Cordless Drill: Smoke From Tool

The armature is the power-producing unit of the motor. Overworking the drill can cause the armature to break down, burning out the windings. To check the armature for damage and continuity, you will have to remove the armature.
Take out the screws securing the cover to the case and remove the cover. Now, remove the two transmission screws on the side of the drill that the cover is attached to. Take off the hold-downs on the motor and then lift the motor and transmission assembly out. Separate the armature and field away from the transmission. Pull the armature out of the field and check for a heavy build up of dirt. If so, clean with thinner, dry thoroughly and test for continuity.
To check for a bad armature, you can perform the 180-degree test. With the armature removed from the unit, stand it up on a bench. With an ohmmeter, attach the two ends to both sides of the commutator to measure the resistance of the windings. As you move it around the commutator, the reading number is not important. You are looking for a consistent reading, indicating all the windings are good. If it varies radically, reading zero or open circuit, then the armature is not good.
Another test is reading. If the ohmmeter reads a zero or open circuit, then that indicates a bad armature. The last test is a bar to ground test, which is done by placing one lead of the ohmmeter to the tip of the shaft of the armature and the other to the commutator. If the armature is bad, install a new one. Install the armature into the field. The field will have a notch on it, indicating the front, which faces the transmission. Reattach it to the transmission. Install the one brush on the housing and then reinstall the motor/transmission assembly back in the housing. Install the other brush into the cover then reinstall the cover back on the housing. Reinstall the two transmission screws and the end cap.

A battery is a device consisting of one, or more, electrochemical cells with external connections provided to power electrical devices. If the battery is smoking then there is internal damage somewhere. Batteries cannot be repaired. Replace the battery with the proper one recommended for your power drill.

The carbon brushes supply electricity to the armature by rotating on the commutator. As the carbon brushes wear down, they can spark more. This can cause a heavy carbon build up between the brushes and the commutator, causing the drill to smoke.
To fix this, you will need to replace the brushes and clean the commutator, which will vary slightly on drills. For some cheaper models, the motors are sealed so you will have to replace the motor.
To do so, begin by removing the end cap on the drill. Remove the two screws securing the transmission to the motor, on the side of the transmission, where all the screws are facing upwards on the case that secure it to the housing. Next, remove the screws securing the cover on the case and take the case off. One of the brushes is located in the cover. Remove the holder from the case and take out the screws securing the hold-down brackets on the motor and lift the motor up, taking out the other brush holder. Remove the brushes from the holder and install new ones.
With the motor removed from the drill, separate it from the transmission assembly and take out the armature from the field. Clean the commutator with fine sand paper, lightly, or use a file. Insert the armature back into the field.
Marry the motor back together with the transmission and insert the brush holder back in the housing. Now, install the second brush holder into the cover and reinstall the cover back on the housing and tighten down. Reinstall the two transmission screws, securing it to the housing. Reinstall the end cap and battery.

A motor is a device which turns electrical energy into kinetic energy. It involves magnets and conductive wire. The electricity creates a current in the wire, which creates a magnetic field and causes the magnets spin. The motor contains the armature, commutator, brushes and field. If any of these parts fail they can cause the motor to smoke.
You will need to remove the motor from the drill to diagnose. For some cheaper model drills, all you can do is replace the motor as they are sealed units. These motors are disposable. On the more expensive models, or heavy-duty built drills, the motor comes apart to be repaired easily. Remove the end cap from the drill and take out the screws securing the cover to the housing. Remove the screws securing the transmission to the housing. Take the motor and transmission assembly out of the housing and separate the motor from the transmission. If the motor is sealed, throw it out and replace it with the proper one for your model. To diagnose motors that are repairable, refer to the “symptoms” on this page for proper repair procedures.

The switch provides power to the motor when pushed. If the switch has become worn, it can short out and produce smoke. Signs that a switch is going bad will occur when the drill begins to not work every time, when pushed. This will eventually worsen with use, to the point where it can smoke.
Remove the end cap on the drill. Next, remove the two screws holding the transmission to the motor on the side of the transmission where all of the housing screws are facing upwards on the case, securing it to the housing. Remove the screws securing the two halves of the case together and separate the halves. Remove the other two screws on the transmission that secure it to the motor. Remove the screws securing the hold-down brackets on the motor and then the motor and transmission assembly. Remove each wire from the brush holder and do not mix up where they originally attach.
Remove the switch from the drill. Inspect the inside of the switch for burn marks. This will indicate it is shorting out or has completely shorted out. The switch will need to be replaced as it cannot be repaired.
Install the new switch into the housing and reattach the wires to the correct brushes. Now, insert the brushes back into the drill housing, ensuring all wires are tucked into the wire channels. Reinstall the motor and transmission assembly back in the drill housing. Reattach the hold-down brackets and secure them with the screws. Reinstall the two screws securing the transmission to the drill case and then the second brush holder into drill. Put the case back on the housing, followed by the other two screws securing the transmission to the motor.

The holders hold the brushes in place on the commutator. If the holders are damaged, they may not be able to hold the brush in the proper position on the commutator, with the correct pressure. This can cause excessive sparking leading to a smoking tool.
Remove the end cap on the drill. On some drills, all that is required to reach the brushes and holders are simply to just remove the end cap.
On other drills, you will need to carry out the following steps. Remove the two screws holding the transmission to the motor on the side of the transmission where all the cover screws are facing upwards on the housing, securing the case to the housing. Next, remove the screws securing the cover on the housing and remove it. One of the brushes is located on the cover. Remove the holder from the housing. Take out the screws securing the hold-down brackets on the motor and lift the motor up and remove the other brush holder.
Inspect both brush holders for damage and wear on the brushes and replace as needed. If they are in physically good shape, then clean thoroughly. Reinstall the one brush holder back in the housing, ensuring it is in all of the way. If the brush holders are not all of the way in or positioned a little out of alignment, it can cause the problem to continue.
Reattach the wire and then reinstall the motor and tighten down the brackets. Reinstall the second brush holder in the cover and reattach the wire. Put the cover back on the case and tighten down the screws. Put the transmission screws back in and reinstall the end cap.