Tightest Class HXC Offers
Precision Spindles

A precision spindle is a rotating shaft designed to carry a cutting tool, grinding wheel, or workpiece in a machine tool — where dimensional accuracy and rotational precision are the primary requirements. Spindle OD and bearing journal tolerances are graded to IT3 or better, roundness is controlled to ≤ 0.001 mm, and surface finish Ra 0.1 µm is standard on bearing contact surfaces. Any deviation from these tolerances directly causes machining error in the parts the spindle produces.

The critical dimensions are: bearing journal OD (IT3–IT5) — sets the interference fit to the bearing inner race; runout of spindle nose to bearing journal (≤ 0.002 mm TIR) — directly determines workpiece concentricity; roundness of bearing journal (≤ 0.001 mm) — affects bearing preload uniformity and vibration; surface finish Ra 0.1 µm on journals — ensures consistent bearing fit. HXC measures all four parameters and reports them on every spindle.

42CrMo4 (induction hardened to HRC 52–58): standard for machining centre and lathe spindles — good fatigue resistance and dimensional stability after hardening. SUS440C bearing stainless (HRC 58–62): for high-speed spindles requiring corrosion resistance and maximum surface hardness. 20CrMnTi (carburized) for heavy lathe spindles. GCr15 (SUJ2) through-hardened for grinding spindles. Al 7075-T6 HA for lightweight routing spindles.

HXC does not rate maximum spindle speed (that depends on the bearing selection and lubrication system), but the machined spindle geometry — roundness ≤ 0.001 mm, journal OD IT3, surface finish Ra 0.1 µm, and dynamic balance per ISO 1940-1 G1.0 — is compatible with spindle designs rated to 60,000+ RPM when assembled with matched precision bearings. Dynamic balance is offered as an option for spindles above 10,000 RPM.

Prototype (1–5 pcs, turned + ground + lapped): 5–8 days. Small batch (10–50 pcs): 8–14 days. Production (100–500 pcs): 12–18 days. Lapping to IT3 / Ra 0.1 µm: include in baseline lead time. Stainless / titanium / dynamic balance: add 2–4 days. Rush production available.

Standard ground OD: Ra 0.4 µm. Precision bearing seats (HXC default for spindles): Ra 0.1 µm lapped. Mirror finish for high-speed grinding spindles: Ra 0.05 µm super-lapped on request. All measured by contact profilometer and reported on the inspection certificate. Bearing journal roundness also measured on a Talyrond roundness machine.

Yes — drawbar bore for tool retention, pull-stud thread (M16 / M20 / M24), spindle nose taper (BT / HSK / ISO / CAT), encoder mounting at the rear, V-pulley or timing-pulley grooves, and through-coolant drilling are all machined in the same multi-axis turn-mill setup, ensuring concentricity within 0.003 mm TIR across all features.

Dynamic balancing removes residual mass imbalance from the finished spindle by measuring unbalance on a balancing machine and removing small amounts of material (or adding balance weights) to bring the unbalance below the target grade. HXC offers dynamic balancing to ISO 1940-1 G1.0 or G0.4 for high-speed spindles above 10,000 RPM — specify your maximum operating speed and we advise on the required balance grade.

All spindles are shafts, but not all shafts are spindles. A spindle specifically carries a machining or inspection function — bearing journals, taper bore (BT / HSK / ISO), or chuck mount — and is held to the tightest accuracy class (IT3–IT5). A general shaft transmits torque or supports a structural load and is typically made to IT6–IT8. The manufacturing process is the same (CNC turning + cylindrical grinding) but spindles require additional measurement steps: roundness, runout, and finish verification at bearing surfaces.