Grinder: Trips the Power Source Circuit Breaker
Does your grinder trip the power source circuit breaker? This can be frustrating, but we are here to help. The likely parts that are causing the issue are the power cord, carbon brushes, switch, armature, field, and extension cord. Read our repair guide for tips on how you can fix your grinder yourself, saving you on time and money. Refer to your owner's manual for advice tailored to your model.
Now, take out the brushes. For some models, they will have caps on the side for easy removal of the brushes. Remove the armature from the field, inside the grinder. Clean the armature with electrical contact cleaner. Once cleaned off, inspect the armature for burn marks which indicates a short. If any burn marks are present, replace the armature.
Check the commutator for...
Now, take out the brushes. For some models, they will have caps on the side for easy removal of the brushes. Remove the armature from the field, inside the grinder. Clean the armature with electrical contact cleaner. Once cleaned off, inspect the armature for burn marks which indicates a short. If any burn marks are present, replace the armature.
Check the commutator for any missing bars. If there are, you must replace the commutator. Clean the commutator with 600-grit aluminum oxide sandpaper by rotating the armature only in the travel of direction to provide a smooth, even surface. Use a plastic scribe to clean in between the bars on the commutator.
To check for a bad armature, you can perform then 180-degree test. With the armature removed from the unit, stand it up on a bench. With an ohmmeter, attach the two ends of it 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 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.
Remove the but securing the armature gear, followed by the armature gear. Remove the gear box cover and bearing by placing the cover on top of a bench vice, with the bench vice open enough for the cover to sit on. Tap the top of the armature shaft with a rubber mallet to remove the bearing and cover. Install the cover and bearing onto the new armature and use a socket that only makes contact with the inner bearing race, to avoid damage. Tap it in place with a hammer.
Reinstall the armature gear and nut. Some armatures are sold with all the parts intact, already as one unit. Slide the armature into the field, inside the grinder. Reinstall the gear box assembly and then the brushes. Reapply the tension springs and reinstall the lower cover back on the grinder. Reinstall the grinder wheel cover and the handle.
For some models, remove the side cover and then the paddle and lock button. Remove the second side cover. Now, locate the brush holders and pull the tension spring to the side and take out the electrical connector and then the brush. Replace brushes 1/8 of an inch, or less, as they are worn out. Install into the brush holder and reposition the spring on top of the brush. Reconnect the electrical connection and then reattach the side cover....
For some models, remove the side cover and then the paddle and lock button. Remove the second side cover. Now, locate the brush holders and pull the tension spring to the side and take out the electrical connector and then the brush. Replace brushes 1/8 of an inch, or less, as they are worn out. Install into the brush holder and reposition the spring on top of the brush. Reconnect the electrical connection and then reattach the side cover. Reinstall the lock button and paddle and close with the other side cover.
There are also models that have brush caps located on the side of the grinder, for easy access. Remove these with a screwdriver and pull out the brush. Brushes 1/8 of an inch, or less, need to be replaced. Insert the new brush into the cap and reinstall the cap.
On some models, there will be two lower covers, a paddle and a lock button to remove. Other models, you will need to remove the brush caps located on the side of the grinder in order to remove the brushes. Pull the armature out of the field and remove the baffle plate. Remove the power switch by holding it in the OFF position, pressing the switch lever...
On some models, there will be two lower covers, a paddle and a lock button to remove. Other models, you will need to remove the brush caps located on the side of the grinder in order to remove the brushes. Pull the armature out of the field and remove the baffle plate. Remove the power switch by holding it in the OFF position, pressing the switch lever forward. When you hear the click, you can remove the power button. Disconnect the wire connections and remember where they attach to for reassembly. Remove the field from the grinder housing. You may have to hang the housing on the table to free the field as it may be tightly secured. Clean the field with electrical contact cleaner and then inspect the field for burn marks, indicating it is shorting out. If you notice burn marks on the field, it probably needs to be replaced.
You can perform one simple test on the field, to check for continuity with a multimeter. Set the multimeter to the ohmmeter and place a lead on each end of the field. If the reading is infinity, the field is bad and requires replacement. Install the field into the body of the grinder, in the correct position for the wires to reattach to their proper connections. You may need a long screwdriver to position the wires, with the openings, during the installation of the field. Reconnect all of the wires back to the switch and brush holders. Push the switch lever forward and reinstall the power switch, making sure the lever on the switch catches the lever. Reinstall the baffle plate and then slide the armature back into the field. Reinstall the gear box assembly back on the grinder and then the brushes back into the holders. Reapply the tension springs, or the brush caps, and install the lower cover. If applicable, reinstall the two lower covers along with the paddle and lock button.