Bosch's new riving knife system on its 4100 series of table saws.
Riving Knives – Not Just for
The Europeans Anymore
Of
all the new things appearing at this year’s AWSF show, the most
exciting is the sudden appearance of true riving knives and sensible
guard systems on a number of new table saws. The rules are changing,
both literally and figuratively. Kelley Mehler, who wrote an article on
European-style table saws for our August 2007 issue, lobbied and worked
with Underwriter’s Laboratories in the development of new rules for
table saw guards manufactured and sold in the United States. These
regulations will require that guards on table saws be easily removable
and replaceable, and most importantly to us, that saws be equipped with
riving knives.
When we reviewed the SawStop cabinet saw in 2005,
we noted that in our opinion, the riving knife was a more important
safety feature than the braking system. When we took our first look at
the Powermatic 2000, we were happy to see a riving knife included. This
year, several more manufacturers are getting on board, in advance of
the new UL regulations.
The SawStop, like airbags in your car,
will provide some protection after an accident has happened. And, like
airbags, braking systems that stop the saw on contact with the blade
add significantly to the cost. What if there were a simple device that
could be easily attached to your car that would prevent most accidents
from happening in the first place? Would you want one? That doesn’t
exist yet for your car, but there is a simple device that attaches to a
table saw that will prevent many accidents.
About Riving Knives
So
just what is a riving knife, and what does it do? There are two ways to
cut yourself on a table saw. The first is to not pay attention to where
your hands are and stick them into the spinning blade. The second is
when part of the board comes in contact with the back part of the blade
– the part that is spinning up from the saw’s table, after the cut is
made. This causes the board to rise and kick back toward the operator.
If your hand is on the board at that point, it can be thrown into
contact with the blade before you know it. A careful worker can avoid
both these situations, but it takes more skill, experience and
diligence to avoid the second one.
A proper riving knife travels
with the blade as it is raised, lowered of tilted, covering the area
behind the back of the blade. It is close to the same thickness as the
blade, so that a piece of wood can’t move into the rising saw teeth,
and your hand can’t come in contact with this part of the blade. It
keeps the wood tight against the fence for a few inches after the cut
has been made. This is an inexpensive, effective and proactive approach
to preventing accidents before they happen. Bosch, Delta, DeWalt, Grizzly,
General, Jet, Powermatic, Shop Fox and Steel City are all displaying saws at AWFS
equipped with riving knives that will are either now available, or will
be available in the next few months.
An inside look at Jet's riving knife system.
In
addition to requiring riving knives the new regulations also will
require that guards can be removed and replaced in less than 20
seconds, without the use of tools. This eliminates the excuse that many
of us use, that it is too much trouble to remove and replace the guard.
The tool companies are taking some different approaches to this. The
Powermatic and Steel City Saws have a lever that releases the guard and
pawl assembly. When that is removed, the riving knife snaps in where
the guard was. Grizzly’s approach is similar but instead of a lever, a nut is turned.
By far, the best systems we saw were on the Jet
Exacta saw, and on inexpensive job-site saws from Bosch and DeWalt. With these
systems, each part of the assembly is a separate component, held in
place with a spring-loaded pin or a lever. If you want to use the guard
and splitter, but remove the pawls, you can do so in just a few seconds.
I
liked the Bosch and DeWalt systems the best, because of the over-blade guard, which
has a clear plastic cover for each side of the blade. When lifted up,
there is a detent at the top that holds the guard above the blade. If
you want to make a measurement from fence to blade, or rip a narrow
piece, you can do so without fighting the guard.
Here is a rundown of what we saw:
Bosch’s riving knife is available on the 4100 series of job-site saw.
Grizzly
introduced its system on a 12” saw last year at the IWF show in
Atlanta. This year it has put the same system on a new 10” cabinet saw
(the G0651 and G0652). In addition, Grizzly has a nice 10”
European-style saw (the G0623X) with riving knife and European guard
with dust collection, a sliding table and a scoring blade for a bit
less than a SawStop 10” cabinet saw.
Jet has a riving knife and
easily removable guard on its 10” Xacta saw. Jet’s hybrid and
contractor saws have an easily removable guard, but riving knives won’t
be available for these in the near future.
Powermatic includes the riving knife on its PM2000 model, which has been available in this configuration since early 2006.
Steel
City will introduce its riving knife and guard system on its hybrid
saws, beginning around the first of 2008. This is the same saw that
surprised the show with a granite top Wednesday morning. This saw will
be available with either a cast iron or granite top. The company’s
larger cabinet saws will incorporate these features next spring.
We
are looking forward to taking all of these saws for a test-drive in our
shop this fall and winter, and we salute these forward-thinking
manufacturers for going ahead and including these features ahead of
schedule.
— Robert W. Lang
read more reports from the 2007 AWFS show