DIY

A Guide to Tool Sharpening Basics

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PHOTO: BROWNIE HARRIS
You simply can't do many jobs with dull tools, and you can perform any cutting task much better and more easily with a sharp one.

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.)

A Guide to Tool Sharpening Basics

I’ve been a tool sharpener for so long my pocketknife blade
can trim a tick’s toenails. My kitchen knives can slice a
potato too thin to taste. And long ago I stopped performing
the so-called expert’s trick of shaving my beard with an
ax. No sir, I use that tool’s edge to floss between my
teeth!

None of the above boasts are a bit true. Actually, I’ve
always 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. You
simply can’t do many jobs with dull tools, and you can
perform any cutting task much better and more easily with a
sharp one.

I finally decided it was time for me to get a handle on the
subject. So I visited local tool sharpeners Roger Korning
(who uses sophisticated Foley Belsaw machinery) and Collier
Davis (a file-and-grindstone man). I got a two hour
personal honing lesson from professional knifemaker Robert
Parrish, who’s famed among the gun and-blade set for his
exquisite RP survival knives. I collected tips from Hollen
Orr, a retired craftsman who’s built a grandfather’s clock
and a set of violins by hand. I spent hours in the shop
with MOTHER’S own workshop wizard, Dennis Burkholder. I
even called up public TV’s renowned woodwright, Roy
Underhill, 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 the
tools my family uses. And here’s betting I can tell other
novice edge-keeners how to do so, as well.

“Do the job right, and you’ll get a good edge
in five minutes.”

 

The pros know a dull tool is more dangerous
than a sharp one.

 

Rough Work With a File

Let’s divvy up the doings right off into two
groups—rough outdoor tools you can sharpen well
enough with a file, and finer blades that need more
specialized care. We’ll start with the file jobs because
they take less skill (if more muscle), yet illustrate many
of the principles of fine-tool sharpening. In fact, let’s
get right to work by discussing tools many people have
never 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-faced
one) will cut through dirt far easier than will a
dull one. All you need for the job is a coarse hand file.
(Hollen Orr says, “Use a file on everything it’ll cut. With
a file you can see where you’ve been.”) It can be either
single-cut (one set of lines—actually, rows of teeth)
or double-cut (two intersecting sets of teeth). The
double-cut will take more metal off with less effort; the
single-cut will do a finer job.

But before you get to filing, let’s look at your digging
tool a second. Is it rusted? Not good. As MOTHER’S Dennis
Burkholder puts it, “The only thing that’ll ruin the edge
on a tool faster than using it is abusing it. And
nothing’ll pit up an edge faster than rust.” So scrape off
as much rust as you can with steel wool, and from now on
clean off this (and every) tool after you use it, and rub
it lightly with oil to keep new rust from forming. This
simple step will greatly extend the edges and lives of your
tools.

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

Sharpening Axiom No. 1: Sharpen
single-beveled tools ONLY on the beveled side

(Figure 2). You can ruin the cutting edge of the
tool otherwise. In real life, you could probably rescue a
rough tool like a shovel from the mistreatment of having
both sides filed. But do that to your scissors or prized pruners, and they’ll
be headed for the junk pile.

So brace your spade or shovel
well—this and, almost every sharpening job will go
easier if you clamp your work with C-clamps or in a
vise—and file it on the top, the beveled side. (Keep
your forgers out of the way.) You can run your file up into
the blade or down the blade, whichever’s easier. Use a file
that matches the contour of the blade: a flat one for that
flat-faced spade and a half-round one for the curved
shovel.

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

Sharpening Axiom No. 2: In general, sharpen
the bevel at the same angle that was already there.
In
other words, if you can tell what angle the manufacturer or
prior 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
(Figure
3). The thin edge produced by low angle sharpening will
obviously be sharper than a wider edge, but it will be more
brittle as well. Since we’re honing a digging tool that’s
likely to strike roots or rocks, a tough edge is probably
more important than a super sharp one, so sharpen your
spade at a fairly—high angle say, one that puts a
shine back only about 1/4 inch into the blade.

Press the
file hard on your forward stroke, going the full length of
the sharpening tool (so you won’t wear the file out in one
spot). Your backstroke should be light, little more than
the weight of the tool, to keep from breaking any file
teeth.

And angle the file across the blade face as you push rather
than going straight into the blade (Figure 4). That’ll help
you sharpen the edge evenly. It may also help you run the
file 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 help
run those teeth right into the work.)

Sharpener Collier
Davis dips his file in water frequently as he works, to
wash off the shavings, and says that this lengthens the
life and increases the bite of the tool. Eventually,
though, any file will wear out. When yours doesn’t work
well anymore, and unclogging it with a wire brush won’t fix
it, replace it.

Once you’ve run the file across the entire
blade a while, you’ll have created a shiny tapered edge. If
you run a finger on the underside of the blade, from the
inside out to the tip, you may be able to feel a slight
burr (also called a wire or feather ) at
the edge. That’s the best sign that things are getting
sharp. The burr is created when the edge gets so thin it won’t
stand the pressure of the file, so it bends over to the
other side (Figure 5). It’s so small you can’t see it. And it
may be hard to feel, almost like running your hand over a
piece of transparent tape. (If you have trouble, try
drawing your fingernail at a 45 degree angle toward the
burr.) Keep filing until you can feel that burr—all
the way along the edge. It’s critical to good sharpening.
Besides, getting a sense of this large, relatively
easy-to-sense burr will help you know what to feel for on
the finer tools we’ll cover later.

Now all that’s left is
to remove this fragile feather. To do so, lightly run your
file 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 an
angle, just filing along it. You might then want
to turn the shovel over and lightly file into your first
side again to remove any burr that got pushed back over to
it, and you’ll be ready to dig like the dickens.

OK, that
job was easy enough. Let’s move on to another commonly used
but rarely sharpened tool—the garden
hoe
. Again, you simply won’t believe how much
better that weed chopper will work once it’s got a good
edge on it. And why make weeding any more work than it is
already?

Use the same techniques described above: Your hoe
(plain or fancy) has a single-bevel cutting edge, so you’re
going to sharpen only that one side. If you can’t tell by
looking, 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 while
its bottom face cuts roots.)

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

File until you’ve drawn out a burr. Then trim that wire off
the other side, and give the first side a couple of extra
light licks. And from now on, whenever your garden weeds
start to feel a bit stubborn (which may happen a couple of
times a day), take a short break and give your hoe a quick
keening. You’ll save time and energy.

Your lawn mower blade, more of the same.
Disconnect the spark plug (just in case the cantankerous
thing gets any ideas), then unbolt the blade and clamp it
in a vise. Tip: If you set it (and other tools) so you can
look “into” the end of the blade, you can better see if
you’re maintaining the proper angle. File the cutting side
only, creating a shiny bevel about 1/8 inch or so wide
(Figure 7). You may want to use a half-round file in the
bowed portion of the blade. Sharpen both ends of the blade
to match, using the single-bevel techniques already
described.

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

Don’t neglect this step: Dennis
Burkholder (who once helped design mowers) says it’s just
as important as sharpening the blade. Otherwise, your blade
may wobble when it spins, and that 3,600 rpm shimmy will
eventually wear out the oil seals on the blade’s shaft.
You’ll find yourself with a strange-and expensive-problem
to fix: “Whenever the motor of my mower warms up, oil runs
out the bottom.

“Once the blade is nicely sharp and balanced, put it back
on the mower-cutting edge up. (That position, coupled with
the airplane like lift created by the up-curve in back of
the blade, helps keep cut grass up off the ground so it can
be blown out. By the way, if you put the blade on upside
down, you’ll be surprised by how poorly it cuts-I sure
was!)

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

Heck, you can even sharpen one of those jagged-edge
hand swing blades (also called grass whips)
with a file. Run it down the bottom cutting side and it’ll
get 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’re
going to have to file back a shine on each side 3/8- to
1/2-inch long, and that means removing a lot of material.
Woodwright Roy Underhill uses a single- or double cut file
for this job, drawing the file back and forth along the
side of the blade with both hands (Figure 10). He says this
technique makes it easier to keep an accurate angle while
you work, keeps you from accidentally pushing your hand
into the blade and leaves a smoother finish.

Some other
sharpeners I met feel that a dull ax requires so much
filing that this is one time a power grinding wheel is a
big help. If you do use a wheel, for Pete’s sake, be
careful. It takes off material awfully quickly, and as
Collier Davis notes, “You can’t put it back on.” Then, too, if you let any part of your tool get too hot
from rubbing against the wheel, its temper will be ruined
forever. (Whenever the tool starts to get hot, dunk it in a
bucket of water.) So go slow—the slower the wheel,
the better. In fact, a hand-cranked sandstone wheel like
Roy Underhill uses would be ideal. And follow these safety
rules: Wear protective goggles with a power wheel. Hold the
ax so it can’t possibly jam or get snapped back at you. And
keep your hands away from that wheel.

First off, file around the edge or carefully hold the ax
edge itself straight into the wheel, perpendicular, and run
that edge tip to tip to wear out any nicks. Then grind or
file all along one side (Figure 11), holding the ax so that
3/8 inch or a hair more of the side is getting worn. (Tip:
If your wheel has a front guard plate, you can tilt it to
the correct angle and rest your ax on that improvised
guide.) You don’t want to grind too far back, or you’ll
make the tip too thin. An ax blade needs to be a bit
thick—more so than a hoe or spade, for
instance—so that it won’t get stuck in the wood
you’re chopping.

Raise a burr all along the edge, flip the
ax over, and grind or file away until you raise a burr on
the other side. That’s it for the rough work. To really
finish the job, you’ll need a good honing
stone—Carborundum, Arkansas, Washite, whatever (I’ll
talk more about them soon). You can hold the ax and rub it
with the stone like the old-time woodsmen do, but that’s a
tough trick, because you’re trying to keep a precise angle
while working freehand with both objects. It’s much easier
to vise or clamp either the stone or ax in place. Then draw
one object across the other so that the stone cuts into the
blade.

The key here is to keep the entire edge at the same
angle, and on both sides. It’s not easy. Fortunately, an ax
is a hard, rough-work tool, so as long as you’re going to
chop wood instead of whiskers, you can get away with some
beginner’s wobbling. It’ll be good practice for knife sharpening and, more
important, you’ll be smoothing out those ground sides and
closing up pores where rust could work in. (For the same
reason, using a stone to finish any of the tools we’ve
sharpened so far is probably a good idea.)

The Art of Sharpening a Knife

OK, let’s put the file and outdoor tools away and come
inside to learn some refined sharpening skills—most
especially, putting a good edge on a knife. I’m afraid that
job won’t be as easy to describe as the others; as
professional knifemaker Robert Parrish puts it, “There’s
lots of controversy over knife sharpening, lots of ways to
do it.” Roy Underhill concurs, noting that “many people are
into the sharper-than-thou thing, saying everything has to be done the right way—theirs.” (Parrish
doesn’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 feels
it helps the stones stay soft and keeps them from getting
“glazed”—gummed up with metal shavings. (He even quotes the Trevisa, a thirteenth-century medieval
encyclopedia that recommends ” . . . diverse maner of
whetsones, and some neden water and some neden oyl for to
whette.”) Parrish doesn’t lubricate his stones, though.
Neither does John Juranitch.

John What? Who’s he? He’s the
guy who wrote the best book we know on this topic, The
Razor Edge Book of Sharpening
. He holds the world
record for rapidly sharpening a dull ax and shaving his
beard with it. He’s made a business of helping thousands of
butchers and packing houses improve their cutting edges. And he’s studied dry- and wet-honed edges under
10,000-power electron microscopes. He says oiling a stone
just creates an abrasive grinding compound on top of the
stone that can actually dull a blade.

Me? I figure if an
expert like that doesn’t go for oiling, that’s a good
enough excuse for a beginner like me to take the easy way
out 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 then
put a steeper primary edge on just the tip of the
blade (Figure 12). However, none of the people I talked with
consistently do this. (Underhill: “Someone who looked in my
tool chest would find tools sharpened all sorts of ways; I
do what it takes to make a tool work.”) Since this is a
beginner’s article, I’ll just go into the more common
single-edge sharpening here. If you want to move onto double-edging after you master
basic sharpening, read Juranitch’s book.

Feud number three:
What kind of sharpening stone should you use? Parrish likes
Carborundum; my editor swears by his Japanese water stones;
Underhill likes Washita or even Belgium white clay pieces
he finds at the junk dealers. Best as I can figure, it
doesn’t much matter. What is important is that you have two
abrasive surfaces: a coarse one to get the hard grinding
done faster and a fine one for the finish sharpening. A
coarse stone wears material away quickly until the blade
angle is what you want it to be, but if you continue to use
it past that point, it’ll take off your sharp edge rather
than finish it.

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

A
couple more things and we’ll be ready to begin. One, fasten
your stone in a vise or clamp, secure it within a small
wooden frame—do something so it won’t move around. You’ll have enough trouble getting a consistent sharpening
angle with only the blade moving. Don’t make things worse
by letting the stone wiggle around as well. Two, for your
first practice sessions, get hold of an inexpensive
high-carbon knife. They wear away a lot more easily than
your stainless steel Swiss Army or kitchen butchering
knife, so you can see results (good and bad) a whole lot
faster. (Besides, with one of those you won’t mess up a
really good knife while you’re learning.) I practiced on a
flea market set of kitchen knives.

Enough preamble.Fasten your rough stone in place. Hold your knife with two
hands, one hand on the handle and the other supporting the
blade (thumb on the blunt back edge). Hold the blade at a
slight—not steep—angle (the magic number is
20 degrees, but who’s measuring?), and push the blade along
the stone as if you were trying to cut a slice out of its
surface (Figure 13).

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

That’s the real problem. Listen to Robert Parrish: “It’ll take an hour for the
average person to sharpen a pocketknife—and it still
won’t be really sharp. Do the job right and you’ll get a
good edge in five minutes. Ninety-nine percent of the
problem is in the angle.” If you keep changing the angle as
you 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 it
dull instead of sharp.

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

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

If you’re getting frustrated or just want to make the whole
job go a lot easier, get a sharpening guide—a little
blade clamp that automatically holds your knife at the
right angle (Figure 16). Buck Knives makes one, called the
Honemaster, and Juranitch offers the Razor Edge Knife
Sharpening Guide. Let me tell you, unlike many sharpening
gimmicks, these two doodads work. You may just want to use
them as training wheels, but beard-axer Juranitch claims no
expert can “freehand” a knife edge as well as an amateur
with a guide can. He’s even proved it repeatedly by having pairs of
novices—his daughters, Boy Scouts, professional
outdoor writers—use his guide to sharpen pocketknives
and then by shaving his own face with those blades.

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

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

Now switch to your fine
stone for the finish work. Stroke once away from you (as
you did at first) and once toward you. Alternate about a
dozen strokes, forward and backward, on the stone. Don’t
press as hard on these strokes as you did on the rough-side
ones. And you can keep lightening up so your last few
strokes carry just the weight of the knife.

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

If it does all that, congratulations! You’ve done
well. If not, repeat your steps on the fine stone. That’ll
probably do the trick. If it doesn’t, you’re most likely
not holding the knife at a constant sharpening angle. Keep
practicing—or get a sharpening guide.

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

Now you can sharpen all the knives in
your home. Most of them will take that same slight angle
you put on your first blade. If you’re honing a butchering
knife that’s going to be going through bone, put a steep
angle on it so the edge won’t be likely to break. If you’re
keening a delicate-work fillet knife, give it a very slim
taper.

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

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

Enjoying the Grind

In short, simply
combine the techniques given here with some serious
dedication to practice (you’ll know you’re practicing
enough if people start asking you why there’s no hair on
your left forearm). Soon you’ll be able to sharpen plenty
of the tools around your place.

And you’ll probably do so
more often than you’d think, because it gets to be an
enjoyable task. I gain a curious sense of peacefulness from
putting an edge on a favorite blade or tool. The slow rhythm of metal stroking on stone is a calming
sound, a serviceable sort of music our forefathers knew
well.

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

Access

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