Replacing the Armature on a Milwaukee Hole Hawg Angle Drill

The armature is the central part of your drill's motor. It consists of windings, the commutator, a cooling fan, and the drive gear. The armature -- along with the field -- create an electromagnetic field that causes the armature to spin. The carbon brushes transfer electricity to the armature through the commutator. Over time, the commutator will wear from this constant contact. If the tool is overloaded, the armature can overheat and the insulation around the windings will burn away (creating a short-circuit). When this occurs, there will be excessive sparking from the motor brushes and smoke (or a burning smell) from the motor.

Let's get started.

REMOVING THE ARMATURE   1. Remove the motor brushes.

a. Use a large screwdriver to remove the (2) brush caps.

b. Remove the (2) motor brushes from the brush holders.

  2. Remove the motor cover.

a. Remove the (4) screws securing the motor cover to the motor housing.

b. Remove the motor cover.

c. Remove the wavy washer from the motor cover (or from the top of the armature).

  3. Remove the armature.

a. Use a screwdriver to carefully pry the armature assembly out of the motor housing.

b. Remove the armature from the motor housing.

c. Remove the insulator ring from the motor housing.

INSTALLING THE NEW ARMATURE

  4. Transfer the bearings.

a. Use a bearing puller to remove the bearings from the old armature.

b. Stand the new armature on the anvil-portion of your vise.

c. Install the bearings onto the new armature and use a socket (and hammer) to seat the bearings onto the armature shaft.

  5. Install the armature.

a. Generously apply fresh grease (Milwaukee Type-E) to the geared-end of the new armature assembly.

b. Install the insulator ring into the motor housing (atop the field assembly).

c. Partially install the new armature assembly into the motor housing.

d. Rotate the armature assembly until the drive gear aligns with the internal gears.

e. Press the new armature assembly firmly into the motor housing to seat the lower bearing.

REASSEMBLING THE UNIT

  6. Reinstall the motor cover.

a. Install the wavy washer onto the armature bearing.

b. Install the motor cover.

c. Secure the motor cover with the (4) screws.

  7. Reinstall the motor brushes.

a. Install the motor brushes into the brush holders.

b. Secure the motor brushes with the brush caps.