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Old 11-11-2009, 02:53 PM   #1
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Learning to sharpen a knife... few thoughts

I now have a wonderful collection of around 7 sharpening stones, one of those retractable pocket diamond sharpening sticks and 1 3 sided pocket sharpening thingy.

I also had about 10 more or less dull knives, 3 pairs of dull scissors and 1 dull chisel. I am not sure of the grit of any of these stones. If any one can shed some light on how to determine their grit I'd appreciate it.
I received all of the stones second hand. I can tell that 2 are oil stones, the rest are water stones.

1st on sharpening the chisel. I noticed that the surface of the rough oil stone was pretty smooth- the surface of the stone seemed almost soft to the touch. When I put a knife to it, it didn't feel right. Dont know how to say it except it didn't feel right. It didn't grind as fast as the water stone did. On the other hand when I put the chisel to the water stone, The chisel was eating it up. Shaving off a lot of the stone. When I put the chisel to the oil stone... with some oil on it, it felt like it was doing the job and didn't feel like I was shaving the stone off and it did a good job of grinding the edge down past several knicks that were in the chisel from hitting nails that were embedded in wood. SO I used the roughest oil stone to pretty much square up or blunt the edge of the chisel.

Then I went to what is probably a medium grit water stone to dry and start making an edge on my chisel, again it didn't feel right so I went the medium oil stone, the back side of the rough stone and it began to grind an edge on the chisel.

One important thought here is... you can see when an edge starts to form. Another important point is... when I was starting to run the blade across the stone. I took my index finger and put it between the rear blade and the stone. I used a finger on the other hand on the top front part of the blade to kind of help maintain the angle. So the angle of my blade to the stone was set to the thickness of my finger. I dont have thick hands.

When I got an edge on the chisel that felt sharp to my finger... that scratched it basically... I put the knife to a pretty smooth water stone... it feels a lot like emory paper. The chisel was no longer digging into the stone. After a few laps on this stone I considered it done.

As for my knives. I only put them to water stones. When I started with some of them, I really couldn't see an edge. After I ran them across the rough water stone for awhile I could definitely see where the stone was wearing the blade down to a fine edge. On the bigger knives or a knife that had a big curve in it, or at the tip or the heel of some knives the edge didn't develop as fast as it did in other places. The advantage that I found in having multiple grits is, as I began to develop an edge that wasn't uniform along the length of the blade, I could use a finer grit to work on the places where the edge was not developing as fast, without grinding down the places that I was happy with as fast. Also I could get a better feel ... the places where the blade was sharper would glide over the higher grit, where the duller places would drag until they were ground down even to the rest of the knife.
Now for my really fine grit stones... When I finished the step above, the knives were sharp enough to slice through the heavy coated paper junk mail advertising stuff that I had laying around... In some cases 4 pages thick with no real effort. I then ran the blade over the emory paper feeling stone maybe 10 times on a side just because. I am not sure that it made a real difference but next go round I will have a magnifying glass to see if I can see a difference.
I am planning on getting belgian blue and yellow stones 4000 and 8000 grit
to see if they make a difference. And then I will possibly move on to some shapton glass stones.... just because... can you ever have to many sharpening stones.

But in the end... sharpening a knife is not something to be in awe of. It probably takes a little practice and to pay attention to what your fingers tell you as you go at it. You can develop a feel for it and with a magnifying glass you can see what you are producing.

Just my .02 cents worth

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Old 11-11-2009, 04:35 PM   #2
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vilasman -

interesting post.
I've been telling people for ages: "Yes, you _too_ can sharpen a knife!" [g]

takes a little bit of 'research' to understand the geometry involved - tough to get someplace if you don't have a good idea of where you want to go - and a little bit of practice. but a PhD in astro-interstellar-geometry is not required. . .

on your second hand stones - their (unknown?) history may explain some of it. an oilstone tends to collect the swarf/itty-bitty metal chunks and get to a "clogged" point. a 'dry' stone has no lubrication, it's grit against metal; water is a lubricant and oil and even better lubricant. both change the 'feel' of a stone.

wood chisels are a really tough nut because the cutting angle surface is so long. taking a nail nick out by hand is certainly time consuming.

as to cutting paper in thin air.... some surprises may find you. when you get into 6-8000 grit stones you're really 'polishing' more than 'grinding' an edge from say 1500 grit will have tiny micro-serrations that are _more_ effective at cutting paper in air vs a triple-razor-sharp "smooth" edge.

now a razor mirror polished 8000 grit finished edge on a wood chisel is a good thing - especially on open grained woods. works well on 0.005 millimeter sushi slices, too.

but for the average kitchen task, probably a bit of overkill.
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Old 11-11-2009, 08:54 PM   #3
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Thanks for the information... as for the potentially clogged oil stone... it did do the best job on cleaning up the edge of the chisel... took about 30-45 mins. Can the swarth be cleaned out of the stone?
The came from an estate sale on ebay...

So... the 1500 grit stone is the most you really need on a kitchen knife?

Do you have any experience with the belgian sharpening stones?

The 4000 grit stones... have you polished the micro serrations away if you use this stone?

So... the shapton 16,000 and 30,000 grit stones are what you would use to get the pretty shiny finish that you see on really expensive Japanese and bowie fighting knives? They are all about the polish and have nothing to do with the sharpness...

And lastly I have a dream of putting one of those compound bevel edges on one of my knives. Not quite sure what the advantage is of having a knife that has a 25 degree bevel and then a 10 degree bevel below that. But I want to see if I can do it. It will be a discount store knife
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Old 11-12-2009, 09:07 AM   #4
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>>cleaning an oilstone

you can try alcohol (from the paint department, not "rubbing alcohol") and an old toothbrush (or similar) if it's old and "caked" you'll probably need to soak it for a hour or so before starting. but be aware, they call 'em "oil stones" for that reason - they become 'finer' with use and the oil lubricates the cutting action. if it performed well, I wouldn't fiddle with it.

>>the 1500 grit stone is the most you really need on a kitchen knife?
that is a matter of much debate - which in the end comes down to personal preference - and "preferences" are based on what you do and you 'need' - in some households a cleaver is all that's needed - if you're into carving radishes into flowers, that's a different "need"

I use my kitchen knives every single day - I really am not inclined to drag out the gear and spend time sharpening them every week. the finer the edge, the more attention it will need _to keep it that way_ - but the question is do you really _need_ it "that way?"
you have to strike a balance between angles, grits, use and time devoted to keeping a knife sharp to your own preference.

"traditionally" the asian designs are more highly polished - i.e. taken to finer grits.
similarly, carbon steel knives are often taken to shallower angles &/or higher polish - based on the theory that carbon steel is harder and holds an edge better,

and the micro serrations don't survive a steel for any length of time, anyway . . . with a magnifying glass - even 10x - you can see how the finer grits and the steel work. it's a very educational exercise to sharpen the knife and using the 10x glass 'see' how it changes with steeling & use.

I have a set of the Wuesthof Classic line - I sharpen by hand twice per year - use a steel in between. the less used knives rarely need much more than a fine stone 'touch up' - those that get heavy use need the coarse stone to re-establish the bevel (I use 15 degrees on mine) - you can find many debates over whether it should be 14 degrees or 15 degrees and on and on . . . you might get the impression I take a very practical approach - I want a sharp knife and I don't want to spend hours per week keeping them that way. that routine works for me - your mileage may vary [g]

the double bevel geometry is aimed at having a thicker bit close to the cutting edge, with a thinner actual cutting edge. a full 10 degree angle edge is much more apt to "roll over" in use. double bevels are tricky to do by hand - there are a number of sharpening jigs on the market that would be very helpful in keeping the angle(s) if you want to go there.
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Old 11-12-2009, 01:05 PM   #5
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Take a look at what Dave Martell is doing in these two videos. There is no one in the country better than he is (from personal experience).



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Old 11-12-2009, 02:06 PM   #6
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Quote:
Originally Posted by vilasman View Post
So... the 1500 grit stone is the most you really need on a kitchen knife?
Stock knives seldom come with anything finer than 1k grit. Not that they can't handle it, but time is money. Even high end Japanese knives are around 2k grit (at most) out of the box. To answer your question, yes.

Quote:
Originally Posted by vilasman View Post
The 4000 grit stones... have you polished the micro serrations away if you use this stone?
Smaller grit doesn't polish serrations away, it merely makes them smaller.


Quote:
Originally Posted by vilasman View Post
So... the shapton 16,000 and 30,000 grit stones are what you would use to get the pretty shiny finish that you see on really expensive Japanese and bowie fighting knives? They are all about the polish and have nothing to do with the sharpness...
You can get a level of polish where scratches are impossible to detect with the naked eye with as little as 6-8k. For extreme brightness, use either a Chosera 10k or even better, a Naniwa 10k Super Stone.

Smaller grits have everything to do with sharpness. The finer the grit, the more "polished" the edge, the more pressure (pounds per square inch) exerted on the target. The other half of the trick is more pure geometry. See below.

Quote:
Originally Posted by vilasman View Post
And lastly I have a dream of putting one of those compound bevel edges on one of my knives. Not quite sure what the advantage is of having a knife that has a 25 degree bevel and then a 10 degree bevel below that. But I want to see if I can do it. It will be a discount store knife
It's a dream all right as it is impossible to have a smaller angle beneath a larger (less acute) angle.

For example let's use a knife made of steel capable of holding a good edge at 30 degrees included angle (15 degrees per side). That knife will cut much better if provided a back (otherwise called secondary or relief) bevel of 10 degrees per side and polished to a high level to relieve friction . The 15 degree per side bevel is then added (micro bevel, primary bevel) below the back bevel to provide strength.

When I do OPs knives I give them a compound edge as explained above but almost never use more than 2k grit stone before finishing with a .5 micron chromium oxide loaded strop. My personal knives are a different matter and once a bevel is cut I progress 800, 1k, 2k, 4k, 8k, 10k, .5 micron chromium oxide, and finish with .25 micron diamond spray on hard felt. I realize you probably aren't aware of what all these things are - just demonstrating a small part of the very diverse world of high end sharpening.

A final comment, stropping. No matter what grit final stone is used be it 2k or 16k, the difference in sharpness between stropping and not stropping is night and day.

Hope this helps.

Buzz
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Old 11-12-2009, 02:21 PM   #7
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Thanks for the responses and I will take the time to check out the video's. I found some really good info on knife sharpening last night on forums called foodie forum and knife forum .com respectively. I also found what I think is the best description of what a sharp blade is on a website called knifecenter.com in his discussion on sharpening a knife.

Having said that... at my house there are 2 groups of knives, the bunch that my wife uses and she does the big cooking at my house. She will grab any knife and pretty much expect it to cut anything. Then there is set I use. I am a sticker for using the right tool for a given job and would love to have a knife that was sharp enough to split a cats whisker. Her knives stay in on a magnetic holder and mine have blade guards on them and are in a drawer where she wont think to look for them. Hers go in the dishwasher. I try to do mine by hand the majority of the time. I wouldn't mind running mine over a stone every 5 to 10 uses. She has no clue what a sharpening steel is used for.
I've finally taught her how to handle well seasoned cast iron.
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Old 11-12-2009, 02:23 PM   #8
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I need a good strop
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Old 11-12-2009, 02:24 PM   #9
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buzzard you have wisdom. Are the belgian stones worth what they cost, and are they a good addition to my collection?
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Old 11-12-2009, 02:25 PM   #10
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but lastly since you know about things like SOG knifes... how do they get that shiny like almost chrome finish on them?
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