knife sharpening

[Hoodoo]

I see a lot of contradictory information about knife sharpening. Or if it isn't really contradictory, it is a form of "more than one way to skin a cat" (my apologies to cat lovers.

Here are two issues I see "experts" disagree on or offer alternative methods.

To use or oil or not to use oil. That is the question. And what is the answer???

Move the knife forward, across the stone, as if you are slicing a piece off the stone, as opposed to backwards, away from the cutting edge ( e.g. see http://www.tichbourneknives.com/ ). Enquiring minds want to know which is the "right" way. And then there is the proverbial circular motion, which is how I learned to sharpen an axe in boyscouts and shop class.



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Hoodoo

No, I do not weep at the world--I am too busy sharpening my oyster knife.
Zora Neale Hurston

Oversharpen the blade, and the edge will soon blunt.
Lao Tsu

 

[johno]

The 'right way' is really whatever works for you, and will vary with what you're trying to do, what you're trying to sharpen, the sharpening tools, etc. Oil vs no oil is merely preference as a bench stone may load up quicker with no oil, different types of stones and different grits vary in how quickly they will load up, but evidently it's a worthwhile tradeoff to some as a dry stone will cut quicker at first and one doesn't have to mess around with oil. I much prefer oil but it's probably because I use 'old tech' sharpening tools. 'It depends' also applies to how one moves the edge across the stone as 'honing' may make sense if you don't finish off on a strop of some sort. I don't 'hone' anymore, instead I use finer and finer stones in a slicing motion and then use a strop, although I may skip finer stones and still use a strop if I want kind of a 'polished saw' edge. In general I've found:

Ceramic stones and sticks work ok dry but they do tend to load up quickly and need to be cleaned with something like Bon-Ami and water. In my opinion medium grit ceramic doesn't work as well as other medium grit media, but I also haven't invested a lot in a variety of ceramic sharpeners.

Arkansas stones used dry load up quickly and are harder to clean compared to nicely oiled stones. I oil new stones daily until they stop soaking oil up quickly, use oil while sharpening, and find that such stones are easy to keep clean while or after sharpening with a bit more oil and a rag. I guess with such a technique they're 'always dirty' and don't need another cleaning step :^)

I also use oil with India, aluminum oxide, and silicon carbide stones, as described above with the Arkansas stones.

I've avoided diamond stones as they're expensive and the traditional oil stones work fine.

 

[Matt Shade]

I have pretty much taught myself to freehand sharpen, and have a bought about one of everything trying to get a good set of sharpening tools. And I've tried all the methods you will hear of.
Basically you can use any of the methods, or a combination of all of them. Whatever your comfortable doing. It is important to be consistent too. Consistent angles and amount of cutting on each side is what will get you a sharp edge.
The circle pattern is what I use with small stones that cannot be laid on a bench or put in a vise to be used. Its a good way to remove a lot of material with coarser stones to. Just work you way up and down the blade 1 or 2 times, them switch sides. Do that until the bevels are completely flat and all knicks and chips are gone, then move to a finer stone.
Moving the blade across like your slicing the top of the stone off is the way to go with bench stones. First lay the bevel of the knife comletely flat against the stone. Then raise the back edge about 15 to 20 degress depending on the sharpening angle you want. Memorize that angle and use it the whole time, never change angles. Now slowly glide the knife cutting edge first all the way to the other end of the stone. While you do this, slide the blade sideways so you end with the very end of the blade when your at the end of the stone. Do that 3 times then switch sides. Its really important that you keep the surface of the stones completely flat.
The only time I draw the knife so that the cutting edge is dragging behind is when I'm using a honing strop. Then it is very important that you lift the blade all the way free of the strop before you flip it over. If you don't you will drag the edge across the strop and round it off really bad. Its important to know how much stropping you should do to a knife depending on its steel. Some steels roll easier than others. ATS 34 and 55 are both good examples of this. I usually don't give more than 10 passes on a strop to my knives that are in the ATS series. When I'm stropping carbon steel blades and other types of stainless that don't roll easily, I use the strop a lot more. Then I usually start with 10 passes on each side, then 9 passes on each side, then 8 and so on down to one.
The question of oil is more a question of what type of stones you are using. If you are using arkansas stones or india stones ( anything specified as an oil stone) you absolutely have to use honing oil. If not, the stone will get completely clogged with the metal it is removing and stop cutting the way it is supposed to.
Japanese water stones and other water stones have to be completely saturated with water in order to work the way intended. The water keeps the stone soft enough that the surface weras away and constantly has a fresh grit exposed. It alos rinses away the metal cuttings so the stone does not glaze over. You can wet a water stone everytime you use it or store it in water. I reccomend storing it in water. If you have hard water(I do)and you let the stone dry each time, it will get mineral deposits in it and ruin it. Its a lot easier to just kep it in water. You may use ditstilled water too.
The only stones that do not need a lubricant used on them are diamond stones and soap stones. Soap stones are designed to wear away like a water stone ( much faster though) and don't need the lubricant. Diamond stones will not clog or glaze over so they don't need a lubricant either.
Hope this answers your question, sorry its so long.
Forgot to mention ceramic stones. They don't need a lubricant because they are so hard. Yo us them until they are loaded up with metal, then wash them with a scouring powder to unload the grit. Then they're ready to use again.
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Fix it right the first time, use Baling Wire !

[This message has been edited by Matt Shade (edited 01-16-2000).]

 

[cerulean]

It's weird that knives have been around for 2.5 million years, yet no one has really figured out how they work. You would think that in such a technologically advanced age as this is, people would have scientifically proven what the best sharpening method is, but there's still a lot of disagreement.

As far as the oil question is concerned: people have traditonally used oil but now some don't. The theory behind not using oil is that small metal particles are suspended in the oil and, when the edge contacts these particles, they cause microscopic damage to the edge.

When you talk about microscopic damage here, you're talking about a very small scale; only an electron microscope can see the chips in the edge that the metal particles cause. But is this "damage" a bad thing, or do the chips in the edge act as "micro-serrations"? Some people claim that the knife cuts better because it's essentially serrated on a microscopic level.

You can probably apply the same arguments that are for and against regular serrations to micro-serrations; serrations are better for slice cuts and plain edges are better for push cuts.

As to sharpening by slicing into the stone or drawing the knife away from the cutting edge, I'm not sure it makes a difference. You do have to pull the knife spine first on a strop though, as the edge would bite into the material since it isn't completely flat.