Precision Ground & Balanced
Motor Shafts

A motor shaft is the output rotating element of an electric motor — it transmits the electromagnetic torque from the rotor to the driven load. Motor shafts must have: precise bearing journal diameters (k5 or m5 fit for press-fit bearing inner races), accurate rotor stack bore or external fits, and a shaft end configured for the driven coupling (keyway, D-flat, thread, spline, or plain). Dimensional accuracy directly affects bearing preload, noise, and motor efficiency.

Motor shafts use k5 or m5 shaft tolerance for the bearing inner race press fit — these provide a slight interference that prevents the inner race from spinning (fretting) on the shaft. k5 for smaller bearings (≤ Ø30 mm); m5 for larger bearings or higher radial loads. The correct fit depends on the bearing bore tolerance class (ISO Normal class uses 0/−tolerance bore) and the radial load. HXC engineers confirm the fit from the bearing designation on your drawing.

Dynamic balance corrects residual mass imbalance in the shaft by measuring the unbalance on a balancing machine and removing small amounts of material. Required when: operating speed > 3,000 RPM; shaft length > 5× diameter; or vibration/noise specification is tight. HXC offers balance to ISO 1940-1 G1.0 (standard industrial motors), G0.4 (precision spindle motors and aerospace), and G6.3 (general industrial). Specify balance grade and operating speed on your drawing.

HXC produces all standard motor shaft end configurations: Keyway (DIN 6885 parallel key); D-flat (hobbyist and stepper motor shafts); Spline (DIN 5480, SAE); Threaded end (metric or UNF, for pulley retention); Taper (ISO 4044 metric motor taper); Smooth cylindrical (for press-fit couplings); or any custom configuration. Both shaft ends can have different configurations — specify each end on the drawing.

Prototype (1–5 pcs, turned + ground): 5–7 days. Small batch (10–50 pcs): 7–12 days. Production (100–1,000 pcs): 10–16 days. Balanced or titanium shafts: add 2–4 days. Rush production available.

42CrMo4 (induction hardened) for servo and industrial motors. C45 / S45C for BLDC and stepper motors. SUS303/316L stainless for food, pharma, marine submersible pumps. Al 6061/7075 hard-anodized for drone and lightweight applications. Ti Grade 5 for aerospace actuator motors. 20CrMnTi (carburized) for high-cycle drivetrain motor shafts.

Standard ground OD: Ra 0.4 µm. Precision bearing seats: Ra 0.2 µm. Mirror finish for seals: Ra 0.1 µm. All measured by contact profilometer and reported on the inspection certificate.

Yes — keyways, splines, threads, cross-holes, flats, and tapers are all machined in the same 5-axis turning-milling setup, ensuring concentricity between all features within 0.003 mm TIR.

Common servo motor shaft diameters: 6 mm, 8 mm, 9.5 mm (3/8"), 12 mm, 14 mm, 19 mm — per IEC 60072 frame standard. HXC machines to any diameter, toleranced to k5/m5 for coupling press fits or h6 for sliding fits. If you provide the motor frame size (IEC 56 to 315 or NEMA 23 to 56), we can confirm the standard shaft diameter and keyway specification.

Yes — HXC regularly modifies existing motor shafts: adding a second shaft end (rear extension); changing shaft end diameter or length; cutting a keyway on an existing shaft; or re-machining a worn bearing journal to accept a sleeve. For shaft modification work, please send the existing shaft drawing or physical dimensions — we will quote for modification rather than new manufacture if that is more economical.