Two-Plane Balanced
High-Speed Rotation Shafts

High-speed shaft design requires: (1) Roundness ≤ 0.001 mm — non-roundness creates a once-per-revolution force at the bearing that intensifies with speed; (2) Dynamic balance to G0.4 or better — residual imbalance creates centrifugal forces that grow with speed²; (3) Surface finish Ra 0.1 µm on bearing journals; (4) Correct material with controlled heat treatment for dimensional stability; (5) No sharp stress concentration features — fillets rather than sharp corners at shoulder transitions.

ISO 1940-1 balance grades: G6.3 — general machinery below 3,000 RPM. G2.5 — electric motors and fans 3,000–6,000 RPM. G1.0 — precision grinding spindles, gas turbine blades. G0.4 — gyroscopes, precision spindles above 10,000 RPM. G0.1 — extreme precision. Specify your maximum operating speed and HXC recommends the required balance grade.

Safe operating speed depends on shaft diameter and length (first critical speed), bearing type, and lubrication. As a rough guide: a Ø20 mm shaft supported at L = 100 mm centres in angular contact bearings with oil-mist lubrication can run safely to ~50,000–60,000 RPM. HXC does not perform rotor dynamics calculations — the system integrator is responsible for critical speed analysis. HXC ensures the shaft geometry (roundness, balance, finish) does not add unnecessary excitation.

SUS440C bearing stainless (HRC 58–62): best combination of hardness, corrosion resistance, and dimensional stability for high-speed spindle shafts. 42CrMo4 (induction hardened): most common for high-speed grinding spindles and motor shafts. Grade 5 titanium: best strength-to-weight ratio for turbine and aerospace shafts where weight contributes to centrifugal stress. Avoid aluminium above 20,000 RPM in steel bearing races — differential thermal expansion can loosen the fit.

Prototype (1–5 pcs, turned + ground + balanced): 5–8 days. Small batch (10–50 pcs): 8–14 days. Production (100–500 pcs): 12–18 days. G0.4 two-plane balancing is included in the baseline lead time. Stainless or titanium: add 2–4 days. Rush production available.

Two-plane balancing corrects unbalance in two correction planes along the shaft (rather than one). It is required for any shaft whose length is significant relative to its diameter, because unbalance can exist as both a static (single-plane) and a couple (two-plane) component. HXC measures unbalance on a balancing machine and removes small amounts of material by drilling in the two correction planes until residual unbalance is within the target grade.

Standard ground OD: Ra 0.4 µm. High-speed bearing journals (HXC default): Ra 0.1 µm lapped. Mirror finish for air-bearing shafts: Ra 0.05 µm super-lapped on request. Roundness measured on a Talyrond roundness machine and reported with the balance certificate.

HXC manufactures the shaft to suit your chosen bearing arrangement — angular contact, ceramic-hybrid, air, or magnetic. We do not supply the bearings themselves, but we machine the journals to the exact tolerance, roundness, and finish your bearing maker specifies, and we can advise on journal fit class for your bearing series.

Yes — impeller threads, tool tapers, pulley grooves, encoder mounts, balance correction planes, and through-coolant drilling are all machined in the same multi-axis setup, ensuring concentricity within 0.003 mm TIR before balancing.