One of the most important aspects of a chisel is the edge. While we often mention how important it is to keep a good edge on your hand tools, it’s not often we stop to focus on the tools needed to get that job done. Here we’ll explore the specifics of keeping a chisel in shape.
Sharpening will improve your results with any chisel, though a high-quality steel will hold the edge for much longer.
STONES & STROPS.
There’s plenty of tools to sharpen a chisel, but let's explore a few traditional options: oilstones, waterstones, and leather strops. These three kinds of tools have helped to hone chisels (and other blades) for centuries. Despite that, these sharpening methods still benefit from modern innovations, whether it’s synthetic stones or abrasive honing compounds.
When you begin sharpening, a honing guide is vital. This tool will keep your chisels (or plane irons) at the proper angle while you work on the edge.
SHARPENING STONES
Chances are you’ve seen sharpening stones before, whether you own a few or not. There are two traditional kinds of sharpening stones: oilstones and waterstones. As the names imply, they use oil and water as lubrication respectively. However, there are more differences than just that.
OILSTONES.
All stone is porous, but oilstones have the finest pores of any. These pores are densely packed, which gives oilstones their high grit. They come in a wide variety as well, from low cost, coarse synthetic stones to expensive, translucent Arkansas stones.
Mineral oil or synthetic honing oil lubricates oilstones, making for a cleaner edge and preventing the minute metal filings from clogging the pores of the stone.
Crystolon and India stones are good options for synthetic oilstones, while hard black and translucent Arkansas stones are excellent natural options.
In general, you’ll want to stay away from cheap options. This is one of those cases where cost does dictate quality. However, not all synthetic options are bad: the crystolon and India stones
shown above are fine choices. They’re made from bonded abrasives and won’t break the bank, but they usually come only in coarser grits.
Arkansas stones are natural oilstones (quarried in Arkansas, oddly enough), and are my preferred type of sharpening mineralogy. These stones (the translucent ones in particular) are incredibly hard and quite high grit.
There’s little to no chance of one of these dishing out over time, and since oil is the lubricant, there isn’t a risk of my chisel rusting if I don’t dry it completely after sharpening. However, the high grit means I reserve my oilstones for keeping my sharp tools sharp. For work on blunter chisels, there’s a better choice of stone.
WATERSTONES
To those outside the spheres of modern tool sharpening, “waterstone” may evoke images of a knight sharpening his sword with a whetstone. This has become a bit of a misnomer — “whet” is an archaic word for sharpen. What he may have actually used was a waterstone. A waterstone has larger pores than an oilstone.
Waterstones need to be soaked. The water seeps into the pores and saturates the stone — once the bubbles stop coming out, it’s ready to go.
For this reason, it needs to be soaked in water to lubricate it, and it has a higher friability than an oilstone. That means that a waterstone will wear down over time. Waterstones will form troughs down the center where the chisel (or plane iron) has, in essence, eroded the stone, but these can be corrected by regularly flattening the stones.
Synthetic waterstones, like this one, offer a coarse and fine stone in one package.
The advantage to waterstones is that they work quite quickly. In addition to the lower grit, wearing away quickly also means they stay abrasive. Waterstones are a great tool to keep around for fixing up old chisels, or sharpening ones that could use a little extra work. Additionally, they tend to be cheaper than natural oilstone.
Natural waterstones often retain their quarry marks along the edge and underside.
STROPS
Although many woodworkers know about the benefits of sharpening with stones, not as many seem to make use of strops. As with waterstones, the popular idea of a strop seems to come from movies: the cowboy walks into the barber shop, the mustachioed barber swipes his straight razor up and down a long, broad strip of leather.
A gunfight probably ensues. While I’m not qualified to speak on the specifics of historical hairdressing, I can say that my strops look a bit different.
Lightly stropping tools like chisels and plane irons after every session will keep a sharper edge, meaning you’ll have to get out the stones less often.
STROPPING TOOLS.
What I use to strop chisels (and plane irons, or any other blade in need) is what you see above: two pieces of leather glued to a block of wood, one side smooth, the other suede. The various compounds you see make the honing more efficient.
A strop is often just a piece of leather attached to a block of wood, with a smooth and suede side. Honing compounds will increase the effectiveness of stropping.
The compounds range from abrasives like aluminum oxide and chromium (green stick) to micron-sized diamonds in a paste. Although stropping with a compound will get you unparalleled sharpness, beware of compounds that are too expensive. Regardless of how high a grit that can theoretically be reached, you’re going to find a point of diminishing returns.
As I mentioned at the beginning of this article, the quality of steel matters greatly when it comes to sharpening and honing an edge. All the work in the world won’t do any good if the steel is too soft to hold a razor-thin edge, or so brittle that it chips. For example, the yellow chisel isn’t worth sharpening beyond a waterstone. By contrast, the blue-handled chisel is a decent quality steel (and polymer — not all plastics are equal). It benefits quite a bit from some fine honing.
HONING
Honing with a strop is a simple task: pull the chisel back along the edge of its bevel. It really is as easy as that, but, like any hand technique, it requires putting in the time to build up the muscle memory before it will come naturally. I start off by applying the compound to the strop (or “charging the leather”).
Many honing compounds come in wax-like sticks, while others are a paste.
Often, as you can probably tell from the strop above, I’ll use an inexpensive compound (i.e., the green stick) to strop the majority of my chisels. The diamond compound is reserved for my paring chisels (and the irons on my smoothing planes). For those tools, I want the very best edge. For the others, it’s not quite worth the investment, cost or timewise.
HONING WITH A STROP.
Spread the honing compound evenly across the strop. Honing compounds come in various
grits for coarser and finer honing.
Begin by laying the chisel down with the edge raised, resting on the crest of the bevel. Lightly press the tip of the chisel down until you fell the bevel making full contact with the strop.
Pull the chisel back across the strop to hone the edge. As you repeat the action, it’ll get easier to find the bevel angle quickly. If you hone consistently, ten to fifteen passes should be sufficient.
Steps 1 through 3 shows how to strop a chisel. Step 1 shows applying the compound, as I mentioned earlier. Honing compounds are abrasives in a bonding agent, so they can cause a bit of irritation if left on your skin. After that, it’s a matter of finding the bevel edge. Begin by resting your chisel on the “nose” of the bevel.
Then tilt it down until you make full contact. Once you do, draw the chisel back across the strop. Unlike sharpening on a stone, you’ll actually be going with the edge rather than against it. Repeat this for a dozen passes and you’ll polish the edge to a mirror-sheen.
WHEN TO STROP.
Although I’ve treated stropping as the last phase in sharpening so far, the truth is that most of my stropping is an everyday task. Stropping has little effect on a blunt edge, but does well at maintaining an edge that is already sharp. For that reason, it’s a good way to keep a keen edge in shape. I try to strop my tools before or after every use (which is why I go with the inexpensive green stick most of the time).
Even if I’m feeling lazy, stropping without any compound is better than not doing it at all. In the end, it spreads out the half hour I’d spend sharpening on one day to a minute or two each day. No matter the task, having the right tool for the job is a necessary ingredient. Thankfully, the tools you need to keep a good set of chisels in shape aren’t too expensive, especially relative to many of our woodworking paraphernalia.
Additionally, these techniques can go a long way in improving a lower quality set of chisels. There are a number of companies that produce relatively inexpensive chisels with decent quality steel, yet they have the stereotypical “cheap” appearance. If sharpened properly, one can work as well as many far more expensive options – if you turn a new wood handle, no one would know the difference.
