10 Essential Sharpening Tricks: Hone Your Sharpening Skills … And Your Tools.Comments (0)
This article is from Issue 62 of Woodcraft Magazine.
Hone your sharpening skills … and your tools.
Sharpening straight-edged tools, such as chisels and plane irons, is a necessary and regular part of ownership. A dull tool is a dangerous tool. A sharp tool cuts better and is safer because you have more control, and the results speak for themselves: You get clean, flat surfaces that are free of scratches, crisp lines that hit the mark without chipping or blowing out, and the joy of pushing or pulling a tool without undue force or stress. In short, a sharp tool is a good tool. Anything less, and it’s time to sharpen.
To keep your sharpening regimen accurate, effective and fast (so you can get back to working wood) I’ve outlined ten tactics for better edges. These sharpening methods are organized into three core categories: grinding, honing and polishing. While I use waterstones for the lion’s share of my sharpening, most of the tips shown here can be used with other sharpening tools, such as oilstones, ceramic stones, diamond stones, or even–if you’re so inclined–sandpaper. Implementing these strategies into your regular sharpening regimen is bound to boost your sharpening skills so you can get back in the game in short order, with edges super sharp for the most demanding tasks.
1 Set up your grinder for success
Shaping new tools, altering bevel angles, or simply removing nicks in an edge are all part of a bench grinder’s job. But not all grinders are created equal. Spinning at 1,750 rpm, a slow-speed grinder generates less heat than a conventional 3,450-rpm grinder, making it less likely to burn, or “blue,” your tools. Listed by the diameter of their wheels, you can choose from 6" or 8" models. Larger wheels grind more steel in less time, but will heat edges more readily; smaller models typically cost less.
For optimum control, position the grinder high, so that the center of its wheels sits at about the height of your bent elbows (typically 44" to 48" from the floor ). This setup lets you lock elbows and use your upper body and forearms for smoother tool movement side to side. Of course, a sturdy tool rest is essential. Look for a large table that’s easy to fine-tune for height and angle, and one that locks securely. A tool rest that’s notched to surround the wheel is a handy feature for light side grinding.
For most woodworking tools, a 120-grit wheel is the best choice. Look for wheels with a vitrified bond. These break down easily in use to expose fresh particles, reducing heat buildup and lessening the chance of bluing. Because wheels wear and collect metal debris, you’ll need to dress the working surface periodically. I use two dressers to keep my wheels clean and to shape them. The first is a diamond dresser that cuts very fast and lets you remove deep grooves and imbedded metal particles. I follow this with a silicon carbide dressing stick to smooth the surface and refine the shape into a slight belly. The belly prevents over-grinding and provides more control, especially with narrow tools. And since you’re cutting in the center, you don’t have to sweep a wide tool completely off to the side of the wheel as you would with a flat wheel.
With the right grinder setup, you’ll automatically grind a slight concavity into the bevels of your chisels and plane irons. This “hollow-grind” (which matches your wheel diameter) has the benefit of making the tool much easier to hone by hand, as I’ll describe on page 38.
2 Reshape an edge to square
A square edge is the goal when grinding most edge tools. The tricky part is marking out an accurate reference line to work to when grinding, since steel resists pen and pencil.
The fix is to spray a coat of fast-setting layout fluid, or machinists’ bluing, on the back of the chisel or iron up to the cutting edge. Use a small square and a sharp awl or other fine-pointed tool to etch through the thin, uniform color close to the edge, exposing a precise line that’s square across the face of the back. You can grind to the line, or simply use it as a mark for eyeballing straight and square. The thin paint comes right off with a swipe of denatured alcohol, or with two or three passes over your stone.
3 Color the bevel to gauge the grind
A consistently ground bevel is key to a well-sharpened tool. But it can be tricky to reliably assess your progress during grinding. A dark felt marker can take the guesswork out of the job, letting you gauge your progress as you grind. Mark the entire face of the bevel, and grind until all the color is removed.
Once you get the knack for grinding a smooth, consistent bevel, take a close look at your work. A pocket magnifier or a photographer’s loupe will help you see the very cutting edge, and whether it’s even and without large chips, or whether you need to go back to the wheel.
4 Put the heat in the sink
Quenching a hot blade in water is a recipe for disaster. Too hot, and the plunge can create tiny fractures in the steel, weakening the edge. Instead, you can cool off a hot blade without stressing the steel by holding it on a computer heat-sink for a few moments. They’re typically free from any neighborhood computer whiz kid.
1 Prep and hold your stones
For good control, set up your honing station relatively low, or about 30"-36" from the floor to the top of the stone. I use a series of waterstones for honing and polishing. For rough work, where the edge is badly deteriorated, start with an 800-grit stone. But for most sharpening, begin with a 1200-grit stone for honing, and then move directly to a 6000- or 8000-grit stone for polishing.
Mark the grit on your stones by labeling their ends (not their sides) with a hard, pointed object such as a carbide-tipped pen. If you use an awl instead, be prepared to resharpen it afterward.
To prevent chipping, slightly chamfer all the sharp edges on both new and worn stones by rubbing them with a 150-grit sanding block or a flattening stone (see illustration at right). Pay particular attention to the ends, where chipping is most likely, making the chamfers wider here.
A simple plywood tray will hold stones securely and can be conveniently dogged to your benchtop. Keep a spray bottle of water on hand to wet the stones as you work. When honing either the back or the bevel, I resist conventional wisdom by positioning the tool sideways on the stone and then moving it forward and backward. I find that this approach provides more control and allows greater tactile feedback while allowing me to maintain the tool at a consistent angle.
2 Keep your stones flat
Flat stones make for precise sharpening, so it’s important to true your waterstones on a regular basis. You can use any stone to flatten another, but commercial flattening stones and diamond stones are much faster-cutting. A coarse (220-grit equivilent) diamond stone cuts faster than a flattening stone and leaves a slightly smoother surface, but it typically costs three times as much.
Using plenty of water, rub the flattening stone back and forth on your honing stone, pushing straight ahead and occasionally skewing it at an angle. Once or twice, turn the honing stone 180° and repeat. It’s flat when it’s an even color, with no dark or light spots.
3 Hone the back flat–fast
The backs of new chisels and plane irons need flattening, and regular sharpening sometimes requires a similar amount of work. To speed up what is often a laborious process, make a 13⁄4 × 4 × 71⁄2" hardwood block and firmly press it 1"-2" over the leading edge as you push both tool and block over the stone. Rub until the back has an even luster.
4 Hand-hone the bevel
A consistent angle is paramount when honing the bevel. And thanks to the hollow-ground bevel left by the grinding wheel, honing by hand is well within the skill set of the novice. Place the bevel on the stone, and rock it slightly until you feel it firmly seated. Grip the tool with one to three fingers on the back (depending on how wide it is) and, similar to grinding, lock your elbows and move the tool with your upper body, not your arms. Your other hand simply supports the weight and helps move the tool back and forth.
Once you feel a full-length burr, flip the tool over and hone the back. For a longer-lasting, tougher edge, consolidate and refine the already sharp edge by flipping the tool repeatedly, decreasing the pressure each time until you finish with a light touch on each side.
1 Look in the mirror
Under a microscope, metal that’s polished to a mirror-shine still reveals scratches similar to those found on a surface with a dull, or matte, finish. Although both are sufficiently sharp to cut wood, a polished surface is tougher and more durable because the edge has shallower scratches.
As you did with the 1200-grit stone, use a 6000 or 8000 stone and hone the back and the bevel, flipping back and forth to remove the burr, while decreasing pressure with each flip. If you’re polishing a freshly-ground bevel, it takes only seconds to create a tiny, polished strip of metal at both the toe and heel of the bevel. The back, however, takes more work, and it’s often prudent to get out your rubbing block again to initiate a shine. As before, you only need to focus on the endmost 1"-2" of the blade when polishing the back. Finish by hand, again with light pressure. It’s a good exercise to inspect the surface under magnification. The goal is to rub until you can see your reflection.
2 Dub the corners
When you need to plane a wide surface, rounding over the corners of your plane irons will reduce track marks on your work. The approach is simple, but care should be taken not to groove your stone. Using a 6000 or 8000 stone, hold the iron at roughly 45° to the surface and drag the tool back towards you. On the first pass, almost lift the blade as you pull, then make two or three more passes with just the weight of the blade on the stone.
About Our Designer/Builder
Andy Rae is an award-winning furnituremaker whose career spans several decades. He has authored a number of books on woodworking, including The Complete Illustrated Guide to Furniture and Cabinet Construction (Taunton Press). He currently makes his home in the mountains of western North Carolina.
You must be logged in to write a comment. Log In