The Bolt On Ripping Knife (BORK) from Bob Ross of Walnutacre Woodworking is a retrofit riving knife that fits several traditional saws that were not originally designed for a riving knife. The BORK attaches to the arbor swing arm, and rises, lowers, and tilts in unison with the blade much like a true stock riving knife does. I’ve had a BORK on my Shop Fox W1677 since August of 2008, and have been very happy with it. It’s available in full kerf or thin kerf widths, and will currently fit Grizzly, Shop Fox, Delta Unisaws, and Jet JTAS cabinet saws, as well as Craftsman, Steel City and some Jet Hybrid saws.
Because the BORK is made to adapt to existing saws, there are challenges that Mr. Ross needed to address. As such, it’s not necessarily as slick as riving knives that are manufactured to fit saws that were designed from the ground up to accommodate the riving knife, but it’s a clever and effective design that offers the benefit of a riving knife to several older style saws that previously could not accommodate one.
Installation is moderately easy, and once adjusted properly, the BORK works quite well, basically mimicking the movement of the blade ... up, down, and when tilted. Note that because the BORK is attached to the end of a swing arm that extends beyond the arbor shaft, the BORK doesn’t necessarily rise and fall in direct proportion to the movement of the blade, though it’s close. As the blade is raised, the BORK travels a slightly greater distance up, and likewise when the blade is lowered, so the height of the BORK will not always be at the exact same height relative to the blade, though it can be depending on where you manually set the blade height initially. This is rarely a problem, and is most easily resolved by setting the BORK height the same as the blade height for common wood thicknesses, which puts the BORK at an ideal location for most boards. It can be easily manually adjusted up or down relative to the blade height to accommodate lower or higher blades heights as needed for exceptions. Also note that proper adjustment requires the use of a custom zero clearance insert to offer lateral support.
Bob Ross is an avid woodworker, very much like many of us, who evolved this device because it was said that it couldn’t be done. He’s also a super guy to deal with, and is honest and open about his invention. He offers discounts to forum members who will write a review of the BORK, and backs his invention with a 100% money back guarantee. The BORK is a unique device unlike any other I’m aware of. It works well and I still get a kick out of watching the BORK rise through the throat insert on my saw.