Chisel Rescue

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This article is from Issue 68 of Woodcraft Magazine.

A grinder, honing stones, and some elbow grease can save a good tool from the scrap heap

By Paul Anthony

Far too many chisels, plane irons, and saws face a premature death or dismissal. Scrap heaps and flea markets are full of tools discarded simply because they’re ugly with rust or battle scars. But any savvy woodworker recognizes that there’s good life, and even honor, in many “trashed” tools, especially older ones. In fact, the quality of the metal in an old chisel or plane iron often surpasses the steel used in new tools.

Chisels are among the best candidates for restoration. As a woodworker, you may already have most of the sharpening equipment you need for the job. As for me, I use an 1800 RPM “slow-speed” grinder for shaping, and waterstones for honing. It’s basically a 3-step process that involves honing the back to a flat, polished surface, reshaping the edge at the grinder, and then finishing up by honing the bevel to a polish. Whether you use waterstones, sandpaper, diamond stones, or oilstones for honing, the basic process is the same. (By the way, some or all of the processes I show you here often need to be applied to brand-new chisels, which usually don’t come with polished backs and nicely honed bevels.) So have at it. Do yourself a favor, and save a chisel in distress. It will pay you back big dividends over its new life.

This once neglected and abused chisel is now proud, looking sharp, and ready to take on a job.

Don’t look naked. Sharpening involves peering into a small world. Don’t expect your naked eye to see what’s important. Use a 10x eye loupe to inspect your sharpening progress under a strong light. If the magnified surface looks good, the tool should work well.

Assess the damage: Is it worth the work?

Before investing time in resurrecting a chisel, scrutinize it to make sure it’s not too far gone. First, clean and inspect the back. It’s crucial that you’ll be able to flatten at least the endmost 1⁄2", and remove any shallow rust pits or scars at the same time. Check the flatness with a small straightedge. If it’s very slightly concave, it’s still a candidate. But if it’s convex at all, it won’t be worth the work. Likewise, if it has deep rust pits or scars near the far end of the back, forget it, as these will eventually intersect the cutting edge, compromising sharpness. That said, any deep pits or nicks at the very end of a candidate chisel can be eliminated by grinding the tip down past them. Don’t worry if the back is rounded over at its end; the steel can also be ground past that damage. However, if the sides are badly rounded over near the end, I’d pass.

Step 1: Flatten and polish the back for precise cutting and keen honing

For a chisel to work well and hone properly, the back must be flat and polished. If it’s badly pitted or out-of-flat, start with a good quality coarse stone like the 220-grit made by Norton. Rub aggressively, working the entire surface of the stone in full-length strokes to minimize hollowing it, and dress it flat occasionally. Apply strong pressure with your fingers spread out across the endmost 11⁄2" or so of the chisel. Be careful not to lift up or you’ll round over the area near the cutting edge. After you’ve produced a consistent scratch pattern on the back of the chisel, move to an 800-, and then a 1200-grit stone, repeating the process. Finally, finish up on a 6000- or 8000-grit stone for the final polish.

Stay dressed. Waterstones cut quickly, but must regularly be flattened, or dressed in use. Here, a 220-grit stone is rubbed across a slotted “flattening stone” to get rid of the slight hollow caused by working the chisel on the stone.
Slurry up. For the most aggressive cutting, keep the stone clean. But as you achieve a consistent scratch pattern, let the slurry of metal particles build up on the stone to serve as an intermediate grit before moving on to the next stone.

Finished back. Finish up the back by polishing it on an 8000-grit stone. Afterward, it should reflect nicely when viewed from an angle like this. Although you’d probably see the light scratch pattern looking straight at it, this is a great polish.

Step 2: Head to the grinder to square the edge and create the bevel

To true the cutting edge and shape the bevel cleanly without burning (bluing) the metal, you’ll want a slow-speed grinder outfitted with a soft-bond 80- or 120-grit wheel. I highly recommend replacing most stock tool rests with a much more adjustable aftermarket rest such as the Veritas model seen in these photos. Before grinding the bevel, swipe it with a marker to help you hit your center-of-bevel target, and then maintain your exact chisel pinch throughout the process. To prevent burning the metal, keep the tool moving, don’t be heavy handed, and cool the steel occasionally. 

Dressed with diamonds. In preparation for grinding, use a diamond-faced dresser to clean and true the edge of your grinding wheel. For best grinding, give the wheel a slight crown.
Nose to the grindstone. To square the edge while removing any nicks, set the tool rest level, and very slowly press the edge against the wheel, moving it slowly side to side. Check your progress occasionally with a small machinist’s square. 
Slide side to side. When grinding the bevel, pinch the chisel firmly, using the second section of your index finger as a fence against the tool rest. Place a finger lightly on the back of the blade to apply pressure against the wheel as you move the chisel slowly back and forth without leaning it left or right. 
Blunt assessment. Proper grinding technique results in the blunted end of the blade gradually and consistently narrowing until it’s just a hair’s width.

Computer cool. Avoid water-quenching, which can fracture a thin edge. Instead, use a heat sink like this one, scavenged from an old computer.

Training wheels. A honing guide will hold your chisel at a steady angle for neatly polishing the end of the newly ground bevel. For the first couple of strokes on a 1200-grit stone, pull the chisel toward you. Then push it back and forth, applying pressure at the tip, until you have established a narrow flat completely across the width of the cutting edge.

Step 3: A few swipes over your finer stones, and you’re killer sharp!

To hone a freshly ground edge, begin with your 1200-grit stone (using a honing guide if you like). As soon as you’ve honed a narrow facet completely across the cutting edge, spritz water on a freshly dressed 6000- or 8000-grit finish stone, and work the bevel on it in a similar manner until the facet is evenly polished, as shown in the photo on page 28.

To remove the fine wire edge created in the honing process, lay the chisel on its back, work it back and forth a few times, then give the bevel a few more strokes. Finish with a few final strokes on the back, and you’re done.

Nice slice. A truly keen edge will allow you to cleanly pare softwood end grain without struggle or crumbling.

Honing by hand

Although honing jigs certainly work, there is a downside to depending on them: they take time to set up. Freehand honing is quicker because you don’t have to mount and adjust your tool in the jig. Of course, in the latter case, you do have to invest the time into learning the process, which simply requires practice.

The secret to successful freehand honing is to concentrate all of your attention at the business end of the chisel, applying strong downward pressure above the bevel with your left hand. Use your right hand to power the chisel, pinching its sides between your index finger and thumb, keeping your fingers dry for good friction. Curl the remaining fingers under the blade, applying just enough lift to keep the handle from falling. (Lefties, reverse all these directions.)

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