When you wanna go low grit... How low should you go?

KennyB said:
Everyone always talks about polishing and honing on super fine abrasives... I want to get a really gnarly, toothy edge, the kind that makes slicing through meat or fibrous materials seem like child's play.

I know a few members here have played around with sharpening on lower grits so I don't think this topic should be too esoteric...

The lowest grit I have personally is a 220 JIS waterstone. I've played around with edges fresh off this before... It can be difficult to remove a burr and get it really refined, but I've gotten edges sharp enough to shave my arm hair--if my skin can bare it. So for that reason I've still wound up finishing on a relatively higher grit. Usually 1000 JIS waterstone or 25 micron DMT, and I find myself liking the edges I get from the coarser DMT a little more but that's just for everyday carry kind of stuff.

I think that if I were going to be cutting something with a lot of abrasive qualities
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Going to come down to the steel in question up to a point. Some stainless and high RC carbon steels will not hold a coarse edge very well, if they can even take one due to chipping along the apex. My opinion is that waterstones are not a good choice for this either, the coarse ones do a good job of metal removal without making deep gouges or causing pressure bulges behind the apex. These qualities make other options more functional, though it can be done. A hard vitreous stone or diamond works better, and edge leading will make a cleaner grind (by hand anyway). My own experiences led me to believe that going under 80-100 grit is not the best idea, and finishing with anything other than plain paper or paperboard for a strop is likewise not the best idea. Even a relatively coarse grit on a strop will eventually smooth the irregularities.

These are the only types of edge prep where I'll use a microbevel.

Also in my experience these edges incur a substantial penalty when chopping or pressure cutting, so while it makes a wicked draw cutting edge it becomes limiting factor as well, something to keep in mind. If it were for a really bruising repetitive task I'd opt for a softer steel, likely carbon, and use a small file to sharpen it. Once had to do a lot of cutting on some fiberglass "supertuff" insulation board. Used an old kitchen knife, glued some 3M 30 micron polishing film to a cardboard tube. Used the film to touch up (sharpen) the edge and stropped on the tube itself. Two rapid 8 foot cuts through this material and the blade was almost too hot to press against my arm - that's abrasive!
 
HeavyHanded said:
Also in my experience these edges incur a substantial penalty when chopping or pressure cutting, so while it makes a wicked draw cutting edge it becomes limiting factor as well, something to keep in mind.
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My experiences are also similar to this with the steels/HTs/techniques that I use.

There are many variables, not least of which is the user and techniques used during work. The best strategy is to experiment, test, and verify what works for your particular set of variables;)
 
james terrio said:
I see what you're getting at, but that's fairly misleading. Hardness has nothing to do with how sharp a blade can get. Dead soft steel will take any sort of edge you want it to - it just won't stay that way very long.

It is true that if you're using a really hard but fairly fragile steel, you may as well go ahead and polish a real thin edge on it, and use it specifically for delicate cutting and slicing; but very hard steel won't "act" that much noticeably weaker in use because it has a coarse edge on it, unless it's really coarse and completely unrefined.

High toughness definitely does not work against/preclude using fine edges, or require using only coarse ones as your statement would seem to imply. O1, 1095 and CPM-3V all exhibit very good to excellent toughness, at moderate to quite high hardnesses, and can all take very nice crisp edges - or toothy coarse ones.



Not as much as you might think, in terms of comparing two vastly-different alloys. You're comparing measurements in microns to serrations of fairly large fractions of an inch, and that vast difference brings a whole other set of factors into play, even if you were comparing the same steel.



(bold added by me) That's pretty accurate, which is why a fairly coarse edge that's properly stropped or steeled will still cut pretty dang well.

I'm over-simplifying all this quite a bit, but you get the idea.
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I was just making some sweeping generalizations there, But I do have a 320 grit "grabs hair above the skin" edge on my Salt-1 right now that I'm trying out. The difference in micron rating between a 4k-6k grit waterstone (which still has a bit of bite) and the 320 grit carbide stone are an order of magnitude different in size so I'm hoping to see a positive change in edge behavior long term.
 
Interesting stuff guys.

This edge here:

IMAG0959_zps17f28265.jpg


Is on my Contego. I used a 120 grit SiC, followed by a 1200 grit ceramic.
It's one of the most aggressive, slicers I've ever produced. You can easily see a reflection in the edge, but clearly there are also some left over grooves in the finish. What's going on with this that is making it so much better than other knives that have the same geometry?
 
Hmm, my misono has a super polished edge via 8000 grit kitayama stone and it goes through red meat fish and proteins as if it werent there.

I have a 400 grit stone and that is for tip fixing or worst case senario re profiling entire blade road.

1000 is the norm for low grit.
 
Strigamort said:
Interesting stuff guys.

This edge here:



Is on my Contego. I used a 120 grit SiC, followed by a 1200 grit ceramic.
It's one of the most aggressive, slicers I've ever produced. You can easily see a reflection in the edge, but clearly there are also some left over grooves in the finish. What's going on with this that is making it so much better than other knives that have the same geometry?
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You basically have 120 grit microserrations that have been made finer (but retain the same microserration spacing) by the 1200 ceramic. It also looks like the ceramic has been used more on the back bevel so it reduces cutting friction over a 120 grit surface finish.

(edit: I should add that this is the same basic principle that Murray Carter espouses with his two stone sharpening process. 1000 grit to set the edge and produce agressive cutting action, and just a few stropping strokes on a 6000 grit stone to refine those microserrations and remove most of the burr before a few strops on some newspaper.)
 
Strigamort said:
Interesting stuff guys.

This edge here:

IMAG0959_zps17f28265.jpg


Is on my Contego. I used a 120 grit SiC, followed by a 1200 grit ceramic.
It's one of the most aggressive, slicers I've ever produced. You can easily see a reflection in the edge, but clearly there are also some left over grooves in the finish. What's going on with this that is making it so much better than other knives that have the same geometry?
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I think you might've answered that yourself. Those 'left over grooves' are adding some 120-grit teeth to your edge. And the segments of the bevel in between the 'grooves' are more highly polished by your 1200 ceramic. So, that should both refine the apex and reduce friction along the bevel, in those areas between the 'grooves'.

That's what I'm seeing, anyway. :)


David
 
I have gone as low as a coarse India stone and once a file. Had to give the file edge back so I didnt get to try it. It would shave my arm though.
 
It does, it's a relatively fine grained, tough, wear resistant, hard steel, basically it will take any edge you throw at it and make it perform to its best ability. (with the possible exception of true straight razor fine edges)
 
Can I leave VG-10 (SOG Tomcat) coarser, or should I polish it up to the max? Its factory edge is realy toothy btw!
 
All I can say is try it and see. I sometimes leave my Delica at a 1K waterstone finish and it works well. Coarser shouldnt hurt anything unless you are doing really rough work.
 
Benchmade stepped up the heat treat of their m4, takes a sweet edge.

Talking abrasives, I had to break down a lot of double thick cardboard, my work beater is my sage 1... I cut maybe 40 feet of the stuff since my utility knife wasn't cutting through, the blade was too hot to hold.

I've talked to Ben Dale and we agreed that 600 grit was about perfect for EDC chores, haven't talked to him about the new 400 grit stones though, for a working edge on 440c, s30v, m4 and vg-10 it's great, for a few guys they really like 220 and 320 after stropping, those low grit edges really dig in. I enjoy it on softer steels because its a quick edge, likely to be used and abused so wasting time on higher grits isn't a factor, the edge will still knock hairs off my head, what I call tree topping sharp.
 
I have a Spyderco Salt2 plain edge that is sharpened on DMT coarse. Not even stropped, but same number of passes each side. It used to lose its edge quickly if mirror polished, but with the coarse edge, it cuts like a demon without needing any touchups to date. I have an Ackerman Serrata in investment cast 440C (big carbides) It also responds well to DMT coarse and a strop. My D2 bushcrafter on the other hand seems to respond best to a polished edge (even though it feels toothy).
 
J-P SAN said:
Can I leave VG-10 (SOG Tomcat) coarser, or should I polish it up to the max? Its factory edge is realy toothy btw!
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VG-10 is one that I believe wiil do excellently at either extreme. Like you, I noticed how wicked coarse factory edges can be (Spyderco Enduras), so I had no complaints there. I did eventually thin & polish the edges on a couple of them, and I've been real impressed with how they've turned out. Good steel (excellent, actually). :thumbup:


David
 
When in doubt, smooth it out. If you don't like it, it's pretty easy to rough it back up again.
 
unit said:
...and you will never know until you try.
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Actually part of the reason behind why I started this thread was because I was debating with myself whether to get a DMT coarse credit card sharpener, or a DMT extra fine credit card sharpener, so I figured I'd hear people's views on toothier edges.
 
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