Hammer Drill: Grinding or Squealing Sound

When the gear-end of the armature shaft wears out, it will cause a grinding sound as it is trying to make contact with the other gear. Begin by removing the handle. Open the case to access the armature – this will vary on all models as they are different. Inspect the armature gear for any signs of wear, such as chipped, broken teeth or anything else out of the ordinary. The gear on the armature is part of the armature, so if it is damaged, you will need to replace the armature.

Remove any shafts and hold-down brackets so you can remove the armature. Remove the brush holders. On other models, remove the brushes simply by removing the hold-down clip and pulling the brush out of the holder. Pull the motor up and slide the armature free of the motor. Slide the new armature into the field and place the motor back down in the case. Reinstall the brushes in the holders and reapply the hold-down clip or brush holders. Reinstall all shafts and fasten any hold-down brackets. Reassemble the case and reattach the handle.

Worn bearings can cause a grinding, or squealing, sound and will usually cause a vibration. To inspect the bearings to see if any are worn out, you will need to remove the handle and then open the case of your hammer drill. Take out the chuck and spindle and any secondary shaft, if your drill has one. Lift the motor up and slide the armature out. Spin all the bearings on the shaft and listen for any abnormal sounds. Bearings should sound smooth and even; not loud and uneven. Repair procedures will vary on models as they are slightly different. To replace armature bearings, use a bearing separator, or puller, to remove the bearings. When using a separator, once it is installed, place it on the bench vice and make sure only the separator is making contact. Place a punch on the shaft and hit it with a hammer, until the bearing become loose. To install new bearings, place the shaft in a vice and then place the bearing on the shaft and use a socket that makes contact with the bearing inner race. This is to avoid any damage to the bearing. Tap in place with a hammer and install back into the case. Close the case and secure it and then reattach the handle.

Replacing spindle bearings will vary on all models, as they are slightly different. To replace spindle bearings, remove the cam plate, leaf spring, change plate, steel ball, gear and the retaining ring. Use a bearing separator, or puller, to remove the bearing. If you are using a separator, once it is installed around the bearing, place it on top of an open bench vice. Place a punch on top of the shaft and tap it with a hammer to free the bearing. Place the shaft in a vice to hold it steady, but not too tight, as you do not want to damage the shaft. Install the new bearing onto the spindle by using a socket that only makes contact with the inner race of the bearing. This is to avoid any damage to the bearing. Tap in place with a hammer. Reinstall the retaining ring, gear, steel ball, change plate, leaf spring and cam plate. Reinstall the spindle assemble into the drill case and reassemble the case back together. Reattach the handle back on the hammer drill.

Secondary shafts usually have the bearing on the end of the shaft. Remove the bearing using a separator or a puller. When using a separator, once it is install around the bearing, place the separator on a bench vice. Open up the bench vice enough so only the separator is making contact. Place a punch on the shaft and hit the punch with a hammer, until the bearing becomes loose. Place the shaft in the bench vice, but not too tight to avoid damage to the shaft. Place the bearing on the shaft and use a socket that makes contact with the bearing inner race to avoid any damage to the bearing. Tap in place with a hammer. Reinstall the shaft in the hammer drill’s case and reassemble the case back together. Reattach the handle.

If one of the brushes breaks off and becomes wedged between the commutator and another part of the drill, it can produce a grinding, or squealing, sound. Excessively worn-out brushes can also produce a squealing sound. To check your drill, begin by detaching the handle. Open the drill case to access the brushes. Remove the brush holder by gently pulling up on them by the wire. Press the tab on the side of the holder to release the brush. On some models, you will leave the brush holder in the case and remove the clip on the holder to access the brushes.

Inspect the brushes for signs of breakage. If you notice a piece is missing, make sure it is not wedged in the drill somewhere, causing the squealing or grinding sound – especially check around the commutator. Spin all moving parts and listen carefully. Replace any broken, or worn out, brushes. Brushes less than 1/8 of an inch are worn out and need to be replaced. Install the brushes in the holder, making sure the tab locks in place. On other models, slide the brush in the holder and fasten the hold-down clip. Install the brush holders back in the case, using a small screwdriver to hold the brush down, giving you clearance of the commutator. Reassemble the case back together, securing it with the fasteners and reattach the handle.

Worn out or broken gears will cause a grinding or squealing sound – depending on the type of damage and how bad it is. To inspect the gears for damage, remove the handle and then open the case of the drill. This will vary on all models as they are different.

With the case open, examine all the gears by turning them, looking for damage. Remove any hold-down brackets, if applicable. Remove the spindle assembly from the drill. Remove the cam plate, leaf spring, change plate, steel ball and gear with the keyway. Some models may have more than one gear here. Remove and install the new gear with the keyway, ensuring the keyway stays in place during installation. Reinstall the steel ball, change plate, leaf spring and cam plate. Some drills will have a secondary shaft with gears. Depending on the model, repair procedures will vary. To replace a gear on the secondary shaft, remove any bearings with a puller or separator. Take out any retaining rings, washer, and the old gear and then install the new one with the keyway.

Reassemble everything back on the shaft in reverse order. Use a socket that makes contact with the bearing inner race when reinstalling to avoid damage to the bearing. Tap the socket with a hammer to set the bearing in place. Reinstall back in the drill case and fasten any hold-down brackets. Reassemble the case back together and then reattach the handle.