- 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 easier.
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 cleaning with steel wool will cause
the stone to shear off the steel wool and fill up the stone even worse! But I
assure you that is not the case, for whatever reason SOS pads clean synthetic
stones, they do not make the stones dirtier. Spyderco and Lansky are some
manufacturers who sell synthetic stones.
Stones with diamond dust embedded in them cut aggressively. You can remove
metal very quickly if you need to, but be careful lest you remove too much too
fast! DMT, Eze-Lap, and Lansky are some manufacturers who sell diamond-based
hones. Some diamond stones have the problem that the diamond dust wears off
quickly, leaving you with a useless stone.
Japanese water stones come in some very high grits -- I've seen all the way up
to 8000! These stones are very expensive. The stones sit in a water bath, and a
slush forms on top that helps the final polish.
Both Japanese water stones and natural stones will eventually dish out in the
center with use. To flatten them back out, put some sandpaper on a flat surface
and rub the stone top on it. Wet/dry 400 grit sandpaper mounted on a table top
or glass is reputed to work well.
- Water or Oil on My Stone?
Basically, the purpose of the stone is to rub against the blade and remove
metal. Slippery liquids, like water and especially oil, make the rubbing
slicker, causing less metal to be removed, causing sharpening to take longer.
On top of that, as your edge is being sharpened on the
stone, the oil-suspended metal particles are washing over the edge and dulling
it again.
On an arkansas stone, the oil is supposedly needed to float metal particles
away from the stone surface, lest the stone clog and stop cutting. Some people
on this group have used their arkansas stones without oil or water, and have
reported good results. However, if you've already used oil on your arkansas
stone, you'll probably need to keep using oil forever on it, because an
already-oiled stone will clog up if not kept oiled. If you have a fresh
arkansas stone, go ahead and use it without the oil, and things should be okay.
Japanese water stones are the one type of stone that need water. The stones are
designed to work with water, and as you sharpen a small amount of the stone's
material breaks off and forms an abrasive slurry along the top.
In any case, the bottom line is: use liquid or don't. Using the liquid will
make the sharpening process slower and messier, but if you insist on using
liquid and are willing to spend more time, that's up to you.
- How Fine Should My Stone Be? Important notes on grits!
The finer the stone, the more polished your edge will become. The rougher the
stone, the more the scratches in the edge function as
"micro-serrations" (see also the serrated vs. plain edge ).
Though
the actual ontological status of the micro-serrations is debatable (Juranitch
says there's no such thing, having looked under a microscope), the serrated
effect of the coarser grind is undoubtably there.
The more polished the edge, the better your edge will work for doing push-cut
applications like shaving, whittling, peeling an apple, skinning a deer. Also,
your cut will be more clean and precise with the polished edge.
A rougher, more micro-serrated edge will work better for slicing-type
applications like cutting through coarse rope, wood, etc. The serrations
present more edge surface area, and tend to "bite" into the thing
being cut.
It is possible to get an edge that will shave hair with a medium (300-400 grit)
stone, with practice [I specifically mention stone grits because many manufacturers
call the 300-400 grit stones "coarse" rather than
"medium"]. The medium stone will have pretty big micro-serrations. In
previous version of the FAQ I stated that I find this too rough a finish for my
general utility edge. However, I've since found this to be a really nice edge
finish for utility work -- it won't shave great, but it does a really nice job
on cutting coarse materials.
Anyone should be able to get an edge that shaves hair easily with a fine (600
grit) stone. I find this to be a pretty useful finishing stone, leaving enough
micro-serrations for general utility work but still being hair-shaving sharp.
An extra fine stone (1200 grit) should start polishing the edge, and you should
end up with a hair-popping sharp edge. This is also a good choice for a general
utility finish, especially on a partially-serrated blade, where the serrations
can be used when the slightly-polished main part of the blade becomes less
effective.
One can buy Japanese water stones with grits up to 8000, which leaves a
polished edge that's so sharp, your hairs will jump off your arm when they see
the edge coming. I would question this finish on an everyday utility knife
which might be called upon to cut through a thick rope or what have you, but it
is a finish that works well when a polished edge is called for.
************* IMPORTANT TIP ****************
Many treatises on sharpening tend
to focus on getting a polished, razor-like edge. This is partially the fault of
the tests we use to see how good our sharpening skills are. Shaving hair off
your arm, or cutting a thin slice out of a hanging piece of newpaper, both
favor a razor polished edge. An edge ground with a coarser grit won't feel as
sharp, but will outperform the razor polished edge on slicing type cuts, sometimes
significantly. If most of your work involves slicing cuts (cutting rope, etc.)
you should strongly consider backing off to the coarser stones, or even a file.
This may be one of the most important decisions you make -- probably more
important than finding the perfect sharpening system!
The tests seem to indicate that you should think carefully about your grit
strategy. If you know you have one particular usage that you do often, it's
worth a few minutes of your time to test out whether or not a dull-feeling
300-grit sharpened knife will outperform your razor-edged 1200-grit sharpened
knife. The 300-grit knife may not shave hair well, but if you need it to cut
rope, it may be just the ticket!
If you ever hear the suggestion that your knife may be "too sharp",
moving to a coarser grit is what is being suggested. A "too sharp" --
or more accurately, "too finely polished" -- edge may shave hair
well, but not do your particular job well. Even with a coarse grit, your knife
needs to be sharp, in the sense that the edge bevels need to meet consistently.
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