Hone an incredibly sharp edge with a $35 combo stone.
by Tom Caspar
For this woodworker, it doesn’t get any better than using a sharp hand tool. Not just kind of sharp, the way new tools come out of the box. I mean really, really sharp, with an edge honed to perfection by a well-maintained set of sharpening stones. In search of that perfect edge, I’ve tried oil stones, diamond plates and sandpaper. With enough time, money or elbow grease, all these materials can deliver top-notch results. But none can beat waterstones, which combine fast cutting, easy maintenance and great value in one package.
Types of Stones
Waterstones were first quarried from small mines in Japan more than 1,200 years ago. Today, most waterstones are made in a factory. They’re composed of aluminum oxide, silicon carbide or chromium oxide abrasives heated at high temperature to fuse into a brick-shaped porous matrix. Many hold water just like a sponge.
Most waterstones come in two sizes: regular and large. Large stones are thicker, wider and longer, so they have more wear surface. The extra width of a large stone is handy for wide plane irons, but not essential.
The least-expensive way to get a decent edge is to buy a regular-size combination stone. Go for a 1,000/6,000 coarse/fine, which runs about $35 (see Sources, page 36). A large stone costs another $15 to $20 and requires reflattening less often. A 1,200/8,000 medium/fine stone, which costs about $45, gives you a slightly sharper edge, but requires more strokes on the medium side to prepare a very dull edge for final polishing.
I use a three-stone system of large single-grit stones: 800 coarse, 1,200 medium and either 6,000 or 8,000 fine. Compared with using the two sides of a combination stone, this set requires fewer strokes on each grit. That produces less wear, so keeping the stones flat is much easier. Buying this set of three adds up to $80 or more, but considering the dough I’ve spent on good hand tools, it’s worth it. After all, your hand tools are only as good as the stones you sharpen with.
If your tools have very high-quality blades, such as A2 or cryogenically treated plane blades, super-fine stones with 12,000 or higher grit will produce an unbelievably sharp edge. They cost from $100 to $400 (see Sources, page 36). These stones don’t help very much, though, on average-quality tools, whose steel won’t hold a super-sharp edge for more than a few licks.
Tips For Using Waterstones
Check the directions that come with your stone; some types don’t require presoaking, and others should not be soaked or they’ll deteriorate. Most coarse and medium waterstones, though, should be immersed in water when not in use. This keeps them saturated so the surface doesn’t dry out quickly when you’re sharpening. If you’ve just bought a new stone, soak it overnight before trying it out. Fine and super-fine stones don’t absolutely require soaking, but if you do soak them, they’ll be ready to go right away. I keep my stones in a plastic tub with a lid. They’ve been soaking since 1979! I add a drop or two of bleach to keep the water free of green scum.
Use Lots of Water
Flood the top of a waterstone with water when you sharpen. This suspends the small particles of worn-off steel in the water, keeping the particles from clogging the stone’s surface. You can use a cup or spray bottle or simply dip your fingers in a water container to continually keep the stone wet. I use a plastic mustard bottle. The undeniable downside to waterstones is that they’re messy—though not as messy as oil stones. Your hands will get wet and grubby. To protect my bench, I place my stones on a cookie sheet. Open-weave shelf liner below the stones and under the cookie sheet keeps everything from slipping. After sharpening, I dry my tools right away so they don’t rust, place the stones back in the storage tub and wash my hands. The gunk comes off quite easily with ordinary soap.
Keep ’Em Flat
Routinely rub your waterstones with 220-grit wet-dry sandpaper placed on ordinary plate glass that’s 1/4 in. or more thick. A waterstone cuts fast because its surface wears down quickly, constantly exposing new, sharp abrasive particles. This wear eventually creates an uneven surface, which produces an undesirable curved edge on chisels and plane irons. Make a squiggle line with a pencil down the length of a stone before you flatten it. Put a little water on the plate glass so the sandpaper sticks. Then put lots of water on the paper and go at it. When the pencil line is gone, the stone is flat. I also sand a 45-degree bevel on every edge of the stone to prevent flaking.
With my three-stone single-grit system, I skip the sandpaper and glass method and simply flatten all three stones against each other. The trick to avoid making concave and convex pairs is to continually alternate sides. Rubbing medium against fine does no harm to the fine stone. This is so easy that I flatten my stones before each sharpening session. It only takes a minute or so. Flattening the sides removes the inked grit numbers, so I write them in pencil on the end of each stone.
Make a Slurry
The secret to sharpening on a fine-grit stone is to build up a paste slurry before you get going. It looks like thin mud. A slurry keeps the microscopic metal particles removed from the tool’s edge in suspension more effectively than water alone. That makes sharpening go faster and results in a better edge. The paste also makes the stone more slippery, which prevents the backs of your chisels and plane irons from sticking to the stone’s surface. You can get by without the slurry, but sharpening will be more difficult.
To create the paste, wet the stone and vigorously rub its top with a Nagura stone, which costs $10 to $20. The Nagura wears away the stone to leave a chalky paste. As you sharpen, the paste will be pushed to the ends of the stone. When that happens, wet your fingers and work the paste back over the whole stone, or rub the stone with the Nagura again. When you’re done, leave the paste to dry on the stone, ready for next time.
Guides Are OK
Some folks claim that the wheel underneath a honing guide will quickly hollow out and ruin a stone’s surface, but I disagree. You just need to use the right technique. I concentrate my finger pressure on the edge of the tool, not on the honing guide itself. The harder you press on the tool’s edge, the faster the stone will cut, but there’s no reason to bear down on the wheel.
This story originally appeared in American Woodworker September 2005, issue #116.
Source information may have changed since the original publication date.
The Japan Woodworker, (800) 537-7820, www.japanwoodworker.com More than 40 waterstones available from $20 to $100. • Shapton Sharpening Systems, (877) 692-3624, www.shaptonstones.com Ceramic stones with 120 to 30,000 grit, $53 to $130.