How to properly replace the brushes of a MILL DC Motor

1. Preparation
Disconnect the power supply: Before replacing the brushes, be sure to disconnect the power supply to ensure safety.
Prepare tools and materials: Prepare wrenches, pliers, new brushes, sandpaper (glass sandpaper), cleaners, insulating tape and other tools and materials.
2. Remove the motor cover
Remove the motor cover: Use a wrench to remove the motor cover screws and remove the motor cover.
3. Remove the old brushes
Remove the old brushes: After removing the motor cover, you can see the brushes of the DC motor. Use pliers to remove the brushes and clean the brush holder.
Clean the brush slot: Use a leather tiger or a hair dryer to carefully clean the dust and debris in the brush slot.
4. Install new brushes
Grind the new brushes: The new brushes should be polished with an arc to make it have a good contact surface with the commutator. Use scissors to cut sandpaper of the same width as the brush, and grind the new brush on the sandpaper to ensure a smooth contact surface.
Install new brushes: Place the ground new brushes into the brush holder, ensuring that the contact surface between the brush and the commutator is not less than 75%. The direction of the brush should be the same as the direction of rotation of the motor.
Adjust brush pressure: Use pliers to press the brush tightly to ensure good contact between the brush and the commutator. The pressure of the brush can be adjusted by the spring on the brush holder. The difference in pressure between each brush should not exceed ±10%, and the pressure should be 20~25kPa.
5. Test the motor
Reinstall the motor cover: Reinstall the motor cover and tighten the screws.
Connect the power supply: Reconnect the power supply, turn on the motor switch, and test whether the motor is running normally. If the motor runs normally, it means that the brush replacement is successful.
6. Notes
Choose the right brush: When replacing the brush, you must choose the same model as the original brush to ensure that the brush brand is consistent.
Avoid mixing old and new brushes: If you need to replace some brushes, it is best to replace them all at once to avoid mixing old and new brushes and causing uneven current distribution.
Light load operation: If more than half of the brushes are replaced at one time, it is best to run at light load for more than 12 hours to make the brushes and collector rings work well together before running at full load.
Cleaning carbon powder: All brush powder and debris should be removed after grinding, and vacuumed with a clean and dry vacuum cleaner.
Adjust the brush holder position: The distance between the bottom edge of each brush holder and the commutator surface should be about 3mm. If the commutator is worn or turned, the brush holder should be moved in time to keep it in a good position.