It’s your table saw and all that happens is a hum. You go to spin up the blade but nothing turn. That hum sounds right through your floor and will make your heart skip a beat.
What do you do? Do you jump to slam the reset button? The answer is typicaly quick and simple.
It isn’t often a bad motor. If it was a bad motor, there would be no sound because the electrical system has life in it. The noise is mechanical system being blocked.
That distinction mean money. You avoid wasting money replacing good components. First though you have to identify source of blockage.
Fixing A Humming Table Saw Motor
Why Table Saws Hum Without Turning
It’s usually the capacitor. That provide a surge of power to turn the motor on. Without that, there’s no starting torque for the motor.
It’ll draw current but just hum. Single phase motor do this a lot. Motors used by brands such as Grizzly or Jet are single phase.
Diagnosing a Bad Capacitor
Examine the capacitor for any leaks or swelling. If it appear damaged replace it. The fix is often immediate and replacement is inexpensive.
To check the capacitor with a multimeter set your meter to capacitance mode and touch the meter leads to terminal. Your reading should be more identical than what is written on the cap. If not, it’s dead.
Do not bypass the capacitor. Running the motor without a capacitor burns out winding. You may be able to get the motor going by turning the blade handle manually.
This won’t last and will cause more problems later. It could also be mechanical in nature. Resin or wood chips can becomes bound to the blade.
Checking for Mechanical Binding
The table is out of alignment. Or perhaps the arbor bearing have seized. To test this, unplug the saw.
Can you turn the blade by hand? It should spin freely with just a little resistance. If not and it’s gritty or locks up then you’ve got a mechanical issue.
Replace the bearing or clear away debriss. That’ll eliminate the humming sound. Another reason is overheating cause.
Resetting Thermal Protection
Newer machine like a Ryobi or DeWalt have a thermal protection built into them. When the motor reach a certain temperature, the thermal protector will cut the power. Sometimes the switch can becomes stuck so that the motor remains energized without being connected.
Allow the motor to cool and then try pushing the reset button (if there is one on your machine). If it trips immediately look at ventilation. Is the air intake obstructed?
Replacing Worn Carbon Brushes
It is possible that you have an older model and worn out carbon brushes is causing your problem. Worn carbon brushes might be the issue in older Craftsman or Delta models that uses universal motors. Universal motors has a commutator that the carbon brushes comes into contact with.
When the brushes get worn all the way down to their spring, they no longer touch the commutator. Now the motor cannot close the circuit so it will make a humming sound. Check the brush holders.
Are the brushes short? Replace them both, don’t ever replace only one brush. You want matching wear for balanced operation.
This avoid premature failure. Always keep safety in mind throughout. Keep it unplugged when removing panels.
Never reach into the guts of the saw when plugged in. Even after being unplugged, capacitors can holds charge and need to be discharged properly before touching. If you’re unfamiliar with anything call in a pro.
Be patient and work your way through the diagnosis. Begin with the most likely causes. Is it the capacitor?
Are there bindings? It’s typically easy and cheap to repair. After fixing it, you’re cutting again.
Your confidence is restored in your tools. The whirring becomes that familiar sound of a blade spinning. The stress melts from your shoulder muscle.
It’s time for you to go back to work. Next time you hear that sound remember this process. Relax, address the basics and fix the problem systematically.