Knife Sharpening FAQ.txt

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Author: Joe Talmadge
Last Updated: May 1998
  Changes: Added a paragraph on the importance of completely removing
           the burr

This FAQ has been improved immeasureably through the tests and
discussions on rec.knives.  I thank everyone who has engaged in
sharpening debates over the years, I've grabbed ideas here and there
from many of you.


  I.  Introduction
 II.  The Fundamentals of Sharpening
      -  Getting a sharp edge
      -  What angle?
      -  What kind of stone?
      -  Should I use oil or water on my stone?
      -  How fine should my stone be?  Important notes on grits!
      -  Stropping
      -  Using a steel

III.  Putting it all together
      -  Freehand tips and tricks
      -  Why does my knife go dull so fast?
      -  Putting it all together

IV.   Sharpening The "Differently-Ground" Blade
      -  Those pesky serrated blades
      -  The Moran (Convex) edge
      -  The chisel-ground edge
V.    Overview of various sharpening systems
      -  Clamp-on sharpening guides (Razor Edge, Buck, etc.)
      -  Clamp-and-Rod rigs (Lansky, Frost, etc.)
      -  V-type sharpeners (Spyderco Triangle, etc.)
      -  Other miscellaneous
      -  Freehand sharpening, and its wondrous advantages!

I.  Introduction
When I started writing this FAQ, I began by writing a detailed
treatise on how to sharpen.  I soon found that there was no way I
could do this in the kind of detail I wanted without ending up with a
book-length FAQ.  As it turns out, someone has already written a book
on sharpening, and done a better job than I could have done.  So the
most important part of this FAQ, for the beginner, is the following
recommendation: the first thing you need to do is buy and read _The
Razor Edge Book of Sharpening_ by John Juranitch.  No matter what
sharpening system you end up using, the fundamentals as laid out by
Juranitch remain intact.  I don't agree with Juranitch on everything,
but the illustrations he gives really help with understanding the

So this FAQ will discuss the central elements of sharpening, and then
go on to more detailed subjects.  Sharpening angles, hones, sharpening
systems, the latest fads in edges (e.g., chisel grinds), etc.
Basically, Juranitch will show you how to get a burr and grind it off
to end up with a sharp knife.  Hopefully, the FAQ will tell you
everything else.

For many people, when they try to sharpen a knife, the knife actually
gets duller!  If it's any consolation, I was in the same boat at one
time.  The best way to start out is to read about the sharpening
fundamentals, and then use some kind of sharpening system (discussed
below) that pre-sets the angles.  That way, you can begin by learning
how to raise a burr, feel for the burr, and then grind it away,
without having to worry about keeping the angle consistent as well.
When you understand how to sharpen, then you can get rid of the rig,
buy some flat hones, and learn how to sharpen freehand.

II.  The Fundamentals of Sharpening

- Getting a Sharp Edge

Okay I lied about not discussing the sharpening ritual itself.  Here's
a much-too-short review of the sharpening process, before we get into
the rest of the FAQ.  If this section is confusing, read _The Razor
Edge Book of Sharpening_.  Many of the subjects in this section (e.g.,
stone grits) are explored further elsewhere in the FAQ.

You grind one edge along the stone edge-first until a burr (aka
"wire") is formed on the other side of the edge.  You can feel the
burr with your thumb, on the side of the edge opposite the stone.  The
presence of the burr means that the steel is thin enough at the top
that it is folding over slightly, because the bevel you've just ground
has reached the edge tip.  If you stop before the burr is formed, then
you have not ground all the way to the edge tip, and your knife will
not be as sharp as it should be.  The forming of the burr is
critically important -- it is the only way to know for sure that you
have sharpened far enough on that side.  Once the burr is formed on
one side, turn the knife over and repeat the process.  

To re-cap, you've sharpened one side only until you felt a burr along
the entire length of the opposite side, then you switched sides and
repeated the process.  I suggest you do not follow the directions that
come with many sharpeners, of the form "Do 20 strokes on one side,
then 20 strokes on the other".  You go one side only until the burr is
formed; if that takes 10 strokes or 50 strokes, you keep going until
you get a burr, period.  Only then do you flip the knife over and do
the other side.

Having raised a burr, our job now is to progress to finer stones, in
order to make the edge smoother and remove the burr.  So now we run
the blade along the stone from end to tip, this time alternating sides
with each stroke.  Switch to a finer stone, and then do it again.

Remember, now that we've gone through all this trouble to raise the
burr, our top objective now is to completely remove the burr.  Perhaps
the best way to accomplish this is by double-grinding.  That is, when
you are done sharpening, raise the angle a couple of degrees, and take
one or two very light strokes across the stone.  This will typically
remove the burr completely.  Also remember that different steels and
different heat treats can affect the burr, both its original size and
how easy it is to grind it off.  Some steels just don't want to let go
of their burr, preferring instead to let it flip flop from side to
side -- you will have to be especially vigiliant to make sure you've
ground the burr back off with these steels.  Double grind it!

Sometimes, the burr is turned directly downwards during sharpening,
and since it is very thin and razor sharp, it seems like an incredible
edge.  This is called a "wire edge".  But being fragile, it will break
off the very first time you use the knife, leaving you with an
extremely dull knife.  If you seem to be getting good sharpening
results on your knives, but they are getting dull very quickly with
little use, you may be ending up with a wire edge.  If that's
the case, you'll need to be careful and watch out specifically for a
wire edge; you should try progressing down to finer stones, try
double-grinding the edge, and give the knife a quick stropping once
you're finished (all these terms are explained below).  If your knife
is fading fast as you're sure it's not because you left a wire edge,
steeling between uses may be what you need.  My last few strokes on
the stone become progressively lighter, to avoid collapsing the edge
and raising another burr.

On a badly-worn or damaged edge, I'll typically start with a medium
(300-400 grit) stone, then move to a fine (600 grit) stone, and then
sometimes I'll finish on an extra-fine (1200 grit) stone if I want a
more polished edge.  However, once my knife is sharp I try to
re-sharpen before it gets too worn down.  In that case, I can usually
start on the fine stone.  But be sure to read the important notes on
grits later in the FAQ.

Lastly, I may use a leather strop on the knife.

On other sharpening systems, the same fundamentals as laid out above
still apply.  For example, on a V-type sharpener, I'll start by
sharpening one side only against the right-hand stick until a burr
forms.  Then I switch to the other stick until a burr forms.  Only
after I've raised a burr from both sides will I follow the
manufacturer's directions and alternate from one stick to the other
between strokes.

- What Angle?

The smaller the angle, the sharper your knife will feel.  But the
smaller the angle, the less metal that's behind the edge, and thus the
weaker the edge.  So your sharpening angle will depend on your usage.
A surgeon's blade will have a very thin, very low-angle edge.  Your
axe will have a strong, thick, high-angle edge.

Something like a razor blade will having an angle of around 12-
degrees, and it's chisel-ground so that's 12-degrees total.  Utility
knives will have angles anywhere between 15- and 24- degrees (30-48
degrees total).  An axe will have something around a 30-degree angle.

For double-ground utility knives, a primary edge of 15-18-degrees,
followed by a secondary grind of 21ish-degrees, works well.  Don't be
obsessed with getting the exact right angle; rather, make sure that
at whatever angle you've chosen, concentrate on holding it precisely.

See also the sections on convex edges and chisel-ground edges.

- What Kind of Stone?

Basically, a stone needs to cut metal off the edge.  The stones below
do this well, and for most of us our time would be better spent
actually learning how to sharpen than worrying too much about the
minor advantages of one stone vs. another.   Get the biggest stones
you can afford and have room for.  Big stones make the job much much

The time-honored stone is the arkansas stone.  Soft arkansas stones
provide the coarser grits, with harder stones providing finer grits.
Many people use oil on these stones, ostensibly to float the steel
particles and keep them from clogging the stone.  John Juranitch has
popularized the notion that oil should absolutely not be used when
sharpening, and indeed results from people using arkansas stones
without oil have been very positive.  However, if you have ever used
oil on your arkansas stone, you need to continue using it, or it will
clog.  If you never put oil on your arkansas stone, you will never
need to.

Synthetic stones are very hard, and won't wear like natural stones (a
natural stone may get a valley scooped out of it over time).  They
clean well with detergent-charged steel wool, I use SOS detergent
pads, they clean very very fast and very well.  I know you're thinking
that ...
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