardened case at the working surface while maintaining the required properties in the underlying material.
The steel grade, however, does not define the finished gear by itself.
Requirements such as surface hardness, effective case depth and areas requiring protection during carburizing should follow the customer's heat-treatment specification and actual operating conditions.
These requirements are reviewed together with the dimensional drawing before the final manufacturing route is established.
 

From Shaft Machining to Spiral Bevel Gear Cutting

Production begins by establishing the shaft geometry and machining references needed for subsequent operations.
A typical route may be:

20CrMnTi Blank → CNC Turning → Shaft & Reference Machining → Spiral Bevel Gear Cutting → Deburring → Carburizing & Hardening → Final Finishing as Required → Inspection
CNC turning establishes the shaft diameters, bearing journals, shoulders and reference surfaces.
The bevel teeth are then generated according to the specified gear geometry using an appropriate spiral bevel gear cutting process.
The actual sequence is determined by the tooth geometry, shaft tolerances, gear accuracy and final requirements after heat treatment. For an integrated gear shaft, these operations are planned around the finished component rather than handled as unrelated machining steps.
 

The Critical Dimensions After Carburizing

For a carburized gear shaft, dimensional control does not end before heat treatment.
Carburizing and hardening can introduce dimensional change. What matters to the customer is whether the finished gear shaft meets the requirements needed for assembly and transmission performance.
Critical characteristics may include:

• gear accuracy after heat treatment;
• bearing journal diameters;
• gear-to-shaft runout;
• concentricity of shaft features;
• surface hardness;
• effective case depth.

If tighter final tolerances require post-heat-treatment finishing, those operations need to be considered before production begins.
Planning around the final hardened condition reduces the risk of producing a good pre-heat-treatment component that cannot meet the finished drawing requirements.
 

Repeat Production Means Reproducing the Same Gear

These gear shafts are supplied to an Italian customer in repeat batches of approximately 300 pieces.
At this stage, the manufacturing challenge is not making one acceptable sample. It is maintaining the same critical characteristics across the batch and again when the next production order arrives.
Consistent machining references, controlled gear-cutting conditions, stable heat-treatment requirements and inspection of functional dimensions all contribute to repeatability.
For a gear shaft, this consistency extends beyond the tooth profile. The shaft journals, bearing locations and their relationship to the gear axis also need to remain within the specified requirements.
 

Inspection Around the Transmission Function

Inspection follows the features that affect how the gear shaft fits and operates.
Based on the engineering drawing, this may include:
Gear Tooth Characteristics · Shaft Diameters · Bearing Journals · Reference Dimensions · Gear-to-Shaft Runout · Concentricity · Surface Hardness · Effective Case Depth
This is particularly important for an integrated gear shaft because the gear and shaft ultimately function as one rotating component.
Rather than applying the same checklist to every gear, inspection is built around the dimensions and relationships identified as critical for the customer's assembly.
 

Custom Gear and Gear Shaft Manufacturing

YS Precision provides custom gear manufacturing and gear machining services for non-standard mechanical transmission components.
Our capabilities can support:
CNC Turning · Gear Shaft Machining · Gear Blank Machining · Spiral Bevel Gear Cutting · Carburizing & Hardening · Post-Heat-Treatment Finishing · Dimensional Inspection
We manufacture custom spiral bevel gears, gear shafts, carburized alloy steel gears and other transmission components to customer drawings.
For an integrated gear shaft like this one, the objective is to supply a finished component in which the tooth geometry, shaft features, heat-treated condition and functional dimensions have been considered together—not simply to complete the gear-cutting operation.
 

Request a Quote for a Custom Gear Shaft

For a new spiral bevel gear or gear shaft project, please provide your 2D engineering drawing and 3D CAD model where available.
Useful RFQ information includes:
Material · Gear Type · Module · Tooth Count · Pressure Angle · Spiral Angle · Gear Accuracy · Shaft Dimensions · Critical Tolerances · Heat Treatment · Surface Hardness · Effective Case Depth · Quantity
With complete technical information, our team can review the machining route, gear-cutting requirements, heat treatment and inspection requirements before quotation.