Popular Mechanics (South Africa)
WOODWORKING:
TOOL SHARPENING EXPLAINED
NO MATTER the type of woodworking you do, whether it’s palletwood plant boxes or mid-century modern reproductions, there is one unwavering constant – something that will give you true pleasure in your planing, joinery and finished pieces: This is the sharpness of your cutting edges.
When it comes to woodworking, tool sharpening is a primary gateway skill. Good quality woodworking requires a great deal of precision and deft tool control, and without truly sharp tools, these are nearly impossible to achieve.
When you start learning how to properly sharpen your woodworking tools, I recommend watching videos of respected cabinetmakers at work. Go on YouTube and watch Matthew Wolfe from Doucette and Wolfe Furniture Makers, Phil Lowe of the Furniture Institute of Massachusetts, woodcarver Mary May, and any other craftspeople at the top of their craft. It’s here that you’ll see perfectly sharpened tools in actual use, which will offer you a much more realistic sharpening benchmark to aim for.
Sharpening is a skill that’s hard to teach yourself in isolation. It’s best acquired by working with and learning from someone else, because until you’ve used a truly sharp tool, you won’t know what results you’re actually trying to achieve. Your blades should cut with minimum effort. The finished surface should glisten and appear waxy, almost like a bar of soap shaved with a pocketknife. When you use a truly sharp tool, only then will you understand your sharpening objective.
It’s time to become close friends with your arris. Don’t know what that is? The arris of a blade is the sharp edge formed by the meeting of two flat or curved surfaces. It’s also the point of this series of articles.
So how do you create a properly sharp arris on all of your cutting tools, and how do you maintain it? Most of us weren’t ever taught the
The majority of tools in workshops have never reached their full potential.
correct sharpening procedure, and the majority of tools in schools, workshops and garages have never reached their full potential, having never been sharpened properly. It’s very important to separately define the two phases of achieving proper cutting edges.
Sharpening: This is generally for new tools that haven’t been correctly flattened and don’t yet have a proper edge, or when a new edge needs to be created from scratch.
Honing: This is the last step in the sharpening process, but it should be the only step required when your tools have begun to lose their keen edge. Honing is what you do between sharpening sessions, meaning that most of your sharpening efforts will actually be honing. Or, at least, they should be.
If you hone well, and with sufficient frequency, you might find that you only need to actually sharpen your tools yearly, or even less frequently.
If you think about your edge-tool sharpening process in the same way as the way you work through various grits of sandpaper to achieve a smooth finish on wood, you are on the right track.
The basic principle is the same. Each progressive sandpaper grit removes the larger scratches left by the previous grit.
The same principle applies when sharpening. There are a number of excellent sharpening machines on the market, solidly led by manufacturers such as Tormek. However, learning to sharpen your edge tools properly does not start with a machine.
My sharpening preferences for all edge tools are Japanese ceramic whetstones that use water as their slurry lubrication medium. Whetstones come in a wide range of shapes, sizes and material compositions. They may be flat, for working flat edges, or shaped, for more complex edges, such as those associated with woodcarving or wood-turning tools. They may be composed of natural quarried material, or of man-made material.
These sharpening stones are widely available in various grades referring to the grit size of the abrasive particulate in the whetstone. Grit size is given as a number, which indicates the spatial density of the particles. A higher number leads to a finer finish of the surface of the tool.
Though ‘whetstone’ is often mistaken as a reference to the water used as a lubricant, the word ‘whet’ actually means ‘to sharpen’. The process of using whetstones is simple, and you will achieve excellent results with a few grades of good-quality whetstones and a little practise.
To start sharpening your hand-plane-, bench-chisel- and marking-knife blades, you require at least the following:
• Wet and dry sandpaper up to 800 grit. • 1 000 grit medium Japanese ceramic whetstone.
• 3 000 grit fine Japanese ceramic whetstone.
• 6 000 grit extra-fine Japanese ceramic whetstone.
• 8 000 grit super-fine Japanese ceramic whetstone.
Higher grit Japanese whetstones (as high as 30 000 grit) are available in South Africa,
but they tend to be extremely expensive. Even though whetstones become more expensive as the grit gets finer, you’ll wear a fine gritstone at a much slower rate than a coarse whetstone (which is much cheaper), so it’s all likely to balance out.
Japanese ceramic whetstones tend to last longer than natural stones, and I feel the distribution of the particulate is much more consistent throughout the stone. The better brands, such as those from Suehiro, each come with their own small specific gritstone called a nagura. The nagura stone is rubbed lightly over the whetstone to create a slurry or mud. This slurry does the major proportion of the actual cutting and also assists in preventing the blade from becoming stuck on the whetstone due to surface tension, which can sometimes be near impossible to shift, especially on finer-grit whetstones.
Keeping your whetstone absolutely flat is critically important. Sharpening experts recommend the use of a diamond plate to flatten your whetstones. These are heavy and dead flat, and covered with industrial diamond particulate in various grades. DMT makes the best ones available in Southern Africa and if you go this route, I suggest you get the ‘extra coarse’ or ‘extra extra coarse’ plate. These are the plates I use in my sharpening regimen. The alternative is to flatten your whetstone by using the next highest gritstone, which is then used to flatten the lower one … and so it continues. This works perfectly well, but you’re also wearing away your second stone in the process. A diamond flattening plate will last for ages and is well worth its price many times over.
A good process to follow is to draw a light 2B or 4B pencil grid on the surface of the whetstone before flattening. When all of the pencil lines have been erased, your whetstone is flat.
To get an old, worn chisel or plane blade back to the point where you can start to properly sharpen it using your whetstone, get your hands on a granite off-cut centre section from your local kitchen-counter supplier. One of these flat blocks of granite, or a thick (6–10 mm) piece of float glass works perfectly with wet and dry sandpaper and a little water for the initial flattening of your chisel, marking knife or plane blade back to 800 grit. This sandpaper system should also be used for new blades where the back of the blade has not been lapped properly by the manufacturer. This system is also excellent for flattening hand-plane soles and sides.
On a new edge tool of really good quality A2-, T10-, O1- or PM-V11 steel – such as blades from Lie-Nielsen Toolworks, Veritas Tools and Luban – there is generally little or no work required on your granite, glass and sandpaper set-up. The initial lapping has already been carried out by the manufacturer and most often you can start work with your 1 000 grit whetstone and its associated nagura.
Always remember that no edge tool, not even those from the premier manufacturers, arrives perfectly sharpened and finely honed for use, no matter what the packaging says. Top brands such as the ones mentioned above are usually well prepared, and therefore require very little work by you to get them properly sharp. But they still require some work.
Keeping your whetstone absolutely flat is critically important.