Commutator Turning Machine
AutomatedSemi-automatic
Finish-turns the commutator surface of the wound armature with a diamond tool to the required roundness and surface finish, then brushes away copper burrs.
✓ Expert reviewed All content on this page has been reviewed by a senior motor engineer.
Selection criteria
Runout and bar-to-bar step achievable, surface roughness, centring method (between centres or on bearing seats), cycle time.
Supply chain
Dongguan and Shenzhen builders make commutator finishing lathes as part of armature lines. Quality depends on spindle accuracy and the diamond tool — ask for bar-to-bar step and run-out measured on your own rotor.
Buyer FAQ
- Why finish-turn the commutator after winding?
- Winding, fusing and impregnation distort the commutator slightly. Finish turning restores roundness and a smooth surface so the brushes run quietly and wear evenly; poor turning causes sparking, noise and short brush life.
- What tolerances are typical?
- Run-out relative to the bearing seats of about 0.005–0.01 mm and bar-to-bar step below about 0.002–0.005 mm for small motors, with a fine surface finish. Undercutting the mica between bars may follow.
- How should the lathe hold the armature?
- On the shaft's bearing seats (V-blocks or live centres), never on the core OD, so the commutator ends up concentric with the bearings. A diamond tool gives the best finish.
Where it is used
Motor assembly process
- 37 mm Brushed DC Gear Motor (spur gearbox)6. Commutator turning