How to Replace the Armature on a Makita Cordless Hammer Drill (Model LXPH01)

Armature hammered? It's time to face the fix. Whether you are a master carpenter or an occasional drill-seeker, eReplacementParts.com provides the parts, procedures and facts you need to fearlessly fix what fails you.

The armature is the central component of your cordless drill's motor. When energized by the carbon brushes, the armature (in combination with the motor's field) creates a magnetic field, which causes the armature to rotate.

If the motor is overheated, the insulation on the armature's windings can melt, causing smoke and excessive sparks between the commutator and the carbon brushes.

The armature assembly includes two bearings. With normal use, these bearings will eventually wear out. Symptoms of failing bearings include squeaking or squealing sounds.

The shaft of the armature also contains a milled gear, which engages the drill's gearbox. Sometimes, the gear on the end of the armature shaft will wear out. If this happens, there is likely to be wear to the gears within the gearbox. (If so, it should also be replaced.)

This article provides step-by-step instructions for removing and installing the armature on a Makita cordless hammer drill.

Let's get started.   REMOVING THE ARMATURE [top] 1. Remove the battery.

Remove the battery from the drill.

  2. Remove the rear cover.

Remove the (2) screws.

Remove the rear cover from the drill.

  3. Split the housings.

Remove the screws from the top half of the housing.

Lift the top half of the housing away from the unit.

  4. Remove the motor brushes.

Use long-nosed pliers to retract the brush spring from the back of the motor brush.

Use a small screwdriver to disengage (pry) the brush clip from the brush holder.

Slide the carbon brush out of the brush holder.

Repeat this step to remove the second motor brush.

  5. Remove the motor and gear assembly from the housing.

Partially lift (pry) the heat sink away from the motor.

Lift the motor and gear assembly (as a single unit) slightly out of the housing.

Disengage the brush card from the armature assembly.

Remove the speed-change lever from the motor and gear assembly. (Be careful not to lose the two springs situated inside the speed-change lever.)

  6. Disconnect the motor assembly from the gear box.

Slide the motor (armature and yoke) assembly away from the gear assembly.

  7. Remove the armature assembly.

Separate the armature assembly from the yoke (field). The two components are held together by a magnet located in the yoke unit. Remove the armature assembly by pulling it firmly away from the yoke.

  INSTALLING THE NEW ARMATURE [top] 8. Install the armature assembly.

Orient the yoke assembly so that the notched portion is facing the gear assembly (away from the armature).

Install the new armature assembly (geared-side first) into the yoke unit. The magnetic force will secure the two components.

Verify that the notched portion of the yoke is on the same side as the armature gear.

  REASSEMBLING THE UNIT [top] 9. Reconnect the motor (armature and yoke) to the gear assembly.

Align the armature gear with the gears inside the gear assembly.

Press the two components (motor and gear assembly) firmly together.

  10. Reinstall the speed-selector lever.

Verify that the two springs are properly positioned within speed-selector lever.

Align the post on the gear assembly with the opening (between the two springs) on the speed-selector lever.

Install the speed-selector lever.

  11. Reinstall the switch.

Align the notch on the forward/reverse change lever with the post on the switch.

Install the switch (and F/R change lever) into the lower half of the housing.

Tuck the switch wires into the channels on the housing.

  12. Reinstall the motor and gear assembly.

The notch on the yoke unit is designed to engage the plastic tab on the lower half of the housing. Rotate the yoke unit (as necessary) to ensure alignment of these components.

Reinstall the brush card over the armature.

Install the motor and gear assembly (as a single unit) into the lower half of the housing.

Manipulate the components (as necessary) until: 1) the notch on the yoke unit engages the tab on the housing; 2) the speed-selector switch is properly seated within the channels on the housing; and 3) the brush card is properly seated in the lower half of the housing.

  13. Reinstall the heat-sink.

Install the heat-sink into the lower half of the housing.

Verify that the wires (extending from the heat-sink) are positioned on the switch-side of the plastic post (not on the motor-side).

  14. Reinstall the top half of the housing.

Inspect all of the wires for potential pinch-points; make adjustments as necessary.

Reinstall the top half of the housing.

Secure the housing with the screws.

  15. Reinstall the motor brushes.

Retract the brush spring from the brush holder.

Install the motor brush into the brush holder.

Secure the brush clip to the brush holder.

Reposition the brush spring onto the motor brush.

Repeat this step to reinstall the second motor brush.

  16. Reinstall the rear cover.

Install the rear cover.

Secure the rear cover with the (2) screws.

  17. Reinstall the battery.

Install the battery.

As you just learned, fixing things yourself means more drilling with less billing. Hopefully, this article has restored your ability to drill holes without replacing your whole drill. And that's just the tip of the bit. Our online repair guides can help expand your skills far beyond drills; empowering you to face power tool problems whenever they arise; and to fearlessly fix whatever fails you.

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