01 / INERTIA
Lower rotating mass
Removing material near the shaft center can reduce mass and system inertia while preserving the outside features needed for bearings, seals and torque transfer.
A useful hollow shaft is not simply a solid shaft with a hole through it. The bore, wall thickness, bearing journals, shoulders, keyways and finished outside diameter have to work as one geometry.
YUBAO manufactures drawing-based hollow shafts for servo motors, industrial automation, reducers, electric drive assemblies and machine-tool systems. The machining route can combine deep-hole drilling, boring, internal grinding, broaching, outside-diameter grinding and coaxiality inspection according to the part design.
Capability values are project-dependent. Final tolerances, material, heat treatment and inspection scope are confirmed after drawing review.
Hollow construction is valuable when it improves system behavior—not when it simply removes material. The design has to protect torsional stiffness, fatigue-sensitive transitions and fit surfaces.
Removing material near the shaft center can reduce mass and system inertia while preserving the outside features needed for bearings, seals and torque transfer.
A through, blind or stepped bore can create space for wiring, tubing, coolant, drawbars or assembly features without adding an external passage.
The bore can be finished as a fit surface, stepped seat, keyway or locating feature. Its relationship to the outside datum is often more important than bore size alone.
Wall thickness, transition radii and heat treatment should be selected around torque, speed, duty cycle and fatigue—not by a lightweight target alone.
These values describe available process capability, not an automatic tolerance on every dimension. The final route depends on geometry, material, heat treatment and inspection access.
| Feature | Capability Range | Typical Control | Engineering Note |
|---|---|---|---|
| Outside diameter | Ø21–350 mm | h6–h9 by feature | Journals and ground areas are assigned from the drawing datum structure. |
| Overall length | Up to 1500 mm | Project-specific | Length capability depends on diameter, bore route, straightness and grinding access. |
| Inner bore diameter | Ø10–180 mm | H7–H9 where specified | Through, blind and stepped bores can be reviewed. |
| Straightness | Down to 0.01 mm | Full-length or defined span | Must be tied to part length, diameter and heat-treatment route. |
| Cylindricity | Down to 0.005 mm | OD or ID feature | Measured on agreed critical surfaces. |
| Radial runout | Down to 0.008 mm | Between defined datums | Runout must identify the reference axis and measured feature. |
| Inner-to-outer coaxiality | Down to 0.03 mm | Drawing-defined datum | Important for wall uniformity, rotating stability and fit. |
| Inner-bore roughness | Ra 0.8–3.2 μm | Process-dependent | Precision internal grinding can be reviewed where required. |
| Outside roughness | Ra 0.2–0.8 μm | Ground surfaces | Applied to fit, seal or bearing-related surfaces as required. |
| Material options | 20CrMnTi, 40Cr, 42CrMo and drawing-specified grades | Material certificate by project | Material selection follows torque, fatigue, wear and heat treatment. |
| Heat treatment | Tempering, carburizing or nitriding | Drawing/application-specific | Hardness and case depth are confirmed for the selected material and duty. |
| Inner features | Keyways, splines, steps and special bores | Customized | Broaching and secondary machining depend on bore size and access. |
The process route is built around the features that must remain related after drilling, heat treatment, finishing and inspection.
CNC turning establishes shoulders and outside references. Deep-hole drilling or boring creates the internal geometry before finish operations are assigned.
Grinding can refine bearing journals, sealing surfaces, fit bores, roundness and surface finish after the major geometry and treatment steps are stable.
Critical bore, outside diameter, shoulder and journal relationships are checked against the agreed datum scheme rather than as isolated dimensions.
The inner-to-outer diameter ratio is a useful early design indicator, but it is not a substitute for torque, fatigue and critical-speed calculations. Transitions, cross holes, keyways and local wall changes can govern the final design.
The ranges shown are discussion guides for early DFM review. They are not automatic design approval or guaranteed mass reduction.
Inspection focuses on the relationships that influence rotation, fit and assembly—not only on individual diameter readings.
ISO 9001 and IATF 16949 systems support documented production control.
CMM and shaft measuring systems support coaxiality, runout and shoulder verification.
Fit bores, journals, steps and internal features are checked to the agreed inspection plan.
Material grade, heat treatment and hardness requirements remain linked to the project.
Inspection and production records support repeat orders and quality follow-up.
Approved features and inspection methods are carried into repeat production.
The same basic geometry can serve very different functions. The final design is always matched to the application, assembly and duty cycle.
Low-inertia rotor shafts, feedback interfaces and internal routing where acceleration response and runout both matter.
Joint shafts with hollow passages for cable routing and compact integration through rotating axes.
Sun shafts, output interfaces and compact assemblies where bore geometry supports mounting or weight control.
Drawing-specific shafts for compact torque-dense assemblies where mass, stiffness and interface geometry must be balanced.
Internal passages for drawbars, coolant or clamping functions, with bore finish and concentricity controlled to the assembly.
Some projects need a hollow bore. Others are better solved with stepped geometry, friction welding, splines or a precision plain shaft.
Yes. The quotation review considers the bore route, outside features, datum relationships, material, heat treatment, inspection scope and expected quantity before a process is confirmed.
Through bores, blind bores, stepped bores, internal keyways and other drawing-defined internal features can be reviewed. Feasibility depends on bore diameter, depth, access and tolerance.
The current capability range includes projects targeting inner-to-outer coaxiality down to 0.03 mm. The achievable value depends on length, wall thickness, heat treatment and the selected datum and inspection method.
Yes, where bore size and access allow. Internal grinding can be considered for improved roughness, roundness or fit requirements after the major geometry is stable.
Common drawing-based options include 20CrMnTi, 40Cr and 42CrMo. Final material selection should follow torque, fatigue, wear, treatment and dimensional-stability requirements.
Send the 2D drawing and 3D model where available, together with torque, speed, duty cycle, material, treatment, critical datums, quantity, annual demand and any assembly or functional requirements.