It almost happened to me: ye olde safety thread

[Bob Hammond]

When I first wired my shop (USA), I ran a three wire circuit, through a double pole 50A contactor relay that has separate low voltage control-contacts. One power leg went to the dustcollector, and the other leg to a power distribution receptacle strip. (Also, I installed a 220V outlet for future convenience). I did it this way for a few reasons, 1) powering two motors on opposite legs reduces voltage drop, 2) so I would always remember to turn on the dust collector when cutting wood, but mostly 3) for safety because it takes two switch throws to energize the woodcutting machines -- first at the contactor power relay and then at the machine's switch. Also, when the d/c isn't running (it's noisy so I shut it down as soon as possible), I know that power to the machine is cut off and so I can do setups and blade changes with reasonable safety. This centralized switch also makes it safer if kids were to come into the shop when I'm not there, because the location of the power relay switch isn't obvious (my wife knows where it is).

However, when I bought a bandsaw, I installed it on a regular circuit, and placed a new motor-rated toggle switch on the arm at elbow height as is done on many machines. There was no secondary guard on the toggle of the switch. Well, I was changing a blade, and it popped off the wheels, and somehow it flipped the switch. If that blade had been a little snugger on the drive wheel or if my fingers had been on the wheel or adjusting the guides, then a very bad accident could have happened.

So the lesson is, always always make sure that a machine is isolated from the power, preferably by removing the plug.

Another thing that I've seen concerns machines that have a magnetic starter relay that is meant to prevent restart of the machine if power is cutoff due to overheating or if the shop supply goes down. This is not necessarily foolproof. Sometimes if the box that contains the stater relay gets a mechanical shock, then the contacts might engage and the machine will start unintentionally. If you have machines equipped with this, then it might not be a bad idea to test by giving the box a whack with a stick. You might get a surprise.

[Mario Proulx]

I dropped something(I forget what..) heavy next to my Unisaw one day and the saw started right up! Startled me, to say the least...! Thankfully, I wasn't at the saw, and I never place "stuff" on or near the blade, so nothing was cut or tossed.

So, it was the mag switch that did that?

[Bob Hammond]

From what you wrote, I think it's a possible if not likely explanation. It might be worth the trouble to try to replicate the disturbance to confirm the sensitivity of the starter. By the way, since I've acquired a table saw (the old Yates American M1701), I always lower the blade below the table surface as soon as I'm finished with an operation. The saw did not come with the bladeguard because it was an optional item back then, but I've studied its design from the manual and parts diagram, and it's an excellent design that I will try to replicate. Then fence works wonderful too, once I figured out how to set it up; the engineers really thought about the design of this machine. No plastic parts anywhere. It will outlast me and maybe the next owner or two, too.

I set up my wiring scheme (with prior review by a electrician (who gave me the 50A power relay) because I started out with only a (excellent quality) radial arm saw and a router, and the dustcollector. With the radial saw, it just seemed too easy to trip the switch while manipulating the height adjustment knob. After making any cut, I always lock the saw carriage in a 'garage/dust hood' so that it doesn't travel unexpectedly whether it is Off or On. A well-tuned radial saw can do useful and interesting things, but carelessness is not tolerated.

Looking back at my bandsaw incident again, I see that I ignored another 'safety' feature that I'd built in. When reconditioning the saw, I set up the lamp wiring so that it is always On when power is available to the saw's motor (i.e. there's no On/Off switch for the lamp). The lamp is convenient because I like to see what/where I'm cutting, and when it's quitting time I can see instantly if the saw is plugged in. But in this instance I ignored what that lit lamp signified -- and I almost had an unhappy moment. I think that I'll run a spur circuit from the power relay out to the bandsaw.

[Darrel Friesen]

Thanks for the heads up Bob.

[Clay Schaeffer]

Sometimes even non magnetic switches can malfunction and unexpectedly turn on equipment. I had that happen on a table saw. Not a good feeling! I like to have tools wired to a plug for that reason. Nothing is fool proof, and the "fool" still has to take the time to unplug the machine, but at least that option is available.

[Jason Rodgers]

My three big tools in the shop - drill press, band saw, table saw - all have the big green and red button switches. Most recently, when I rewired my new-to-me Craftsman table saw, I bought one of the models with a big hinged "stop" plate, so I can easily slap it off. I'm thinking of replacing the switches on the other two machines with these units, too. I like the idea of having to deliberately push a button with a bit of force to turn it on, but easily shutting it down with a quick bump. Even though toggle switches flip down for off, the switches on other tools I have (like the jointer, belt/disc sander, and oscillating spindle sander) are small, and I don't want to have to carefully aim a finger in an "Oh $#it!" moment.

[Bob Hammond]

I wonder if we could start a permanent thread of 'best possible practices', about how good work habits save fingers and eyes, and result in better workmanship and save much time, too. Some people on the site know that my job is as a physiologist, as a Research Scientist and Associate Professor Surgery at a big hospital in the Midwest. Every week, as part of the educational process, I attend a review of injuries and illnesses that are caused by chance, mistakes of judgement, or just plain ignorance of what might happen. I'll tell you, that when I come home and spend a few minutes or a day in my shop, I don't want to think about the gory parts -- I want to think about how to make something. I don't do much in a day, but I try to do it well. And if I make a mistake with piece of something, then I either fix it or live with it, or discard it. When people are concerned, if I make a mistake, then I try to make it right - that's the best that I can do.

That said, I think that building instruments is not at all like building houses or fences. It's about thinking about how to solve technical problems of shaping materials with a high degree of accuracy and precision to make an object that satisfies one's imagination. It's also about how to choose from amongst the tools available, about how to accomplish that intention.

I can't quite get out what I have in mind yet, but I hope that you might offer ideas.

[Jason Rodgers]

No, you're making sense. There are two categories that I think you're describing, though they overlap, or may be sides of a coin: tool safety in use, and tool safety in selection. The first is like avoiding injury by staying out of the path of cutting edges, and the second is avoiding injury by using the right tool for the job. The first case might seem obvious, but sometimes poor choices or inexperience with the second case results in dangerous ends.

I can say that I've probably spent as much time (or more) in my shop staring at a problem and scratching my head for a solution as I have actually taking action. It has led to a lot of jig making and tool purchases, but I have all of my fingers and I'm satisfied with my part fabrication.

[Bob Hammond]

(I'm waiting for a CNC person to tell us that the best woodcutting tool is one that you don't touch when it's running.)

[David King]

My TS and jointer are three phase so I have to start up the rotary converter before either machine can run. That said the converter is so quiet that I can't always hear it and I occasionally forget to turn it off. I'll think about how to incorporate a pilot light to remind me that the tools are energized. One of my magnetic switches seem to be on a hair trigger. I'd like to make it a little less sensitive if possible.

[Simon Magennis]

Can't recall if it was a post here or if someone I met told me about it. The guys in question had a big sign on the entrance to the workshop: "count your fingers". Just a reminder of what can happen. I know one professional maker here in the Frankfurt area who is missing a finger due to just the kinds of thing mentioned here. I never thought to ask him was it a table saw or a bandsaw of something else.

[Mario Proulx]

My Dad only had 2-1/2 fingers left on his right hand. Saws know no mercy...

[Gilbert Fredrickson]

"The bandsaw is a meat saw. It will cut your danged arm right off." Mr. Fitzhugh, shop teacher. I have reshaped the "P" in my P-I-M-A twice. Fortunately, the side of the thumb that plucks the string is still intacted. And, never wipe the sweat from your brow with the chisel still in your hand, unless you want custom ear lobes. That's my motto.

[Bob Hammond]

All of us have had 'near misses' and some of us have taken a hit, or know someone who has. Perhaps relating personal stories is a reminder to ourselves about that, and by doing that we hope that those who read about our misadventures will heed the words of caution. For myself, I have little desire to tell you about some injuries that have been presented in cold clinical detail on a Tuesday morning at 7AM. Nowadays, my imagination is likely better than yours, about how things can happen and how it might change the course of a person's life and their family too.

What I'd like to do, is to create a handbook of sorts for small (one man) shop builders. Something about how to be careful when buying a new tool, about how it might add to doing work efficiently, instead of satisfying 'tool lust' (yeah, you know what I mean). The next thing is about recognizing dangers that are inherent to particular types of machines, and so how they might be set up for use so that safer practices are followed as a matter of course of doing the work.

[Jamie Unden]

How about taking too big a bite using a router table to smooth a body down to the template... and going out to pick up the chewed up body in the yard...

[Jason Rodgers]

I did something like that once, when I was greener with the power tools, attempting to profile a neck (don't ask about the setup... geezus... stupid!). Not only am I lucky that I still have most of my left hand, but I'm also lucky I didn't ruin my new PC router and $60 big ass flush trim bit. Bogged that sucker down and near tossed the neck.

As for the little handbook you describe, Bob, I think that angle is a good idea. Something like "The Idiot's Guide to Keeping Your Fingers," or under you own name, "Doc Hammond's Handbook of Powertool Husbandry." There are plenty of books out there on setup and such, but something specifically geared toward what a tool can and can't do, and typical safety lapses, might be well-received.

[David King]

I'll bet OSHA has a starter doc somewhere online.
https://www.osha.gov/Publications/woodw ... a3157.html
There are dozens of other online docs we could peruse but it might be more compelling if we reinvent that wheel with a view to instrument building's particularities.

One generalization I can make is that no one was ever injured as a direct result of a tool being too sharp. The times I got into trouble were when blades or cutters got just a little too dull.

[Bob Hammond]

I don't want it to be about me. I want to encourage people to think about 'being aware', and explaining about how one goes about setting up a tool, laying out the work so that there is no drama about cutting it, and then pausing before throwing the switch-- to think about how unexpected things might happen -- and where to be if that might happen.

[Jason Rodgers]

Yeah, but there's nothing like a little worst-case-scenario from someone who's seen it to hammer (or slice) the message home.

[Tim Douglass]

I find that the personal horror stories are, most of the time, the best reminder to me. Even after 40+ years of working with power tools (or maybe especially after) it is easy to forget and do something dumb. Every time I read about someone else getting bit I am more cautious for a few weeks. A book, however good, will only be looked at once. Then, forever after or until you screw up, you will think you know how to be safe. The book has its place, but without constant reminders we get complacent - "familiarity breeds contempt".