Grit finish in function of steel hardness

B

brasileiro

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Aug 26, 2011
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I read somewhere that harder steel hold edge longer if you finish it on a determinate grit (like coarser or polished I can’t remember) because of the steel particles size. Just like this, soft steel hold edge longer with opposite grit. I don’t remember where I read it. Is it true? Why?

Thanks.
 
The harder the steel, the better the edge holding (in general....you can have a steel that is so hard it just chips out on you). Particle size? Not sure what your source of information was trying to say with that.

If you have a softer steel, like mid 50s HRC, then a toothy edge/draw cut will help the edge to last a bit longer than if it was polished. A general rule too.
 
Steels with finer particle sizes (some might refer to it as 'finer grain') are generally assumed to be better at taking fine edges, and also being generally stronger or tougher (resistant to breakage). But the 'particle size' of the steel can vary all over the place, independent of the hardness of the steel. If the steel is well-executed in terms of heat treat and is pure, fine-grained and adequately hard, it should take and respond well to virtually any chosen edge finish. That's one of the things that makes quality steel so good. A few of my favorites, in that regard, are Schrade's older 1095 blades, Victorinox's stainless, and other modern knives in Sandvik steels like 12C27 (their manufacturing process keeps the steel very pure and fine-grained). I've liked those examples, because they'll take and hold edges with virtually any edge finish I've chosen to give them. And hardness isn't necessarily a commonality between them either, with Schrade's 1095 up to 60+ HRC, and Victorinox blades around 56 HRC, with the others somewhere in between.

The rate at which the steel itself wears is essentially independent of the edge finish anyway. Wear is a property of the steel itself, and very coarse teeth in a given steel will wear just as fast as a polished edge in the same steel, when exposed to the same forces of wear and abrasion. How long the edge stays useful, in spite of some wear, will depend on the task being done and the edge finish chosen for that task. Some edge finishes will work better, for longer, at specific tasks. But, how a certain finish works at a given task isn't really dependent on the grain (particle) size of the steel, or even the hardness of it, to a large extent. It depends more on the specific task itself.


David
 
Some super steel will work better with a course edge. Mostly those with high carbide steel.

It would also appear that some steel works very well keeping an edge with polished edges like 8cr13mov.

Or so that's what I've seen.
 
Thank you Samurai.
Thank you David.
Thank you Mo2.
This is is very clarifying.
Its like a equation without rule.
Angle~finishing grit~steel (hardness, heat treatment...)~cutting tasks (in what the blade will be used)~kind of cutting (chopp, slice).
First I thought that edge holding was all about sharpening angle. Then I thought it was about grit finish. Then I discovery steel hardness (what help in edge holding by the way). Now it’s clear (or a bit more) for me that everything have influence on edge holding.

There is a world of knowledge that I must to learn.
When I was sharpen my first knife I thought that was just rubb the blade on top of dual side sic stone. Never had one sharp or honed.

I read that for general purpose 600 grit is a good choice. Then I use to work my blades in it and strop after done. For my eyes, 600 grit diamond stone with strop after it looks like many factory edge visual, so I presumed factory edges like spyderco could be “cloned” (without being pretentious) with my tools if I work that way. Maybe until 1200 and strop. That way I still can see the finer scratches and get a razor knife.
I don’t dislike polished edges, but I can’t find a purpose on my every day use. Maybe on a kitchen knife, but I’m not a MasterChef.

About degrees I’ve use 10dps with micro at 20dps. Just for testing my skills. Then I read a topic about grinding above the bevel and what low angle does. Now when I pick a very used blade from my parents, sister, cousin, neighbor... that have about 1mm thickness above the bevel I grind it to mantain the cutting ability on that blade but no micro. I know I can be changing the blade geometry, but is what I can do with the tools that I have. And then I just put 20dps. But there is a theory that said lower angles increase edge holding and it make sense when you take the principles of aerodynamics. Just thoughts.

About the grit finish, beyond the beauty is the efficiency. When I sharp a knife for my sister, I would like it last longer as possible without taking into account the types of use because when you hone a knife for others you can’t control what they are cutting.
Im not a professional, I’m just a perfectionist enthusiast.
By the way if the knife belong my mother-in-law I would like it last forever. Or never. ;)

Thank you all. I really appreciate your work.
 
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David gives straight dope about grain size. "Particle size" is a confusing term in steel, one we don't really use. Aus grain? Carbide size? combo of the both? I can't think of an instance where you would want large aus grain. Carbide size is generally preferred to be small as well, but some steels like D2 have large Cr carbides that help with a "working edge". But, again, generally speaking, you want the finest aus grain, and the finest carbides, and well dispersed carbides, as you can get. I know many smiths who use D2 actually don't like using the CPM version of that steel. The small Cr carbides in CPM D2 change the characteristics of regular ingot D2. A little off topic....

About polishing edges....I also like a 600 mesh diamond plate apex finish. Works very well. A highly polished edge is a pretty thing to look at, but I don't find much use for them, even the kitchen. A general rule is push cutting go with higher polish, whereas slicing/draw cut, use a more coarse edge. If you're shaving, especially the face, then you'll appreciate the higher polish. Also woodworkers...the higher the polish on the edge, the more refined the cut. (less sanding later)
 
Im leading to use 600 grit with strop after hone just to be sure the burr is gone. I’m having good results on slice cut. I don’t use to push cut and for slice really is better tooth edge IMO.
I have 2 pictures from brand new kitchen aid knifes and look to be something around 600 and 1000 grit. But I feel I’m not having excelent results with 1000 grit on another knifes. The steel of the knife I sharpen with 1000 is unknown but For sure is a cheap one.
Anyway there is another one knife that look hold edge better on 1000 grit. I’m not close the knife to tell the brand just to give you a notion.

The one I believe is around 600:
QecjuN7.jpg


The other one I believe is around 1000:
w5cMwBT.jpg


My blades are clean and dry after each use and stored on a stand or separate containers. Sometimes I use on plastic board and sometimes on wood board.

Thanks for tricks.
 
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