Popular Woodworking 2004-06 № 141, страница 57
On the JET JBGS-82, set the angle of your tool's bevel by lining up its front edge with marks on the jig. Three common angles (25°, 35° and 40°) are called out. Changing the belts on the JET JBGS-82 is extraordinarily fast. Push the front wheel forward and it locks with the belt in a slack position. Replace the belt, push a switch and you're done. to remove the burr on the backside of a tool's edge as you move to finer grits. It may be tempting to remove the burr by touching the backside to the flat platen of the jig, but because it's moving so quickly, I wouldn't recommend it. You'll have to remove the burr on a fine sharpening stone or on fine sandpaper. That's not a big deal, but it is an extra step and another thing to purchase. Second, because the wheel you sharpen on has a small diameter, you will grind the edge quite hollow. In other words, the bevel is very concave, even compared to the hollow that's created on a 6" grinder. Sharpening experts assert that a hollow-ground edge isn't as durable as one that is ground with a flat bevel (which is what you get when grinding with a flat sharpening stone). Also, the jig will hold most Western chisels and plane irons up to 27/l6" wide. But it won't hold short-bladed tools such as Japanese chisels, butt chisels and spokeshave blades. So how does the edge look? We sharpened several chisels on the Multitool using 3M's Trizact abrasive, available from Multitool USA. This high-tech sandpaper is made up of consistent pyramid-shaped structures instead of paper coated with randomly arranged grit, which is how traditional sandpaper is made. We used the Trizact A6-grade paper as the final grit. This abrasive is equivalent to 6-micron sandpaper. In the world of abrasive grading, that puts it near a 2,000-grit Japanese waterstone. By way of comparison, most wa-terstone sharpeners finish chisels on a 4,000-grit stone. Some, like me, take their edges up to 8,000 for an ultimate polish. Looking at the edge from the Multitool under a 30x jeweler's loupe (see "$10 Magnifier Improves Edges" on page 57) it was amazingly consistent, but it didn't look as polished as you'd get from a Japanese waterstone. Veritas Mk. II Power Sharpening System As the name implies, this is the second generation of this sharpening machine. The first version was bigger, more complex, more expensive and (some claimed) a bit underpowered. Unlike the Jet Multitool, the Canadian-made Veritas Mk. II is designed for one operation: sharpening plane irons and chisels. And it excels at that. To sharpen a tool, you first place it in a jig (included with the machine) that sets it square and positions it so that the proper amount of the tool is projected. The jig rides on a tool rest that's suspended above a flat platter of sandpaper that spins at 678 rpm, according to our tests. That translates to 1,419 feet of abrasive passing under the tool's edge each minute - three times slower than the Jet. The height of the tool rest determines the angle you grind at - anywhere from 15° to 45° in 5° increments. The machine comes with two platters. One is for grinding and has #80-grit Zirconia paper on one side and #150-grit aluminum oxide paper on the other. The other is for honing and has #320-grit aluminum oxide on one side and 9-micron paper on the other. Other grits and additional platters are available as accessories for special applications. One of the real strokes of genius with this machine is that the platter used for honing is 1 millimeter thinner than the platter for grinding. This creates a 1° mi-crobevel on the edge of your tool, which greatly speeds sharpening. Also, the jig holds a variety of tools, including short-bladed ones (as little as 13/4" long) and wide ones (up to 21/2" wide). Plus there are retractable stops on the jig that allow you to wedge skew chisels in place for honing. This is the only machine in our test that is designed to flatten the backside of the tool - the critical first step to sharpening a new tool - and to remove the burr on the backside that develops during grinding and honing. The speed of the platter is just right for this: it's slow enough to keep the tool under control, but fast POWER SHARPENING SYSTEMS Brand/model Price RPM Feet/ Avg. temp. Amp. Max. tool Coarsest grit Finest grit Website at tool minute increase draw width available available JET JBGS-82* $435** 5,557 4,280 12° 4.3 27/is" 24 grit 5 micron www.wmhtoolgroup.com Veritas Mk.II $300 678 1,419 9° 2.5 2V2" 80 grit .5 micront leevalley.com Warrior M-2000-PKG $350 5,463 4,288 5° .25 23/s" 80 grit 10 micron jooltool.com * The JBGS-62, a 6" model, also is available. ** Doesn't include the $75 sharpening jig. t With honing compound. Prices as of publication deadline. popwood.com 55 |
