Sharpening to (very) high grits/fine microns while maintaining aggression/bite?

[OhioApexing]

Setting aside the whole "coarse vs. polished" debate, I'm wondering how some of you manage to take your edges extremely high levels of sharpness on fine (sub-micron) abrasives while maintaining that "sticky," aggressive, biting edge. This is truly the type of edge I prefer - tree-topping sharpness that will still grab your skin when running your thumb along the edge. I watched one of Michael Christy's videos recently (I can't remember which) and he described it as a "polished, coarse edge." It sounds oxymoronic, but I know some of you understand that.

First off, just to be clear, the "bite" comes from micro-chips/micro-serrations along the apex, correct?

I understand that some of it is a function of the steel: carbide-rich steels are more apt to have said carbides exposed along the apex thus leading to that serrated effect. Conversely, fine-grained steels are more inclined to produce a more razor/scalpel-like edge.

I've produced the edge I'm seeking on several occasions -- the most memorable of which was an S30V edge that I took to 0.003 micron. I could barely handle the thing; it just grabbed and ripped into anything it touched on contact. The problem is, I can't repeat it on-demand.

In sum, what is your approach to getting polished edges with plenty of bite?

 

[miso2]

Subscribed.

 

[SteelJunkee]

me too.

 

[JJ_Colt45]

I don't go for polished edges so I can't help much ... I understand the edge you are talking about ...

but although it may be pretty or flashy ... it will lose that bite very quickly ... there is a big trade off in performance IMHO.

 

[WhitleyStu]

This is just one method, but I reduce the angle of the final sharpening step, which for me is stropping. I drop the strop angle by approximately 2°/side. This prevents any chance of rounding the edge and keeps the edge "aggressive".

 

[Wowbagger]

Sounds like I could learn something from this thread so I look forward to that.
When you describe the sticky on the skin thing I immediately think Murray Carter and his three finger feeling the edge thing.
Then I think about his sharpening technique and cringe.

Next I think about what I cut, some pretty challenging things from very soft rolls to quite hard rubber which has additives in it to allow it to be used as a braking material without melting or wearing quickly. That rubber is AAAAAbraaaaaasive stuff that takes the edge off a Case or SAK in a New York minute.

I am so please with the edges that come off my Edge Pro Apex. That and having finally figured out edge geometry for folding and small fixed blades. THANK YOU BLADE FORUMS FOR THAT ! ! !
I could not be happier nor wish for improvement in the performance . . . on soft bread, tomatoes or hard rubber etc.

Then I think about my woodworking edges. I have finally conquered any challenges there in my strictly hand tool woodworking hobby. I use zero (nada) sand paper; I rely solely on edge tools to finish the surfaces as well as dimension the rough planks from the saw mill.
I could not wish for better results. I am so, so happy that after years of struggle I am where I want to be with those edges

So . . . I suppose I could sharpen to 120 and strop with diamond or 400 and strop with diamond or etc., etc., etc . . .
and I could snag my skin . . .
but
I am more than pretty DAMBED sure it would be a step backward in edge performance for what I cut. If I want a saw I will just reach for a saw.

Give me Edge Pro Apex edges (or other jig sharpening equipment according to edge tool), apex with something coarse, refine to somewhere around a some what polished edge (Shapton Glass 4,000 for knives . . . Shapton Pro 8,000 for wood tools). Keep the strops in the drawer or give them away . . . I don't care.
And we're good ! ! !

NONE of my super enjoyable edges that are producing flawless surfaces in crazy difficult wood species or that have stellar longevity in the seriously challenging materials I cut at work as long as the blades are high alloy tool steel (leave out the butt load of chromium, thank you very much ) . . .
have the least bit of snaggy skin about the edge characteristics. I mean AT ALL.

There now . . . convince me

 

[Obsessed with Edges]

This is just one method, but I reduce the angle of the final sharpening step, which for me is stropping. I drop the strop angle by approximately 2°/side. This prevents any chance of rounding the edge and keeps the edge "aggressive".

There's a lot to be said in praise for that.^

Real crisp cross-sectional geometry does a lot for keeping that initial 'bite' as the edge first contacts the material being cut; the edge just plunges straight into the material at the first contact. The challenging thing in polishing to a high finish, especially if it's done freehand, is preventing even the slightest amount of edge-rounding in doing so, at which point, any of the very small & fine 'teeth' still present will be scrubbed right off the apex. If the apex geometry can be maintained crisp throughout the polishing sequence, it makes a big difference.

I believe there are some low-alloy, fine-grained steels that are still capable of maintaining that fine 'micro-serrated' character at pretty high polish. As an example, I've noticed that trait in Opinel's stainless blades (Sandvik 12C27Mod), which seem very responsive to polishing to a pretty high degree (at/above 1000) while still holding onto some of that bite. Other steels of similar composition, like 420HC or 440A, seem to lose most of their 'teeth' at anything much above ~ 600 or so. This isn't to say they can't be made hair-whittling sharp at such a finish (420HC does this very well), but it comes with a noticeable reduction in that toothy aggressiveness.

 

[FortyTwoBlades]

Most of that initial bite is just the edge being nice and crisp. Finishing with a sintered ceramic (with a surface that isn't worn out!) can help with that since it's both fine AND hard. It's a great finishing step regardless of your second-to-last stone's grit. However, if polishing the edge to an overall high grit you're going to have reduced overall slicing aggression regardless. Another trick you can use is a heavy slant to your strokes, which makes the scratch pattern more aggressive in cuts moving into the direction of bias.

 

[miso2]

Just some thoughts on this.

If you can polish #400 edge with 0.1 micron diamond, you may be able to keep some of the coarse micro-serration structures for slicing aggression.
But the edge bevel won't be very polished because you don't want to overdo with the high grit.
I have not tried it extensively yet, but it did work to create a semi-polished-toothy edge.

Also, I have seen a report of a plane edge finished at #1,000 on the front side and #30,000 on the back side creating a consistent few micron thick wood shavings with more smooth bite than fully polished edges.

 

[Mo2]

So my buddy does alot of sharpening and most of them are polished edges. He always finishes on diamond spray strops to get that kind of apex on a polished edge. I'd have to agree with what I've seen but I don't often do polished edges myself.

His progression is usually diamond to reprofile, shapton glass to set the apex and polish, then up to 3 strops with diamond spray. Everything he uses is from Cktg. Edge pro for the sharpening and freehand on the strops.

The diamond makes a coarse edge despite the mirror. So you still get the aggression while maintaining the polish.

 

[HeavyHanded]

The finishing surface needs to be hard. Whether a fine polishing stone or stop, it has to be a firm backing the abrasive is working against. Yes, this leaves a slight bit of irregularity but with a very thin cross section, rather than a variable cross section with the same amount of up and down.

The craziest catchy fine edges I have made were using fine abrasive on a hardwood backing. The edge was paper cut catchy and under 400x magnification you could see wicked projections. I doubt it would have the same longevity as an edge with a bit less projection, but it is the edge that caused more accidental cuts than any other I have made.

 

[Wowbagger]

doubt it would have the same longevity as an edge with a bit less projection

I like the idea that a continuous "edge", think continuous line, is stronger that a row of independent points.
Sounds good doesn't it ?
Seems like I saw a post or article at the science of sharp along those lines . . .

it is the edge that caused more accidental cuts than any other I have made.

Makes me think of when I tried Japanese woodworking hand saws. I had been in the habit of pulling little bits of wood out of the teeth on my Western style handsaws when I was finished with it before I hung it up.
I kept trying that with Japanese style saws and invariably ended the day with my thumb and finger tips having micro lacerations. Took me for ever to break that habit.
On the same note those saws are very iffy when cutting seriously hard wood because the teeth can break off.

I'm just saying.

 

[samuraistuart]

I also think an edge that is more polished (a line) is stronger than a less refined edge (series of points). But if the material that is being cut is soft, then the “series of points/less refined edge” can be plenty strong enough, and actually perform better, in THAT application.

Sort of reminds me of the I beam. It isn’t stronger than a solid billet, but it’s lighter and strong enough, and works better for construction.

 

[WhitleyStu]

I think there is sometimes a "perceived" feeling of how sharp an edge is and how long it should last. We do the thumb drag on a new edge or cut paper and we develop an idea of how the blade will later preform. When I cut up a lot of cardboard boxes I usually first install a new blade in my box knife. It is surprising how soon the factory grind edge dulls with normal use. The next time I use the box knife I am cognizant of the reduced performance compared to the last item I use it with the new blade. Anybody else notice this in their EDC or often used kitchen cutlery?

 

[Wowbagger]

The next time I use the box knife I am cognizant of the reduced performance compared to the last item I use it with the new blade. Anybody else notice this in their EDC or often used kitchen cutlery?

No

I sharpen my box knives. See further elaboration below.

My EDC hard users are all super steel mostly M4 and they can go a month of almost daily use and still shave hair. (a Spyderco Ultra Fine Ceramic rod often brings it back to hair whittling).

My kitchen cutlery I use on softish white plastic cutting boards which are extremely kind to my White Paper Steel edges that blow me away at their edge holding (hair whittling for a year / same edge shave sharp for a year and a half).
No I'm not making any of this up.

PS: sure the box knife drops off fast but I make up for that by using 0.4mm standard Stanley blade rather than the 1mm "heavy duty" blades. I grind off the transition line on a coarse stone . . . call this reprofiling or convexing if you like. Moslty I polish the side of the blade and the edge and even wax it with candle wax. They tell me toothy box knives are better. I'm still attempting to prove that to my self.

As far as a high use box knife I set them up at work with a three foot long rough side up strop.
We never replaced box knife blades just stropped.
Always sharp dude.

 

[lutejones]

I agree with obsessed with edges here, in that it has to do with keeping the geometry right and reduce rounding on the final stropping steps.
Ironically a poorer primary grind geometry, a thicker one, allows for better angle control when freehanding because the secondary bevel is wider and easier to keep flat on the abrasive.
Also it’s easier to keep that bite if you’re working for performance and not for looks, with this I mean that an immaculate mirror polish is more likely to lose the crispness than a 10k edge refined till the edge is perfect but not looking for pretty bevels.
Last time I’ve achieved(with mirrored bevels) it was on a s30v para2, hanging hair test 4-5 and really dangerous to handle.
my whittling blades are really scary to touch too, although not pretty

 

[WhitleyStu]

No

I sharpen my box knives. See further elaboration below.

My EDC hard users are all super steel mostly M4 and they can go a month of almost daily use and still shave hair. (a Spyderco Ultra Fine Ceramic rod often brings it back to hair whittling).

My kitchen cutlery I use on softish white plastic cutting boards which are extremely kind to my White Paper Steel edges that blow me away at their edge holding (hair whittling for a year / same edge shave sharp for a year and a half).
No I'm not making any of this up.

PS: sure the box knife drops off fast but I make up for that by using 0.4mm standard Stanley blade rather than the 1mm "heavy duty" blades. I grind off the transition line on a coarse stone . . . call this reprofiling or convexing if you like. Moslty I polish the side of the blade and the edge and even wax it with candle wax. They tell me toothy box knives are better. I'm still attempting to prove that to my self.

As far as a high use box knife I set them up at work with a three foot long rough side up strop.
We never replaced box knife blades just stropped.
Always sharp dude.

You are one fortunate fellow!! Kitchen cutlery that stays razor sharp for a year and a half, EDC hard use knife with super steel that stays shaving sharp for a month and a job that affords you the time to custom sharpen box knife blades. You are truly walking in sunshine. What a lucky lucky guy!! It must be time for me to rethink my sharpening methods and time management.

 

[lonestar1979]

Its easy to round off the edges when polishing too much,i strop just on bare leather,and off norton stone my edges are hair whittling sharp,and very agressive.you can strop on newspaper ,how Murray Carter does.Diamond paste is also good to get agressive edge

 

[FortyTwoBlades]

No

I sharpen my box knives. See further elaboration below.

My EDC hard users are all super steel mostly M4 and they can go a month of almost daily use and still shave hair. (a Spyderco Ultra Fine Ceramic rod often brings it back to hair whittling).

My kitchen cutlery I use on softish white plastic cutting boards which are extremely kind to my White Paper Steel edges that blow me away at their edge holding (hair whittling for a year / same edge shave sharp for a year and a half).
No I'm not making any of this up.

PS: sure the box knife drops off fast but I make up for that by using 0.4mm standard Stanley blade rather than the 1mm "heavy duty" blades. I grind off the transition line on a coarse stone . . . call this reprofiling or convexing if you like. Moslty I polish the side of the blade and the edge and even wax it with candle wax. They tell me toothy box knives are better. I'm still attempting to prove that to my self.

As far as a high use box knife I set them up at work with a three foot long rough side up strop.
We never replaced box knife blades just stropped.
Always sharp dude.

Here's my most-used box cutter with the original blade on it. It's had a short primary grind established on it, and I give it a few swipes on an American Mutt stone as needed, which isn't often! That particular stone makes the most aggressive cardboard-cutting edges I've ever come across. I've been using the same side of the same blade since I got the thing years ago.

 

[Obsessed with Edges]

I've started sharpening my own box/utility knives' edges too. A DMT DiaFold-style hone is perfect for it. The forward end of the utility knife's handle is straight & flat (like FortyTwo's pic above), and angled in such a way that it orients the rake angle perfectly to the edge of the DiaFold for the sharpening passes. Just draw the blade's edge along the length of the hone, keeping the handle's forward end in flush contact with the edge of the hone during the pass. It's like the two were made for one another.