From The Workshop: Table Saw Modifications
The workhorse of the new shop is my 3 HP Jet tablesaw. I'm not writing a tool review, so I won't go too into detail about the specs. Instead, I want to talk about the safety modifications I've made to make it safer to use while I'm the only one home.
Saw Shutoff Pedal and Paddle
Unlike most of the similarly priced competition, the JET saw I bought has a magnetic starter with a very small off button. Even my contractor's Makita saw has a paddle switch for easier shutdowns, albeit connected to a regular switch and not a "starter." Regardless, the small switch makes turning the saw off while both hands are on the work-piece impossible, and makes blind shutdowns (where I don't want to take my eyes off the blade or work-piece) very tricky.The internet is full of DIY off-switch "paddles" ranging from small flaps to a full fence-rail length knee board. I settled on a compact design by TD69Mustang on lumberjocks: because of the way I have my starter mounted to the fence-rail a big wooden enclosure or hinge attachment would interfere with the fence. I would make mine out of the same 1/2" plywood I use for everything else instead of the plastic "Mustang" used. I would screw the hinge block directly to the front cover of the magnetic starter and add a metal safety bar to protect against accidental starts.
What is a Magnetic Starter Anyway?*
A magnetic starter is essentially a contactor, which is another name for a big relay, used to safely connect and disconnect motors from high voltage power mains. From what I can tell, most starters do not have magnetic blowouts in the contactor, but most have some sort of thermal overload protection integrated to prevent exceeding the motor's load rating. They are actually quite clever, where a momentary NO switch energizes the relay to close the primary contacts that powers the load. The relay also closes a secondary set of contacts that self energizes the relay. A second momentary NC switch (the off button) is wired in series to the secondary contacts and opening the switch allows the relay to de-energize and open both sets of contacts. In some starters, the relay is run off of a lower voltage, say 20-40VAC, but the one on the JET is fully 220V.So why does any of that matter in the slightest? Some of the paddle switches I found were designed to be foot operated and I thought "what a good idea!" Unfortunately, the paddle switch design I settled on rather limits the size of the paddle: there was no good way to make it reach the floor. So instead, I looked into making an actual foot switch that I could place wherever I needed it.
A not-so-quick amazon hunt returned this momentary switched pedal:
There were cheaper options available from the same company, but I liked the look of these and the reviews were promising. While they wouldn't be required to break the full 20A from the motor, they do need to be able to handle a few amps at 220V AC required to keep the starter secondary relay energized, and this fit the bill. I had to source some flexible power cable and dig out some smaller cable glands to make everything work, but overall it was a pretty simple modification.
I don't actually use it as often as the main paddle, but it has come in handy on a few occasions.
220V Circuit Kill Switch
One of the things I took away from my time working in manufacturing was the importance of LOTO and similar safety procedures. For the table saw (and most tools), this generally consist of making sure that the saw is disconnected from the mains before changing the blade or removing the riving knife. As unlikely as it sounds, the last thing I want is to accidentally bump the on button while trying to remove the blade. In my home workshop setting, I don't feel like a full LOTO system is necessary, but I would still like a way of fully breaking the connection between the saw motor and the mains. Unfortunately, when I ran the 10/3 romex for the 220V 30A saw circuit, I neglected to install any kind of switch so I could shut off power to the outlet. For most people, this wouldn't be a huge issue: they could simply unplug the saw any time they needed to mess with the blade. Lucky for me, both the way I ran power to the saw and the twist-lock plug make unplugging the saw a real hassle. Furthermore, I don't find unplugging and re-plugging to be very convenient and if it isn't convenient, I know myself enough to know I will consciously skip the step once in while (forgetting is an entirely different problem). The same reasoning is why just walking the 15 feet to the breaker panel was also not a viable solution (in addition to the fact that breakers aren't designed to be used as switches repeatedly). I really didn't want to open the wall I had just sealed up a week earlier, but in the interest of safety, I bit the bullet and installed a proper 30A DPST from hubbell so I could break both hot legs in the circuit. Ugh.
I still want to install french doors to the saw "room" in the future, so I had to decide which side of the wall I wanted the switch (I only thought of installing one on either side after I sealed everything up for the second time). I decided on placing the switch on the "outside" of the wall, reasoning that it would also make for a good emergency shutoff switch in case of operator incapacitation (i.e. I chop my arm off).
The hubbell switches have a really heavy actuation that makes them feel really sturdy. On the other hand, stiff action makes them a bit uncomfortable to flip (hey, I have soft hands) and as an emergency shutoff, any toggle switch lacks contact area, even when compared to a decora style switch. To address both shortcomings, I designed a linkage attached to the wall that flips the toggle when pressed.
I also sourced an aluminum sign from amazon and mounted it to the linkage to further increase the contact patch and to make sure the intent was blindingly obvious.
I really like the way it turned out and try my best to use it whenever I change the blade or perform maintenance. It's so easy to use, I really don't have any excuse.
*I am including this little lesson because I had to figure this out myself. Although their operation and use is widespread, i had trouble finding an internet source that clearly explained how the circuit actually worked to keep itself energized when the on switch was released.
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