Comet II Motor Brush Inspection

Safety First

  1. Unplug the lathe from the power outlet.
  2. Allow the motor to cool if it has been running.

Inspection

  1. Locate the two brush caps on opposite sides of the DC motor housing.
  2. Remove one brush cap at a time.
  3. Carefully withdraw the brush and spring assembly.
  4. Check:
    • Brush length
    • Free movement of the brush in its holder
    • Spring tension
    • Excessive burning, chipping, or cracking

Replacement Criteria

  • The manual states: "Motor brushes should be checked every five years and replaced when the brush length is less than 6 mm (1/4 inch)."

Reassembly

  1. Reinstall the brush so it slides freely in the holder.
  2. Reinstall the spring and brush cap.
  3. Repeat for the second brush.
  4. Run the motor unloaded after service to confirm smooth operation.

Additional Notes 

  • New brushes require a break-in period of approximately 30 to 45 minutes running at higher RPM with no significant load. A clicking or swishing noise during this period is considered normal.
  • The troubleshooting section notes that motor vibration or noise can sometimes be caused by new brushes wearing in, and this often improves after a few hours of operation.