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Delta Unisaw Won’t Shut Off

1953 Views 12 Replies 11 Participants Last post by  Kudzu, 
Elyons
Need some help everyone,
I just inherited a 1963 Delta Unisaw 34-450. The saw is running great; I cleaned it up and have been using it for a few weeks. Tonight, for whatever reason it wouldn’t shut off and and I had to pull the plug.

I’m assuming it’s the switch, but I’m new to machine electrics. I’m reading it could be the motor as well. I pulled off the switch cover plate; nothing seemed off, connections were tight.

Thought I’d reach out for ideas and suggestions on a replacement switch if that is the issue.
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G
The motor will not keep running if the switch has cut off all electricity to it. But if it does, then you need to figure out how/why and patent that immediately.

It is possible that dirt/debris has gotten in the switch and preventing proper movement of contacts. Try cleaning. If that does not work replace switch.

George
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Tony B
I'll bet one of your wires is shorting to the cabinet.
In one of my old shops we had a ghost operating the Delta Contractor's saw. It would turn on and off by itself. It was a loose wire shorting to the frame.
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DrRobert
It’s not the motor. It’s not stopping b/c the juice didn’t stop flowing.

Need to know what kind of switch. Magnetic switches are very reliable, but if it’s original, it’s almost 60 years old….

Does it have the original motor? Is the switch wired directly to the motor or does it go to a box? Many of that era were 3 phase, often there’s a 3 phase converter rather than change motor. You can tell by looking at the motor plate, plus the old 3 phase motors were much bigger. I mention this b/c I believe on that type setup the switch controls the converter not the motor directly.

Post a pic of your switch and motor.
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TimPa
i can't imagine the problem being anything but the switch, as it controls the electricity to the motor circuit. when unplugged, remove the cover and try blowing it out with compressed air. then try spraying electrical/electronic cleaner into the switch anywhere it allows you to. operate the pushbuttons. spray some more. re-assemble and try.

still doesn't work? order a new switch.

edit
NOTE: THIS IS A SAFETY ISSUE, SO PLEASE DO NOT OPERATE SAW UNTIL THIS IS RESOLVED!
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woodnthings
Elyons said:
Need some help everyone,
I just inherited a 1963 Delta Unisaw 34-450. The saw is running great; I cleaned it up and have been using it for a few weeks. Tonight, for whatever reason it wouldn’t shut off and and I had to pull the plug.

I’m assuming it’s the switch, but I’m new to machine electrics. I’m reading it could be the motor as well. I pulled off the switch cover plate; nothing seemed off, connections were tight.

Thought I’d reach out for ideas and suggestions on a replacement switch if that is the issue.
Click to expand...
What Tim said^.
I had a magnetic switch go bad on my 220 bandsaw. Those are quite expensive, so I just replaced it with a 2 pole 2 throw switch capable of 220 volts, much cheaper.
A home shop does NOT need the "restart" protection of a magnetic/relay type switch, in my opinion. If the power goes out during the day, then all light and tools with shut off. If it goes out at night same will happen, but if it comes back on within a minute, the machine will restart with an ordinary non-magnetic switch, but you'll have enough time to manually shut it off ....... if you can find it!
A paddle switch is much safer regardless of the type like this:
www.grizzly.com

Paddle Switch 120/230V at Grizzly.com

This dual voltage, single-phase Paddle Switch is rated for 120 volt, 2 HP motors up to 35 amps and 230 volt, 3 HP motors up to 20 amps. The large paddle makes this switch ideal for emergency shut offs. Fits basic electrical boxes.
www.grizzly.com www.grizzly.com
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Domo
First I'd try compressed air into and around the switch as you move the switch back and forth WITH THE SAW UNPLUGGED!!!!!!
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S
The unisaw is made for industrial applications. Therefore they put a magnetic switch on them. That way in the event of a breaker tripping someone doesn't walk the length of a warehouse and flip the breaker and have the saw come on. Someone unsuspecting may get hurt if it seems to come on by itself. Using the saw in a home shop you could replace the switch with a simple toggle switch. Looks like a normal light switch but is made for 220 volts. You just may need to relocate the box so you don't accidentally bump the switch turning the saw on. If though you want to put the saw back like it was note how the switch is wired and remove it and take it to an electrical supply shop for a replacement. Just expect the price to run in the 50-100 dollar range.
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F
It sounds like the contacts on the mag switch may have welded themselves together, may just be a matter of replacing them.
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Elyons
4
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Thank you everyone for the replies. For simplicity I’ll respond to most questions at once.

- It is completely the original switch/motor. It’s a bullet style repulsion induction motor.

- I blew out the switch (unplugged), toggled/tested. No change.

- I don’t believe these style switches are magnetic, is there a way to confirm?
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TimPa
do you have a multimeter, and know how to use it?
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Rick Christopherson
I'm glad I was too lazy to respond earlier, because I would have totally looked like an idiot. I have not seen a Unisaw like this before, especially that note about reversing the motor.

Does the motor restart when you plug it back in to power?
-- If so, then disconnect the wires to the On/Off switch and see if it still restarts when plugged in. (switch fused contacts)
-- If not, ......hmmm....I haven't a clue.

Pop those 2 covers off the back of the motor and show me what is under them. There's some funky stuff going on back there that I haven't heard of on a 3450rpm motor.
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Kudzu
Very rare to have the original switch that works. No, that is not a magnetic switch either. My 1946 Unisaw has the same switch and still works to my surprise. My 1946 shaper came with the same switch but has been replaced. But as everyone else has said it has to be the switch.

UNLESS somehow the wires have shorted around the switch. But if you have a meter you can test that switch really easy and confirm it is bad. There is no way for the motor to run unless power it going through (or around) the switch.

There are people like me that really like the original switch and some of them have taken them apart and repaired it. I have never tried. But I bet some of the guys would love to have it if you have to replace it.

Your lucky too to have the old R/I bullet motor. I am betting that was motor came off a shaper since it is reversable. It maybe say 1-1/2 hp but it has more torque than the newer 1-1/2 hp motors. More like a 3 hp today. Again, highly sought after by some of the us. You have a good saw there.
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