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ATTENTION!!!
This article DOES NOT advocate the modification of
a manufactured tool. ANYTIME YOU MODIFY A MANUFACTURER'S PRODUCT YOU
ASSUME ALL LIABILITY FOR THAT PRODUCT. However, a lot of carpenters
use their jobsite table saws WITHOUT guards--which is a major modification.
If you or your employees suffer an injury while using the tool without
a guard, you will be liable for all consequences! |
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You many not know it, but a portable table saw guard
is really a combination of three separate safety devices: a splitter,
anti-kickback pawls, and a clear plastic cover. The reason you may
not know it is because you never took a good look at your guard before
sticking it in some dark corner of your shop, or more likely, sending
it on a short trip to the landfill. Portable table saw guards aren’t
known for their ease of use, so most carpenters don’t use them.
In a recent poll of professional carpenters, 99% of those who responded
said they never use a guard on their portable table saw. Why? Because
most guards are hard to remove; they’re even harder to re-install.
And you have to remove them frequently: they interfere when
making thin rips, rabbets, blind kerf cuts, dadoes, steep bevels—just
about anything difficult (and nothing is easy on a jobsite). The anti-kickback
pawls are nearly always in the way, they jamb when you’re making
thin rips, and if you need to back off a touch or change your mind
and want to stop in mid-rip…good luck. The splitters are another
sore point for carpenters. Being on a portable tool, the splitters
take a beating. They’re rarely aligned with the blade. Ask any
carpenter and they’ll tell you—with at least one expletive—that
splitters cause more binding and kick back then they prevent. But
universally carpenters hate the plastic covers most. After spending
years developing a “good eye,” it’s tough trusting
a saw to cut something you can’t see.
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| European saw guards and some cabinet saws are different. There’s
more room—and more budget—for guards that don’t
combine all three elements. Besides, after market guards are available
for cabinet saws—overhead guards with integral dust collection,
splitters with anti-kickback pawls that are easy to remove, and covers
that can be lifted neatly out of the way. Best of all, some cabinet
saws, and many European saws, come with a riving knife, not a splitter. |
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| Because so many carpenters use their portable saws
without guards, exploring alternative safety measures is important. |
| A riving knife travels with the blade, it’s
always just a bit below the teeth, so it’s never in the way
of a rabbet cut or a blind kerf. And a riving knife follows the blade
tilt, too; without pawls or a cover that binds against the saw table,
a riving knife is never in the way of a bevel cut. |
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| One of the nice things I’ve discovered about
my Bosch portable table saw—besides the one-wrench blade change,
the smooth low-vibration cut, and the low-decibel motor—is that
the blade guard attaches to the saw carriage and travels up, down,
and sideways with the saw. I also discovered that it’s easy
to remove the pawls and the plastic cover. I pried the keepers off
the cover bracket with a screw driver and needle-nose pliers. I drilled
out the large rivet running through the pawls, then drove the pin
through with a nail set.
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| All in all, I spent only a few minutes more than it takes to throw
the guard away, but that extra time was well worth the effort. Fortunately,
the front of the splitter was already cut neatly to follow the saw
blade. To turn my splitter into a riving knife I only had to cut the
back a bit, and grind a chamfer on both edges of the front. I used
a jig saw with a metal cutting blade to cut the back. I made sure
that the top of the riving knife would be about 1/4 in. below the
saw blade (recommended height varies from 1/4 in. to 7/16 in. below
the saw blade). The splitter that came with the saw was also the perfect
thickness, just over the width of the saw-blade body, but thinner
than the kerf. |
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| Installing the knife (and removing it) is easy on
my saw if you raise the motor all the way and tilt it to a 45 degree
bevel. The riving knife is secured by two studs and a plate. Loosen
the plate, lift it out of the way a little, then slide the knife under
and onto the studs.
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| The plate is secured with only one Allen
bolt, which makes the riving knife easy to remove, but I only need
to remove it when I put on a smaller dado blade set, or make a plunge
cut, which I don't do every day. |
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| Adjusting the knife so that it's perfectly aligned with the blade
isn't difficult at all. I loosened the top two Allen bolts and eyeballed
the knife into alignment with the blade, then tightened the bolts
real good. Because the knife descends with the blade, it doesn't stick
up above the table when I carry and store the saw in my truck. That
saves the riving knife from the beating most saw guards take during
transportation, which is the main reason saw guards require frequent
re-alignment. |
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| A riving knife is a splitter that never interferes
with the cut. A large percentage of table-saw accidents are the result
of kick back. Kick back can be caused by several things: a misaligned
rip fence, a badly twisted or warped board, or stress built up in
lumber that’s sometimes released during a cut and closes the
saw kerf. When the kerf closes and pinches the saw teeth at the back
of the blade, the work piece can shoot right at you. A narrow strip
becomes a spear; a wide board becomes a battering ram. Even worse,
if you’re using your hand as a featherboard near the blade and
pushing the board against the fence, when the work piece shoots out
of the saw, your hand won’t be pressing on anything but air—at
least not until it hits the blade. A riving knife helps eliminate
kick back from most causes. |
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| A riving knife adds another degree of protection from
two other common table-saw accidents: projectiles and tired hands.
Small cut offs often vibrate on the table and walk themselves right
into the back of the blade. That’s when the saw teeth pick them
up and shoot them at you like a bullet. But a riving knife will help
prevent more then just cutoffs from contacting the back of the blade.
One of the most common table-saw accidents doesn’t happen near
the front of the blade but at the back of the saw. Too many tired
carpenters have reached around behind a table saw blade and missed
the safety zone by a fingertip—or more. A riving knife helps
protect your hands from the back of a saw blade, too. Of course, if
you used the guard that came with your saw, you'd have even better
protection. But who does?
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