Multi-Tool: Grinding or Squealing Sound

If the housing is worn, the armature could move around, rubbing and spinning freely against the housing. This can cause grinding and squealing sounds, accompanied by a vibration, and the possibility of a burnt-plastic smell. Check the outside of the housing for any visible signs of damage and then remove the collet nut, collet and the front cap. Remove the brush caps, brushes and separate the two halves of the housing to inspect the inside of it. Remove the power cord connector and any screws holding down the motor assembly. Pick up the motor assembly with the switch, circuit board and cord all together, as one unit. Inspect the inside of the housing for marks, indicating the armature is moving and causing problems. If these symptoms are apparent, replace the housing. Place the motor assembly with the switch, circuit board and cord into the new housing. Install the hold-down screws and the power cable connector. Secure the two pieces of the housing together and screw the front cap on an the collet. Install the brushes and brush caps.

A bearing is a device use to enable rotational, or linear, movement and reduces friction and handles stress at the same time. Bearings are a wear item and, over time, will need to be replaced. When a bearing wears out, it will produce a grinding, growling or a rumbling sound and will be accompanied by a vibration.

To check the condition of the bearing, you will need to access them. Remove the collet nut, collet and unscrew the front cap. Remove the brush caps and pull out the brushes. Remove the housing screws and separate the two halves. Take out the power cable connector. Remove the screws holding down the motor assembly and pull the motor out. Separate the motor from the switch and the circuit board. Slide the armature out of the field. Remove the rubber ring on the lower bearing. Spin the bearing to determine their condition – bearings should spin freely, with no noise. If the bearing spins rough, makes noise or has play, then install a new one.

To replace the lower bearing, use a bearing puller. Wipe the shaft clean and install a new bearing into the shaft, tapping it in place with a hammer and a socket. The socket must only make contact with the bearings inner race to avoid damaging the bearing during installation. Reinstall the rubber ring.

To replace the upper bearing, use a bearing separator to remove it. Place the separator under the bearing then place the separator on top of an open bench vice and tap on the armature shaft with a rubber mallet, or brass hammer, to avoid damage to the armature. Hold on to the armature so it does not fall to the floor, when its free. Clean the shaft and install the new bearing by placing a socket on the bearings inner race and tap it into place. Slide the armature back into the field. Reconnect the switch and the circuit board and install into the housing. Reinstall the hold-down screws and the power cable connector. Rejoin the housing back together and screw the front cap back on. Install the collet net with the collet. Finally, reinstall the brushes and caps.

Some multi tools have a coupler that connects the armature to the drive shaft. If the coupler breaks, or wears out, the multi tool will make a grinding/squealing sound. The motor will also turn, but the shaft will not or may turn slower. To replace the coupler, remove the collet nut and front cap from the tool. Remove the brush caps and pull the brushes out. Separate the two halves of the multi tool by removing the screws and pulling apart the two halves. Lift up the drive shaft and remove the broken coupler, then slip the new one onto the armature shaft and drive shaft. Place the drive shaft back in the housing. Close the housing and secure it. Install the front cap, collet nut, brushes, and brush caps.