Popular Woodworking 2004-06 № 141, страница 56
on sharpening stones. As a result, proper sharpening is an expensive and time-consuming process. But in the last 12 months, three manufacturers have introduced machines that try to make sharpening simpler and faster. These machines both grind and hone the tool's edge using progressively finer grits of sandpaper. The coarse sandpaper shapes the tool's edge much like a grinder, while the fine grits polish it to a mirror, similar to a set of sharpening stones. For the last few months, I've sharpened dozens of tools on these machines and have been impressed with their speed and accuracy. But each machine is radically different in the way it approaches its task. And each has strengths and weaknesses. If you're considering one of these machines, here's what you should know about the Jet Multitool, the Veritas Mk. II and Jooltool's Warrior. Disc sander Traditional grinding wheel Jet JBGS-82 Jet Grinder & Multitool Jig To create its sandpaper grinder, Jet Equipment & Tools combined a traditional Chinese-made grinder with a rugged Australian-made jig that spins a 2"-wide x 36"-long sandpaper belt. The jig part of this machine, called the Multitool, has been for sale for years as an aftermarket accessory in Australia and is now imported here by Multitool USA (800-660-0880 or ausmultitool.com). In Australia, the Multitool jig is popular with The JET JBGS-82 combines the Multitool jig with an 8" grinding wheel and a 7" disc sander. It's a complete sanding and grinding station. The sharpening jig (shown at right) screws into place on the Multitool jig. Use a light touch when sharpening - this thing is aggressive. TRUE GRIT - THE DIFFERENT SYSTEMS One of the difficulties in understanding sharpening is knowing how the size of the grit is measured.The Japanese have one system, sandpaper in the United States is measured using another system (called CAMI, the Coated Abrasives Manufacturers' Institute), and the abrasive in really fine sandpaper is measured in microns (one micron is equal to one millionth of a meter). It's all quite confusing. Here are the rough equivalents for the three systems, from coarsest (at the top) to finest. Japanese grit CAMI grit Microns — 36 535
10,000 2,000 1 hobbyists and professionals who use it for a variety of woodworking and metalworking tasks. In fact, sharpening is one of this machine's side duties. It comes with a traditional 6" or 8" grinding wheel on one end of its arbor. On the other end is the Multitool jig and a disc sander. You can sand curved work, grind, polish and even clean up welds on the belt (we're told that auto enthusiasts love this machine). To sharpen tools, you must purchase a separate $75 accessory tool rest from Multitool USA. This tool rest sets the angle of the bevel on your tool and holds it square against the belt as you sharpen the edge. One of this machine's virtues is how easy it is to change the belts to finer grits. It takes about five seconds total. Just press the front wheel forward until it locks in a retracted position. This slack ens the belt. Then you remove one belt, slip the next one on and flip a switch to engage the tension. It's very smart. Sharpening is also remarkably fast. The grinder's motor spins at 3,450 rpm, while the small 31/2"-diameter wheel spins at 5,557 rpm, according to our tests. This translates into 4,280 feet of sandpaper passing under your tool every minute. In other words, you need to be careful about your tool heating up to the point where it turns blue and loses its temper, rendering it unable to hold a sharp edge. You need to use light finger pressure and touch the tool to the sandpaper for only a couple of seconds at a time. If you bear down on the tool even a little bit, you will cook its edge instantly. We destroyed several chisel edges before getting the hang of it. The Multitool has a few drawbacks, though. There isn't a way 54 Popular Woodworking June 2004 |
