A hollow shaft only works when the bore and outside features are treated as one part. Wall thickness, journals, shoulders, keyways and datum relationships all affect stiffness, runout and fit.
YUBAO manufactures made-to-print hollow shafts for servo motors, industrial automation, reducers, electric drive assemblies and machine tools. Depending on the drawing, the route may include deep-hole drilling, boring, broaching, internal grinding and outside-diameter grinding, followed by coaxiality and runout inspection.
Capability values are project-dependent. Final tolerances, material, heat treatment and inspection scope are confirmed after drawing review.
Hollow construction can reduce rotating mass, create a passage for cables or fluids, or provide an internal fit. The benefit depends on keeping enough wall thickness and controlling the bore to the same datum structure as the outside features.
Removing material near the center can reduce rotating mass while journals, seals and torque-transfer features stay where the assembly needs them.
Through, blind and stepped bores can carry wiring, coolant, drawbars or locating features without adding an external passage.
The bore, wall thickness, shoulders and bearing seats are reviewed together because runout and fit depend on how those features relate.
Reference ranges for early project screening. Final feasibility depends on the bore type, bore depth, wall thickness, material, heat treatment, datum structure and inspection access defined in the drawing.
| Feature | Reference Capability | Engineering Relevance |
|---|---|---|
| Size & Bore Range | OD Ø21–350 mm · ID Ø10–180 mm · finished length up to 1500 mm | Early screening depends on bore depth, wall thickness, length-to-diameter ratio, section changes and machining access. |
| Bore Types & Internal Features | Through, blind, stepped and drawing-defined special bores · keyways and selected internal splines | The route changes with tool access, bore depth, feature position, chip removal and inspection access. |
| Accuracy & Datums | Straightness down to 0.01 mm · cylindricity 0.005 mm · radial runout 0.008 mm · inner-to-outer coaxiality 0.03 mm | Final values must be tied to the functional datum plan, finished length, wall uniformity and heat-treatment movement. |
| Surface & Fit | OD Ra 0.2–0.8 μm · ID Ra 0.8–3.2 μm · H7–H9 fit bores where geometry allows | Finish and fit are assigned only to bearing, sealing, locating, fluid-routing or precision assembly interfaces. |
| Materials & Process | 20CrMnTi, 40Cr, 42CrMo and drawing-defined steels · deep-hole drilling, boring, broaching, internal and OD grinding | The practical route depends on load, fatigue, wear, bore geometry, annual volume, heat treatment and inspection requirements. |
Open a group only when the drawing needs a deeper review of bore access, wall design, precision finishing or inspection.
| Review Item | Reference Capability | Engineering Note |
|---|---|---|
| Bore Type | Through, blind, stepped and drawing-defined special bores | Process selection depends on bore depth, entry access, internal steps and the required finished surface. |
| Deep-Hole Drilling | Bore Ø10–80 mm · L/D up to 20:1 reference | Actual depth depends on diameter, stock condition, straightness requirement and drill access. |
| Boring | Bore Ø50–180 mm · H7 reference where feasible | Used where the bore is accessible and the required diameter, fit and surface can be reached by boring. |
| Fit-Bore Tolerance | H7–H9 where specified and feasible | The tolerance must be reviewed against bore depth, diameter, material, treatment and finishing access. |
| Internal Keyways | 5–22 mm reference · JS9 where applicable | Broaching or secondary machining depends on bore size, keyway position, through-access and inspection method. |
| Wall Thickness & Bore Ratio | Drawing-defined | Wall thickness should be verified against torque, speed, torsional stiffness, fatigue, heat-treatment movement and local stress concentration rather than a weight target alone. |
| Control Item | Reference Capability | Project Note |
|---|---|---|
| Straightness | Down to 0.01 mm | The requirement must be tied to finished length, diameter and the agreed measurement span. |
| Cylindricity | Down to 0.005 mm | Applied only to agreed outside, inside, journal or fit surfaces. |
| Radial Runout | Down to 0.008 mm | The reference centers, datum axis and measured feature must be identified in the drawing. |
| Inner-to-Outer Coaxiality | Down to 0.03 mm | Important for wall uniformity, rotating stability, fit and repeatable assembly. |
| Surface Finish | OD Ra 0.2–0.8 μm · ID Ra 0.8–3.2 μm · internal grinding down to Ra 0.4 μm where geometry allows | Applied only to functional surfaces where sealing, bearing, locating, flow or precision-fit requirements justify it. |
| Internal Grinding | Bore Ø20–150 mm · roundness down to 0.005 mm reference | Feasibility depends on bore length, wheel access, material, treatment movement and inspection access. |
| Materials | 20CrMnTi, 40Cr, 42CrMo and drawing-defined steels | Material selection follows torque, fatigue, impact load, wear and the intended heat-treatment route. |
| Heat Treatment | Tempering, carburizing or nitriding | Hardness, case depth, distortion allowance and final grinding should be planned together. |
| Surface Hardness | 55–62 HRC reference where applicable | Only applicable to compatible materials, surfaces and treatment routes defined by the drawing. |
| Inspection & Records | CMM, runout and coaxiality measurement · material, heat-treatment and batch records | Critical characteristics and the inspection scope follow the agreed project control plan. |
The process route is set around the features that must stay related after drilling, heat treatment and grinding. Inspection follows the same datum plan used to machine the part.
CNC turning establishes journals, shoulders and outside references. Deep-hole drilling or boring creates the internal geometry. Broaching and internal or external grinding are added where the drawing calls for them.
Coaxiality, runout, fit bores, journals and shoulders are checked against the agreed references. Material, heat-treatment and inspection records can be carried into repeat production.
YUBAO matches the bore, journals and interfaces to the duty shown in the drawing—from responsive automation to compact drives and special equipment.
For robotic and motion-control assemblies where response, runout and repeatability matter.
For compact drive parts balancing torque, stiffness, concentricity and package size.
For spindle and actuator systems requiring coolant, drawbar or clamping passages.
A hollow bore is not always the best route. Compare these alternatives before the drawing is finalized.
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.
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.
