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  Clean Cuts

Sharpening tips for your woodworking tools

Using Oriental Waterstones


What goes into a waterstone?
The basic set of three man-made waterstones includes a coarse grit stone, a medium grit stone and a super-fine grit stone for final polishing. They're made by fusing hard abrasive particles together with a tough bonding agent inside an electric furnace (see Fig. 1). It's the same basic process whether it's an oilstone or a waterstone. However, waterstones have larger pores between their hard, steel-cutting abrasive particles.

Fig. 1 Waterstones generally have larger ?pores? than oilstones...and use different adhesives to hold the abrasive particles together.

According to one expert, most 800-grit, 1000-grit and 1200-grit waterstones are probably made with Aluminum Oxide...the same abrasive material that goes into what we often call India stones. The finer (4000-grit through 8000-grit) stones are usually made with Rare-Earth Compounds...exactly which compound isn't popularly known. It seems like the manufacturers of these waterstones shy away from revealing what they call their trade secrets. Some woodworkers have guessed that the super-fine polishing stones are made of cerium-oxide, the very same polishing agent used to polish telescope lenses. However, the makers have clearly stated that this isn't the case.

The bonding agent used to cement the waterstone's abrasive particles together is different from that used for an oilstone. It's a special adhesive that actually loosens with the application of water and friction, allowing the abrasive particles to move around as you pass your tool over the stone's wet surface. During use, the very top layer of abrasive constantly wears off, exposing a fresh layer of abrasive underneath. This is a lot different than the action of an oilstone...in which the abrasive particles are designed to be locked fast in a tight holding bonding agent matrix. When using an oilstone, the abrasive particles are worn completely away - but not moved around.

So, although waterstones are more porous than oilstones, glazing-up with swarf is less of a problem. Many users claim that a waterstone is practically impossible to glaze-over in the same way as an oilstone.

Routine differences
With waterstones, you need water to store them in...water to make them work...and even more water to clean them with when you're finished. This is an advantage in at least one way over oilstones: If you're in a hurry to use a newly honed chisel and fail to take the time to clean your hands after honing, you won't have to worry about bringing oily fingers to your wood project. However, it is important to remember that water is also an alien in the workshop environment. It rusts tools and stains raw wood. For that reason, you should keep a more-generous-than-normal supply of soft, absorbent rags close by when using waterstones. Fortunately, from a safety standpoint, storing water-soaked rags in the shop creates little risk, compared to the dangers of spontaneous combustion posed by storing oil-soaked rags.

When using waterstones, remember to avoid splashing water onto nearby items that don't like water. It's a good idea to build a splash tray for waterstones, like the example shown in Fig. 2. It's make from a laminated kitchen sink countertop cutout, available inexpensively from your nearby home center, lumberyard or countertop fabricator.

Fig. 2 A splash tray can be made from a sink cutout. The area on the right side is for flattening stones. Click on image for larger view.

When you're finished using waterstones, be sure to dry your sharpened tools immediately to prevent rust and the leaching of moisture into your toolbox. For storage, it's a good idea to keep them wet...even when you're not using them...by totally immersing them in a sealed plastic container or bucket. This way, when you're ready to use them, you can just remove them from storage and go immediately to work, knowing that they're both clean and properly soaked. Failure to do so means that you'll have to anticipate each use, then soak them until the bubbling stops (about three or four minutes) before getting started.

It's important to note that leaving your waterstones continually wet will not harm the stone or its wooden base (attached permanently to many finishing stones) - although in some cases, the water can get pretty raunchy, pretty fast. You might want to add just a few drops of chlorine bleach for each gallon of water to retard bacterial growth. Remember, too, that if your shop isn't heated, never let a wet stone get so cold that it freezes. If this happens, the water will expand during freezing and cause the stone to crumble.


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