Lower Assist Shaft Manufacturing
Jinhua Machinery manufactures lower assist shafts to approved customer drawings for steering and motion-transmission assemblies. This component uses multiple spline and machined features to transfer torque while maintaining the fits and datum relationships defined by the customer. It is supplied as a made-to-drawing part rather than a standard catalogue item.
Verified component specification
- Material: Medium-carbon steel with cold-drawing pretreatment.
- Spline forming: Cold forging for the external and internal splines, with gear shaping for the secondary external spline.
- Machining: Turning, milling and grinding for the remaining functional features.
- Hardness: HRA 58–64.
- Dimensional control: Outer-diameter tolerance ±5 μm and inner-diameter tolerance ±15 μm.
- Traceability: A laser-marked 2D code is applied to the shaft.
Manufacturing process
The manufacturing plan begins with review of the released drawing, spline definition, datums and critical characteristics. Material preparation and cold-drawing pretreatment are followed by cold forging of the principal spline features. The secondary external spline is gear shaped, while turned, milled and ground features are completed in the sequence required to protect datum relationships and final fits. Hardness and dimensional checks are incorporated into the agreed inspection plan, and the finished shaft receives its 2D traceability mark.
Quality inspection
Inspection is based on the approved customer drawing. The review can cover spline geometry, outside and inside diameters, datum-related dimensions, machined surfaces, hardness and the required identification mark. Sampling level, report format, certificates and traceability records should be stated with the RFQ. See our quality inspection and process-control approach for the wider project workflow.
Applications and project fit
Lower assist shafts are reviewed for steering and related motion-transmission assemblies where torque transfer, spline engagement and controlled shaft fits must work together. Final suitability depends on the customer’s assembly design, load case, mating components and released specification.
Information required for quotation
- 2D drawing and available 3D model
- Material grade and governing standard
- Prototype quantity, production quantity and annual demand
- Critical dimensions, spline standard and tolerance requirements
- Hardness, surface and marking requirements
- Inspection reports, certificates and traceability requirements
- Target delivery schedule and destination
For related capabilities, review our spline shaft manufacturing page. To request a manufacturing review, contact Jinhua Machinery with the available project data.