Table Saw Electric Motor Problems

[Angie Orfanedes]

Need motor advice, please.

My old Craftsman saw has some motor problems. I have been using a 1 HP 110v compressor duty motor I bought from Northern Tool about six years ago - it is an open motor. Worked fine until six days ago. Just a humming and no shaft rotation. Checked the capacitor as well as I could with a volt-ohm meter per web instructions, and it seemed okay. Blew it out with compressed air, but no success.

So I replaced it with a Leeson motor, also compressor duty - but 2 HP (also 110v) this time - it worked about six days and quit yesterday....humming, trying to start rotation, until it blows circuit breaker. I am sure I made the right connections for 110v.

1. I realized that a fully enclosed fan cooled motor would be better, but even the original motor on this saw was open - is that my problem?

2. Is the compressor duty motor for some reason not able to live on a table saw? Maybe starts per hour is too high for this motor?

So last night I got a replacement motor replacement...also 2 HP compressor duty, open, and I wonder if I should install it.

Thanks for any help/advice.

[Dave Wagner]

I would check your power source, outlet, breakers and wiring and make sure it's not something simple that's affecting the motor(s). Try a different outlet, flip the breaker back and forth, make sure it didn't partially trip or something.

[Mike Cruz]

I come from the school that says replace with what the factory put on or better. I don't THINK that TS's should be run on compressor rated motors. I BELIEVE they are intended to run on continuous duty. Both of mine have been continuous, as are my BS, Planer, and Jointer. I THINK compressor duty motors are for compressors and would stick to a continuous duty for your TS. Enclosed is always better when dust is present, but if the manufacturer put on an open, then open ought to be fine. My two cents...

[Curt Harms]

Connect the "bad" motor to another circuit? Could there be something in the saw's electrics causing a problem? It seems strange for two motors to have the same problem.

[Howard Miller]

Here are the Lesson table saw motors.

http://www.leeson.com/Products/products/ACMotors/1Phase/woodworking.html

[Howard Acheson]

What is the amp rating of your motor at 120 volts? A true 2 HP motor running on 120 volts should be plugged into a circuit with a capacity of more than 20 amps.

[Joe Scharle]

You could have a low voltage situation, causing the start windings and capacitor to draw a lot of amps. I'll assume that the caps have blown for the moment, so see what the voltage drops to, at the new motor terminal when you press START and what it is before pressing START. You should see 120V, a quick dip, then return to 120V (no load). You should not have over 50ft of wire between the motor and the main panel on a 120V run. A low voltage (brown-out) situation will eat motors. A friend had a similar problem for years. His saw was in his garage, not 10 feet from the panel. However, the electrician had wired the box with a 100ft spool and left it coiled in the ceiling!

[Gary McKown]

When I lived in Louisiana, my old 1975 Craftsman (1 hp, open case) would occasionally suffer the same symptoms you describe - hum, trying to rotate. If I gave the blade a (careful!) whack in the direction of rotation when humming, it would start running fine. The first time this happened, I replaced the capacitor to no avail. Compressed air did not work, either. I finally took the motor apart at the end with the switch and found humid sawdust gumming up the works. Cleaned everything well, reassembled, and it worked as expected. After one more episode, I learned to turn the vents on the motor downward and installed a cardboard shield to keep dust from spraying into the vicinity. I also vacuumed or blew it out frequently.

Since moving away from the swamp and keeping up the cleaning regimen (plus adding dust collection), it has not clogged up again in 25 years.

[Josiah Bartlett]

Do you have an AC volt meter? Check the voltage available on your circuit while running another motor. Then check the voltages at other sockets available in your shop. Watch and see if the lights get noticably brighter or dimmer when you run a tool. You may have a bad neutral. I had one go bad in my garage a couple of years ago. It was ok most of the time since I was running balanced loads since all my big tools are 240V. I didn't notice, until I was bogging a 2hp router and the lights got really bright and the router stalled. It turned out that I had some corrosion and a loose screw on the main panel end of my garage feeder.

[Tom Veatch]

...
So I replaced it with a Leeson motor, also compressor duty - but 2 HP (also 110v) this time - it worked about six days and quit yesterday....humming, trying to start rotation, until it blows circuit breaker. I am sure I made the right connections for 110v.
....

Sure sounds like a defective start capacitor. If you're sure the cap is good, look at the centrifugal switch that connects/disconnects the cap to the windings. If sawdust or other debris has jammed the switch in the open position, that would present the symptoms you describe and could easily happen in an open frame motor.

[Angie Orfanedes]

Thanks for all the helpful hints. The new 2HP motor was on a 20 amp circuit - maybe that was the basic problem...although I wonder if it was drawing more than 20 amps why didn't the circuit breaker trip the first time I ran it...oh well.

I decided to return the 2HP motor and I have ordered a totally enclosed 1 HP motor.

[Pete Bradley]

Compressor duty motors are cheap because they aren't designed to run continuously. They're designed for a duty cycle with short runs followed by cool down time. It could be you're getting what you paid for, and It's possible that your wiring is contributing to the problem by creating a voltage drop. Given how quickly you're killing motors, I don't think the traditional cap/switch issues are likely culprits.

[Rich Neighbarger]

Here is a good read on electric motors. Duty cycle and Service factor ratings.

http://www.electricmotors.machinedesign.com/guiEdits/Content/bdeee1/bdeee1_3.aspx

[Angie Orfanedes]

Just to finish the story, I ordered a totally enclosed 1 hp motor from Grizzly last Thursday, and it arrived today (three business days). It was already set up for 110v, so it was a fairly quick install. Works great. It cost about $140 with freight, which was cheaper than the open motor I bought locally. I continue to be impressed with Grizzly's prices, quality and service.