EV Motor Shaft with 0.008mm Runout and Keyway Milled, Hardened 55-60 HRC Bearing Journal Shaft for CNC Lathe Machining

• Journal Runout0.008 mm
• Journal Roundness0.004 mm
• Order Size1 Piece
• Prototype Lead Time3–7 Working Days

Motor shafts machined to drawing with bearing journals ground after heat treatment — not before. Materials include 40Cr, 42CrMo, SCM415 and 20CrMnTi, induction hardened to 55–60 HRC. Exporting since 2008 under an ISO 9001:2015 quality system.

A motor shaft carries the rotor on one diameter and the bearings on two others. Buyers quote the journal diameters, but noise and bearing life are decided by three things the diameter does not describe: journal runout, roundness, and whether the two bearing journals are coaxial with each other. A shaft that is 0.01 mm over size but perfectly round runs quieter than one at nominal with 0.02 mm of lobing — because a lobed journal pumps the bearing cage every revolution.

On top of that, heat treatment moves the part. A shaft turned to size and then induction hardened will come out of the quench bowed and slightly eccentric, so journals that were round in the soft state are no longer round. Our sequence is therefore rough turn, stress relieve, semi-finish, harden, then finish turn or grind the journals from the hardened state with the part held between centres — the geometry is generated after the movement, not before it.

Balance is quoted separately because it depends on the finished assembly: a bare shaft behaves differently from a shaft with the rotor fitted. Tell us the service speed and whether you want the shaft balanced alone or as a rotor sub-assembly, and the grade is set in the quotation rather than assumed.

• Material: 40Cr, 42CrMo, SCM415, 20CrMnTi (case hardening), 45 steel, 17-4PH, 304/316L for corrosion or food-contact drives, 6061 aluminium for low-inertia shafts.
• Treatments: induction hardening, carburising, nitriding, black oxide, zinc or nickel plating, DLC on request, stress relief.
• Features: single or double keyway, spline, thread with undercut, circlip groove, O-ring groove, taper seat, flange, cross hole, centre bore, hollow shaft.
• Geometry: 2 to 6 stepped diameters, journals from 6 mm to 120 mm, length 50 mm to 1200 mm.
• Balancing: G6.3, G2.5 or G1 at your service speed, with a printed record.
• Input: STEP, IGES, DXF, PDF drawing, or a sample shaft we measure and re-model.

A shaft drawing carries the rotor seat diameter, the bearing fit, the keyway position and often the motor's power class — enough to describe a drivetrain. Before any file is opened we sign a mutual NDA — ours in English or Chinese, or your own form — and return a countersigned copy before work starts. Access is limited to the project engineer, the lathe programmer and the cell supervisor, with the file in a restricted folder rather than the open shop network. The cell is camera free: no photographs for our catalogue or website, no customer part kept on display or reused as a sample, subcontracting only with your written approval, and at program close drawings and inspection data are deleted or returned with written confirmation.

Dongguan Changxinda Precision Technology Co., Ltd has machined custom metal parts since 2008: 15+ years, 90 to 100 staff, 50–60% of output exported to North America and Europe, 200+ customers served, turnover in the RMB 10–20 million band. The plant runs CNC lathes, turn-mill combined centres with live tooling and sub-spindle, and 4-axis / 5-axis machining centres under an ISO 9001:2015 quality system, serving medical, robotics, automotive, aerospace, automation, laser, LED, lithium battery and precision instrument programs. Turning, hard turning, keyway milling, heat treatment coordination, balancing and inspection are managed in our own plant in Dongguan.

Turned shafts and drivetrain parts from this plant ship into ten sectors. The list is what customers order, not a marketing wish-list.

All ten sectors run through the same plant and the same ISO 9001:2015 inspection discipline — only the material, finish and documentation package change.

• Prototype: 5–8 working days when heat treatment and finishing are included; 3–5 days for an unhardened sample.
• Small batch 10–100 pcs: 10–18 working days with hardening and balancing.
• Repeat orders: released from archived program, centres and tool list — journals come off the same setup, so runout repeats.
• Capacity: 10,000 pieces per month across the plant.
• Visibility: a dated progress note with photos of your actual shafts at finishing, keyway milling and inspection.
• Shipping: journals wrapped and protected, shafts in v-groove cradles or tube, so a long shaft cannot bend in transit.
• Rush: hardening and balancing slots booked weekly; tell us the deadline and we confirm before the order.