Table saw safety / blade changes
Here is a safety question. Is it safe to change the blade on a cabinet saw without pulling the plug from the outlet? Here are the facts:
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I just installed my new cabinet saw. On my previous contractor’s saw, which ran on 100V, I always pulled the plug out of the outlet, when I wanted to do a blade change. The new table saw runs on 220. Not only is the plug harder to pull out of the outlet, but the latter is also harder to reach. The saw has a magnetic switch, with a recessed push-button to turn the saw on, and the switch can be locked in the “off” position. Hence, with the switch locked, there does not appear to be a risk of accidentally turning the saw on. In these circumstances, is there any chance that the saw may accidentally start, while I am changing the blade or installing a dadoset?
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As ususal, thanks in advnace for your insight.
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Guy L.
Replies
Frenchguy -
Mine is only a personal 'attitude', if you will, but I don't care how fail safe the switch mechanism might be, the fact that power is available to any machine makes it a potential dissmembering mechanism. I unplug the table saw, jointer, etc., any time my hands have to come in contact or even in close proximity to the cutters. The only exception is the drill press. I suspect it's a matter of how valuable you consider your associated body parts.
You should definately cut the power to the saw when doing any maintance. I have seen a couple posts here over the years about magnetic switches spontainously engaging! Sounds nuts, but I trust the posters. If the plug is hard to get to (or even if it isn't) you should have a "disconnect" near the machine. I think it is suposed to be 20 feet by code. I use regular breakers, they are not really rated for disconnect use but they are cheep and effective. The down side is that they will wear out prematurely if you flip them a lot. Your local Big Box store will have a manual disconect desinged for airconditioning units. They only cost $20 and they are mounted in an enclosure and ready to install, They provide no over current protection. There are special disconnect breakers that are rated for that use as well.
Having said all that I never bother to kill the power to the saw when changing blades.
Mike
I hard wired my 5 HP PM66 to a disconnect with in arms reach of the saw. Always pull the the plug on that baby when changing blades ect....
There is talk on other forums of shutting down/securing the power to the whole shop when not present to avoid tampering and posible electrical fires.
"I hard wired my 5 HP PM66 to a disconnect with in arms reach of the saw." Tyler, could you explain specifically what you did? E.g., did you simple put a separate outlet near the saw that you could unplug? I'm not following what you mean by "a disconnect."
Have been thinking for quite awhile now that it'd be nice to have an outlet right on the saw that has a cord running to the wall outlet, and the saw would plug into it. I always unplug the saw when changing blades!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Jamie -A "disconnect" is a box with a pullout plug that cuts the power to the piece of equipment it controls. On my DC and air compressor, both 220v machines, the electrician installed these disconnects. They're both 'hard wired' into the circuit eg they have no plug per se. Of course one can always throw the breaker but the disconnect is the code way to provide a way to 'disconnect' the power.On something like a table saw I personally don't see the need unless it's a high amperage machine that's hardwired into its circuit. For most saws like you and I would be using, an ordinary plug of the appropriate configuration for the voltage/amperage should be sufficient I'd think. Plus having it easy to get to.Don't know if you noticed in my shop how I have the power pedestals under the saw's outfeed table. One for the saw and another fourplex for the planer and whatever. Got tired of trying to keep the accumulated sawdust and dirt vacuumed out from around the unistrut the electrician used to support the boxes and conduit in the slab so I carefully masked off around the boxes and built a little form up tight against the face of the outlet and poured a little concrete pedestal around them. Really easy to sweep around now.
If you want to visit the ER with your fingers in a bag, don't unplug the power to your equipment when you change cutters or make adjustments. It takes a while to find them in the dust collector, especially when your body is involuntarily going into shock. You will feel pretty smart every time you explain what happened. Actually, you will be a genius the moment it happens. Getting them sewn back on isn't a given and if they do, they won't work very well or look too good. Don't worry, you'll eventually get the hang of wiping your butt and picking your nose with a stub. Are you getting my drift? This is no joke! Move your plug to a convenient place.
Beat it to fit / Paint it to match
Well, you have a wicked sense of humour! I hear you loud and clear. Though it makes me wonder why some people wire their saw directly into their electrical panel.
Thanks everyone.
Guy L.
"Though it makes me wonder why some people wire their saw directly into their electrical panel." 'Cause "some people" ain't too smart.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
FG
In some situations hard wiring of machines is the only logical option. I have 3 machines wired this way (by a registered sparkie) but all have 2 switches in line. It's just the way things are done on 415V 3 phase circuits here. As an additional safety (& convenience factor) the saw arbours are bored to take a tommy bar which drops thru the table & locks the spindle. End result is that blade changing is easier but more importantly the saw arbour can not rotate even if the saw is turned on.
Don
it makes me wonder why some people wire their saw directly into their electrical panel
You can use the breaker as a disconnect. There are no exposed connectors on a breaker, so it may be even safer than pulling a plug.
Not sure what this does to breaker life. If there's no load when you flip the switch, I don't think you'd be contributing to conductor pitting, etc., so it wouldn't have the same sort of life-shortening effects that, say, testing a GFI does. Just mechanical wear.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Actually you shouldn't use the breaker as a disconnect.
Code requirements vary, but typically a machine of 220V or higher "should" be hardwired to a fusible disconnect switch (one-arm bandits) within 6' of the machine operator's position. Often another disconnect is required at the splitter by the main panel.
When I worked with big commercial 14" and 16" machines, I always pulled the disconnect before changing blades because of the ordeal involved.
That said; my 220v tablesaw is hooked up with a 575v rated flexcore twist lock connection. And I rarely unplug it. Stupid? Maybe, but its how it is.The older I get, the better I was....
Actually you shouldn't use the breaker as a disconnect
My code inspector (this is for a residential installation) said I could and should do so. IIRC (I finished my installation a month or so ago), the NEC says the disconnect must be within 20' and visible and in the same room; it explicitly says the disconnect can be in the panel.
Why should you not use the breaker as a disconnect where code allows? Does it cause mechanical or electrical breaker failure?My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I once worked in a factory as a security guard. It was my job to turn the lights on in the morning for the workers. The factory had no other switches that the breakers. These were turned on and off each work day, some times seven days a week. These were old breakers, but I'm not sure how old. Scores of them. The factory evidently thought it was cheaper to operate them than to put in regular switches.
My breakers cost me about $17 and take me three minutes to change out. If I have to replace one every three years, how long will it take before the cost of replacing breakers equals the cost of putting in $100+ disconnect switches (add boxes, labor, inspection) for each of the five circuits I put 220v tools on?
The equation changes drastically if using the breaker in this way may make my breaker fail in an unsafe way, like my old Zinsco breakers were prone to do. This is why I asked what might happen if I use the breaker as a disconnect. Money isn't everything.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Please don't take this as an argument because I might very well do as you are inclined. Perhaps the breakers would go bad in twenty five years instead of three. And perhaps there is no danger of them causing trouble because of use. Of course, I am theorizing and I think you are to an extent. Most of us just don't know.
I had a 50 amp breaker go bad just through age. It kept tripping when we had two burners on the kitchen range. You should have thrown that Zinsco panel out before it was installed. I am in the apartment business and have inherited a bunch of Federal Pacific panels. I have been junking them out at every opportunity. They are just plain dangerous. Best of luck with your wiring. I pull the plug out and hang the plug within view to remind myself that it is pulled.
I've changed my mind based on what I've heard from folks here. When the equation was $100 + box, about $130 total, I figured I'd just use the breakers. Now that it appears I can do the whole thing for $30 and mount it right on the saw, I think it's too easy to pass up. Honestly, I'm not doing it to spare the breakers, I'm doing it to save myself the walk to the breaker box every time I touch the blade.
Couldn't agree more on the Zinsco. Piece of crap, it was in the house when we bought it. When I took it out, under one of the breakers there was a HUGE pitted burnt area from a previous arc fault. Previous owners just took out the melted breaker and popped in another one.
Replaced it with a Square D QO, and I'm MUCH happier when I go to sleep. It's not for me so much, but my five kids and wife live in this house.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
"I hear you loud and clear"That's one of the nicest things anyone has ever said to me, Guy!
A simple solution is to attach a receptacle box on your machine close to the switch. You can then run a short cord with a plug from the switch box. It will be right there when you need to disconnect.Beat it to fit / Paint it to match
Why take a chance? .. Pull the plug!
It's a machine and i do not trust them. They are designed to spin and cut things. With the power attached they have the possibility of spinning and cutting things. I like my fingers where they are and I do everything to keep them that way. So i'd say unplug the saw.
Has anyone heard of a cabinet saw just activating without anyone touching the power switch? Ever? I've tested mine, and if power goes off while the saw's running, when power's restored the saw doesn't start up.
When I'm working in the shop with my boys, I pull the plug before messing with the TS blade. When I'm on my own, I don't usually pull the plug.
I might start slipping a cotter pin or something through the power switch lock though, so no Rube Goldberg chain of events can let me push in the switch with something falling off my TS, trapped between switch and leg, pressing in the recessed switch.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
I've had a couple of machines that started by themselves, both had mechanical switches. One was a circular saw, it actually gave me a shock a couple of times before it decided to come on by itself. A switch wire had worked almost loose and was grounding across a screw in the handle, that's where the shock came from, as my skin contacted the screw. The other was a RAS that came on when a board was dropped on the table. Magnetic switches are electro magnets, you know what happens with a magnet. It only has to get close to iron and it will suck it in. A slight push or inadvertent hit to the on button may cause it to do it's thing. Any switch mounted on a machine is subject to vibration as well as the wear of constant cycling and perhaps accumulation of debris. They are just as likely to fail as any other thing. In safety, we guard against that one chance in ten thousand. Just when that number will come up is like playing the lottery. The consequences of having a switch failure while your hand is holding or in the cutters path is potentially very serious. I have a reconstructed thumb from an accident with a hard wired machine and a magnetic switch. I would not recommend the experience to others.Beat it to fit / Paint it to match
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7286.16 in reply to 7286.15
Has anyone heard of a cabinet saw just activating without anyone touching the power switch? Ever? I've tested mine, and if power goes off while the saw's running, when power's restored the saw doesn't start up."
I'll agree with you that I never heard of a saw starting without hitting the switch, but if its plugged in there is always that chance. A million to one shot sort of thing but it only takes one time.
Well, someone else already kicked in and said he's seen it twice. I may have to reconsider my habit. But I'll probably use the breaker instead of unplugging or buying disconnects, unless someone comes up with a reasonable explanation why that's bad.
My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Edited 12/14/2005 2:53 am by John_D
We once had a small band saw with a magnetic switch that would start up if the machine was bumped into, needless to say, we replaced the switch.
Using a circuit breaker to disconnect a machine is an acceptable practice, at least in a home shop, and certainly better than nothing. The down side is that breakers wear out and can become unreliable when used a lot, I've seen this happen several times. Usually a worn breaker will start to trip too easily at loads that shouldn't set them off.
Using a disconnect switch, which can be mounted right on the machine, saves wear and tear on the breakers, and, by being very convenient, encourages safe practices. A disconnect switch costs around $20.00, and comes mounted in its own box, so the installation is simple, no harder than wiring a simple light switch.
John W.
Edited 12/14/2005 12:07 pm ET by JohnWW
Edited 12/14/2005 12:12 pm ET by JohnWW
The down side is that breakers wear out and can become unreliable when used a lot, I've seen this happen several times. Usually a worn breaker will start to trip too easily at loads that shouldn't set them off.
This is a failure mode that doesn't bother me. The Zinsco problem is the opposite -- the breaker won't trip when it should, clearly a much worse failure.
Using a disconnect switch, which can be mounted right on the machine, saves wear and tear on the breakers, and, by being very convenient, encourages safe practices. A disconnect switch costs around $20.00, and comes mounted in its own box, so the installation is simple, no harder than wiring a simple light switch.
If it's that cheap, it's a no-brainer. I looked on McMaster and disconnects for 25A were about $100. Can you point me to a supplier, or maybe I'm just looking for the wrong thing.My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
Look at air conditioner disconnects rated at 60 amps, they sell for around $20.00. The AC type switches have a connector block that you pull out to make the disconnect. You can find these at Home Depots.
A single phase, 240 volt, 30 amp, fused, throw handle type of safety switch from Square D, shows in my Grainger catalog for $40.90 plus another $5.00 or so for the fuses. Their part number is 1H247. Grainger also shows a similar switch for under $30.00 but I'm not sure it is rated for motors. I've seen similar switches sell for less, check with an electrical supply house or look in other catalogs. You don't need a fused switch.
John W.
I think I will visit the Borg and get an AC disconnect. Another benefit is, I can disable the TS by just taking that removed part and putting it out of reach.
I wasn't arguing that others shouldn't use disconnects, or unplug. Just reported my own practice... which looks to be changing thanks to good advice and assistance.
Thanks!My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
A power cord from the ceiling with a plug about a foot above and just beyond the extension table is far easier to use and pretty foolproof if the dummy (er,saw operator) will use it. Just make sure to install it with strain releifs at both ends(per code).
Not sure why you're saying unplugging is easier or safer than having a disconnect... ?My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
That statement was in response to something about a plug being hard to get to. Perhaps I misunderstood something. Personally, I like it if I have to double check to see the plug laying on the side table below the plug-in on the drop cord. Idiot proof if you know what I mean.
For a bit of further reinforcement, tie a bit of red ribbon about the cord by the connector. Kinda looks like what one may see on certain horse's tails. ;-)
Hey ED, if you need that reinforcment, than it is all yours.
"I've tested mine, and if power goes off while the saw's running, when power's restored the saw doesn't start up." That's because it has a magnetic switch. I'll guess that in most "hobby-shops" you'll find very few tools that have magnetic switches with this power-interruption safety protection. I guess most cabinet saws have it, and I know some of the better jointers do, but it is not standard in most equpment that falls in the class discussed here -- contractor saws, benchtop planers, 6-inch jointers, etc., etc.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
"Has anyone heard of a cabinet saw just activating without anyone touching the power switch? Ever?"
Well, no, but I've seen machines accidentally started when some joker has dropped a piece of wood onto the start button to "give you a surprise, ho, ho". I've also seen stuff dropped onto switches by flukey accident. Most industrial machinery in this part of the world has a rotary isolator switch on the machine control panel or at the rear of the machine which cuts power to all the live cables. Educational machines here are also required to have electro-mechanical interlocks on all the covers, something one or two big names like Altendorf do as a norm on machines like panel saws. But I still wouldn't depend on them. Rotary isolator switches can't be accidentally turned on and are lockable as well. If I buy a new machine and one of these isn't fitted it doesn't get used until one has been fitted. This allows me to lock and secure machines when they are out of service, etc. The same approach in a home shop would stop prying little fingers getting where they shouldn't when you aren't around.
As another poster said - you only get one set of fingers and they don't glue back on too easy, so take care of them.
Scrit
I seem to recall from a few years ago someone reporting an accidental saw start when a loose play-ball from a child hit the switch. Anything can happen! No way I change blades without unplugging.
A memory from back in the 1960's: Big thunderstorm in Kansas, out in the cornfields sitting in the dark living room of a farm house. I swear one of the table lamps lit up! Could this be? I've not been sure whether that was an overactive imagination or it really happened. There were no countable time delays between some of the lightening and the thunderclaps -- lightening strikes were at most a couple hundred yards away.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Could it be? Probably. The principle of induction is used in lots of things including dust extraction starter switches (like the Ecogate) where an induction coil is wound round a motor lead - turn the motor on, current flows and the secondary circuit is live, too. I've also seen a magic trick where two people were holding opposite ends of a flourescent tube with one of them also holding an earth rod. The other then touched the top of a Van der Graaf generator and the tube lit up - something to do with high voltage and almost no amperage I seem to recall. I reckon for your light bulb to come on you must have been awfully close, though.
Scrit
I don't think I followed all that, LOL. I guess I've always figured that if that lamp did flash on at the moment of a lightning strike it would've meant that some burst of electricity came through the wire and jumped the switch.
Speaking of lightning (apologies to the O.P.), my sister had a flash go through her house one day, from the handle of the front door, through the living room and dining area to the sliding glass door handle on the other side! Yikes! I don't trust electricity, no way, no how....forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
"you can take the girl out of the forest.."
Now tell me it wasn't lightening that did it...........
"Now tell me it wasn't lightening that did it..........." My mother, not much difference, LOL!forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
Hard to reach and hard to unplug: the saw is on a 220 circuit and won't affect your lighting, turn the breaker off and reset when you finish.
I want to take a moment to second what Hammer 1 said about fingers in a bag, in ice I hope. Before I burned out and dropped uot of health care to become a self employed carpenter and cabinet maker I worked for 31/2 years as a surgical tech at a hospital that was also known as " The Institute for Limb Preservation". Spent many a long night helping to try to save severed fingers, etc. Disconnecting a saw only takes a moment, each finger severed will need about four hours under the microscope if it can be saved at all(depends on what's left to work with). Rehab is a year or more, and there are no gaurantees that they will ever work again. Meanwhile you are unable to work, yet the usual bills still need to be payed plus your those for your ongoing medical issues. Microscope, surgery, surgeon, anesthesia, PT, etc.,etc.. After all of that, how are you going to earn a living now? I am sure that you got the point. Take a moment, unplug the saw. Trust me on this one. Might I suggest that you run the cord under the extension table and set up a drop cord and female plug to hang about a foot above and just left of the table? If it is easy to use then you will be more likely to use it; and it is real easy to look over and see if you did unplug it. Just don't forget to use strain releifs at both ends of the drop (per code). Mine were set up by a licensed sparky.
All of this is just a suggestion, they are your fingers to do with as you see fit. Best of luck.
Edited 1/8/2006 4:58 am ET by BigK
GoodOnYa for taking the time to write that, BigK.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
In reading this thread re accidents, i come across the phrase " one in a million". Well, if my math is correct, in a world of 6 billion people a "one in a million" chance could occur 6000 times a day!
Excellent point, and probably not far off the mark. Ouch.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)Another proud member of the "I Rocked With ToolDoc Club" .... :>)
I wouldn't do it with the saw plugged in. On my Unisaw the switch box is conveniently located so that I can turn it off with my thigh (off is a mushroom button). The on button is recessed in a shroud but I have things in my pockets (keys, etc...), and I'm sure that if I don't have it disconnected then I'll turn it on with the contents of my pockets. It too can be locked, but for me it's less hassle to unplug, plus it removes *any* concern from my mind. If there's a short or some other electrical failure it could just turn on. Stuff happens. The odds are probably small -- but the consequences are serious.
Last year my AC compressor stopped running. Found the breaker tripped. Reset it, and it immediately tripped again. Start tracing things down. Opened up the external disconnect box (Square-D QO with a switch that looks like a breaker but isn't) and there's melted plastic and aluminum. Stuff happens.
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