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,
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
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
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.
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 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.
who needs to hear the rest of that story
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.
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.
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.
"Replace?" Better to change the switch than to repeatedly need to change
"Repairable?" That depends on the design of the switch, and how/why it is
being 'balky', and exactly how the unexpected power-up came
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"
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.
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.
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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