Hammer Drill: Bad Vibration

A bearing is a device used to enable rotational, or linear, movement as it reduces friction and handles stress. A worn bearing will make a growling, humming or low moaning sound and may be accompanied by a vibration. Bearings should sound smooth and even; not loud or uneven.

The following repair procedure will vary as all models are different. To replace a bearing that has worn out, remove the handle then proceed to open the drill case by removing the screws holding it together. With the case open, remove the spindle/chuck assembly and the lift the field up and remove the armature out of the field. You may have to remove the carbon brushes before taking out the armature. Now, you can check all of the bearings by spinning them by hand and listening for an abnormal sound. If the bearing does not spin, then it is seized.

To replace a bearing on the armature, use a bearing separator. Once you install your separator on the bearing, place the separator on top of a bench vice open far enough that it will not make contact with anything but the separator. Tap on the shaft with a punch and a hammer, until the bearing is free. For this step, you also can use a bearing puller to remove the bearing. To install a new bearing, place a socket on the inner race of the bearing, to avoid damage to the bearing, and tap it in place with a hammer. Reinstall the armature into the field and then the carbon brushes and spindle/chuck assembly back in the drill housing. Secure the case back together and reattach the handle.

The following repair procedure will vary between models. To replace a bearing on the spindle assembly, remove the cam plate, leaf spring, change plate, steel ball, gear, and the retaining ring. Use a bearing separator, or a puller, to remove the bearing from the spindle. Install the new bearing on the spindle by using a socket that only makes contact with the inner race of the bearing to avoid 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 assembly into the drill case and reassemble the case back together. Reattach the handle back on the hammer drill.

The carbon brushes ride on the commutator, supplying electricity for the armature. Badly worn carbon brushes can cause a vibration in the power tool. To access the carbon brushes, remove the handle and separate the drill case. Locate the brush holder at the rear of the armature. Gently pull up on the brush holders. You may need to use a small screwdriver to gently pull up on the other side for even lifting. On some models, you do not have to remove the entire holder. Remove the clip in the brush holder to remove the brush. Examine the brush for wear – brushes 1/8 of an inch, or less, are worn and require replacement. For some models, the brush holder and brush are a complete unit and will be removed and replaced as such. Install the carbon brushes into the holder, reapply the spring tension, or clip, and reconnect the wire connector. Reassemble the case back together and install the handle back onto the hammer drill.

Gears transfer power between shafts. If a gear is broken, chipped, missing or has badly worn teeth, it can cause a vibration and will usually be accompanied by a grinding noise. To check and replace the gears, remove the handle and the front gear case cover, if applicable, and open the drill case. Rotate all the gears, looking for damage, and replace any that do. Remove the spindle assembly from the drill. Then, take out 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. Put the spindle assembly back in the drill case and fasten the case back together and/or reattach the front gear cover with the handle.

Some models may have a secondary shaft, with gears, that you can remove at the same time with the spindle/chuck assembly. To replace gears on this shaft, remove it from the drill case and remove the bearings with a separator or puller. Remove any retaining rings and then the gear or gears with the keyway. Install the new gears on the shaft with the keyway, ensuring the keyway stays in place. Reinstall any retaining rings and the bearings. When installing the bearings, use a socket that makes contact with the bearing inner race to avoid damage. Tap in place with a hammer then reinstall the secondary shaft into the drill case.

If the worm gear on the end of the armature is worn, or broken, it is usually part of the armature itself, therefore requires the replacement of the armature. Lift the field up and remove the armature out of the field, using a bearing puller or separator to pull out the bearings (if the new armature assembly does not come with bearings). Install the bearings in the armature by using a socked, placed on the inner race of the bearing and tap it in place with a hammer. Reinstall the armature in the field and reassemble the case. Reattach the handle.

The handles can work themselves loose over time due to the punishment they can take from the hammering. Ensure the handles are tight. Add a little loctite. The threads on the handle can weaken over time, requiring you to tighten them more often. If this occurs, replace the handle simply by removing it and installing a new one.

The housing houses all parts of the hammer drill. If the housing is cracked, or broken, it can become not structurally sound and cause the hammer drill to vibrate. If you notice the housing is damaged, especially if it is severe, then it is a good idea to replace the housing. Replacing the housing is simple and straight forward. Begin by removing the handle. Remove all the screws securing the cover and separate it. Take off any brackets holding any parts in place. It is a good idea to take a picture to reference later on. Remove the spindle/chuck assembly out of the housing and then the field and armature. Disconnect any electrical connections. Remove the switch and power cord. Now, transfer everything over to the new housing and install. When doing this, remember to reconnect any electrical connections. Reinstall any hold down brackets and tuck all wires into their appropriate channels to avoid damage. Once all the parts are transferred, assemble the housing together and reattach the handle.

A worn, or bent, spindle can cause a vibration in the drill. The following repair procedure will vary on models as they are slightly different. To replace the spindle, begin by removing the handle and then the chuck by inserting the proper screwdriver in the chuck to take out the screw at the bottom. The chuck screw is reverse thread. Insert a big allen key in the chuck and tighten it down against the allen key – the chuck is reverse thread. Hit the allen key rapidly with a hammer to break it free from the spindle.

Continue to remove the chuck. Remove the front gear cover and/or separate the two halves of the drill case, depending on your model. Remove the spindle and separate the cam plate, leaf spring, change plate, steel ball, gear with keyway and retaining ring. Remove the bearing from the spindle with a bearing separator or puller. Take out the compression spring and install on the new spindle. Install the bearing on the new spindle by placing a socket on the inner race of the bearing to avoid any damage to the new bearing. Tap in place with a hammer.

Reinstall the retaining ring, gear, steel ball, change plate, leaf spring and cam plate. Reinstall the spindle assembly on the drill case and fasten the case back together and/or reattach the front gear cover. Secure all fasteners and thread the drill chuck back on the spindle. Open the chuck and insert the allen wrench. Clamp the chuck down on the allen wrench then turn it to hand tighten the chuck. Reinstall the chuck screw and tighten it, remembering it is reverse thread. Reattach the handle.