Scary Mag Starter Sw Failure = HAND-burger


Folks -
Okay, since the TS mishap last summer and my conversion into a "Safety Saint" - it has paid off, blade protection, eye protection, kickback pawls, hearing protection...... I have often wondered about the efficiency of unplugging the TS when changing blades - it has a magnetic starter... it seems that perhaps I'm being a bit anal about it... I've wondered.... but I *still* unplug equipment I'm working on.
Anyway, over at the school woodshop, they've got a 20" Jet planer with a mag switch... It has been "balky" and doesn't always start when you hit the "go" button... Yesterday, I was cleaning it up, adjusting the belt and checking it out... I plugged it back in, and was about 6 feet away and all of a sudden, it just starts right up! Holy You-Know-What! Jeeeeezus! What if that switch had been on the TS, and I *didn't* unplug it before mounting a dado stack? It puckers every orifice that I have just thinking about it!
Can magnetic switch be reliably repaired? Can I use this replacement from Grizzly? The planer is a 3 horse single phase...
(Amazon.com product link shortened)14040969/sr=1-2/ref=sr_1_2_etk-tools/103-8682843-3881407?v=glance&s=hi&n"8013
SO, guess what - I am going to keep unplugging equipment when I work on it, regardless. Scary.
Just thinking about what could have happened puts me in a cold sweat. 'preciate any feedback y'all can give about repair or replacement of that switch...
John Moorhead
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Unplugging the machine is not anal, it smart. You should unplug ANY machine before you stick your hands anywhere near a blade, cutter or belt. If you don't, sooner or later you will loose some part of your body. Even if you did not get cut by any moving parts, you could still obtain injury as you jerk back as a reflex from the machine starting. Things happen that you can't plan for when you leave it plugged in. Someone comes along and pushes the start button because they don't see you, you accidentally bump the start button, you drop something on the start button or as your example shows, something goes amiss in the starter and it fires on it's own. You should consider yourself very lucky that you had this lesson and no one got hurt. You mention that you had a table saw accident a while back. I had a accident with a jointer about 20 years ago, I didn't loose any digits, but I lobbed the side of last digit off of my ring finger off because I was working while I was tired and did something stupid.
The mag starters on most imported machines are not very good quality. If I were installing machines in any environment, especially a school shop, If I was forced to use imported machinery, the first thing that I would do would be to pull the cheap mag starters of and replace them with a real NEMA mag starter. A good starter will set you back $200 to $300 dollars but if you look at the guts of a quality NEMA starter and the guts of one of those imported starters, you would see that you get what you pay for. Furnas (Siemens), Allen Bradley, Square D all make good NEMA starter. The overload protection of the cheap starters is also not very reliable. It is very common to fry a motor on a machine with a cheap starter because of the poor overload protection.
Chris

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John Moorhead wrote: snip

Me too. Nobody has ever lost a finger to a machine that started up when turned off AND unplugged.
Dave in Fairfax
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Dave Leader
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Hell John - a real Safety Saint would have replaced the balky switch before getting into the situation you described. Come to think of it, even a non-Safety Saint would have done that.
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-Mike-
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Blow any collected dust out and clean the contacts.
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Mike -
Cut me a bit of a break, mate.... I had *just* gotten to the machine and discovered that the switch was punky. The kids haven't been "cleared" to use the machine, and I was testing it out to put it into service when I discovered the problem.
John

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Mike,
John seems a might sensitive this week. Not only did the machine challenge his manhood and authority in the shop, he had a middle-aged birthday, and still hasn't told us why Rose needed him to bring the pickup truck to the lunch date. Maybe it really was a load of organics that needed picking up.
<bseg>
Patriarch, who needs to hear the rest of that story
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You confirmed that an experience I had was not dreamed. I accidentally dropped something heavy on my table saw above the starter a couple of months ago. The saw started on its own. It scared the pee-turkey out of me. I've been pretty religious about cranking the blade below the table when not in use since that time. I also turn off the circuit breaker at night when I close up the shop.
Bob
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Take a hammer to the thing so it never gets used again and fit a real NVR switch, with an electrically pulled in contactor (i.e. the buttons are completely remote).
These US-style "mag starters" scare me. Their safety relies on the function of a tiny wear-prone ratchet tooth.
Using a contactor also means that remote control (good for DCs) or remote stop (knee-paddle stop switches) are easy to arrange.
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snipped-for-privacy@codesmiths.com writes:

Are you talking about the type of magnetic switch on a Unisaw. A big box on the back of the saw with the buttons on the front of the saw?
Brian Elfert
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John If I remember right you are now teaching a class. Great life experience to share with those kids... I worked at a cabinet shop for a few years and all the equipment had disconnects clearly in view of the tool. Even had locks so if you shut it off you locked the disconnect and put the key in your pocket. Even then I was uncomfortable changing blades as my entire life I have always unplugged the machine and stood on the end of the cord when hands entered the workspace..Now thats anal! You're doing just fine. As far as the switch the Grizz one is still low quality import. It's a school make them buy something safe and reliable.
Knothead
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"Replace?" Better to change the switch than to repeatedly need to change underwear!
"Repairable?" That depends on the design of the switch, and how/why it is being 'balky', and exactly how the unexpected power-up came      about.
The power-up event you describe indicates a _compound_failure_ of the switch -- well, assuming it was _not_ running when you (or whomever) pulled the plug. (If somebody pulled the plug _while_ it was on, and it started immediately _as_ you plugged it back in, it *could* be a 'simple' failure, one of two varieties, in the switch. Unlikely, but possible. Doesn't seem to be the scenario you're describing, however.)
It's also one thing if it powered up immediately, _as_ you plugged it in, and a different thing if it "randomly" powered up *after* it was plugged in. (Assuming it was 'off' when unplugged, _either_ event requires multiple failures, but the actual failures involved are *different*.)
"Powered up unexpectedly" is an entirely _different problem (and failure mode) from 'not starting when the button is pushed'.
By casual estimate, you've got *at*least* THREE _different_ things wrong in that switch.
Given the failure modes exhibited -- and the risk of injury should they re-occur -- I would *strongly* recommend that _any_ attempted repair be done *only* by a _professional_ who will GUARANTEE their work *and* who has adequate liability insurance in the event of a "post-repair" failure.
I'd regard that machine as "unsafe to be connected to the mains", PLACARD it with a notice to that effect, pull the plug, and *PADLOCK* it so that it _cannot_ "accidentally" be plugged in. If the plug has holes in the blades, a little lock through one of those holes works. If not, "something more creative" is called for.
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snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) wrote in

http://www.osha.gov/SLTC/controlhazardousenergy /
DAGS for lockout tagout to turn up links for suppliers. We have this stuff all over the labs here at work and yes, it is used.
Regards, JT
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Robert -
The machine does not power up upon being plugged in. It *frequently* started upon hitting the on button, and *always* turned off when hitting the stop. If it was plugged in, it would just start of its' own accord, and run until the stop button was hit. Way scary. I have removed the power cord from the machine pending replacement of the switch.
John
wrote:

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In the machine shop all the machines are hardwired, but each machine has one of those Square-D disconnects right on the wall next to it. They are the ones that look like a large metal box with a lever on one side. Also some of the machines (the lathes) all have two switches as well as the disconnect. One switch must be turned to arm the machine. The second switch is a lever on the carriage itself.
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