Dumb question about magnetic switches

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Forum topic by Bertha posted 04-14-2011 08:19 PM 1304 views 0 times favorited 2 replies Add to Favorites Watch
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13528 posts in 2692 days

04-14-2011 08:19 PM

My vintage band saw is equipped with a replacement magnetic swith (Square D). The seller asked me if I knew how to use a magnetic switch and I nodded dumbly. There is a start and a stop, what more could there be to it. Am I missing something? Is it like a diesel that I’ve got to build a fire under? I’m pre-troubleshooting because my wiring is bad.

Many thanks in advance.

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

2 replies so far

View superstretch's profile


1531 posts in 2692 days

#1 posted 04-14-2011 08:23 PM

How Can This Be? What is a Magnetic Starter?
Magnetic start switches are different from normal on/off switches. They are used on medium and larger power tools as a safety device. Among other features, they prevent the tool from remaining in the “on-state” after it is unplugged or a power loss occurs. (To test whether your tool has a magnetic starter or not, turn the tool on, unplug the tool, and if the tool begins running when you plug it back in, then it is NOT a magnetic starter.) A Magnetic starter uses a spring loaded, self-sustaining relay.

What this means, is that when you press the ON button, you physically push a set of contacts together which starts the tool. At the same time, there is another set of contacts which supplies power to a small magnet. This magnet “holds” the contacts together until either the power gets turned off, or you physically separate the contacts by pressing the OFF button.

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My guess would be that if you had a temporary power outage, tripped breaker, etc, when it came back to life, it wouldn’t destroy anything nearby it.

-- Dan, Rochester, NY

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13528 posts in 2692 days

#2 posted 04-14-2011 08:36 PM

Thanks Stretch! I’m wondering why he “warned” me about it, maybe he was just bragging that he added it. I didn’t give it a second thought until the saw wouldn’t start due to bad wiring. I thought there was something magical about the switch that would excuse a neutral being connected to the ground, it appears now:)

-- My dad and I built a 65 chev pick up.I killed trannys in that thing for some reason-Hog

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