Sharp tools are dangerous, but blunt tools, too, may cause accidents. The proper sharpening of tools is very important. With sharp tools you can make more beautiful surfaces and work more safely, too. You don’t need to apply extra force to your tools hard if they are sharp enough. Sharpening requires a lot of practice and patience. You should start it only when you have enough time and do not need to hurry. Sharpening techniques are worth familiarising with, especially considering that you can even use them for sharpening your kitchen knives and make your work with them easier. Should any of your tools get extremely blunt or their blades broken due to incorrect use, take them to a workshop; restoring them by hand would take too long.
Unfortunately some tools cannot be sharpened or are not worth sharpening due to the poor quality of the material they are made of. You should not waste your time and energy on these. You can probably use them for testing or practicing sharpening, however. Good quality tools should, on the other hand, not be overused just because you are inexperienced in sharpening. Old knives, saws, planers or chisels that have proven to be good and have durable blades should be sharpened.
Place the saw into a saw vice as close to its teeth as possible; if you do not have a vice, hold them tight between two strips. Be careful not to damage the kerf. Unfortunately I do not have a saw vice so I use wooden strips when sharpening saws.
(Saw held tight by strips)
(Check the straightness of the teeth with a ruler)
File the teeth of the saw that are longer to ensure that they are of the same length as the other teeth. Using a triangular file, file the teeth in a way keeping the angles of the teeth until the cutting angle gets sharp enough. File all the teeth to the same extent; avoid making teeth of various sizes. The usual practice is to file the side opposite the blade, as you can see in the illustration.
(Sharpening a saw tooth. Blunt (1) Sharpening (2) Sharpened tooth (3))
(Filing saw teeth)
After sharpening, check the kerf or the setting of the saw. There are several types of setting so if necessary you have to set the teeth anew, in the same direction as they were set before, up to one third of the blade.
(Setting the teeth of the saw)
Setting can be perfectly made with setting pliers.
(Setting pliers in use)
The blades of Japanese saws and coping saws cannot be sharpened; new blades have to be bought.
The sharpening of tools and knives made of tool steel:
Let us learn about sharpening stones first. Sharpening stones are specified based on various characteristics. One is the material and size of the grains. For sharpening, the size of the grains is the most determinative. This is measured in µm, which is the one millionth part of a metre. Depending on the grain size, there are categories set up depending on three decisive standards. The first one is the category of the FEPA-P standard (materials with grain coating) like sanding papers from P12 (1815µm) to P2500 (8,4 ± 0.5µm); the second one is FEPA-F (sanding materials with glued grains) like stones, ranging from F4 (4890µm) to F2000-ig (1.2 ± 0.3µm); and the third one is the category of the JIS standard. JIS uses a logarithmic instead of a linear scale. JIS ranges from J100 (125µm) to J30000 (0,5µm). It is therefore not enough to specify a number only. For instance, 2000 can refer to sanding material with a grain size of 8µm, 10µm or 1.2µm. The binder used, which is most frequently ceramics or resin and the porosity of the stone are also determinative for stones. For sharpening you can buy very good stones with various combinations of the two sides. The combinations F280/F800 ≈ J400/J2000 are suitable for roughing and F1000/F2000 ≈ J3000/J8000 for honing and deflashing. Sanding leather creates a surface with a grain size of approximately J12000. Under a grain size of J8000, you can use stones for the sanding of glass, mirror and optical lenses only. In the case of sharpening these, you can mirror finish the surfaces at a relatively decent price using paste only.
Sharpening stones can be natural or artificial. The best-known natural stones are the hard and the soft Arkansas stones and the green jade stone. In olden times, masters of woodwork sharpened their tools with flat stones found on river banks. Artificial sharpening stones come in various types (various profiles, sizes, grains, binders, etc.)
(Various sharpening stones)
The first and foremost thing to keep in mind is that sharpening tools should be performed in a well lit place. If necessary, use a magnifier.
Sharpening should always be performed in a comfortable position and with even movements at an even pace.
Do the sharpening with stones soaked in water or lubricated with oil; do not use dry stones. If you sharpen with a stone soaked in water, soak the stone half to one hour before sharpening. For sharpening with an oily stone, apply a few drops of oil to the stone before use. Use a piece of cloth or paper towel to wipe off stone and metal particles from the sharpening stone from time to time. You can continue work after oiling anew. Stones soaked in water, too, need regular cleaning: wash the stone regularly. Also, turn the stone from time to time to ensure even wearing off. As for the oil, I recommend mineral oil because it does not go rancid. I use regular machine oil but any oil is good enough.
Sharpening can be performed on an evenly flat stone only. Before use, you can check the surface of the stone using the edge of a ruler, from several directions. If necessary, you can make the surface evenly flat using another, coarser stone or flat concrete pavement. For help you can draw a grid on the surface to be improved in pencil and if the pencil has been removed evenly, you have successfully evened your stone.
(Evening the stone surface)
For sharpening bending surfaces, make a wooden holder for your sanding paper matching the bend in the surface.
It requires great practice to guide your tool while precisely keeping the angle when sharpening. It is therefore advisable to use sharpening guides for chisels and planer blades. With the help of sharpening guides, angles can be kept precisely and you get a properly sharpened tool in the end. The softer the wood you work with, the acuter, the harder the wood, the obtuser the angle of the bevel edge of your chisel should be. In the case of tools that have worked well, keep the original bevel angles.
(The angles of a planer blade. Bevel angle: 25º)
(The bevel angle of a chisel)
(Sharpening guide with an inserted planer blade)
(Check the precision of the position)
Perform the sharpening in at least two steps. In the first step, shape the bevel angle of your tool on a coarse stone with a grain size of J400 or J2000. Keep sharpening using less force against the bevel and more at the back of it until you have raised an even burr on the bevel.
If no burr has been raised, there is no sharp bevel yet so you cannot proceed further. Once you have an even burr on the bevel, proceed to step 2 by continuing sharpening on a stone with a grain size of J3000- J8000, using less force and deflashing the bevel. Be careful not to break off the burr; by breaking off the burr you damage the bevel itself. Remove the burr by fine movements, using little force.
(Tool inserted in a sharpening guide, on a stone)
When you have removed the burr, lay the blade on the stone with its back and push the blade towards the side a couple of times. You have now practically finished sharpening your tool.
(Tool with its back on the stone)
It may happen, especially in the case of knives, that you need an even finer edge. In this case, use a leather strap attached to a wooden board for further refinement. By this refinement you get a mirror-like finish. Do not apply any force because if you do so the edge of the knife will drive into the leather and get rounded. Lubricate the leather strap beforehand. The best lubricant is the mixture of petroleum and ash. Since I do not smoke, I apply a drop of machine oil to the leather.
(Obtain a mirror-like finish on leather)
(Sharpening leather straps)
Take care of your tools and sharpen them frequently, whenever you feel they are getting blunt. You can leave out three or four roughing movements and sharpen just the edge.
Knives can have various blade configurations. We’ll examine the parts of kitchen knife blades, which are the actual bevel (1) the tip (2) and the blade (3). The tip may have various shapes. In the case of (A) it is concave, in the case of (B) it is straight and in the case of (C) the tip is convex. Try to sharpen your knife by keeping the angles as much as possible. In the case of (A), the shape of the tip can be kept by using a machine or a profile sharpening stone only. In the case of carving knives, there are no such strict distinctions.
(Kitchen knife profiles)
In the case of carving knives, the two sides of the tip constitute the actual bevel, too. It is because of this double-sided profile that carving knives are able to cut wood nicely. Shepherds’ knives used to have a similar profile in olden times.
(Carving knife blade profiles)
When sharpening kitchen and carving knives, you follow a technique similar to sharpening tools. Sharpening is performed in at least two steps. The bevel angles of carving knives are usually between 7º and 20º, depending on how hard wood or bones the particular knife is sued for. The bevel angles of chef’s knives vary between 20º and 30º; those of boning knives between 30º and 45º. When sharpening, the knives should be kept on the stone in an angle half of the bevel angle. You can use knife sharpening guides but can do without them, just keeping the knife with your hand while sharpening. A protractor comes in handy for measuring the angle.
When sharpening a knife, lay your stone at the edge of the table. Place a silicone rubber pad or a piece of cloth under the stone to prevent the stone from slipping out. At this stage you can choose from two techniques: the Japanese and the Western style sharpening.
I prefer the Japanese method. Hold the knife with the blade edge towards you. Hold the handle with your right hand and the blade with your left hand from the bolster, supporting it with your thumbs. During sharpening, do not put your fingers in front of the knife because a blade that gets stuck may cause injuries. Holding the knife correctly, push it along the stone while pressing it evenly. Then, pull it back with the edge facing you, exercising less force. Repeat this movement again and again, putting a different part of the blade on the stone, until the whole blade has been done. Then, turn the knife around and sharpen the other side, too. Sharpen both sides the same way. I keep watching the time while sharpening and turn the knife every minute. I turn it 5-6 times before I get an even burr. Then I refine the burr on a fine stone with the same movements.
(Push it pressing hard)
(Pull it pressing with less force)
The other, Western type sharpening is when you push the edge of the knife blade along the stone with a single movement, from the tip towards the handle.
(The direction of the movement of Western style sharpening)
Whichever sharpening technique you work with, if you do it correctly, keeping the right angle, you can hear it when the blade sits on the stone evenly for it makes a different sound.
In the case of carving knives, the shortness of the blade allows you to lay the whole knife blade on the stone.
Using sharpening steel, you can smooth out any inconsistencies or bends in the blade, temporarily improving the quality of the blade. Non-corrugated and somewhat flattened sharpening steel is the best. If you keep the knife in the right angle, the sharpening sound changes. You must use the sharpening steel against the blade, on both sides of the knife.
(Honing a knife on steel)
Accessories used for sharpening:
1 Sharpening stones soaked in water
2 Leather strap glued on a wooden board
3 Rubber pad to be put under the stones
4 Lubricating oil
5 Two-sided oilstone
6 Protractor to measure the angles to keep
8 Piece of cloth