The scattered chips of a woodcarver and other weighty matters.
Friday, March 30, 2012
Tool Sharpening Tips and Techniques
Killing time and slaying dragons!
I've found that there are two types of carvers when it comes to tools. Those
that see the tool as just a means to carve the wood, and those that see the
wood as a chance to use the tool. I fall into the later category.
With a bent blade, the first type sees this as a loss of carving time,
while the second type sees this as a chance to reshape the tool. Now you may
fall into the first type, but even if you don't really like messing with your
tools, you will find a great deal more freedom when you develop the skills to
fix and reshape your tools. So here goes.
When I started carving, I was extremely frustrated with sharpening. I
finally found that practice was what made the difference. Sharpening a tool
is not rocket science, its being able to hold the tool in the same position
repeatedly while going through the sharpening process. The other part is
having some basic knowledge about edge shapes. If you are at all mechanically
inclined, and can visualize what the edge looks like, then you have all you
Pictures make all the difference, but text editors don't do them, and I'm
no good at doing that funky ASCII art. So here are words for some basic
1. The shallower the angle (smaller), the sharper the knife edge.
Conversely the shallower the angle, the weaker is the edge. So for choking
done trees, you need a much steeper angle then for shaving your beard. Angles
in books are nothing more then general guidelines. If you are too shallow,
then the knife cuts great, but gets dull quickly. If too steep, then the
knife cuts less great, but does it for a lot longer before resharpening. As
you continue wood carving, you will form opinions about what that angle
should be based on the particular tool, the wood being carved, and your own
particular style. Don't agonize too much over the proper angle.
"Good-enough" goes a long way here, but I like 27.43 degrees.
2. It is the microscopic edge (the leading edge) which determines how
sharp the blade is regardless of the angle used. That's why you can shave
with an axe that's well sharpened. Once you have an appropriate angle, all of
your effort is to make this microscopic edge; clean, polished, and true. How
this is accomplished is where you get all of the differences of opinion.
3. You can sharpen your knife with a flat rock found in the back yard. It
will turn out just fine. But, it will take a lot of work, and it will be a
pain. You will need to buy some things to make your job easier. What you buy
though is wide open. It mostly depends on:
- $ or $$$$
- Are you high tech or low tech
(new fangled vs old fashioned)
- You like hand tools or power
- You just want it sharp, or you
want to perfect the craft of sharpening.
- Big workshop or small box in
the hall closet
--> I am a cheap, low tech, tool sharpener with a garage (part of it at
least, the rest keeps filling up)
Now, since you have no opinions, and are looking for specifics, I will
give you my idea of the basics you should have. This is roughly in order of
1. a double-sided carborundum stone at least six inches in length. This
can be found in any hardware store. This is your basic stone for reshaping
and establishing the edge. It has two sides, a rough side, and a medium side.
Note: you will need to use oil or water or spit to keep the pores clean while
cutting (see 2 below). For these stones I find spit best. Oil is too messy,
and water soaks right through too quickly.
2. a soft Arkansas stone, again at least six inches in length. These are a
little harder to find, but any store that handles knives will have one of
these. You should get a small bottle of honing oil for the stone. It usually
comes with the stone. The oil keeps the particles of metal from getting
embedded into the pores in the stone (the little crystalline cutting edges
which do the work) and clogging them up. You can use any light oil for the job,
including cooking oil. Water or spit works too, but I like to stay consistent
with a stone.
3. a honing strop (sp). This you make your self. Instructions below.
4. polishing compound for the strop. These look like big fat Crayons. It
is a polishing powder mixed with wax to hold it together. You rub it on the
surface of your strop, or on some cotton or felt power sharpeners. You can
find this at many hardware stores hidden away someplace. Also you can find it
at jewelry supply and some auto supply stores. It comes in different colors
(the color of the powder used). They have different hardness and polishing
characteristics. The box they come in will give you some guidelines. I've
just always used the red rouge and never really experimented with the rest much.
You don't need much. It goes a long way I still have the original set after
20 years (but I don't use power buffing tools much).
5. two good flat files. A medium one, and a fine one. By good, I mean not
too small, and one with a decent handle.
At this point you have everything you need. It's about as cheap as you can
go. From there on, you are getting into specialty items which can make things
easier or faster. You can get:
- harder Arkansas stones for
- specialty ceramic stones instead
- Japanese water stones instead
- Diamond surfaced stones instead
- cotton and felt polishing pads
for a bench grinder
- belt sanding rigs replacing the
- water bath power sharpeners
- bench grinders for fast
reshaping and blade making
Ok, now how do you fix the point on your new knife. I have not had much
success with bending the points back. If you have a hammer and a solid
surface (like a metal anvil) you can try hammering it flat. It will still
need some fix-up, but not as much.
With your file, file off the bent point. When it starts to get flat, you
can switch to the rough carborundum. Work on it until all of the bend in the
metal is gone and you have only the original "plane" of the blade.
Then its decision time.
You said it was a roughout knife. Not knowing what it looks like, but
clueing off the word roughout, I'm figuring that a pointy type end is not
real important. If so, you are almost home free. You just resharpen the end
to make it match the rest of the blade.
- well no, not really because you will find that you are going to put an
entirely new edge on the blade anyway which take some time.
If you think you want a point back on, or want to reshape the end, then
you are going to do some major surgery. This is the real hard part - it takes
faith - take the edge off your knife with the rough stone so you don't cut
yourself while reshaping. Have faith, you will get the edge back on.
With your file, filing perpendicular to the edge, file the point until the
shape looks right. You can use the rough stone here too. You aren't trying to
put an edge on, just to get the shape (profile) right.
Ok, now how to resharpen. I would use this as an opportunity to practice.
This will take about 30 minutes, so get a good flat surface, and a chair to
sit in. You are going to go rough side, medium side, soft Arkansas, and
strop. You want to develop control and consistency. You want to experiment
with pressure, and with different postures of hands and body which help the
consistency. Some people use a round-and-round motion when sharpening. I just
do a sweep in one direction - cutting edge leading rather then trailing. I
will use a round-and-round motion when I want to take off metal faster,
particularly at the start, but then switch. This is personal preference (and
it works for me)
Ok, here is where the visualizing comes in. What your are doing is
grinding a face on your blade. In the books and instructions, this face looks
nice and flat, but because you can't keep the blade at exactly the same angle
your face will be more rounded. The flatter the better (consistency). As you
are working you blade, stop, wipe it off and take a good look at the edge. If
you have a good magnifying glass, use it. Also, get a black magic marker and
go over the edge with it. Then go back to the stone for a little. Stop, and
look at the edge. You can see real clear where you are grinding and where you
are not. Bright light helps too.
You will likely get a bias in the blade from change in angle as you move
it across. This means that one side is at a different angle then the other,
or that the front or back of the knife is at a different angle. Try to
minimize this bias.
To test the knife, use your fingernail rather then shaving your arm. Push
the edge across your thumb nail as if it was the sharpening stone (not a
slice or saw motion). Don't push down on the knife, let the weight of the
knife be the pressure. When it starts to get sharp, it will "grab"
the nail rather then slide over it. This is rather dramatic, and you will
know it when it happens. Also slide the edge of the nail along the knife edge
feeling for smoothness. You can feel the slightest micro-nicks this way. Do
this slowly and cautiously. We don't want to cut ourselves.
You will spend the most time on the rough stone. Your are going to remove
a lot of metal. Stay with it until it starts to catch your nail, and has a
good face on the edge. Figure 15-20 minutes here (but it depends).
Next go to the medium. You want to make sure to keep the same face angle.
The magic marker works well here. You are also smoothing the scratches from
the rough stone. You are done here when the edge starts to look polished, and
there is a significant increase in sharpness. If you "think it feels a
little sharper", then you aren't done. If you aren't making progress,
then you are probably changing the angle and are trying to grind a new face.
This is the mistake I always made. With a magic marker and a magnifying glass
this is real obvious.
With the Arkansas stone, you want to finish the polishing of both the edge
face and the edge edge. Watch your angles here. Check yourself. You will see
some improvement in the sharpness as measured on your thumb nail, but it will
be more refined. Keep going as long as you see increased progress. Use the
magnifying glass and watch the edge.
When you think you are ready, You want to put about 5-10 strokes on each
side at a steeper angle - just slightly steeper, say 5 degrees. This puts on
your micro-cutting edge. It is this micro edge that you will be
reconditioning as you resharpen your knife while carving. You don't have to
go back to this major resharpening as described here until you no longer have
success in touching up the micro edge. The strop and Arkansas stone will be
your tools for the touch-up.
Wipe the knife, and then under a bright light gently press the knife
almost flat on your thumbnail. If you have done the job right, you will see
the extreme edge appear to bend (the reflected light lets you see this). The
part that is bending is called the "wire edge". It is very thin,
and is an artifact from the sharpening process. If used this way, it will
break off causing micro-nicks (can't see them, but can feel them with the
nail). We use the strop for this.
Take the strop, and lay the knife flat on it and use some pressure pushing
it against the strop. Then draw the knife with the edge trailing (else you
cut the leather strop) across the strop switching from side to side. 10
strokes usually does it. If you test the knife for sharpness on the thumb
nail, you should see a dramatic increase in sharpness. Keep stropping until
it doesn't improve. Use this same procedure to touch up your knife while
carving. When you don't feel an improvement, then go back to the Arkansas and
re-do the micro-edge. Eventually you have to go back and put the face back
on. How often depends on the steel, the original face angle, and the carving.
Re-doing the face is never as dramatic as putting the original face on the tool.
The knife should now catch immediately in your thumb nail. It doesn't skid
at all. You are doing this with little or know pressure. The weight of the
blade is all it takes. If your are unsure of the feel of this, get a razor
and test it on the nail. This should be your benchmark.
Now, how to make a strop. Get a 14-16 inch piece of 1x2 pine. Carve a
decent handle in the first six inches, and leave the rest flat. Now get a
chunk of leather at least 8-10 inches long and 2 inches wide (and not real
thin). Glue the leather onto the rest of the stick. White glue or contact
cement work fine. Clamp or weight the thing down to set overnight. When set,
use a sharp knife to trim off excess leather. Take the polishing compound as
described above and rub it all over the leather putting on a reasonable coat.
Every so often I will scrap off the old stuff and put on a fresh coat. Well,
there you have it.
Any sort of buffing with any type of wheel/strop/buffer will EVENTUALLY
round off a tool's edge. That is because the is always a little deflection of
the buffing wheel as it comes off the tool,... as sort of depression... that
rounds the tool edge ever so slightly. The buffing wheel, though, rounds the
edge off less than, say, a stitched cloth wheel. Unless of course, the person
at the "handle end" of the tool is causing the tool to contact the
felt wheel at too "blunt" an angle.
I watch my students buff their tools on my felt wheel, and honestly,
sometimes I just cringe. They may as well just push the "sharp"
edge right into the wheel, the way they are attempting to buff the tool. When
a tool's cutting angle becomes blunt from buffing, it is a very simple matter
to take the tool to the bench stone, dress the edge with a few stroke, take
the burr off with slip stones, and buff the edge to a fresh, sharp finish. I
can do this in less than 3 minutes in a pinch.
No sharpening system is EXACT, especially when it comes to buffing. This
is because the person who holds the tool is not EXACT (like a machine) and
also because buffing wheels/strops deflect. Instead of trying to find
something that is EXACT, try your best to develop the SKILL you need to keep
your tools in shape. It takes practice, but the effort is worth it.
Just accept the fact that ONCE IN A WHILE you will have to reshape the
edge on your bench stone to bring the cutting angle back to specs. It's a
fact of life where sharp edges are concerned. Hope this helps.
Grande Prairie, Alberta, Canada
One of the major advantages of felt is that it will deform to the shape of
the applied object - it has some "give" to it. How much it will
round (or deform) the edge depends on the amount and aggressiveness of the
compound applied, the angle at which the edge is introduced, the length of
time in contact, and the force with which you apply the edge to the wheel.
With that out of the way, yes it will round your edge, but how much and
how soon depends on your individual sharpening practices. I personally use
two cardboard wheels to sharpen with, one charged with 220 grit aluminum
oxide abrasive and lightly coated with wax. The second is plain cardboard
with slots across the face, and a buffing compound, usually white rouge
applied, for honing.
I use the grit wheel for normal sharpening, which is only required
occasionally, unless an edge becomes damaged. I use the honing wheels for
final honing and light touchup. This is on all knives and the outer bevel of
all sweeps and gouges, including vees. The commercial name of this system is
Frizzell's Razor Sharp, but I have seen similar under other names.
I also use a muslin buff, a fairly stiff one, as a final touch to remove
all traces of rouge from the edge and on the inside of gouges.
I know many professional carvers who use felt wheels, but always in
conjunction with some sort of hard wheel, most frequently a conventional
If you use felt, eventually the edge will round enough that you must go
back to something else to flatten it.
If, however, your edge will cut a thin curl across the end grain of a
piece of basswood, that is a curl thin and smooth enough to curl near full
circle before breaking, it is suitable for carving.
Regardless of all the theories and pundits - myself included - the
ultimate standard in sharpening has to be the ability to cut clean and
smoothly, without requiring excessive force.
From: Graeme Vaughan (firstname.lastname@example.org)
The best information I have received on sharpening (after a good deal of
reading and asking and trying) is from Les Miller at the recent Working with
Timber show here in Melbourne (Les also produces videos on this and other
subjects but I don't have the contact details - sorry! perhaps some other
Ozwoodie can help).Advice as follows:
The sharpening process is best divided into three parts:
grinding or setting
stropping or polishing
For this you will need a soft
start bench grinder with an 8 inch white Aluminum oxide wheel (NOT the
Silicon Carbide wheel which is sold with most bench grinders), 46 grit and
rated K or J for hardness. The wheel is large, quite coarse and soft. The reason
for this is that it enables material to be removed quickly without heating
the tool and ruining the temper. There is no need to dip the tool in water to
cool it as it remains cool throughout the process. To clean and true the
wheel do not use diamond sticks etc, but use a silicon carbide dressing stick
as this keeps the wheel true. You will also need a tool rest which adjusts to
any angle. Daniel Starbuck's point about maintaining the bevel is absolutely
spot on. It is very difficult to maintain the correct angle freehand.
For honing, use a diamond
impregnated steel plate or Arkansas slate slipstone (the former is
preferred). Use WD40 to keep the stones clean. For plane blades, chisels etc,
use a bought or shop made holder to keep the blade at the correct angle to
the plate. See any good sharpening book on the techniques. Hone the flat side
of single bevelled tools first.
For this you will need a leather
wheel and polish rouge. There are power strop systems available for power
drills. Hope this helps. Cheers. Graeme