Older Radial Arm Saw Problem

Doug Miller

Member
Messages
277
Location
Hardinsburg, KY
I spend most of my time in Lathe Land but have a problem with my radial arm saw. DeWalt/Black&Decker radial arm saw. Quit working all of a sudden. Changed the start capacitor with no success. Guy at the B&D store was pretty sure that I would find that the switch was bad. I've now pulled it out of the saw. One button on, one button off. Four poles on the back side labeled L1, L2, 1, and 2. Any suggestions on how to test this switch? I can put it back into the saw if necessary.
 
No Larry. One switch, two buttons. You push the on button in and the off button pops out. Push the off button and the on button pops out. It's like they see-saw back and forth.

Can I check resistence between poles or do I check power going through the poles? And which poles?
 
On I get zero resistance between L1,1 and L2,2.
Off I get zero resistance between L1,1 but infinity between L2 and 2

Pretty obvious that all 4 poles need to be cleaned well.
Having no resistance between L1 and 1 with the switch off doesn't sound right does it?
 
...Having no resistance between L1 and 1 with the switch off doesn't sound right does it?

I believe if those poles are for the common leg, then perhaps it's intended to be that way. It's only necessary to break the connection on the hot leg to turn the motor on and off.

Since you are getting no resistance on both sides of the switch when it's in the 'On' position, I don't think the switch is the cause of your problem. It sounds like it's doing its job. Out of curiosity, have you checked L1 to L2 and 1 to 2? Both should show infinite resistance regardless of the switch position. If not, then perhaps we're incorrect suggesting the L1 to 1 and L2 to 2 orientation.
 
Is it a TEFC motor? If it is, just take off the back over the fan and centrifugal switch and blow out with your air hose. Might work. I learned that here for a piece of my equipment. Simple and never had a problem again.
 
The double pole switch is to make your saw safer by disconnecting both sides if you use it wired for 240. If you wire it for 120, the white wire should go to the side that doesn't turn off (L1). If it is wired for 240, it will work, but it isn't real safe since part of the motor will be hot (120 volts above ground) when the saw is off. For 240 volts I would replace the switch.

If you have an ohmmeter, you probably also have a voltmeter - you should read the line voltage between 1 and 2 when it is on, and zero when it is off. You should have the line voltage between L1 and L2 all the time. If not, check the plug and outlet.
 
Thanks guys. I have to go to Louisville tomorrow. I'll take the switch by and see what the guy there says about it. If it is bad, I know B&D wants $30 for it. Couldn't I get a double pole single throw switch from the hardware store for $10 and be just as well off other than fit and finish?
 
...Couldn't I get a double pole single throw switch from the hardware store for $10 and be just as well off other than fit and finish?

As long as the switch is rated for the voltage and amperage of the saw, no problem. My Harbor Freight DC has a "custom" three-position toggle switch for the power. The factory switch died, and the only switch the local Radio Shack had in stock that would handle the power was an On-Off-On switch. I didn't care, since I just needed one side of it. (It stays on all the time anyway, since I use a remote for the DC.)
 
The $40 switch went out on my Sears RAS, and I used a <$10 switch for a year or more, but fit and finish was ugly, and it didn't have the "remove part of the switch so the kids can't turn it on" feature. I finally sprung for the $40 factory replacement, and have hard feelings for the rip off price each time I use it.

Since the ohmmeter test sounds like the switch is working, I suspect the plug or power cord, or other wiring, more that the switch. I would put a jumper wire around the L2 to 2 contacts that change when you use it... that should make the saw run continuously. If it does you need the switch, but if it doesn't, it is time to play with the wiring or other parts.
 
May I interject some ideas? "Stopped suddenly" Is it on a GFI and might it have tripped?


Tripped a breaker? broken wire in the power cord, etc.

Did you smell the factory smoke?

Can you give the blade a spin and then hit the switch and it start (sign of a capacitor)

Did you look to the red button on the backside? May have tripped and need a reset. Perhaps clean the switched , resets etc.

If it is on a GFI Often a trip will kill it.

I would make sure there is a source of electric power before addressing the guts of the motor.

I too have one of these Dewalt devils....
 
In order,
Yes, no
no, no, no
no
tried it, no
tried it, no
again, no
did, 120 at socket

I'm still not so sure, but am starting to believe that the switch has to do with the problem. I'll find out when I take it in to the shop. If that's not it, I'm guessing that I'll have to somehow pack the entire saw into the shop. What a pain that's going to be.
 
Lots of people giving advice so I have just stayed out of it. But here are the logical steps.

1. Check for power at the outlet. Plug something else in there to and power it up too! You can have 120 volts and no amps.

2. Check your power cord. Measure the resistance from the plug to the end of the wire where it attaches to the switch (and ground). That will make sure the cord is not the problem.

3. Check the resistance through the switch. Make sure you have no (or very little) resistance through the switch.

4. Check the cord from the motor connections to the switch. Same thing, no or very little resistance.

If all that checks good then the odds are it is the motor.
 
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