Folks,
I can’t find a previous discussion through search/advanced search so I’ll ask, but I’m surprised this hasn’t already been discussed to death.
In any case, I need to find a replacement safety switch for my tablesaw. I’ve googled every term I can think of and have found *very* few options, none I really like as they offer barely more than what I already have which is an ON and OFF button. Magnetics are not safer, apparently, as they can be “knocked” into “ON” with a good rap, not my idea of safe. But essentially, I want a bigger, much bigger, target on the OFF button.
Can someone point me to a source of Tablesaw Safety switches, hopefully multiple sources? I’ve already checked out Grizzly and, so far, they are the best options I’ve found but I’d still like to find a more substantial paddle on the OFF button.
Thanks,
KWL
Replies
Incidentally, a magnetic switch *is* safer. If, without a magnetic switch, you loose power (or pull the plug) with the switch on, once power is restored the machine will begin running.
For what it's worth, some folks have "modified" the power switch to accomplish what you want by hinging a vertical board over the switches so that the board turns off the saw when touched by your leg (or foot if you like). Drilling a hole in the board allows digital access to the "on" switch.
IMO, jim
You want a big stop button? I put a bunch of these in a school shop. They are large and often require a mounting bracket to get them in a good position. They seem like pretty cheap plastic but once set up, they do their job well. You just have to barely touch the stop plate.
http://www.reitech.com/products/info.asp?pid=6
Hammer1, Wow! Pretty amazing, as soon as I saw them I remembered seeing these several years back, completely forgot about them. But, more importantly, why are they not showing up in *any* of the many different searches I could think up? I've been looking for a while now. The marketing guys over there should definitely renew their google subscription. They'll certainly do the trick. Working alone, as many of us do, it doesn't take but two or three close calls to realize those switches need to be changed out for those that do not require a third, and substantially long, extra arm. Thanks, KWL
It was quite a few years ago when I ordered 50 Reitech switches. I replaced every switch I could in the shop. The company seemed to be having some problems but I don't know what they were or are. I was not getting my order filled and they were not returning phone calls. Eventually I spoke directly to the owner. He offered no explanation. I received all the switches I ordered but it took some time and a few irate calls. I thought my order was large enough to warrant some special attention. It wasn't easy Googling them up for you and I knew the company name and spelling. The switches worked as they were supposed to. In fact, you had to be careful not to accidentally touch one with your knee. I'm guessing the company had/has some financial or supply difficulties.Beat it to fit / Paint it to match
KWL: In industrial electrical setups there are large headed (mushroom head) stop pushbuttons that stay in (the off position) till pull out. These won't handle the load of a saw though, you need a motor starter with the coil feed by the on/off switches. You can get a manual starter with low voltage release which means no restart after a power failure. This is accomplished by a small coil that drops out on power failure and needs to be reset before the control circuit will activate the starter. These are pricey and the same effect can be had with any type of control switch: push buttons, toggles, selector switch feeding the contactor. The manual switch on my Dewalt 746 has a large "paddle" that can be found easyly with a knee or hand, it probably is availabe as a spare part and could be adapted to most any saw. Here are the part #'s from Dewalt. I'm not sure this is the compleate switch, you might want to give them a call.
Good Luck, Duke
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Duke, Thanks, I'm going to spend some time running down the info. you provided. Ideally I'd like this switch to be above the table and in a place where, as I feed stock in, my balance places me and my reach, at the most advantageous to safely keep an eye on the stock, the blade and still turn off the saw. I'll see if there's a ready solution based on your comments about components. I'll also check out the dewalt switch for availability, I had seen these in my searches but thought there *had* to be a after-market source for safety switches out there somewhere that were as good or better than the dewalt switches. Thanks, KWL
An electrical supply house should have what you want. McNaughton McKay is a good one. Square D probably provide one too.
Frosty
Thanks Frosty, I've checked out McNaughton-McKay, if they don't have it noone does, that's for sure.
Thanks,
KWL
KWL, For you to state, < Magnetics are not safer, apparently, as they can be "knocked" into "ON" with a good rap, not my idea of safe.> makes me wonder if you have tried this? If the answer is yes, you do need to replace the start button part of the switch.
I would suggest that you take a small rubber mallet, and rap the switch box, and see if you can make it come on without hitting the switch. You may find some peace of mind by giving it a test.
If not, I wonder about your electrical knowledge. I just thought I would mention that you can put as many off switches as you want on a magnetic starter, just keep in mind that you will need to use normally closed, wired in series.
KeithNewton, As to my "electrical knowledge" this isn't a discussion of my competency in any field, I'm looking for an after-market accessory with the help of this community. And while I was going to ignore it, personally, I don't care for the tone of that comment. If you'd like to educate yourself to the issue of magnetic switches accidentally coming on when impacted please feel free to use google search as I have done. KWL
KWL, I am sorry if my post was offensive to you. You did not fill out any of your personal profile, which gives no indication of your status as a woodworker or electrician. Most electrical problems are solved by process of elimination. I think Rick has given some good advice there, and if you go back and look, my advice was to give those switches a whack to see if YOURS can be turned on this way. If not, I would not worry about it. That is exactly how Rick found that there was a problem, and I suspect he will give you the same advice. There is another accidental start hazard that you and everyone else should be aware of. Most start buttons are just under the top on the right side. I carry my pocket knife in my front pocket, and have started one of my table saws accidentally by leaning into the saw top, The end of the knife handle went right into the start button while it was in my pocket. If any of you carry a knife, or wad of keys in your pockets, you should go out to your saws, and see if you can start your saws intentionally with whatever is in your pockets, just so you know whether you have the same hazard. Once again, I am sorry if it came off as a personal slam, I was only trying to be helpful.
On very rare occasions, a badly worn out or damaged magnetic switch can get to the point that it will turn on if hit hard, but you shouldn't dismiss them outright since they have a number of safety and motor protection features that make them very useful.
John White, Shop Manager, Fine Woodworking Magazine
Folks, Thanks to all for your replies.Hammer1, I was concerned when I visited their website, parts of it are in disarray. I wasn't left with the best impression but I'll call them before I proceed. As to Magnetic Switches, searching as I was for a replacement switch I first turned to magnetic switches as a first choice. But then I came across more than one discussion of how, when accidentally bumped, the impact *could* cause the switch to engage and turn on the machine. There are more than a few discussions on this issue, and while I understand the safety of the switch provides for turning off the power when power fails so that the machine does not automatically come on when the power returns, there is still that issue of accidental start. If there were a supplier that sold a magnetic switch that is explicitly stated as being designed to correct that problem then I would seriously consider that switch as a replacement and add a large paddle if it didn't already come with one. Thanks, KWL
JohnWW, I believe that, that magnetic switches are likely the safest available, but, as I know this is the next question someone will ask, here is the text from one posting on the web, not a discussion on a board, of which there are several, but just a posting to warn others: How Safe Are the Tools in Your ShopA Warning about Magnetic Starters
By Rick ChristophersonUpdate 1/20/99: I met with the Woodworking Products Manager from one of the largest woodworking companies in the country today, and mentioned the concepts presented below. He confirmed that his company had recently become aware of the problem, and is taking steps to correct it in current and future tool designs.
Several months ago, a question was posed by a woodworker regarding how his table saw could start unexpectedly, costing him several fingers during a blade change. At the time, it was assumed his knee had struck the recessed on-switch. While the recessed switch is designed to prevent this, it apparently happened: So we all thought!I have recently learned that any tool with a magnetic start switch can be started without actually striking the on-switch directly.This information probably comes as a shock not only to woodworkers, but to the tool manufacturers as well. Make no mistake, this is not intended to criticize tool manufacturers. This merely reveals an inherent problem associated with many magnetic starters.Where this all Began
Let me start by explaining how I came to this observation. A fellow woodworker had stopped over to my shop one Saturday to glue up some pine panels. While we were working at the far end of the shop, a board fell against the tablesaw. We watched in amazement as the saw started up on its own, even though it didn't look like the board had struck the on-switch. Puzzled; we went to the saw to investigate, and found a track in the dust on the saw's power cord where the board had struck. We just shrugged it off and went back to work.Later that day, I started to wonder about this further. So I went back to the shop, picked up the board, and struck the lower corner of the plastic case of the starter. The saw started up, and I was positive that I had not struck the on-switch itself. This was really odd.Suddenly, I started putting the pieces together. Several times in the past, my planer had turned on when I inadvertently banged into the starter with a sheet of plywood. I rapped on the junction box containing the magnetic starter. The planer started. Next, I turned to the shaper. I banged on the sheet metal pedestal next to the starter. On the third try, the shaper started. So I grabbed a screwdriver and opened the junction box of the planer's magnetic starter. With the actual starter exposed, I rapped on the starter's face with the butt-end of the #2 phillips screwdriver. The planer again started.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.The key to this, is that there is a small spring which keeps the contacts apart unless the magnet (called a solenoid) pulls them together. This is not a very strong spring, otherwise the magnet couldn't hold the contacts together when it needs to.Let's look at an analogy. The springs in your car are strong enough to support your weight when you get into the car, but if you jump on the back of the car, your own body weight could compress the springs to the point that the car "bottoms-out". The same is true with a magnetic starter. While the spring is strong enough to hold the contacts apart, if jarred, they will bottom-out, the motor will start, and the relay will be energized-holding the contacts together. That is, once contact is made, the relay will remain active even though the actual on-switch button was never pressed: The tool will run as though the on-switch had been pressed.Placement of the Switch Body
Each tool in my shop required a different amount of force to start. The planer was the easiest, the table saw was next, and the hardest (best) was my jointer. This all relates to how the starter control is mounted. The starter control on my planer is mounted on a thin bracket on the side of the planer body. The flex of this bracket allows the starter control to literally bounce upon slight impact (even the butt-end of an eight inch screw driver was enough force to start the planer). The table saw control is mounted via a short nipple to the bottom of the fence rail, which also has some bounce. The shaper is surface mounted to the cabinet pedestal, but there is still enough flex in the sheet metal. The best tool, was the jointer. In this case, the control was also mounted to the pedestal, but it was near the corner of the sheet metal, which is very resistant to flexing and bounce.It is the bouncing of the switch body which permits the relay contacts to touch , which starts this whole thing rolling. If the switch was mounted on a rigid platform, then, like my jointer, it could not be jarred hard enough to cause the initial contact. What's important to remember, is that regardless where your switch is located, there is always the potential for any tool, magnetic start or other, to start unexpectedly in the presence of a sharp jolt. The next time you loosen the arbor nut on the table saw, just think how simple it would be for your knee to hit the edge of the starter control.Be safe, and always unplug the power cord when doing any type of maintenance on a power tool.
I didn't realize that a properly maintained switch would be that sensitive to jarring. I'll do some more research on the subject.
John White
Hi John,
Keep us all posted on what you uncover in regards to magnetic switches
Paul
Hi All,
Interesting discussion on magnetic switches. Lets see what John and Fine Woodworking come up with. I 'm going to go out to my shop right now and see if I can get any of my 7 or 8 magnetic switches to turn on as described.
With regards to large off switch plates. Bigger is better .... to a point. I think they need to big enough to easily activate when needed but not inadvertently bumped during the middle of a cut. Especially with a table saw when the slowing of the blade with improper feed rate could cause kickback.
Paul
ps I've been operating table saws and all types of woodworking machinery on a daily basis professionally for the past 35 years and never had a magnetic switch activate from a bump. That certainly doesn't mean they can't. Just my experience. Now, out to the shop.
I'm well aware of magnetic switches and the bump factor for many years. I've seen it many times. The contactor is held back by small springs. As many know you can energize the switch by pushing in the contactor manually. Normally when you hit the start button the magnet overcomes the resistance of the spring and pulls the contactor in. It's a fine balance of the springs to hold back the contactor versus having them too strong so the electro magnet cannot pull the contactor in. I've seen this happen on old and new switches.
While it's safety issue of sort I don't see it as a reason not to have a magnetic starter. When changing blade you should disconnect the power so this wouldn't affect anything. I find the hinged paddle is the best addition one can add to a switch as you can hit it with your knee. Plus with magnetic starters you can add off and on buttons any where you want. I find that you want to keep both hands controlling the wood so it would be difficult to reach a switch and risk loosing control of the wood where you could risk a serious kickback. I don't know of any better swtch on the market than the hinged kneeboard which you make yourself. Safey is a touchy subject for manufacturers. Take the simple pork chop jointer guard. Better than nothing but not as good as the Martin jointer guard. There was a company called Surty that made a very innovative replacement jointer 30 years ago but the are long gone.
I've been involved with set-up, repair and restoration of machine for 20 years with a total of 30 years in the woodworking business in general and have worked in factories, small custom shops and as a tech for a machine dealer working on many brands of machines from Delta, SCMI, PM, Adwood, Paolini, etc. so have been to many vocational schools and other shops.
Good morning Rick,
I agree. The knee activated OFF paddle on a table saw is about as safe as it can get as long as it's in one general area and not enormous like the one pictured through a link in a previous post. It , I'm sure, would have other applications though. I just don't think I would want one that big on my table saw.
I just purchased, among other things, a 15 year old Rockwell spindle shaper. Now I know who to pester for pointers if it needs refurbishing. :)
Paul
Good morning All,
Went out to the shop last night and beat my magnetic switches to death. Couldn't get any to close. It seem a little odd ( interesting ) that peoples experiences are so varied. Like the account of a gentleman in a previous post that had several switches activate from bumping. Curious
Paul
That to me would indicate that the bumping issue of a mag starter isn't that common. I have seen about half a dozen over a 30 year period but I've been around more machines than most people might see in a lifetime.
Folks,I thought the issue was relatively well known, I had no idea it was not known in general across the industry. The problem though is not that we are lax, I think we trust manufacturers are actively providing the best products. However, apparently, the switch manufacturer industry has not, in the years between knowing of the issue and now, offered a line of magnetic switches that are designed to avoid this issue explicitly. That is what I wanted to find as I searched for a replacement "safety" switch, a magnetic switch with the explicit and stated design to avoid inadvertent starts through, admittedly a pretty good whack, from some means. In my shop I know this will be an issue. As I am in an 11x17 foot space that must be closed for AC and must hold all stock, machinery, storage cabinets, etc....; bumps, whacks and pretty good knocks are common enough as I move stock, machinery and everything else around to progress through every project I undertake. In larger floor space I can imagine this is less of an issue but, as the Christopherson(sic) post relates, even in these shops the potential exists. If that "safer" Magnetic Switch becomes available I'll buy it and add a reasonably-sized paddle to the configuration. It's what I wanted to find to begin with, but I don't want to trade one problem for another. Above all, thanks for the forum to ask questions, share information and find out what the "unknown knowables" are. KWL
All: An improvement can be made it the circuit under discussion by changing the stop button to a maintained switch where it can be done. This will prevent the contactor from latching although it could, if susceptible, close for the time it takes to "bounce" back open. The normal setup is for the stop switch to be a normally closed momentary switch. If it is a maintained type the control circuit would be kept open and the motor would not run. This might not be good enough for some but might put minds at rest. In my thirty years of electrical work I've never seen a contactor pull in because of a bump. That doesn't mean it didn't happen or couldn't. No one I knew went around banging on starters and I never heard any of the carpenters/cabinet makers in our wood shop mention it. I relied on various safety schemes when working on machines or power circuits, none of which were just depending on a open contactor. Usually opening the safety switch and tagout lockout. It all depended on the situation but always a higher level then needed but less then the max possible. I've heard other electricians talking about pulling fuses and disconnecting wires in factories where someone might disregard a tag. In many places cutting off someone's safety tag is grounds for immediate firing.
Duke
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Edited 3/21/2007 10:37 pm by dukeone
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