Overload switch keeps tripping - what would you do?

[dspeer]

I own a 1.75 hp Jet table saw that's about 20 years old. It seems like a good saw, but it has a problem: The overload switch trips much too quickly. At moderate feed speed in 1 1/2 inch oak, I can rip for about 10-12 inches before the switch cuts power. 

I am noticing that when the motor starts, the lights on the same circuit flicker. And cutting though oak, they keep flickering under load. I use only the cord on the saw to plug into the outlet (110V), not extension cord. 

I am completely electrically challenged and have no idea. Is this a sign of the motor going bad? Or is it just the switch?

What do I need to do in order to remedy this ?

Any help would be greatly appreciated.

Dietrich

[tablesawtom]

From what you have said it kind of sounds like your motor needs attention. A 1 3/4 HP motor should cut oak with no trouble. A bad switch shouldn't cause lights on the circuit to dim and flicker during the cut. A bad switch or even a bad compasitor would give you start up problems. Usually the biggest electrical draw is at start up  on a motor, not during the cut.

Tom

[Cecil]

I would start with an air blast.  Then I would check the brushes.

Beyond that I would take the motor to a local repair shop.  We have a fairly good one local to me, but your mileage may vary.

[dspeer]

From what you have said it kind of sounds like your motor needs attention. A 1 3/4 HP motor should cut oak with no trouble. A bad switch shouldn't cause lights on the circuit to dim and flicker during the cut. A bad switch or even a bad compasitor would give you start up problems. Usually the biggest electrical draw is at start up  on a motor, not during the cut.

Tom

[daddo]

The breaker or the switch on the motor?

Read the amp and voltage rating on the motor plate.

If it's a capacitor motor- check or replace the capacitor.
Check the wires at the motor for good connections. (Bad connection, burnt connection, frayed wires)
Check the voltage to the saw while it is running. (Bad breaker or connection or wire size)
Check the amp draw while it is cutting.
Check that motor turns freely and no bearing noise or runout. (Belt off)
Check all the other bearings as in the arbor/pulleys for free turning.

This is a good start.

[Phil Thien]

Does the motor labor/slow down before the unit trips?

Are you using a sharp blade? Have you tried a thin kerf blade?

Unplugged, does the blade turn easily? If you start and then turn off the saw, it spins a while, doesn’t come to an abrupt stop?

Have you tested voltage at the receptacle?

Do you have an ammeter?

[mike4244]

I own a 1.75 hp Jet table saw that's about 20 years old. It seems like a good saw, but it has a problem: The overload switch trips much too quickly. At moderate feed speed in 1 1/2 inch oak, I can rip for about 10-12 inches before the switch cuts power. 

I am noticing that when the motor starts, the lights on the same circuit flicker. And cutting though oak, they keep flickering under load. I use only the cord on the saw to plug into the outlet (110V), not extension cord. 

I am completely electrically challenged and have no idea. Is this a sign of the motor going bad? Or is it just the switch?

What do I need to do in order to remedy this ?

Any help would be greatly appreciated.

Dietrich

I am no expert on electrical myself. First try plugging into an outlet on another circuit. Sounds like your saw plus other things, lights radio  etc  may be overloading the circuit. You can use an extension cord to get to another circuited receptacle if needed.12/2  wire should be okay.
I doubt the motor or the switch is the problem, just an overloaded circuit. Also the receptacle may not be getting full 110/120 volts. Does the motor get hot? Are you using a rip blade when ripping oak? 

mike

[TDKPE]

Since the question is what would I do, as already suggested I would slap an ammeter on a conductor and compare to the nameplate current while cutting (have someone else watch the meter).  I would also check the voltage at the receptacle while cutting (same thing - have someone else do it), which is easy if it's running on 120V and plugged into a duplex with both receptacles on the same circuit.  That's the first thing I'd do, and it would take a whole minute to do it.

Is this a new phenomenon?  Is it plugged into the same receptacle it has always been plugged into?  Are you doing something different in ripping oak?  

Lights flickering on the same circuit means a) there are other loads on that circuit (those lights that are flickering, for starters), and b) it may be a 15A circuit, as it's more common for lights and receptacles to be on 15A circuit than a 20A, though that's hardly proof of anything, and a 15A circuit for such a big motor being pushed hard is just not good.  

What's letting go, the circuit breaker, or the motor's internal overload device (little red pushbutton reset - it shouldn't be automatic on a saw).  

A 1-3/4 hp motor is about the most you can theoretically put on a 15A 120V circuit, and that's not counting voltage drop in the wiring which caused it to draw even more current.  Realistically, it should be on a 20A circuit, with nothing else on it, and short supply wiring from the panel to the receptacle.

[Roly]

I would expect the lights on that circuit to flicker when the motor starts.   Does it sound normal when it starts up and runs without a load ?   Does it cross cut ok ?   Could it be saw alignment be causing the wood to bind up ?
  Roly

[Pondracer]

Since the question is what would I do, as already suggested I would slap an ammeter on a conductor and compare to the nameplate current while cutting (have someone else watch the meter).  I would also check the voltage at the receptacle while cutting (same thing - have someone else do it), which is easy if it's running on 120V and plugged into a duplex with both receptacles on the same circuit.  That's the first thing I'd do, and it would take a whole minute to do it.

Is this a new phenomenon?  Is it plugged into the same receptacle it has always been plugged into?  Are you doing something different in ripping oak?  

Lights flickering on the same circuit means a) there are other loads on that circuit (those lights that are flickering, for starters), and b) it may be a 15A circuit, as it's more common for lights and receptacles to be on 15A circuit than a 20A, though that's hardly proof of anything, and a 15A circuit for such a big motor being pushed hard is just not good.  

What's letting go, the circuit breaker, or the motor's internal overload device (little red pushbutton reset - it shouldn't be automatic on a saw).  

A 1-3/4 hp motor is about the most you can theoretically put on a 15A 120V circuit, and that's not counting voltage drop in the wiring which caused it to draw even more current.  Realistically, it should be on a 20A circuit, with nothing else on it, and short supply wiring from the panel to the receptacle.

Everything this guy said.  You could be starving it on the supply side, but if you are using the same receptacle you always have and this just started then maybe not.  Depends on what else is plugged in.  Had a problem like this at work, we kept tripping an alarm on a UPS and thought it was a battery.  Turned out it was my coffee maker.