Riving Knives , Not Just forThe Europeans Anymore
Of all the new things appearing at this years AWSF show, the most exciting is the sudden appearance of true riving knives and sensible guard systems on a number of new table saws. Both literally and metaphorically, the rules are changing. Kelley Mehler, who contributed an article about European-style tablesaws to our August 2007 issue, worked closely with Underwriters Laboratories to develop new rules for table saw guards that are manufactured and sold in the United States. These regulations will require table saw guards to be easily removed and replaced, and, most importantly, that saws come with riving knives.
In 2005, when we reviewed the SawStop cabinet-saw, we noticed that the riving knives were more important than the brake system. We were pleased to see the Powermatic 2000 include a riving blade when we first looked at it. In advance of the new UL regulations, many more manufacturers have joined the Powermatic 2000 this year.
Like airbags in your car’s trunk, the SawStop will offer some protection in an accident. The cost of braking systems that prevent the saw from coming in contact with the blade is significantly higher than airbags. Imagine if there was a device that could attach to your car and prevent accidents from ever happening. Would you like one? It doesn’t yet exist for your car but there is an easy device that attaches on a table saw and will help prevent many accidents.
Riving Knives
So just what is a riving knife, and what does it do? There are two ways you can cut yourself on a tablesaw. First, don’t pay attention to your hands and stick them in 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 saws 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 cant move into the rising saw teeth, and your hand cant come in contact with this part of the blade. After the cut is complete, it keeps the wood against the fence for about a couple of inches. This prevents accidents from ever happening by being cost-effective, proactive and effective. 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 Jets riving knife system.
The new regulations will not only require riving knives, but also that guards must be replaced within 20 seconds without the need for tools. This eliminates the excuse that many of us use, that it is too much trouble to remove and replace the guard. This is where the tool companies have different solutions. 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 method is identical, but instead of a lever a nut is turned.
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. The guard is held above the blade by a detent at its top when it’s lifted up. 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:
Boschs riving knives are available on the 4100 series job-site saw.
Grizzly introduced its system on a 30 cm saw last year at the IWF show in Atlanta. This year it has put the same system on a new 25 cm cabinet saw (the G0651 and G0652). Grizzly also offers a 25 cm European-style saw (the G0623X), which is slightly less expensive than a SawStop 25cm cabinet saw. It comes with a riving knife, European guard with dust collection and a sliding table, as well as a scoring blade.
Jet has a riving knife and easily removable guard on its 25 cm Xacta saw. The guard on Jet’s contractor and hybrid saws is removable, but there won’t be riving knives for them in the near future.
Powermatic offers the riving blade on its PM2000 model. This configuration has been in use since 2006.
Steel City will introduce its riving knife and guard system on its hybrid saws, beginning around the first of 2008. The same saw that wowed the audience Wednesday morning with its granite top. The saw can be ordered with either a granite or cast iron top. These features will be added to the company’s larger cabinet saws next spring.
We look forward to having all these saws in our shop for a test drive this fall/winter. We also salute the forward-thinking manufacturers who included these features earlier than expected.
