It is a sickness, even though I'm not a metal worker nor can I stand endless rubbing of the backs of cutters to flatten them, I have a sharpening jones.
Over on SMC there is a thread on Ark stones. I decided to expand it to include JNats. Here is what I published.
While natural stones have been around much longer than synthetic stones
they are not as easy to classify and to understand. The other thread on
the forum about Ark stones sent me to the shop this afternoon to check a
couple of things out. I like natural stones for honing and polishing
and will normally use man made stones to grind. For grinding the most
important thing is speed with less importance for the scratch pattern as
long as it isn't too deep or inconsistent. For honing and polishing
speed is pretty far down the list, what is important is the scratch
pattern. How deep, how steep, and how random the scratches left by the
stone are the three things that determine the quality of the cutting
edge.
Synthetic stones are easy, a 5,000 or 10,000 grit stone is, within
reason, pretty much like any other stone of the same grit. So the
sharpening process is easy to figure out, a 1000 grit to grind, a 5000
grit to hone and a 8000/10000 to polish and it makes little never mind
what make of stones you use. Heresy I know, one of the reasons civil
wars are so ugly is because they are fought over such small differences.
With natural stones grit has no meaning. Sometimes you will see a grit
range assigned to a stone but what that is telling you is the stone may
give a finish similar to a synthetic stone of that grit range. The only
real test is to take metal to stone and see what it does.
With Ark stones specific gravity can be a good starting point, the
higher the specific gravity the finer the stone will usually cut. With
JNats hardness can be a clue but so many things can affect the quality
of the finish the only way to know if a stone is a soul mate is to use
it. The reason for that is in the structure of a JNat. A synthetic stone
is made of sized grit particles that break free during the sharpening
process and while they will break down some they remain more or less
square particles. A JNat cutting particles are flake like and while they
do not change much in size in the slurry they do get thinner and
because they are flake like the scratch pattern is smoother.
This is just my opinion with nothing to back it up but one of the
reasons synthetic stones give such a shinny surface is because of their
sharp sided scratches. With JNats some of the most prized stones leave a
Kasumi or cloudy surface. In fact my favorite JNat finishing stone
isn't very hard but it makes slurry very easily and leaves a beautiful
Kasumi finish and edges that last a long time.
ken
I have my original King waterstones and newer Sigma Power ones that are close enough in grit. The experience and feel are very different between the two stones. The Kings aren't very good with highly alloyed steels.
ReplyDeleteI do find that relying on coarser stones of whatever type makes the job of 1000+ grit stones easier and less frustrating. I try to do without guides but once a bevel is set with a guide, the rest of the work is just a few strokes away with a microbevel.
Steve,
DeleteAs you can guess I'm a sucker for new stones and what have you. In fact I ordered a new Ohira Range Suita today.
I saw my first King stones in a plastic box a while back. I was surprised they were still around and you are correct they were not very good stones.
ken
Interesting. I long believed that the flatter the shinier (less scratches), but years ago LV introduced a new rotary lapping machine, which they used to flatten the back of their blades. They claimed a significant advance in flatness and their blades came out a mat grey instead of shiny, Huh?? Been wondering ever since why or how but never really came across a better explanation.
ReplyDeleteBob, back home with a peeling nose :-)
Bob,
DeleteWelcome back. It is good to get away from Winter.
I could be full of it but, I know something flat sided will reflect more light back at you than something rounded. I expect we have been sold a crock as usual with the mirror finish BS. Shapton stones will blind you with their shine after just a couple of passes on the stone. When you look at the surface with just a 10x loupe you can see ordered deep scratches. It is the same with all grits I've used, as you go up in the grits it is the same, just not as deep.
If you look at a surface finished on a natural stone, there is not as much shine and the scratches are not as ordered nor as deep and sharp sided. BTW, a strop with "green stuff" acts kinda like a Shapton stone. It will make your surface shine by I think changing the scratches left and not necessarily in a good way. Where a strop helps is in getting rid of the burr without ruining the edge and that can be done with a bare/oiled strop and just a few pulls. unlike the 20 or 30 pulls some advocate.
As always I could be full of it and YMMV,
ken