Waterstones Canadian Woodworking Magazine

Sharpening Technique 

By Hendrik Varju

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Waterstones



Illustration by Mike Del Rizzo

Although learning to use hand planes and chisels takes practice and patience, the learning process is made much easier if you know how to sharpen those tools. My new students often say how much they dread the hand planing portion of a course. When I hear that, I know it’s because those students have only ever used dull tools. Once they've learned how to properly sharpen their tools, hand planing and chisel work become surprisingly enjoyable.
 
Select the Right Grits
The key to proper sharpening is to use good quality waterstones (see the sidebar 'Stone Tips'). These versatile synthetic stones can repair mildly damaged cutting edges and take you right up to razor sharpness. If you can only afford a single stone, I would recommend a combination stone with 1000 grit on one side and 4000 on the other. 1000 grit will give you a basic edge, while 4000 grit will give you a razor sharp edge.

If you have a more flexible budget, I recommend a 220 grit, which will rapidly remove material, a 1000 grit stone for initial edge-forming, a 4000 grit for further honing, and an 8000 grit to get a mirror-like finish. Having separate stones means that a lower grit stone can be used to flatten a higher grit stone. So, you can use a flat 1000 grit stone to flatten both your 4000 and 8000 grit stones. However, some other method must be used to flatten your lowest grit stone. I use 90 grit silicon carbide powder on a thick sheet of glass to get my lowest grit stone flat. You can also use a diamond bench stone or wet/dry sandpaper.
 
Keep Them Flat
Remember that waterstones cut remarkably quickly because their surfaces wear quickly, constantly exposing fresh material to cut metal. That also means that waterstones wear quickly, so keeping your stones flat is an on-going process you need to do regularly. I like to do a bit of flattening every time I pick up a stone out of its water bath. If the stones aren’t perfectly flat, they’re incapable of creating truly sharp cutting edges.

To reduce bacteria build-up, rinse and store them in fresh water after each use. Very fine stones (6000 grit and higher) don't need to be soaked prior to use, just splash water on them when using. When sharpening don't wash away all the slurry, it helps speed up the sharpening process.
 
Honing Guides
Honing freehand requires some hand skills, so some of you might prefer to use a honing guide. The guide will help you maintain the correct angle for honing your blades. The correct angle is around 25º for softwoods and a little closer to 30º for hardwoods. I hone mine in the range of 27 to 29º so that they hold up fairly well for hardwoods but still aren’t too difficult to push. A honing guide will help you develop a primary bevel of around 25º. Then, by pulling the blade further into the guide, you can add a secondary bevel of around 27º or more, just at the tip of the blade.
 
Hollow Grinding
My preferred technique is to hollow grind my cutting tools on the round edge of a grinding wheel. I use an inexpensive slow rpm wet-wheel grinder because it is slow enough not to blue the steel and draw the temper of the tool. Being in a water bath also keeps the steel cool. These kinds of grinders cut a lot slower than the high rpm grinders, but they give better results without damaging the tool. Good results don’t come quickly.

The beauty of hollow grinding is that it leaves a concave shape on the bevel side of my hand plane irons and chisels. When I hold the concave bevel on the surface of a stone, I can hold the tool at the correct angle by feel. With only two contact points on the stone, it’s easy to tell if you are holding the tool at the correct angle.


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Hollow Grinding

Waterstone Technique
Once you’ve learned this holding technique, you can draw the tool backwards (pull it towards you) on the bevel side for four or five strokes on the 1000 grit stone. Then flip the blade over and push the tool forwards on the flat side for the same number of strokes. Pushing the blade on the bevel side is likely to catch badly on the stone if you aren’t really careful, but pushing the blade on the flat side is easy and cuts off the metal burrs folded over from the bevel side.

If this establishes a clean, shiny cutting edge, then you can move on to a higher stone grit. If not, do more strokes on both sides again. When satisfied, move to your 4000 grit stone and do the same, and then on to your 8000 grit stone if you have one.

On the final stone, I like to do five strokes on each side of the cutting edge, then four, then three and so on. A certain number of strokes on the bevel side creates a certain size of burr on the flat side. By using the same number of strokes on each side and working your way down from five strokes to one, you methodically work towards sharpness.

Your goal is a cutting edge with almost zero thickness, which is the definition of true sharpness. Try to use all the surface of your stone when sharpening, or else you'll quickly create a 'valley' in the stone.
 
Start Shaving
When you’ve achieved a truly sharp edge, you’ll be able to shave the hairs off your arm or leg. My left arm is half bald for most of the winter months, while my left leg is half bald in the summer months when I’m wearing shorts. But it’s a small price to pay for tools that cut well.


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A  Norton 220x
B  1000x/4000x combination
C  8000x 'Gold'
D  DMT 600x/1200x diamond stone
E  Kell honing guide

Stone Tips
Select a synthetic waterstone; they are less expensive than natural waterstones, and more consistent in quality. Unlike oilstones, which use oil as a lubricant, waterstones use water. Because they are not as hard as oilstones they cut much more quickly, so you'll get back to work sooner, and you won't risk getting oil on your work.

Before using your waterstones soak them in water: about 5 minutes for a coarse stone or 15 minutes for a medium stone. In fact, you can store them in a plastic container filled with water. Lee Valley's 'Stone Pond' is an excellent waterstone storage container.