Delta Unisaw question (motor stalling)

[John Prexta]

My Unisaw is about 5 years old now. I'm a home hobbyist. Lately (the last year or so), whenever I run (rip) several boards, it'll shut down on me in the middle of a cut. I'll take the board out, wait 5 minutes or so, and I'll be good to go again. Seems to me the motor is overheating? Some sort of thermal overload? Store I bought it from said the motor isn't the best - should I look to get a replacement motor, or is it something in the switch? Any thoughts or ideas would be appreciated.

[Duane Meadows]

Possibly a bad motor... I'd check the start/run cap first though. If you have an clamp on ammeter, check the current draw. If its normal could be a bad overload(unlikely) or a bad magnetic switch.

[Mike Bain]

I had a problem like that and it turned out to be a loose wire in the switch.

[Chris Rosenberger]

Take the cover off of the magnetic starter. The inside should look similar to the picture below.
If yours looks this, there will be a dial similar to the one in the lower left corner of the one in the picture.
Make sure the arrow is pointing to a number at least equal to the amperage listed on the motor name plate.

http://i123.photobucket.com/albums/o303/chrisrosenb/Shop%20Album/20100126_3.jpg (http://s123.photobucket.com/user/chrisrosenb/media/Shop%20Album/20100126_3.jpg.html)

[John Prexta]

Yes Chris mine looks quite similar to that. I did check that, and checked all connections making sure nothing was loose. For the last several months, it would just shut down after several long rips. It seems after I wait for it to "cool off" it's fine again, then stops again - quite annoying - that's why I'm thinking of just replacing the motor.

[John McClanahan]

My guess is that Unisaw motors are expensive. I would take it to a motor repair shop and tell them what it's doing. It may have an internal thermal overload that's failing.

John

[Charles Lent]

+1 Take the motor to a motor repair shop and have them look at it.

While the motor is out you should also check the arbor bearings and the belts for wear or damage and replace them if you find anything wrong. If they are more than 10 years old they should be replaced even if they look OK. Buy the belts as a set, because they are matched. The bearings are cheaper if bought from a local bearing supply. The number on the side of them is all you will need to get the correct ones. Replacing these now while the motor is out is cheap insurance for a trouble free future. That motor is heavy and hard to get to so it's not something you will want to do very often.

Charley

[Chris Rosenberger]

Yes Chris mine looks quite similar to that. I did check that, and checked all connections making sure nothing was loose. For the last several months, it would just shut down after several long rips. It seems after I wait for it to "cool off" it's fine again, then stops again - quite annoying - that's why I'm thinking of just replacing the motor.

The reason the motor shuts off is because the overload in the starter is tripping. The overload automatically resets after a short time, just as yours does. Be sure the overload dial is set to the correct amperage. There was a problem with Delta setting the overload at an amperage lower than the amperage of the motor.

[Jerry Thompson]

I bought my Unisaw 25 years ago. It shuts off when in use sometimes but I cannot relate it to time in use. thickness of the lumber etc. It may go months without cutting off. I wait until I hear a little "Click" and it is good to go. I just put in a new main panel as the old one would not allow me to get homeowners insurance. I will see if this changes things. Only time will tell.

[Duane Meadows]

I would still check the motor current to be sure its is correct. Setting the overload to allow it draw to much current is not a good idea!

[Chris Rosenberger]

I would still check the motor current to be sure its is correct. Setting the overload to allow it draw to much current is not a good idea!

I did not say to set the overload so it would draw more current. I said to make sure the overload was set to the correct amperage.

[David L Morse]

That saw probably has a TEFC motor. If the fan vents get blocked by a buildup of sawdust the motor can overheat.

The thermal overload switch in the motor is there to protect your shop from burning down. It does not to protect your motor from being ruined. When the thermal overload protection trips it's best to find and fix the problem immediately. Repeatedly pushing the motor to high temperatures will significantly shorten it's life.

[Lornie McCullough]

The first thing that popped into my head is: are you using an undersized extension cord to run the saw?

Lornie

[Duane Meadows]

I did not say to set the overload so it would draw more current. I said to make sure the overload was set to the correct amperage.

I fully realize what you said and what you meant. However presumably if he has had this saw for 5 years, it did at one time work properly. It's probably the technician in me, but the actual amp load would be the first thing I would want to know. If he is cutting 12/4 stock and never done that before(or something similar), I could perhaps see it being set wrong from the factory, but....

If the motor current is normal and the motor isn't unduly hot, yes I would look at the mag switch. If the motor current is too high, then it is pretty much a motor issue. Low supply voltage could be an issue as well, but there again... measure it! Kinda of what troubleshooting is all about!

[Bruce Wrenn]

First the dumb question, is your blade SHARP? Second, take a volt meter, and check voltage to saw with it running and while ripping. You will need someone to watch the meter, unless you have a recording meter (think $$$). I think you will find you are experiencing voltage drop, and thus overheating.

[Lee Schierer]

The first thing that popped into my head is: are you using an undersized extension cord to run the saw?

Lornie

I had the same thought. My other thought was what changed in the shop in the past year in regards to the saw.
Here are some ideas:
Is it plugged into a different outlet?

Is there anything else on that circuit that could be running at the same time lowering the voltage to the saw.

What voltage does he read at the outlet when the saw is running. What voltage does he read at the starter when the saw is running?

[Lee Schierer]

The first thing that popped into my head is: are you using an undersized extension cord to run the saw?

Lornie

I had the same thought or the cord could have been damaged in the past year. Is the cord cold, warm or hot immediately after the saw stops running? A warm cord would indicate it is too small for the saw.

I also thought that he needs to consider what has changed in his shop in the past year that might be causing the problem. Some ideas are:

1. A very dull or gummed up blade.

2. Did anything get added to the circuit like an air conditioner, compressor, etc. that might be running at the same time he is making cuts.

3. What voltage does he read at the outlet when the saw is running?

4. What voltage does he read at the saw when it is running.

[Marvin Wilson]

The thermal overload is located in the magnetic starter not the motor on this saw. The top section is the power contact and the bottom section where the dial is located is the thermal overload. You may have to set it as much as 2 amps above recommended to get it to work right again. Example 22 instead of 20, try it one amp at a time. The overloads can 'drift' and the dial indicator may be out of sync with the internals. Everything about this problem can be expensive so don't pass up the simplest solutions or you may end up throwing away good money. Get out the manual and start digging it probably has an answer.