The art and science of sharpening.
That's because he went back to school in the early '70s to get his Ph. D., and now makes his living as a psychologist. He still does some sharpening for friends... and might do it again for pay if he had to.
I don't know if the following information is "dated" or not, but one thing's certain: it's light-years ahead of what most people know about sharpening tools.
ART HORN 6 SOUTH FORK RD. MARSHALL, NC 28753
Safety First: One thing to remember about sharpening any used edged tools: This is an inherently dangerous undertaking. If a person is not somewhat handy (i.e., has decent eye-hand coordination, etc.) they may well be injured, perhaps seriously, attempting to sharpen. I am skilled and handy and I have a scar from eight stitches across the end of a finger where I lost concentration for an eyeblink while too-rapidly sharpening a knife. The knife did what it was supposed to do and went through my tissue without hesitation. I have had other blood-gushing gushing cuts and slashes from sharpening, as well as some near misses from exploding grinding wheels. When sharpening I always examine my hand positions, machine guards, etc. and ask myself, "How will I get hurt if the worst happens?" Sometimes I adjust my methods of holding tools or stories after this question.
Numerous other things can contribute to accidents when handling sharp tools or powered cutting or grinding tools. I heard of one experienced woodworker who lost four fingers when his large dog jumped against his back, probably playfully, when he was cutting a piece of wood on his table saw. People get hurt all the time reaching underneath lawn mowers without pulling the spark plug wire off. You have to think about these things and decide if you are handy enough to tackle them and what level of risk you are running. You may decide to take your sharpening to a pro if you are not handy and do not want to entertain the risk.
On the plus side, sharp tools work better, control better, cut cleaner, require less effort, follow cut lines more accurately and generally increase the quality of our work and lives.
I hope that what I have to share will increase the average homesteader's understanding of these critical tools and will enable informed purchasing decisions when replacing worn tools.
Cutting tool materials
We need to consider what cutting tools are made of. There are glass (obsidian), flint, quartz, bone, antler and shell cutting tools. These are the historic choices for arrowheads, scraping, cutting and weapons, and have been widely used. These are very effective tools in their niches an easy to make if you know
Bone scrapers may even be superior to steel in working hides, depending on who you talk to. Antler "gluts," big wedges used to split logs, are also preferred to steel by many craftpersons. Some (very small) surgical knives are made from obsidian, as it is capable of holding a sharper edge than anything else we have.
All of these require specialty sharpening skills. Many of these skills are available in workshops.
Some of these skills can be resurrected by a self-taught craftsperson. Heidi Knecht ("Late Ice Age Hunting Technology," Scientific American, July, 1994, pp. 82-87), using replicated "Ice Age procedures," recreated antler and bone spears from the period 35,000-22,000 BCE and tested them on goat carcasses. She found that these sophisticated tools were up to the job. They could drive right through the vertebrae of the targets.
Nicholas Toth and his colleagues ("The Last Stone Age Ax Makers," Scientific American, July, 1992, pp. 88-93) studied a highland village in New Guinea where stone axes are made the old-fashioned way, by napping and grinding. These people use techniques which have probably remained unchanged for 10,000 years. The axes are ground on sandstone, with a water lubricant, for their final sharpening. The people there use. flaked edges for light duty, hunting-type jobs, and the stronger ground edges for agricultural work. Two men can take down a telephone pole size tree in three minutes with a pair of these axes.
Tungsten carbide, titanium and ceramics are also used in cutting. Tungsten carbide or "carbide" tipped rotary saw blades and router bits are extremely useful and generally superior to steel in the same applications. They are widely found in woodworking. Tungsten carbide is sharpened with diamond grinding equipment. I have done a fair amount of this type of sharpening in tool shops. Nobody should try this at home as it requires specialized equipment.
Titanium knives are coming into the specialty knife market and are also something you need specialized power equipment to sharpen. The new U.S. Navy SEALS underwater knife is titanium and very useful in its mission, prying apart magnetically-triggered explosive devices underwater. (Titanium is non-magnetic.) If you do much of this on your farm you might want one of these.
Bronze knives are available. They are a novelty. Use one and you'll see why. You will then know why our ancestors scrapped their bronze tools in favor of beaten iron as soon as they could.
Ceramic knives, such as those from the Boker Company, are very expensive described as highly resistant to wear. I do not know how you would sharpen these. I do not believe the claims of "wearproof" materials. Even diamonds wear in cutting and abrasive jobs: I have worn out quite a few.
I prefer to use steel for most applications and carbide saw blades and router bits in their niches.
The majority of cutting tools are made of steel. Steel is basically iron which is mixed with various elements such as chromium, vanadium, nickel, magnesium, manganese, cobalt and - of great importance - carbon. The percentage of carbon in a steel is the most important thing in determining how hard the steel can be made. This mixing process is called "alloying" and the various ingredients are called "alloys."
Steels come in a bewildering variety of types. For our purposes, tools are usually made from steels which can be hardened and tempered. Hardening, tempering and annealing are accomplished by exposing the steel to cycles of heat and cold. Collectively these processes are called "heat treating." Heat treating alters the grain, crystallization pattern, and some aspects of the chemical/crystal structure of the steel. The alloy profile and heat treatment procedures determine how hard and tough a steel can become. Of these two the alloy pattern or chemical formula for the steel is most important.
Although it may seem odd to talk about the relative hardness or softness of steel - it all seems pretty hard if you bite it - this is an important factor. The common hardness measurement of steels is expressed in Rockwell units or "Rc". The scale ranges functionally from 1-100. Rc 100 is the hardness of diamond. Most "soft" or "machinable" or "mild" steels are below Rc 18 or so. Most tool steels are worked in their "soft" state. Knife steels are hardened up to the Rc 55-61 range. High performance tool steels are hardened into higher ranges. Tungsten carbide, of which there are several hardness types, gets very hard. There is a method for estimating steel hardness by using a file. The details of this are in the Andrews book Edge of the Anvil, mentioned below.
Hardness refers to the resistance of a material to the penetration of a diamond-pointed probe and is accomplished by "hardening." "Toughness" refers to the resistance of steel to plastic deformation and is brought about by the process called "tempering."
Generally speaking, hardening involves heating steel to a high temperature, around 1400-1600 degrees F. (or more), and rapidly "quenching" the steel in a heat-absorbing medium such as water or oil. Simply hardened steels are quite brittle.
The process of tempering involves reheating the steel to a lower temperature 400[degrees]-650[degrees] F.) and quenching. This process may be repeated several times and may use exotic quenches such as acetone in dry ice for "ice tempering."
"Annealing" involves heating to the high heat range and cooling slowly, such as in a bucket of hardwood ashes. Annealing takes the hardness and tempering out of steel.
Steels which can be hardened, etc., can be referred to as "tool" steels, and those which do not have the chemical components to harden can be called "mild" steels. There are alternative methods of describing steels and entire manuals are dedicated to such terminology.
The significance of all this for our purposes is that some tools are very hard, such as fine knife, razor or chisel types; and some are relatively soft, such as corn knives or lawn mower blades; and you need to have an appreciation for this in sharpening and maintaining them.
Soft steels can be sharpened with files, but hard steels will dull a file. For safety purposes, you would not expose hardened blades to sharp impacts, as you could shatter them. Ax heads, rotary mower blades, machete/corn knives etc. all are of relatively soft or mildly tempered steel, as they have to be able to "give" rather than break when encountering stones.
There is a limit to the ability of hardened/tempered steel to absorb deforming blows. Hammer heads are specially hardened and tempered to take sharp impacts within their design ranges.
Big tools like hammer heads, ax heads, and most knife blades are "zone hardened" or "zone tempered." This. means that the working (cutting or pounding) edges are harder than the rear edges. The less hardened portions of the tool are designed to act as shock absorbers for the harder and more brittle portions. The accomplishment of this zone heat treatment technique is a skilled craft.
If you place your sledgehammer heads in an open fire to burn the broken shaft parts out of the eye holes you will pull the temper out of the working face, and that face will deform when you use it to whack into wedges. You may then defend your ignorance and denounce the tool as "cheaply made."
Until the 20th century, tool steels were made in tiny batches by individual craftspersons. This was a sort of alchemy, as little was generally known of the properties of the chemical elements until this century. Tool steels were not really standardized by a numbering system until World War II. Several parallel steel identifications are currently used. These include the SAE (Society of Automotive Engineers) system, and the AISI (American Iron and Steel Institute) letter-number system. Generally I have found only AISI number codes on commercially produced knives.
The size of the available blocks of tool steels has increased in the 20th century as we have learned how to make them. The long-standing problem has been that obtaining an even and thorough mixing of the elements of the steels and the annealing of the virgin billets of the steels is difficult and was not really perfected until the post-WWII period. Prior to that, "hard spots" were endemic in tool steels in their soft states, and if you encountered these while machining the steel they tore your cutting tools to shreds. In the 1960s I actually worked on some of these old steels with hard spots. They shredded carbide lathe tools. When you are dealing with old tools, steel types in them are anyone's guess.
In earlier periods, (colonial Virginia, for instance), a small sliver of a tool steel would have been obtained and welded (by forging techniques: remember, they did not have arc or other modern welding technologies then) into the working edge of a tool. A relatively large piece of mild steel would be shaped into an ax head or a hammer head and a sliver of tool steel would be hammer-welded into the working edge.
Under these conditions preservation of the tool steel was critical. Nowadays it would be considered a waste of time to take all this trouble, and a tool will be made out of one type of steel. The tool will be heat-treated so that different portions of the steel will have different levels of hardness and tempering.
Note, however, that some tools are still made with this technology. "Laminated" steel knives have a core of high hardening steel and outer layers of shock absorbent or stainless steel.
Even though all manner of great tool steels are available cheaply, this does not mean that tool makers use them. Another problem for knife makers specifically is that there is no ideal knifemaking steel available commercially. I find this amazing, given the size of the knife market, but have been reading about knifemakers trying out one steel or another for suitability. Currently there is a rage over a re-rolled bearing steel which some people are all enthused about. The Hand Forged Knife by Karl Schroen is a review of the knife-making properties of 12 tool steels drawn from seven of the major categories of tool steels. Schroen is a master bladesmith. This is an advanced text for individuals familiar with forged blade making.
Another type of steelthat shows up in knives, hopefully with increasing rarity, is called "case hardened. "Case-hardening technically, carburizing) is the process of cooking already-made parts in an environment (usually a steel container) which is sealed off from actual flame and which contains a supply of carbon. At very high temperatures the carbon will be absorbed into the surface of the steel and produce a surface hardening. This is a useful technique for increasing wear resistance and is widely used in gun barrels and machine parts.
However, in knife work it has two liabilities. One is that case hardening produces a more brittle steel. I have known cheaper versions of this type of knife to chip at the sharp edge. The second liability is that knives are ground to sharpen them, and all of us who have had case-hardened knives which we have actually used frequently have the experience of grinding past the case hardening and into the softer steel, which will not hold much of an edge. I do not ever advise people to purchase or rely on case-hardened knives.
Finally, there is the problem of stainless steel. From a tooling point of view most stainless steels are soft. (Technically, many of them also stain readily, and the German term "rust-free" is a more accurate description of their unique properties.) Many of the stainless steels are not very good at hardening or taking an edge. The speed with which automated factories produce kitchen knives may explain some of this. Martensitic (hardenable) stainless steels are very sensitive to working in narrow heat ranges and heat treating them is more difficult than heat treating common tool steels. The producers are in a situation which requires increased quality control while they are manufacturing for a lowest-possible-price market. Guess what suffers.
Because of this, many Americans have become accustomed to using stainless kitchen knives which are perpetually dull.
Along with the expectation of dullness we have developed a set of dangerous behaviors around knives, which include freely contacting the cutting edge with our fingers, rattling them around in dishwater without seeing what we are doing, dropping them (on our feet), slamming them into crockery (this dulls them), using them to open packages (thus bending them), storing them in crowded drawers with other knives (this results in nicks in the cutting edges), and finally, using immense levels of force in order to cut anything.
Manufacturers mainly produce named or designated stainless steel knives in "440-B" and "440-C" stainless steels. Martensitic or hardenable stainless steels include the designated 44-B and -C, 154CM, Bg42, 440V, and ATS-34. These steels are difficult to work, so the resultant knives are expensive. In my experience the knife makers always advertise the fact if their knives are made out of one of the numbered stainless steels because of the price premium they want for them.
The good news: Common kitchen stainless knives can be sharpened relatively easily with some new technology I will review. They won't stay sharp very long, but they can be made sharp easily.
What is sharpening?
Anything that increases the sharpness of a cutting edge could probably be considered "sharpening," although several parts of the process have traditionally been given different names, such as drawing, filing, grinding, lapping, stropping, honing, buffing and scraping. I will consider these processes in detail below; however, they break down into two families of techniques: drawing, and stock removal. (Stropping is sort of in-between. See below.)
Drawing techniques are done either hot or cold and use a hammer and anvil to pound on the thin edge of the tool such as a scythe blade or ax, drawing out a thin sliver of metal along the edge, producing a new, sharp edge.
Scythe blades can be cold-drawn in this fashion with a little hammer and a little anvil which is mounted on a fence post or tree stump. Axes, picks, digging bars and other large tools can be hot-drawn by heating in a blacksmith's forge and hammered with a (minimum) three pound sledge against a big anvil. They then require a re-heat-treating, as the heating process changes their metallurgical properties.
"Hot drawing" or "hot sharpening" is a traditional blacksmithing technique and was considered a very big trade secret in the past. Anyone wishing to learn blacksmithing would be advised to both read about the subject and take a class. You cannot learn this from books alone, although you need to know some of the metallurgy that is in the books. The best beginning book I am aware of is Edge of the Anvil, A Resource Book for Blacksmiths, by Jack Andrews (Skip-Jack Press, 1991). Excellent introductory classes in basic blacksmithing are taught by Frank Turley at Turley Forge in Santa Fe, New Mexico (address below). The major resource center for blacksmithing supplies is Centaur Forge in Burlington, Wisconsin (414) 763-9175 (see below).
Filing is a technique which uses files on relatively soft steel surfaces. It can be considered a very coarse type of grinding. The shavings are similar, as is the metal removal theory. Filing is the only way to sharpen most hand saws, since grinding saw teeth is impractical. The exceptions to this are chain saw and bow saw blades, which will be discussed in a later article.
Rotating lawnmower blades can be filed, although it is easier to grind them. Machetes and corn knives can be filed.
Filing is done with either a cross-cutting or a draw-filing motion. In cross-cut filing one takes a file across the edge or area of interest, pushing down when going forward and releasing pressure when going backward. When you sharpen a long edge such as on an ax or machete, this leads to numerous little flat spots. Cross-cut filing is the best way to hog off or remove a lot of stock.
To obtain a smooth cutting edge you must skillfully blend the flat spots when you finish. One way to blend the flats is to first file down one that will be lowest, such as at a deep nick in an ax blade. Then lap the file 1/4 of its width or so over that initial flat spot when filing the adjacent spot and stop filing when you hit the initial flat.
You can also draw-file the finish cuts.
The general rule of thumb on file coarseness for a particular job is to have a file that is fine enough so that at least three file teeth are always in contact with the work. This is also the rule for hand-powered sawblade cutting of anything.
Draw-filing is the process of pushing or pulling a single cut file down an edge the long way. (File teeth are either single or double cut. Look at the file face to determine this. Double cut file faces look like a field of Xs; single cut faces look like a field of parallel lines.) This results in a relatively smooth surface and was used as a finish technique in some older gun and knife factories prior to heat treating the parts.
The keys in draw filing are to have a well-supported work piece, usually clamped to something like a bench top or bench fixture, a relatively clean (new) file and a file card or alternative tool to clean the filing debris out of the file grooves following a few strokes. Depending on the slant of the file teeth, you pull it or push it, or you can reverse it if you prefer to pull or push. Generally speaking, pulled hand tools are easier to control than pushed hand tools. This is why Japanese wood-working tools are all reversed from Western tools.
Draw filing is not a bad way to put a quick sharp on relatively soft steel tools. It's a lot of work if you need to take off a lot of steel, but so is any other technique.
All sharpening techniques destroy the metal of the cutting edge of the tool. Drawing techniques are more conservative in their destruction of the tool than are stock removal or grinding techniques. Grinding and other stock removal techniques scrap a lot more tool steel in the abrasion process.
Stock removal techniques include several varieties of grinding with abrasives and scraping, which is cutting the unwanted material away with harder materials. There are also some hybrid forms which I will discuss later.
Grinding with grinding wheels, sandpaper, abrasive stones or diamond plates all involve moving an abrasive surface against the steel and removing particles of it. The abrasive surface also decays in this process, throwing off particles of grit and matrix.
Abrasive surfaces like grinding wheels perform abrasion because they are made of very hard, tiny particles of "grits" held in a "matrix." The matrix is usually a ceramic and, under a microscope, looks a little like a sponge with air holes in it. The grits are particles of various natural or manmade materials such as aluminum oxide, industrial diamonds, garnet and other substances. When abrasive contact is made the grit particles shave off wee little shavings of steel which, under a microscope, look like any other little steel shavings (such as from a milling machine or a hand file) when viewed at high magnifications.
In this process some of the teensy little shavings - referred to by the technical term "dust" - do not fly off the surface and instead become imbedded in the matrix. This is called "pinning," and eventually the surface of the abrasive is filled with this dust and it glazes over. The greater the amount of pinning the less the amount of cutting gets done. However, energy is still being converted to heat at the point of contact, and it becomes easier to burn whatever we are grinding on when the wheel glazes.
There is a great deal of engineering involved in the design of grinding matrix materials which will perform in special ways. Some are designed to flake off and expose new grit. Some are designed to not flake off and must be dressed with carborundum or diamond dressing stones. Some wheels are "softer," and some are "harder." Some run under water baths and some run dry.
The old rule of thumb in the tool shops was "The softer the steel the harder the wheel, and the harder the steel the softer the wheel." Hard wheels which hold their shape are used to perform "profile grinding," in which a shape is carved into the surface of the wheel and then transferred to the steel. Usually only professionals do this sort of thing; however, I have seen some schemes for simple wheel shaping to sharpen bow saw blades.
For most purposes the degree of smoothness of the grind is determined by the size of the grinding grit. Finer grits should produce smoother surfaces. Engineers and real pros describe surfaces in terms of their micron-scale deformation, such as a "five micron surface." Most mortals only worry about "coarse" or "smooth" surface grades. The grit size of an abrasive is determined by what fineness of screen the grits will fall through. A size 10 grit (which would be enormous) would pass through a screen made of 10 wires per inch each way, but not one made with 12 wires per inch. A size 1000 grit would pass through a screen with 1,000 wires per inch, but not one with 1,200 wires per inch.
Functionally, grits range from about 40 to 600. (I know, I know... floor sanders use titanic grits. But don't try to sharpen steel knives with a floor sander.)
This is the American method of measuring grits. Japanese waterstones are measured by a different system. I was initially disoriented by seeing advertisements for 6000 and 8000 grit waterstones. I will say more about Japanese stones later.
Industrial diamonds are cheap and readily available in some forms. Diamond grinding wheels (which are not cheap, last time I checked) are randomly oriented diamond particles held in a matrix. They are used to cut carbides and ceramics.
Diamond plates are becoming quite common and deserve a mention. Diamond plates are not bad at shaping hardened steel such as will be found in most knives. "Monocrystalline" diamonds are special diamonds which are grown in the shape of little needles. They are held in a matrix and oriented so that one end is toward the top (or working side) of the matrix and one is toward the bottom.
When you use these plates the abrasive action exposes a cross section of the diamond as it is abraded away. It is easy to see tiny little sparkling points on the surface of the plate.
The plates also have small holes filled with a soft plastic spaced throughout their surface. These holes are for grit relief and serve the same function as the gullets of a saw tooth, to clear the debris away from the cutting area.
General grinding procedures
With a severely abused, chipped, or deformed edge, grinding usually starts with a coarse grit and proceeds to finer grits. This is true whether you are using hand or power stones. Some edges, like my axes or machetes, are just fine with a coarse grind on the edge and I do not bother refining the surface to "a five micron finish."
Coarse grinding is sometimes referred to as "shaping" and produces a lot of heat when performed with power tools. Because of the heat and the potential for "burning" the tool, many sensible people keep containers of water close to their grinders and dunk the tool into the water to avoid inadvertent heat treating, thus ruining the edges. When the edges start to turn colors you have burned late.
Please note that you can overheat and burn a thin tool edge with any grit of abrasive.
Many woodworkers prefer using water bath grinders to avoid burning fine and expensive tools. Water bath grinders are more expensive than dry grinders, but much safer, both for edges and your lungs. They are also a hassle to use, with water flying around. I nevertheless prefer them for most general grinding.
Dry grinders produce clouds of flying grit and steel which are inhaled by the operator. This is very bad for your health and can produce a variety of serious lung problems. Water bath grinders do not produce anything like the level of flying dust that dry grinders produce.
In industry we used elaborate air exhaust/vacuum systems to control the dust. These huge, expensive systems were not completely effective, and for an individual shop they are out of the question. I would not want to hook up a shop vacuum to my grinder, as the sparks are alive, and when subjected to air blasts will keep burning, igniting anything around them.
My compromise with dry grinders is to use them outdoors, with a mask. I sometimes wear a mask and blow a fan over the working area if I cannot get outside. I try to minimize my use of dry grinders.
Beware of sparks, too. Once in industry I set a rag down behind a big dry bench grinder while sharpening a lathe bit. I did not know the rag was in the path of sparks from the grinder. I set the rag on fire. Very exciting.
Water bath grinders include several types with plate-shaped stones which rotate in a horizontal plane and several with traditional big round wheels running in a water bath. An unusual new form of grinding wheel (on the Tormek machine) uses a coarse wheel in a water bath to perform most rough work, and a special dressing to convert the wheel surface to a finer grit for finish grinding. Since I have never operated this machine, I would be skeptical about the claims, except that several people I trust sell them and swear by them. (See Highland Hardware and Country Workshops, below.)
I have a version of the flat rotating grinder and three stones: a coarse 120-grit green wheel, and 1000 and 6000 grit stones (Japanese numbering system). I got the machine to resharpen long jointer and planer blades for my shop. For that purpose the machine is as good as any of the professional machines I used in industry. (It is a Makita, from Highland Hardware. Similar machines are widely available.) I also use this machine on ax blades and for some freehand sharpening of various other blades.
The Tormek appears to have the best jig and fixture system for the widest variety of blades. This is the critical point for a lot of grinding: you need jigs and fixtures to get the most out of the equipment.
Basic edge shaping is done with the coarsest grinding media. What you do after the coarse grinding is to refine or polish the edge established by the coarser procedure. In some cases I may start with a coarse carborundum stone and that will be it, for a lawnmower blade. In other cases I may start with a 120 grit on the wet grinder or a similar hand stone and repair an abused edge, then move on to finer grits. When resharpening knives that I have already sharpened I generally start with finer grits, as the basic edge shape is still intact and I will not need to hog off a lot of stock.
There are some special finishing and balancing techniques for different tools which I will look at below. I follow the general procedures here for most grinding, including that done with wet and dry power wheels, sandpaper, hand stones and diamond plates.
Grinding wheel basics
When using dry grinding wheels you need to remember that they cannot be fitted to the grinder out of the box without "truing" or "dressing" operations. Truing is a process of getting the wheel to run in a true circle. This is accomplished by holding a tool against the face of it, when it is started for the first time, and grinding off the eccentric material. This is a very dusty process. Each time a wheel is dismounted and remounted it must be retrued.
In industry, fine grinding wheels are not held onto an arbor with a nut like on the cheapo bench grinders you will buy for a home or homestead shop. Real industrial wheels are mounted on "quills," which are never removed until the stone is scrapped (or if they or the wheel will need to be re-trued).
Quills fit into/onto tapered shafts. Because of the tapered parts, the wheel is re-mounted within very tight tolerances to its last rotation pattern. This way we would cut a profile into a wheel, remove it from the machine, and remount it, without losing a lot of time or abrasive surface. This was on the world's finest tool grinding machine, the Browne and Sharpe #13 Universal-type grinder. Larger grinders such as big surface grinders did not use quill mounting.
Currently available truing and dressing tools include a rotating wheel affair, hard carborundum hand stones (which I like better), and industrial diamonds mounted in brass rods. On the homestead the carborundum is probably as sophisticated as you would need, but diamonds are the best.
Dressing the wheel surface involves cleaning the pinning debris out of the little holes in the abrasive matrix. Usually I run a carborundum stone over the surface to do this. This is done by having the wheel turning under power and holding the stone against the tool rest so that the face of the stone contacts the wheel at about a tangent angle. I slowly move the stone across the face of he wheel. This abrades off some of the face of the wheel.
Diamonds will do this job equally well or better when mounted in a fixture to keep them from bouncing against the wheel face. The big stones are usually massive enough and you can hold them down with enough friction to keep them from bouncing.
Note that because the wheel surfaces pin and must be cleaned, any of the little sealed motorized "knife sharpeners" found on the backs of can openers or other appliances will eventually stop working. If you cannot disassemble the machine and dress the wheel it eventually simply will not work. I have always found these things to be a waste of time.
Typical grinding wheels are not made to resist side pressure. Do not use them on the sides. If you want to use the side of the wheel to grind get a wheel that is made for this purpose. "Dish" shaped wheels are usually made for this. Wheels built to resist side grinding should be thus specified by the manufacturer.
This is serious safety stuff. Exploding grinding wheels can maim and kill. Respect them.
My grandfather had an eye out from an old style sandstone wheel. I had a friend whose father was killed by a chunk of a high speed wheel going through his skull like a bullet. I have detonated three large wheels myself. The worst one was due to my not checking to see if a wheel was installed properly prior to starting it up. That one weighed 90 pounds and was driven by a 30 hp motor at 1000 rpm. When it broke loose it threw 10-pound fragments out under the guards. They sprayed out and went off like fragmentation grenades when they encountered solid objects. No one was hurt. I believe in divine intervention because of this episode.
Most of the wheels provided on typical mass market grinding machines are carborundum type. I use these for rough applications only. It is very easy to burn things with these because the wheels do not flake off and consequently get pinned easily. If I am careful I can put a quick sharp on a lawnmower blade or machete with one of these.
"Coarse," "medium" and "fine" grade grinding wheels are available in most hardware stores. This classification seems to refer to the grit size (mostly) and the fineness of the matrix in the wheel.
Actually, grinding wheels are specified as to grit size, friability (flake quality) of the matrix, grit compositions, etc. You will see this on the label of some wheels in the form of a long string of letters and numbers. The typical consumer will probably have to settle for the color coded trio mentioned above plus the ubiquitous carborundum wheels.
It does not matter much because you will probably be repeatedly sharpening the same stuff over and over. If the wheel doesn't work well or burns the material, get a different one.
Hand held or "body" grinders
These are widely sold and are available with lots of different cutting wheels. They are high speed (10,000+ rpm) tools with most of the cutting end of the wheel outside a guard. They are really a professional's tool which migrated to the European hobbyist woodworker market and thence to the USA. Although useful, these things can be horribly dangerous.
Take some advice I got from a friend: If you need one of these, get one that you cannot lock in an "on" position! A fellow had one grab his shirt and cut a three foot long trench in his abdomen going up one side, across and down the other. I try to buy power tools that cannot be locked into "on" because of this story.
Lapping is different from grinding. In grinding, a matrix holds a grit against a piece of work. In lapping, two surfaces are rubbed together and a grit is placed between them. The grit lodges in the softer surface and abrades the harder surface. Lapping is usually a lubricated process.
I use lapping to flatten large surfaces. Carborundum grits, for instance, are placed on a soft steel plate on the bench, wetted with water, and a harder surface, such as a chisel back, is held against it and moved in a figure eight pattern. (You must use figure eight patterns in any surface lapping or grinding on a flat stone to avoid a hard spot digging repeatedly into a single place on a tool surface and carving a hole there.) As the grits break down they re-adhere and cut some more.
This process produces a progressively finer cutting media and can, with a lot of practice and skill, produce impressively flat and smooth surfaces. Barber's power cutters are flattened this way on a power rotary lap.
In a college model shop we used a rotary table with a wet felt mat on it charged with Bon Ami cleanser to lap scratch marks off blocks of plexiglas which contained biology department specimens.
Stropping is a technique for removing the fine burr that results from grinding an edge. When stropping, you drag the tool, with the sharp edge trailing, back and forth against some softer material.
Most strops are made out of leather or linen. I have found that cotton blue jean material works well for small knife blades.
The idea here is to flex the burr against the sharpened edge and snap it off. On a long knife this burr is sometimes called a "wire burr" and it can be pulled off like a wire after it has been flexed a bit.
On a microscopic level, steel is very flexible, and these burrs build up as the steel is bent out of the way by the grinding material. If you do not remove them, the burrs will act to dull the new edge by folding over onto it.
Some of the water stone makers advertise that water stones sharpen so well they do not form burrs. I have noticed that my water stones form much smaller burrs than oil stones, but they are not burr-free.
I also use a micro-bevel strategy (explained below) which further reduces burrs. Nevertheless, I still strop fine tool edges.
In some applications wire burrs may be desirable, as they are very sharp and will cut for a short while. During a hog butchering operation I participated in, the farmer used a scraping-type sharpener to rapidly raise a wire burr edge on his large knife. He would then make a few cuts and re-scrape the knife edge. I don't believe he understood the basics of sharpening a blade, and I did worry about leaving small chips of steel in the meat we were packing, but he was able to keep a cutting edge on his knife through a long, hard day.
This is a technique for refining the surfaces of cutting edges by charging a power wheel, usually cotton, with an abrasive grit called a polish or buffing compound. The object here is to produce a "mirror finish" on the cutting tool without dulling the cutting edge or raising another burr.
I never use this technique. It's true that a mirror finish will be smoother and cut better than a ragged finish in some circumstances; however, it is real easy to rapidly destroy your cutting edge this way.
Buffing is done with the edge face away from the buffing wheel, but you do run onto the edge. If you do not get the angle right or keep a light touch against the wheel you may abrade off the fresh edge.
This finishing technique is mostly used in woodworking by turners working on lathes. In this context it makes sense, as they need a very clean finish cut, and if sharpened right, the tools last longer and cut cooler between resharpenings.
This term has no single meaning in English. Supposedly it refers to a fine grinding process and to the grinding tool as well. It has been taken into the general language in phrases such as "honing the edge" or "honing your skills" and is used as a literary reference ad nauseam. In industry we used "honing machines" to perform fine finish grinding such as the refinement of bearing surfaces. These machines used a fine grinding stone, usually held in a special jig, and an oil bath to accomplish their tasks.
In the modern world the term "honing" refers to a wide variety of grinding and cutting tools most of which have to do with preparation of edges. For my money the term "honing" can be replaced by the term "finish grinding.
There is a special and useful group of sharpening tools which are marketed as "hones," "sharpeners" or whatever their marketers are calling them. Some of these are real useful in sharpening kitchen knives and scissors.
Scraping is a more general type of surface preparation in which very hard, usually carbide, bits are scraped over a surface somewhat like we use a paint scraper. You use these by drawing them down the edge of knives or scissors.
I had never given these serious consideration because the older types that I had handled, which had little round discs of hard steel, merely raised a nasty wire burr and produced a short-lived edge. This is the scraper type that my friend used to sharpen his hog butchering knife.
The new variety of these sharpeners is much improved and better than grinding when working with typical stainless kitchen knives. The new variety uses two carbide bits set in a plastic housing at an appropriate angle (either for knives or scissors: you need different ones for each) and sharpens by pulling the edge through the V-shaped gap. Sources for these are given below. I mostly see these offered between $6 and $12. The carbide bits will wear out eventually. Mine have reversible bits. I am told you can obtain replacement bits cheaply.
The reason these scrapers work is that they actually scrape the blade and thin out the area behind the cutting edge. The ones I have chatter back and forth and actually make a micro-serrated edge as they sharpen. Roofers carry these to sharpen their razor knives nowadays. This is very efficient for them. You can also quickly sharpen the curved edge of a linoleum knife with these.
The reason I use and recommend these scrapers for kitchen knives is that nothing you do to sharpen a kitchen knife will do much more good than these. Typical stainless kitchen knives are usually such soft steel and are used so harshly that the edges erode rapidly no matter how you sharpen them. These scrapers work in almost no time compared to other methods. Before you could take the knives out to the shop to sharpen them on a belt sander or grinder or pull out the hand stones you could have them sharp with one of these scrapers.
Their other advantage is that scrapers do not require much skill. The scrapers do produce waste steel and you need to wash off the knives prior to using them.
If you are sharpening fine cutlery, such as name-brand Swedish or German cutlery, these scrapers may not work well as these knives are usually made from harder steels and it is likely that someone at the factory actually supervised the heat-treating. I would not use the scrapers on 440-type stainless.
I have also found the scrapers a quick way to sharpen big cleavers (I know, I know, the edge on a cleaver should be blunter as you use it to pound. Nevertheless these scrapers will whip an edge on the cleaver right quick and setting one up to grind it is a chore.)
Sharpening-what are we attempting
Knives, axes and simple single edges:
The edge refining techniques mentioned above constitute the major methods we have of sharpening most of our tools. When we are attempting to refine an edge we need to have in mind some idea of what the finished product should look like. I will discuss some basic tool geometry here:
There are three basic cross-sections to simple cutting tools. (Saw blades are different and more complex as are form relieved and profile relieved edges. They will be discussed in a later article.) Below we see the basic single bevel, double bevel, hollow-ground, single bevel chisel type, and abortive "puff ground" blade shapes. Most of the common blades are one or another of these shapes. (See illustration, next page.)
The single bevel edge is the basic cutting edge and occurs on two forms. The sides of the triangle can be referred to as "lands." On a single bevel knife we have only a single or "primary" land. On a double bevel we have a "secondary" land as well.
In the form found on most knives, cleavers and axes we have the sharp edge centered in the material of the knife body. In tools such as swing blades, chisels, plane blades, draw knives, adzes and special broadaxes we have one side of the bevel as the flat side of the tool body and the angled side forming a long slope to it. This blade profile is referred to as the "chisel edge" or profile.
The single bevel is probably the best and most desirable form of simple cutting edge. The angle formed by the two sides of the bevel is called the "included angle." Included angles range from about 20[degrees] for fine knives and kitchen knives, to 25[degrees] for heavy outdoor knives to 30[degrees] for heavy chopping knives such as wire cutting knives and carpet knives. Sharper angles, such as 17[degrees], are only useful for razors.
One drawback to specifying angles of sharpness like this is that few people have enough control over their sharpening to actually produce a specific angle on an edge. This is why I recommend fixtures for sharpening most anything. Then you can get in the general range of a particular angle.
Another drawback is that only really good knife steels are going to perform well enough to worry the perfect angle. Most kitchen knives are so soft that even though you put a 20[degrees] bevel on them they will dull out quickly.
Fine tools (chisel blades) should be sharpened to specified angles because they will retain them in use. Good, inexpensive fixtures for this are available. See below under "Sources."
Double bevel shapes have one blunter angle truncating a sharper angle. Many people sharpen this way when they cannot sharpen a big wide primary land and think they can beat the game by going with a blunter angle in the tip. The trouble is that this produces a very blunt edge. The edge so formed may be good for chopping a few things, however, most materials will drag on the shoulders of the bevel and decrease the cutting efficiency of the knife. Double bevel shapes are usually the result of poor steel or ill-informed sharpening.
Some steels will not hold a single bevel and need to have a blunter angle. These are not good knife steels. Double bevels are mostly sneered at by serious tool people.
Note that the double bevel is just in the cutting area, not way back on the blade. Some blades have a general triangular shape from the heel toward the tip. This is interrupted by the actual angle of the sharpening. These are single bevel knives.
One of the most misunderstood knife forms is the "hollow ground" form illustrated above. It is called "hollow " because the material is removed from the sides with a grinder and hollow pockets result. These hollow pockets have no structural material supporting the blade edge. The included angle of this blade is from the heel to the tip and is usually quite small - 17[degrees] or so.
The only type of steel which will really hold up with hollow grinding is relatively brittle or hard steel. This sort of angle is good for straight razors. The hollow pockets result in low drag when pulling the edge through something or over something that is already relatively smooth and lubricated.
Note that when you sharpen a swing blade for a lawnmower with the round edge of a grinding wheel you are giving it a very slight hollow grind. This is not the same thing as a razor-type hollow grind. The edge of the swing blade will quickly be beaten back in use no matter what kind of grind you put on it. The cross section of a razor is thin like a piece of paper out toward the tip.
Unfortunately some manufacturers make soft stainless kitchen knives which they more or less hollow-grind. These distort, bend and break easily. I had some hardened kitchen knives once which were hollow ground. They chipped out dramatically when my assistant and I were butchering some goats and she chopped into a bone. (Yes, I know she should not have been chopping with such a tool. This is the type of accident which happens all the time however because people do not know the limits of their tools.)
I shaved with straight razors back when I bothered shaving. To sharpen a straight razor you need a special fine stone, special oil, and a good strop. The razor is honed on the stone with the heel of the blade against the stone. (The stone is a very fine grit and the oil is thin bodied so it will get down into the stone's cavities and lube the grinding.) The blade is then stropped to draw the edge out as fine and burr-free as possible. The edge must be straight, not serrated, and burr-free, or it turns your face into chopped meat. Real barbers mostly stropped their razors between customers and only infrequently honed them, or so I am told.
If you are going to try to maintain the angle on a hollow-ground knife blade or razor, you need to rest the heel of the hollow grind on the stone as well as the tip to maintain the angle. Good luck.
Knife sharpening - at last!
Okay. Now, at long last, we can discuss knife sharpening. I want to denote three general classes of knives and some other simple blades of interest to the homesteader. The knives are kitchen knives, small pocket and folding knives, and utility or heavy fixed blade knives.
Most kitchen knives are made either from good steel or some semi-soft stainless, and most are abused. For the soft stainless ones I use the scraper sharpeners. These sharpeners are so fast that they make up for most of the shortcomings of the steel in the knives and the abuse they suffer at unskilled hands. The scrapers will adjust the included angle on hollow-ground kitchen knives. These knives usually have too narrow an angle on them anyway. Big kitchen knives which are soft and flexible, such as the double handled knives chefs use to cut cheeses, are draw filed in a single bevel shape. Cleavers can be filed; however, I use the scrapers because of speed. If I were sharpening for a commercial kitchen or a run of butchering I would draw file the cleavers because the blunter edge is stronger.
I grind my good hard steel knives. I also do not encourage their use for everyday kitchen cutting unless they are paring knives. The paring knife is frequently used and the cook deserves a good reliable edge. For paring knives I have a bunch that I bought from a catalog closeout (see catalog sources below) and I grind them. This keeps the cook, my wife, in reasonably sharp edges. To grind most knives I use one of two fixtures.
For small and medium length knives I use a Lansky-type fixture. This type of fixture (there are several manufacturers, see the catalogs below) has a little winged vise that holds the knife by the heel of the blade and a set of stones mounted on plastic holders with steel rods in the ends. The rods go through holes in the wings of the vise and the stone is drawn back and forth. The fixture keeps the angle of the grind constant.
The coarser stones are good at shaping an edge and the finer ones polish it. I shift to a wider angle (whatever the next wider angle available on the fixture happens to be) with the finest stone and grind a very narrow microbevel as the finish. This is not a double bevel but a strengthening maneuver. If I were to keep grinding this would produce a noticeable new land and actually form a double bevel. I stop the microbevel after a few strokes, when a bare glint of light will reflect off of it. I then strop the edge.
I do not fool around attempting to follow the serrations of steak knives, although one can buy special stones for this purpose and which work in the fixtures. These knives stay fairly sharp because the cutting edges in the pockets are kept from slamming into crockery by the foreword edges of the serrations. I merely grind these back along the front edge as if they were a straight blade. This sharpens the leading edge and opens a little bit more of the pockets. Eventually I will grind the serrations out into a straight edge but I have never done this as this type of knife is so infrequently sharpened.
Bigger knives and cleavers will not fit into the Lansky-type of fixtures properly. The wide blades will decrease the angle of grind too much. For the big knives I use a little jig that fits on the back of the blade and is designed to hold a particular angle. Again there are several manufacturers of these jigs.
I sharpen these big knives on water stones. Water stones are available in large sizes which helps with this sort of sharpening.
To make a microbevel you reposition the jig further forward on the blade (toward the cutting edge) when you get to the finest grit stone you own. Then you finish by carefully grinding alternating sides until you can barely see the light glint off the new land. I finish all of my fine cutting tools such as plane blades and wood chisels with the microbevel.
When grinding, I only move the knife with the cutting edge foreword into the cutting material or vice versa if the knife is fixed and the cutting material is the moving part. If you were to draw the knife backward you would pull out a much larger burr. This complicates stropping. The water stones seem to make smaller burrs than oil stones. The fixtures I mentioned above all have diamond and oil and water stones available. Take your pick.
When grinding knives, I have noticed that most people reverse the blade on a stone with every move back or forth. This is a waste of energy and destructive of good edge building.
Grind one side of the knife until you feel a burr forming on the other side of the cutting edge. To test for this burr very carefully draw a fingernail away from the cutting edge on the other side from the one you have been grinding. (If you move into the cutting edge you will likely be cut.) When you feel a little burr forming you have sharpened the land back far enough that you have a flat surface which terminates in the cutting edge.
You then reverse the blade and grind on the other side until the burr flips over and you can feel it on the first ground side.
I perform this with the coarsest grinding media I have because frequently a lot of stock must be removed. After flipping the burr over I then reverse the blade and shift to a finer stone and repeat the process. After the initial grinding has flattened the lands the progressively finer grinding stones polish the lands quickly. I save the finest stone for establishment of the microbevel. I then strop them.
The object of sharpening knife, machete, chisel, ax and similar blades is to end up with two flat planes which intersect in an angle with no burr. If you freehand sharpen, particularly if you flip the blade over on every stroke, you are not going to hold the blade at the same angle. This is particularly true if you need to hog off a lot of stock from the blade, because your wrists will fatigue.
Very few people have the necessary concentration to freehand sharpen anyway. What you end up with are two curved planes intersecting in a sort of an angle. This is sort of the opposite of hollow grinding and could be termed "puffed" grinding because it looks like you would if you puffed out your cheeks.
Puff grinding is a lot like grinding many bevels. The final result is that the edge will not act like it is sharp, or as sharp as it could be.
People who think they are sharpening a knife with a steel stick are probably at best wicking up a wire burr along a blunt edge not too different from this intersection of puffed curves. These puffed curves will not give you control in precision applications such as wood carving, riving, splitting, etc.
I am aware that American-made axes come from the factory with puffed cutting edges. This is because they are "finish sharpened" on a high speed belt sander and the belt curves around and gouges off the leading edge, which is thinner. I have encountered some poor guys who thought they should replicate that puffed bevel when they resharpened their axes. Too bad. (Go to a high-end hardware store and inspect a Japanese-made ax and see if you find a curved bevel on that.)
A pet peeve: slab handles with rivets
I have so far failed to mention one of my other pet peeves about cheap kitchen knives: They have slab handles - two pieces of wood held on with rivets.
Real knives have a waterproof crossguard at the end of the blade. Real knives also have handle slabs - wooden or some other material - glued with epoxy to the steel of the blade tang. Nothing can get under them unless the glue cracks free from one surface or the other.
Slab handles allow oil and water to wick up under the handle, or to get into the handle material, and later re-emerge to taint food. When you are sharpening with oil be sure to wash the blades off in heated detergent-bearing water to prevent this as much as possible. Real sharpening shops use "butcher's oil" to sharpen meat cutting tools as it does not have the taste of regular cutting oil. I have never found a source for this oil. Butcher's oil will also get under slab handles and must be washed off thoroughly. I don't know why people do not get poisoned by this more often.
If you ever break a wooden or plastic handle off a knife that has been in kitchen use, you will be amazed by the garbage you will find under it.
Pocket knives: Pocket knives come in a bewildering variety of types. From a safety standpoint, folding blades will fold back easily and will cut you. Some people carry "lock back" folding knives and may imagine that these are safer. Guess again.
Atlanta Cutlery tested a bunch of well-made lockbacks some years ago and found that only a few of them would resist 20 foot-pounds of torque before the mechanisms failed and the blades folded back. Twenty foot-pounds 'tain't nothin' if you are a working person and you are seriously doing something.
The thing about pocket knives I find indispensable is their utility. I carry pocket knives with tools other than blades on them. I prefer the " Swiss Army" type (we used to call these Boy Scout knives) as a pocket tool chest. I also carry a tiny SAK type knife on my key ring because it has a little pair of scissors which I use all the time. Between the two, I use these knives at least 10 times a day.
The SAK type knife is one of the most popular current pocket knives. There are several manufacturers. I have owned knives from four or five of them. Unfortunately, with the exception of SAK knives made by PUMA, all of the manufacturers use relatively weak blade steels. This has always surprised me because the little scissors hold up tremendously well, as do the little prys and openers and awls.
PUMA made a limited run of SAK type knives with 440-C stainless knife blades. Everybody who used mine wanted one. Unfortunately, they are no longer available.
I have a test for determining how good your knife blade is. I got it from a more elaborate and scientific version Consumer's Reports published some years ago when they tested cutlery. It is simple, and valid.
Sharpen the knife and cut up a bunch of cardboard boxes. Cardboard is rough on knives because it contains crystals of glue which abrade the blade. Sharpen another knife and cut up some more boxes. See which one lasts longer.
If there is an obvious difference it is probably a real difference.
I sharpen pocket knives with a fixture the same way I sharpen the better kitchen knives. I follow the established angles on the knife, although with a blade that is wider or narrower than usual, the fixtures will change the angles slightly.
On all knives, I have noticed that the manufacturer usually blows it as far as centering the blade edge during the factory sharpening. The initial sharpening takes time, as you need to get a symmetrical primary land, and even expensive name-brand knives are usually somewhat off-center or ground more heavily on one side. This is the result of high-speed machine production and is probably unavoidable.
Third, big utility knives: If you are doing anything serious with your homestead, you will eventually figure out that you need one of these. Hopefully this moment of insight will come before you push your nifty lockback belt knife into a situation where it folds back on you and cuts off a finger.
This class of knives is referred to as "military" or "utility." These knives are big enough to handle light chopping tasks, some prying, and some pounding, as well as typical cutting jobs. They do not replace real two-hand axes or machetes. A tremendous variety of these knives is available. Some of them cost enormous amounts of money.
After years of helping impoverished homesteaders I have observed that one inexpensive knife in this class holds up phenomenally well. This is the U.S. Marine Corps issue Ka-Bar. (Ka-Bar is the name of the knife manufacturer. I have no financial interest in this or any other manufacturer.)
Two of my associates who have been homesteading in the deep South for 15 years have carried this same knife on their belts all this time. The deep South has an energetic level of underbrush and vine growth unknown in colder and drier climates and you must deal with it or it will deal with you. It tears down fences, tears siding off houses and rips electric conduits off walls. No kidding.
I have sharpened these friends' knives on rare occasions and have gotten to see their pattern's of wear. They do not wear much. Several other associates of mine who carried these knives in the USMC absolutely rave about them. I bought one recently and I like it.
There are other big utility knives available, but this one is relatively cheap - around $30-$35, with sheath. The flat end of the pummel is designed to do light service as a hammer. The steel is not fancy. It is described as 1095, which is a fairly typical carbon steel without exotic alloys.
The reason it's rust-resistant is that the blade is coated with an epoxy. The 1090-1099 steels are described by Andrews (p. 127) as having "fair toughness, hard with medium cutting edge."
Hot spots on handles
I like the way this knife fits my hand. This brings up another point: "hot spots" on knife handles. This refers to the tendency for big knife and machete handles to have spots on them which do not conform to the shape of your hand and will raise blisters on your hand. You will not discover this until you actually use the knives in a situation where you are putting some elbow grease through them.
I have found hot spots particularly common with machetes. The solution Is to take a sander (hand sandpaper or power) and sand down these spots. It is very easy to ruin a handle this way, particularly with a power sander. Be cautious. It may be easier to trade the offending knife to someone else and acquire a better fitting one.
I sharpen the big utility knives (not machetes) with a clamp-on-the-blade jig and big water stones. I follow the same procedure as explained above.
One exception is that I pressure these blades both into and away from the cutting edge. In other words, I grind them continuously in a figure-eight motion, only stopping when I raise a burr. When these big babies get dull or chipped it is a big job to get them sharp because you have to remove a whole lot of steel. This will take a while, and if you only grind in one direction you double your grinding time.
The sharpening terminates in a micro-bevel and a stropping. I spray WD-40 on the blade edge to keep down rust in this humid climate, and also spray it into the sheath.
Some manufacturers advertise their big knives as capable of cutting barb wire. They have blades with little holes in them to fit a special lug on the sheath which then forms a sort of scissors. These are for military applications. I might use them like this, or even whack away at wire on a post, but only in a serious emergency. You will pay a high price for this in blade repair.
If you look at your fence pliers you will note that the wire cutter consists of two 90 degree angle scissors blades. This is the appropriate tool for cutting wire, not a knife blade which is sharpened to the 20-30 degree range.
The military knives may use the back of the blade, but that is still going to deform over time. The back edge of almost any blade, and particularly a large blade, is softer than the cutting edge. As I mentioned before, they are made this way so the body of the blade has more capacity to absorb shock. The harder front edge cuts well, but doesn't flex well.
The outdoor outfitters have special scaper-type sharpeners for this size knife. I will not use them on my big knives because the micro-serrated edge they leave is inferior to what I can do with my water stones. You may choose to use the scraper sharpeners if you are not the grinding type. The straighter the cutting edge of the knife, the better it is supported and the less power will be required to cut anything. It should also wear best.
Before I get off the subject of big utility knives I want to say something about limited edition, custom made, hand-made or other expensive, usually fancy knives.
I have never purchased a knife much fancier than the Ka-Bar. That is my personal bias. Knives with very fancy handles and artwork grade Damascus steel treatments are probably more artwork than field tool. At this time, good steels are around and good bladesmiths are working relatively cheaply. A well-made custom or limited edition knife that is designed to work rather than live in a showcase may be a very good investment. The Ka-Bar is humble 1095 steel and a leather handle. It is not even rustproof. It is a tremendous knife. Fantastic high performance steels and similar handle materials are available in knives which are more expensive than the Ka-Bar but which could very well outlast several generations of users.
If you are handy, you can get kits from Atlanta Cutlery or another supplier and make a very superior knife. I have several of these in different degrees of completion in my shop.
Fourth, axes and hatchets:
The word "hatchet" is actually a derivative of ax as in "ax-ette."
The simplest way to deal with these edges is to acknowledge that they are for either rough or fine work, not delicate work, and sharpen accordingly. Several friends of mine who work with the ax to fell logs keep relatively sharp "felling axes" separate from their splitting axes and grubbing axes. This is reasonable. The ax you slam into the ground to sever tree roots will encounter stones and get nicked and blunted but hopefully not flake off chips. You might want to keep a blunt, maybe 30 degree angle on this one.
The felling ax should be sharper, maybe 20 degrees, and intermediate axes would be in-between.
The point is that if the angle of the sharpening is too narrow for the work you use it for, it will bend and distort easily; if it is too blunt it will not cut.
Some people do fine woodworking (riving and shaving work: see Drew Langsner's books, below) with axes and hatchets and they must get to know their tools and replicate the angles they need. Those folks do not need to read this sort of article.
I use a power grinder for ax sharpening because it is relatively fast. I have found that the power water stone grinder is very quick and accurate with the coarsest wheel. I also get a flat included angle, no hollows or puffs.
In his book on sharpening, Juanitch has plans for a jig for grinding axes on a standard dry power grinder. The problem with this jig is that you are sharpening on the periphery of the wheel and are thus producing a minor hollow grind. I prefer the true, straight, single bevel on my axes. If I did not have the wet grinder I would probably make up a jig like this because of the next option ... hacking away with a file.
Most axes are relatively soft and can be filed. However, you need to remove a lot of material if you get them dulled down. This will take a while.
Most people have no idea of the variety of files available at a real hardware or tooling store. Large files which cut aggressively will make a difference in the amount of elbow grease you need to put out.
The biggest problem with filing axes is that most people need to make a fixture to hold the ax flat. When I sharpened them this way I clamped them to a bench with the edge hanging over.
I follow the same procedure on axes as I do on knives: abrade off one side until I turn a burr, then turn it over and repeat. You can go to the trouble of fine-finishing with finer stones and a micro-bevel. (Juranitch is the guy who does this with a double-bitted ax - then shaves with it.)
I usually don't bother refining the edge too much. If you had a body-grinder you might be able to rapidly rough out the edge of an ax and refine it with a draw file finish. I would chuck the ax handle in a vice and grind away from the edge in this option, because I would be afraid of wandering into the cutting edge with one of the little high-speed grinders.
The final option would be to reforge the ax head. Wait until the handle breaks off for this one. Reforging would give you a chance to re-temper it and would be more conservative of the material, as well as giving you a tougher ax head.
These edges all feature the "chisel" profile. It looks like you only sharpen one side of this edge, but in fact you sharpen both. The trick is to make the back or "flat" side perfectly flat. This counts less in rough work tools such as froes, machetes and corn knives. On those blades all you need is to be sure that there is a flat back, not a sloped one.
Even fine knife and chisel sets do not come from the factory adequately flattened on the back side. Even a slight slope on the back side will rapidly reduce the cutting utility and control of these edges.
Japanese chisels and plane blades are somewhat of an exception. If you use these you are probably more advanced than even most fine woodworkers and you know the necessity of drawing those blades prior to flattening and sharpening. This is a skill which has artistic elements.
The best two techniques I know for sharpening the back sides of chisel profile blades is to either lap them on a series of large bench stones (I use my water stones after flattening a face on them) or to lap them on a steel plate using carbide crystals. The second method works best and produces a flat side which reflects like a mirror. You want it to reflect like a mirror.
These techniques are both difficult and time-consuming. Fortunately, you only need to perform them once, generally, in the life of the tool. It costs a bit to acquire a set of large bench water stones which cover the grit ranges from real coarse (Japanese grade 700 or 800; coarser are avail able) to very fine (Japanese 6000). You must remove a substantial amount of steel on a plane surface without rocking the tool and breaking its flatness.
With the water stones, I flatten a face by lapping the stones on a surface made of a scrap glass mirror covered by a carbide-impregnated screen. (Highland Hardware is my source for all these supplies.) This is lubricated with water. A figure-eight motion is used. When all of the stones in the series have a flat face I clamp them into the bench holder, starting with the coarsest, lubricate with water, and place the blades on them, back side down.
I have made a series of wooden cradles for the chisels and plane blades which have a little hollow in them which cradles the front side of the blade, which is on top. The covers extend over the shaft of the tool and are held on by one hand while the other guides and keeps pressure against the chisel through the wood covering over the blade. This keeps my fingers away from the sharp cutting edges and allows a better grip and distribution of force.
Work slowly, with a figure-eight motion and some pressure. Heavy pressure will cause control problems and you might get cut.
After getting a flat surface with the coarsest stone, proceed to finer stones and finish with a light lap on the finest stone.
Be sure to wash off the blades between stones and to keep the stones separate or there will be a slight chance that large grits from coarser stones will migrate to the finer stones and gouge the surface you are preparing.
This method works fine, but the water stones are soft and will tend to develop hollowed surfaces. In this case I stop and reflatten the water stones.
To use a lapping plate and carbide crystals you must accept the fact that you will get unbelievably dirty as the microscopic carbide will get under your skin around your fingertips. It will not wash out. This can be a big surprise to people who go to "clean hands" office jobs.
Lapping plates and a selection of grits (the grits come in little plastic photography film type containers) are less expensive and appear to do a faster and somewhat better job than water stones. The key here is that the grits break down as you use them (this is also a water-lubricated process) and so develop a surface which is constantly becoming more refined. Instead of changing stones, you develop your own abrasive media as you sweat. I use the same little wooden tool cradles for this process as I use with the water stones.
If you want to perform this technique I recommend you talk to the people at Highland Hardware for reference to a book with illustrations for the beginner. There are always several of these in print.
The front edge of a chisel blade is sharpened the same as other blades, only you work with one side.
There are several very good inexpensive sharpening jigs for plane blades. I use the same approach with planes and chisels as I do with everything: get the primary land in thoroughly, then shift the jig and cut a wee little microbevel, then strop.
Books on the subject give highly precise angle specifications - some in 1/2 degree intervals - for various blades and cutting tasks. I have never found these useful.
Draw knives are not usually flattened as precisely on the back as are plane blades and chisels. They are hand guided and twisted in the grain to change directions when cutting. Chisels have a flat side so that they can be guided precisely when paring or slicing in a tight corner, such as a dovetail. This is very different from a drawknife or froe operation.
Adzes are a hewing tool and also will not benefit from flat side refinement beyond a certain point.
Broad axes are a sort of hewing and slicing tool. They are mostly used to slice off the round outer edges of a log when preparing to rip cut planks out. Because they are somewhat precision-guided, they need a good sharp side and a flat back, but not necessarily a mirror-reflecting back.
Blacksmithing Frank Turley, Director Turley Forge Blacksmithing School Rt. 10 Box 88C Santa Fe, NM 87501 (505)471-8608
Frank started out as a farrier and has kept growing all of his professional life. His classes are an excellent introduction to the basics of blacksmithing.
Centaur Forge, Ltd. 117 North Spring Street PO Box 340-B Burlington, WI 53105 (414) 763-9175
This is the major USA supplier of farrier and blacksmithing supplies. They also have a huge selection of books and videos on a variety of manual trades, horses, carriage making etc.
Blade Magazine Krause Publications 700 East State Street Iola, WI 54990-0001 (715) 445-2214
Blade is primarily devoted to reviewing the high end of the knife industry-handmade and artistic knives. They have some good articles of field trials of knives and technical aspects of knife making. Their advertisers include a wide selection of tool makers with knife kits, blades, parts, leather sources, etc.
Atlanta Cutlery 2143 Gees Mill Road Box 839 Conyers, GA 30207 (800) 883-0300
These guys are strong on knife kits, including kitchen cutlery, parts, practical knives, books, sharpeners and some artistic knives and swords. Their sister operation deals in theatrical supplies such as swords, armor, renaissance reenactment costumes, etc. We don't hold many sword fights or jousts at our farm but if you do, now you know where to get your equipment.
Cutlery Shoppe 5461 Kendall Street Boise, ID 83706-1248 (800) 231-1272
This catalog actually prints the specifications of the knife steels as part of the entries for many of their knives. This is a huge advantage for the informed shopper. They are also strong on sharpening materials and quality kitchen cutlery. This catalog is pricey; however, I have found that they have regular sales which are impossible to beat.
Smokey Mountain Knife Works PO Box 4430 Sevierville, TN 37864 98000 251-9306
This outfit produces a huge catalog of knives and related stuff. Some of the entries have wholesale prices noted. They have low-end as well as middle- and high-end goods so buyer beware.
General Tooling: Highland Hardware 1045 North Highland Avenue NE Atlanta, GA 30306 (404) 872-4466
This store actually has two graduate engineers for owners and is staffed by, and the phone is answered by, people who know what they are talking about. They have a good variety of sharpening materials including water stones, high-end woodworking tools, saw sets, special saw files, Japanese tools etc. The catalog is great.
Langsner, Drew. Green Woodworking: Handcrafting Wood from Log to Finished Product. Rodale Press, 1987.
Langsner, Drew. Country Woodcraft. Rodale Press, 1978.
Drew Langsner's school: Country Workshops 90 Mill Creek Road Marshall, NC 28753 (704) 656-2280
Drew Langsner teaches woodworking seminars and hosts woodworking seminars with an occasional blacksmithing seminar thrown in. The teachers he brings in are some of the top people in the USA and abroad. He also sells a variety of hard-to-find woodworking tools and some sharpening tools like the Tormek grinder. Drew specializes in green woodworking without power tools. This is the old-fashioned technology. In many applications this technology is superior to machine-made, particularly chairs and some tools.
Andrews, Jack. Edge of the Anvil, a Resource Book for Blacksmiths. Skipjack Press, 1991.
Schroen, Karl. The Hand Forged Knife. Knife World Publications, Knoxville, TN, 1984.
Spielman, Patrick. Sharpening Basics. Sterling Publishing, 1991.
This is a good general introduction to a wide variety of sharpening tasks. It is primarily oriented to the woodworker market; however, it is well illustrated and easy to follow.
Juranitch, John. The Razor Edge Book of Sharpening. Warner Books, 1985.
This guy has a good sharpening jig as well as a good basic book on sharpening technology.
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|Title Annotation:||includes list of manufacturers and sources; sharpening tools|
|Publication:||Countryside & Small Stock Journal|
|Date:||Jul 1, 1995|
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