Monday, October 5, 2009

Radial Arm Saw Fix for a Scary Problem

Yesterday afternoon, in the middle of constructing cold frame lights, my Radial Arm Saw stopped working. This saw is the central machine of my shop: I use it to do just about everything from ripping to chopping to mitering. And though replacing it would be possible, it would hurt—in more ways than one.

Before I turned it off, the saw worked fine through all the cuts I performed, and it did not slow or stop until I turned the switch. There was no smoke or hot smell, and the cuts were not through overlarge or dense material. But when I turned the switch again the saw just buzzed; the blade moved almost imperceptibly in the wrong direction but did not turn at all. After a few tries with the saw still buzzing—turning off, turning on; unplugging, replugging; pressing the reset button, and poking the blade with a stick (probably a dumb idea as I think on it)—there was a little click and the saw no longer reacted to the switch at all.

Perhaps everyone in a situation like wonders if they caused the problem somehow. I wondered, because this once, for the first time, I had turned the switch in the opposite direction from usual. It had to be just coincidence that the two events occurred together. But it was the only thing I could think of that might have caused the saw to stop.

I took out the switch, checked the connections, and reassembled it. Still nothing. My saw is wired with a plug and socket between the switch and the motor so the motor can be easily taken out of the arm and taken elsewhere. I thought "Maybe I can plug in something else and test the switch?" but the plug was on the switch side and the socket on the motor side. So I swapped the two and was ready to test the "broken switch" theory. I plugged in and ran a shop lamp and then the shop vacuum: the switch was definitely OK.

It was in the motor. Again I pressed the red reset button several times and tested the saw with no result. It seemed I was going to have to open the motor to get this fixed, but I'd been in the shop for much of the day and I was frustrated: I decided I wasn't going to get it fixed that day.

Later I had a chance to talk with my friend Sean, who suggested I visit the Old Woodworking Machines forum to look for (or ask for) help. Sure enough, I found a comment string that suggested some possible actions that didn't involve taking apart the motor.

Back in the basement I pressed the reset button harder. There was a promising click. I plugged the saw back it and it was back to buzzing (but still not turning). I was making progress! On to step 2. I rapped on the motor housing—especially near the reset switch—with the handle of a screw driver. Believe it or not, after that the saw worked.

So for the moment, all is well again.

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Anonymous John said...

That's a great looking classic saw! Glad you got it working again. My grandad was a contractor and I inherited many of his classic woodworking tools. I had a scary incident with a smoking switch on one of them that was just sitting in the shop plugged in. Five more minutes and it would have been a fire. I unplug everything and turn off breakers to others. Do yourself a favor; don't trust them plugged in.

December 3, 2009 10:09:00 AM EST  
Blogger rookster said...

Thanks for the comment, John. I generally don't leave it plugged in anyway, just because I want as many steps as possible between me and a spinning blade.

I don't think that mine will catch fire like yours did, but I'll still be more consistent about the unplugging!

December 3, 2009 11:47:00 AM EST  
Anonymous Damien said...

Looking at the article, I checked, (some) dewalts have a single phase capacitor start. When the capacitor is disconnected the saw will hum and overheat fast, until the overheating security kicks in. You can manually push the rotor forward (don't do that with a saw blade). Once the saw is on speed the capacitor is not needed any more. Success with your saw.

February 8, 2010 4:16:00 PM EST  
OpenID rolandgsl said...

Sounds like a sticking centrifugal start winding switch. A good blow out with compressed air may help.

February 22, 2010 10:32:00 AM EST  

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