Multi-Tool: Bad Vibration

A bearing is a device used to enable rotational, or linear, movement and reduces frictions and handles stress at the same time. When a bearing wear out, it will produce a grinding, growling or a rumbling sound and will be accompanied by a vibration. Remove the collet nut, collet and unscrew the front cap off of the multi-tool. Remove the brush caps, located on the side, and take out the brushes. Remove the screws and separate the two halves of the housing. Remove the power cable connector and take out any screws holding down the motor assembly. Now, pull the motor out. Separate the motor from the switch. Slide the armature and field apart from each other. Remove the rubber ring on the lower bearing. Spin the bearings to determine which one needs to be replaced. Bearings should spin freely, with no noise. If the bearing spins rough, makes noise or has play, it needs to be replaced. To replace the lower bearing, use a bearing puller. Wipe the shaft clean and install a new bearing in the shaft and tap it in place using a hammer and socket that only makes contact with the bearings inner race, to avoid damage to the bearing. Reinstall the rubber ring. To replace the upper bearing, use a bearing separator to remove it. Clean the shaft and install the new bearing by placing a socket on the bearings inner race and tap it in place. Slide the armature back in the field. Reconnect the switch and the circuit board and install in the housing. Reinstall the hold-down screws and the power cable connector. Rejoin the housing back together and screw the front cap back on and install the collet and collet nut. Reinstall the brushes and caps. 

The carbon brushes are in constant contact with the commutator, supplying power to the armature. These brushes wear out over time and will need to be replaced. Worn brushes can cause a vibration in the motor. Check the condition of the brushes by removing the brush caps. Brushes measuring 1/8 of an inch, or less, are worn. Look for abnormal wear too. One brush wearing out faster than the other, or is damaged with cracks and chips, it can also cause vibrations. Replace brushes if you notice these symptoms or anything else out of the ordinary. Install new brushes and then tighten the caps.

If the housing is worn, the bearings could spin freely against the housing and cause vibrations and a burning smell of plastic. First, check the outside of the housing for any signs of damage that could impact the multi tool. To check the inside of the housing remove the collet nut, collet and unscrew the front portion off of the multi tool. Remove the brush caps and brushes. Separate the two halves of the housing and then remove the power cord connector. Remove any screws holding down the motor assembly. Then, pick up the motor assembly with the switch, circuit board and cord all together, as one unit. You are now going to inspect the inside of the housing for marks where the bearings are placed, indicating a free-spinning bearing against the housing. Make sure the bearing itself is not seized as this can cause the same symptom. If the bearing is seized, look under “armature bearing replacement” for further instructions on how to replace these bearings. Place the motor assembly with the switch, circuit board and cord into the new housing. Reinstall the hold-down screws and the power cable connector. Secure the two pieces of the housing together and secure the front piece on and install the collet nut, with the collet. Install the brushes and caps.

The multi-tool has a rubber ring on the rear bearing to absorb vibrations. If this rubber ring is damaged or has worn out, it will not be able to absorb the vibrations as good. To replace the rubber ring, remove the collet nut, collet and unscrew the front cap off of the multi-tool. Remove the brush caps and pull the brushes out. Remove the screws securing the two halves of the housing together and separate the housing. Remove the power cord connector and then any screws holding down the motor assembly. Separate the motor from the switch and circuit board. Remove the rubber ring from the bearing and install a new one. Connect the motor back to the switch and circuit board. Reinstall the motor assembly into the housing and secure it. Reattach the power cord connector and then reassemble the housing. Reattach the front piece with the collet and collet nut and reinstall the carbon brushes and caps.