A Guide to Tool Sharpening Basics

MOTHER's Handbook: Let's cut the mystery away from this vital tool sharpening skill. Coaxing an edge onto a trusted tool can be a peace-bringing and fulfilling process. (See the slideshow for tool sharpening figures 1 to 19.)

I’ve been a tool sharpener for so long my pocketknife bladecan trim a tick's toenails. My kitchen knives can slice apotato too thin to taste. And long ago I stopped performingthe so-called expert's trick of shaving my beard with anax. No sir, I use that tool's edge to floss between myteeth!

None of the above boasts are a bit true. Actually, I’vealways found tool sharpening to be very intimidating,partly because everybody else seemed to be an expert at it.Still, I knew it was an important skill to master. Yousimply can't do many jobs with dull tools, and you canperform any cutting task much better and more easily with asharp one.

I finally decided it was time for me to get a handle on thesubject. So I visited local tool sharpeners Roger Korning(who uses sophisticated Foley Belsaw machinery) and CollierDavis (a file-and-grindstone man). I got a two hourpersonal honing lesson from professional knifemaker RobertParrish, who's famed among the gun and-blade set for hisexquisite RP survival knives. I collected tips from HollenOrr, a retired craftsman who's built a grandfather's clockand a set of violins by hand. I spent hours in the shopwith MOTHER’S own workshop wizard, Dennis Burkholder. Ieven called up public TV's renowned woodwright, RoyUnderhill, for advice!

The result? I’m not ready to trim my face fuzz with an ax,but I can now put a decent working edge on most of thetools my family uses. And here's betting I can tell othernovice edge-keeners how to do so, as well.

"Do the job right, and you’ll get a good edgein five minutes."

The pros know a dull tool is more dangerousthan a sharp one.

Let's divvy up the doings right off into twogroups—rough outdoor tools you can sharpen wellenough with a file, and finer blades that need morespecialized care. We’ll start with the file jobs becausethey take less skill (if more muscle), yet illustrate manyof the principles of fine-tool sharpening. In fact, let'sget right to work by discussing tools many people havenever even thought about sharpening—spades and shovels.

You won't believe it until you try it, but a sharp spade(the flat-faced digging tool) or shovel (the curve-facedone) will cut through dirt far easier than will adull one. All you need for the job is a coarse hand file.(Hollen Orr says, "Use a file on everything it’ll cut. Witha file you can see where you’ve been.") It can be eithersingle-cut (one set of lines—actually, rows of teeth)or double-cut (two intersecting sets of teeth). Thedouble-cut will take more metal off with less effort; thesingle-cut will do a finer job.

But before you get to filing, let's look at your diggingtool a second. Is it rusted? Not good. As MOTHER’S DennisBurkholder puts it, "The only thing that’ll ruin the edgeon a tool faster than using it is abusing it. Andnothing’ll pit up an edge faster than rust." So scrape offas much rust as you can with steel wool, and from now onclean off this (and every) tool after you use it, and rubit lightly with oil to keep new rust from forming. Thissimple step will greatly extend the edges and lives of yourtools.

Now for the real work. First, run your file around the topof the edge some, if need be, to smooth out any nicks inthe blade (Figure 1). Then consider: A shovel or spade is asingle-beveled tool. It has only one sharp edge, whichleads us to:

Sharpening Axiom No. 1: Sharpensingle-beveled tools ONLY on the beveled side(Figure 2). You can ruin the cutting edge of thetool otherwise. In real life, you could probably rescue arough tool like a shovel from the mistreatment of havingboth sides filed. But do that to your scissors or prized pruners, and they’llbe headed for the junk pile.

So brace your spade or shovelwell—this and, almost every sharpening job will goeasier if you clamp your work with C-clamps or in avise—and file it on the top, the beveled side. (Keepyour forgers out of the way.) You can run your file up intothe blade or down the blade, whichever's easier. Use a filethat matches the contour of the blade: a flat one for thatflat-faced spade and a half-round one for the curvedshovel.

What kind of angle should you sharpen at? Ah, that takes usright to:

Sharpening Axiom No. 2: In general, sharpenthe bevel at the same angle that was already there. Inother words, if you can tell what angle the manufacturer orprior sharpener used, follow it. If you can't tell, move on to:

Sharpening Axiom No. 3:Sharpening at a steep angle gives a more durable edge;sharpening at a low angle gives a sharper edge (Figure3). The thin edge produced by low angle sharpening willobviously be sharper than a wider edge, but it will be morebrittle as well. Since we’re honing a digging tool that'slikely to strike roots or rocks, a tough edge is probablymore important than a super sharp one, so sharpen yourspade at a fairly—high angle say, one that puts ashine back only about 1/4 inch into the blade.

Press thefile hard on your forward stroke, going the full length ofthe sharpening tool (so you won't wear the file out in onespot). Your backstroke should be light, little more thanthe weight of the tool, to keep from breaking any fileteeth.

And angle the file across the blade face as you push ratherthan going straight into the blade (Figure 4). That’ll helpyou sharpen the edge evenly. It may also help you run thefile teeth at a more effective right angle to your work.(Does that sound cuckoo? Look at the lines of file teeth.If they run at an angle, working the file across can helprun those teeth right into the work.)

Sharpener CollierDavis dips his file in water frequently as he works, towash off the shavings, and says that this lengthens thelife and increases the bite of the tool. Eventually,though, any file will wear out. When yours doesn't workwell anymore, and unclogging it with a wire brush won't fixit, replace it.

Once you’ve run the file across the entireblade a while, you’ll have created a shiny tapered edge. Ifyou run a finger on the underside of the blade, from theinside out to the tip, you may be able to feel a slightburr (also called a wire or feather ) atthe edge. That's the best sign that things are gettingsharp. The burr is created when the edge gets so thin it won'tstand the pressure of the file, so it bends over to theother side (Figure 5). It's so small you can't see it. And itmay be hard to feel, almost like running your hand over apiece of transparent tape. (If you have trouble, trydrawing your fingernail at a 45 degree angle toward theburr.) Keep filing until you can feel that burr—allthe way along the edge. It's critical to good sharpening.Besides, getting a sense of this large, relativelyeasy-to-sense burr will help you know what to feel for onthe finer tools we’ll cover later.

Now all that's left isto remove this fragile feather. To do so, lightly run yourfile flush with the unbeveled surface of the spade. I know,I told you not to sharpen that side. You’re not, because you’re not filing into the blade at anangle, just filing along it. You might then wantto turn the shovel over and lightly file into your firstside again to remove any burr that got pushed back over toit, and you’ll be ready to dig like the dickens.

OK, thatjob was easy enough. Let's move on to another commonly usedbut rarely sharpened tool—the gardenhoe. Again, you simply won't believe how muchbetter that weed chopper will work once it's got a goodedge on it. And why make weeding any more work than it isalready?

Use the same techniques described above: Your hoe(plain or fancy) has a single-bevel cutting edge, so you’regoing to sharpen only that one side. If you can't tell bylooking, the cutting edge is at the bottom of the tool,running right along the ground when you’re using the hoe.(A hoe's flat upper edge pushes dirt out of the way whileits bottom face cuts roots.)

Sharpen the beveled side wellwith your file. At what angle do you sharpen? Follow theexisting angle or try Dennis Burkholder's old-timey trick:Scrape the tool along some cement, standing just like youwere using it to weed (Figure 6). Then sharpen where you seescratch marks. That way you’ll be setting the cutting edgeat the perfect angle to suit your height and posture.

File until you’ve drawn out a burr. Then trim that wire offthe other side, and give the first side a couple of extralight licks. And from now on, whenever your garden weedsstart to feel a bit stubborn (which may happen a couple oftimes a day), take a short break and give your hoe a quickkeening. You’ll save time and energy.

Your lawn mower blade, more of the same.Disconnect the spark plug (just in case the cantankerousthing gets any ideas), then unbolt the blade and clamp itin a vise. Tip: If you set it (and other tools) so you canlook "into" the end of the blade, you can better see ifyou’re maintaining the proper angle. File the cutting sideonly, creating a shiny bevel about 1/8 inch or so wide(Figure 7). You may want to use a half-round file in thebowed portion of the blade. Sharpen both ends of the bladeto match, using the single-bevel techniques alreadydescribed.

All done? Whoa, don't put the blade back on yet. First make sure it's balanced end to end. Set the center ofthe clean (no grass on it) blade on the corner of your fileand see if both sides weigh the same (Figure 8). (The centershould be at the middle of the main hole. You can measurein from both ends to make sure.) If one side sinks, file alittle bit off the back edge of that heavy side, andbalance it again.

Don't neglect this step: DennisBurkholder (who once helped design mowers) says it's justas important as sharpening the blade. Otherwise, your blademay wobble when it spins, and that 3,600 rpm shimmy willeventually wear out the oil seals on the blade's shaft.You’ll find yourself with a strange-and expensive-problemto fix: "Whenever the motor of my mower warms up, oil runsout the bottom.

"Once the blade is nicely sharp and balanced, put it backon the mower-cutting edge up. (That position, coupled withthe airplane like lift created by the up-curve in back ofthe blade, helps keep cut grass up off the ground so it canbe blown out. By the way, if you put the blade on upsidedown, you’ll be surprised by how poorly it cuts-I surewas!)

Pruning shears? Grass clippers? Tin snips? You canfile them into shape, no problem. Remember, they’resingle-beveled tools. So if you mess with the insides of those closing blades(except to lightly remove burrs), don't blame me for whathappens. Actually, if your pruning shears aren't cuttingwell, it may be that there's too much play between theblades. Tighten the nut in the middle and see if thathelps.

Heck, you can even sharpen one of those jagged-edgehand swing blades (also called grass whips)with a file. Run it down the bottom cutting side and it’llget both the peaks and valleys of the blade (Figure 9).

OK, it's time to move on to a more labor-demanding subject: the ax. To sharpen most dull axes, you’regoing to have to file back a shine on each side 3/8- to1/2-inch long, and that means removing a lot of material.Woodwright Roy Underhill uses a single- or double cut filefor this job, drawing the file back and forth along theside of the blade with both hands (Figure 10). He says thistechnique makes it easier to keep an accurate angle whileyou work, keeps you from accidentally pushing your handinto the blade and leaves a smoother finish.

Some othersharpeners I met feel that a dull ax requires so muchfiling that this is one time a power grinding wheel is abig help. If you do use a wheel, for Pete's sake, becareful. It takes off material awfully quickly, and asCollier Davis notes, "You can't put it back on." Then, too, if you let any part of your tool get too hotfrom rubbing against the wheel, its temper will be ruinedforever. (Whenever the tool starts to get hot, dunk it in abucket of water.) So go slow—the slower the wheel,the better. In fact, a hand-cranked sandstone wheel likeRoy Underhill uses would be ideal. And follow these safetyrules: Wear protective goggles with a power wheel. Hold theax so it can't possibly jam or get snapped back at you. Andkeep your hands away from that wheel.

First off, file around the edge or carefully hold the axedge itself straight into the wheel, perpendicular, and runthat edge tip to tip to wear out any nicks. Then grind orfile all along one side (Figure 11), holding the ax so that3/8 inch or a hair more of the side is getting worn. (Tip:If your wheel has a front guard plate, you can tilt it tothe correct angle and rest your ax on that improvisedguide.) You don't want to grind too far back, or you’llmake the tip too thin. An ax blade needs to be a bitthick—more so than a hoe or spade, forinstance—so that it won't get stuck in the woodyou’re chopping.

Raise a burr all along the edge, flip theax over, and grind or file away until you raise a burr onthe other side. That's it for the rough work. To reallyfinish the job, you’ll need a good honingstone—Carborundum, Arkansas, Washite, whatever (I’lltalk more about them soon). You can hold the ax and rub itwith the stone like the old-time woodsmen do, but that's atough trick, because you’re trying to keep a precise anglewhile working freehand with both objects. It's much easierto vise or clamp either the stone or ax in place. Then drawone object across the other so that the stone cuts into theblade.

The key here is to keep the entire edge at the sameangle, and on both sides. It's not easy. Fortunately, an axis a hard, rough-work tool, so as long as you’re going tochop wood instead of whiskers, you can get away with somebeginner's wobbling. It’ll be good practice for knife sharpening and, moreimportant, you’ll be smoothing out those ground sides andclosing up pores where rust could work in. (For the samereason, using a stone to finish any of the tools we’vesharpened so far is probably a good idea.)

OK, let's put the file and outdoor tools away and comeinside to learn some refined sharpening skills—mostespecially, putting a good edge on a knife. I’m afraid thatjob won't be as easy to describe as the others; asprofessional knifemaker Robert Parrish puts it, "There'slots of controversy over knife sharpening, lots of ways todo it." Roy Underhill concurs, noting that "many people areinto the sharper-than-thou thing, saying everything has to be done the right way—theirs." (Parrishdoesn't think much of disputes over techniques: "Basically,they all work.")

For an example of these hones of contention, consider:Should you oil or water a sharpening stone? Underhill feelsit helps the stones stay soft and keeps them from getting"glazed"—gummed up with metal shavings. (He even quotes the Trevisa, a thirteenth-century medievalencyclopedia that recommends " . . . diverse maner ofwhetsones, and some neden water and some neden oyl for towhette.") Parrish doesn't lubricate his stones, though.Neither does John Juranitch.

John What? Who's he? He's theguy who wrote the best book we know on this topic, TheRazor Edge Book of Sharpening. He holds the worldrecord for rapidly sharpening a dull ax and shaving hisbeard with it. He's made a business of helping thousands ofbutchers and packing houses improve their cutting edges. And he's studied dry- and wet-honed edges under10,000-power electron microscopes. He says oiling a stonejust creates an abrasive grinding compound on top of thestone that can actually dull a blade.

Me? I figure if anexpert like that doesn't go for oiling, that's a goodenough excuse for a beginner like me to take the easy wayout and not do it either.

Another big dispute I’ve run into is double-edging.Juranitch says to put a low secondary, or relief,angle on the sides of the blade with a coarse hone and thenput a steeper primary edge on just the tip of theblade (Figure 12). However, none of the people I talked withconsistently do this. (Underhill: "Someone who looked in mytool chest would find tools sharpened all sorts of ways; Ido what it takes to make a tool work.") Since this is abeginner's article, I’ll just go into the more commonsingle-edge sharpening here. If you want to move onto double-edging after you masterbasic sharpening, read Juranitch's book.

Feud number three:What kind of sharpening stone should you use? Parrish likesCarborundum; my editor swears by his Japanese water stones;Underhill likes Washita or even Belgium white clay pieceshe finds at the junk dealers. Best as I can figure, itdoesn't much matter. What is important is that you have twoabrasive surfaces: a coarse one to get the hard grindingdone faster and a fine one for the finish sharpening. Acoarse stone wears material away quickly until the bladeangle is what you want it to be, but if you continue to useit past that point, it’ll take off your sharp edge ratherthan finish it.

The fine one gives you that final keen,smooth edge. If you want to use natural stones for these jobs, rememberthat a soft stone is more abrasive than a hard one. (Thefine, glasslike surface on a hard stone is for finishing.)Seems to me, the easiest thing to do is drop by your localhardware store and get a two-sided (one rough, one smooth)Carborundum stone. They work swell. What ever stone youuse, do get a big one, at least six inches long, so you’llhave enough room to do a full sharpening stroke. (Aseven-inch Carborundum runs around $12 in our area.)

Acouple more things and we’ll be ready to begin. One, fastenyour stone in a vise or clamp, secure it within a smallwooden frame—do something so it won't move around. You’ll have enough trouble getting a consistent sharpeningangle with only the blade moving. Don't make things worseby letting the stone wiggle around as well. Two, for yourfirst practice sessions, get hold of an inexpensivehigh-carbon knife. They wear away a lot more easily thanyour stainless steel Swiss Army or kitchen butcheringknife, so you can see results (good and bad) a whole lotfaster. (Besides, with one of those you won't mess up areally good knife while you’re learning.) I practiced on aflea market set of kitchen knives.

Enough preamble.Fasten your rough stone in place. Hold your knife with twohands, one hand on the handle and the other supporting theblade (thumb on the blunt back edge). Hold the blade at aslight—not steep—angle (the magic number is20 degrees, but who's measuring?), and push the blade alongthe stone as if you were trying to cut a slice out of itssurface (Figure 13).

Sound easy? It's not. You want to sharpen the whole edge of the blade with everystroke, so you’ve got to move the blade diagonally as youpush it forward so its tip will make contact with the stonebefore you reach the end of the stroke (Figure14)—that's why you want a good-sized honing stone.You’ll also have to lift up on the handle of the blade abit as you get to the tip, or that curved edge won't reallymeet the stone (Figure 15). And—most important ofall—you’ve got to keep the same angle on the bladewith each and every stroke.

That's the real problem. Listen to Robert Parrish: "It’ll take an hour for theaverage person to sharpen a pocketknife—and it stillwon't be really sharp. Do the job right and you’ll get agood edge in five minutes. Ninety-nine percent of theproblem is in the angle." If you keep changing the angle asyou work (ever so slightly, ever so unintentionally),you’ll keep hitting edge to stone at different points and,in effect, rounding off the edge of the blade, making itdull instead of sharp.

It sure happened to me. Parrish gave me a good one-on-one lesson, went off to helpa customer, came back and found I’d made my pocketknifeduller instead of sharper. I figured R.P. had moreimportant things to do than watch me mess up, so I wenthome to do what he (and all the other experts I talked to)emphasized: Practice. (It helped.)

Some other tips: Holdthat thumb backstop on the blade so the side of it touchesthe stone while the middle of it holds the blade at theangle you want. Sharpen by pivoting your body at the waistso you’ll have your wrists and elbows locked. And you can,if you’d rather, do your rough honing by moving sections ofthe blade round and round in a circular motion. Underhillfigures that makes it easier to keep the correct anglebecause you’re not repeatedly lifting the blade off thestone.

If you’re getting frustrated or just want to make the wholejob go a lot easier, get a sharpening guide—a littleblade clamp that automatically holds your knife at theright angle (Figure 16). Buck Knives makes one, called theHonemaster, and Juranitch offers the Razor Edge KnifeSharpening Guide. Let me tell you, unlike many sharpeninggimmicks, these two doodads work. You may just want to usethem as training wheels, but beard-axer Juranitch claims noexpert can "freehand" a knife edge as well as an amateurwith a guide can. He's even proved it repeatedly by having pairs ofnovices—his daughters, Boy Scouts, professionaloutdoor writers—use his guide to sharpen pocketknivesand then by shaving his own face with those blades.

OK,guided or not, work that one side of the blade until youcan raise a burr along the whole edge. Keep working untilyou get that burr—let it be your teacher.

Once you’vegot a full-length burr, turn the knife over and sharpen theother side by pulling the blade toward you. Your blade handposition will have to change here. This time put your fingers behind the blade and let yourthumb press down on the side (Figure 17). Everything else isthe same. Keep a constant blade angle (the same one you hadon the other side), stroke the whole blade on the stone,and lift the handle some as you get to the tip so it willget sharpened too (Figure 18). Work that side until you raisea full burr going the other way.

Now switch to your finestone for the finish work. Stroke once away from you (asyou did at first) and once toward you. Alternate about adozen strokes, forward and backward, on the stone. Don'tpress as hard on these strokes as you did on the rough-sideones. And you can keep lightening up so your last fewstrokes carry just the weight of the knife.

You’re done—or are you? How can you tell if yourknife is sharp? Well, you can run your thumb over (notdown—ow!) the edge and feel if it tends to catch inyour thumbprint grooves. You can hold a piece of paper bythe corner and see if your knife will cut (not tear) intoit. And you can try to shave hair off the back of your armwith it.

If it does all that, congratulations! You’ve donewell. If not, repeat your steps on the fine stone. That’llprobably do the trick. If it doesn't, you’re most likelynot holding the knife at a constant sharpening angle. Keeppracticing—or get a sharpening guide.

Once you’ve gota fine edge, you might want to put an extra finishing touchon it by stroking it down a steel or a pair of ceramicsticks. Most of these are set at an angle. All you have todo is hold your blade vertical and run it straight down thestick, drawing the full blade against it as you do. Regular use of these last aids will help keep a good edgeon a blade, but they will not fix a dull one. Put that kindback on the stone.

Now you can sharpen all the knives inyour home. Most of them will take that same slight angleyou put on your first blade. If you’re honing a butcheringknife that's going to be going through bone, put a steepangle on it so the edge won't be likely to break. If you’rekeening a delicate-work fillet knife, give it a very slimtaper.

Let's move on and sharpen a wood chisel ora plane. Another two-stage job, roughthen fine. You can do the rough work with a coarse stone, afile or a grinding wheel (if you’re real careful).Remember, the most important thing: This is a single-bevelblade so sharpen it only on the angled side or all is lost.Follow the original bevel unless you’re going to be cuttinginto very hard wood—in which case, you’d want asteeper (tougher) angle.

Hollen Orr clamps his chisel in avise, so that the edge is horizontal, then runs his filedown the face of it until he raises a burr (Figure 19). Note:He uses a fine file for this operation, following the rulethat the harder the object, the finer the file. (A finefile's tiny teeth can better reach into the fine pores of ahard object.) He smooths the burr off by rubbing the backside with a fine stone set flat (not at an angle), thentouches up the cutting side a bit with the fine stone. Whenhe's done, that chisel will pop the hairs off his arm. Ifyou’re not so confident about your own freehand sharpening,you could use Juranitch's knife sharpening guide (but notthe Honemaster) on it and be sure you’ll maintain a setangle.

In short, simplycombine the techniques given here with some seriousdedication to practice (you’ll know you’re practicingenough if people start asking you why there's no hair onyour left forearm). Soon you’ll be able to sharpen plentyof the tools around your place.

And you’ll probably do somore often than you’d think, because it gets to be anenjoyable task. I gain a curious sense of peacefulness fromputting an edge on a favorite blade or tool. The slow rhythm of metal stroking on stone is a calmingsound, a serviceable sort of music our forefathers knewwell.

It's one that's well worth your, and my,rediscovering.

The Razor Edge Book ofSharpening and Razor Edge Knife Sharpening Guide areavailable for $12.50 and $9.95, respectively, from RazorEdge Systems, Inc., Ely, MN. Add $3 shippingand handling per order. The Honemaster is available forapproximately $9 at shops where Buck knives are sold.