9,4,20, whatever your chopper is

neffarious

neffarious

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Jun 23, 2012
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How sharp is too sharp? I could put a mirror edge in it but is seems like it's overkill and would it be ideal and quickly degraded. It takes a bit of time to accomplish. So how sharp is sharp enough? 400 grit? 600 grit? I would think 1k or 3k would be too much. What about you all? How sharp do you make your chopper?

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If it can cut me, it's sharp enough. As a chopper it doesn't need to be too sharp.
 
I was thinking 40* inclusive either 240 or 400 grit.

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I can convex pretty easy with my worksharp and it is beyond shaving right now and has held up pretty good so far.. Just my personal experience


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1x30 is a harbor freight belt grinder. Other people make them, but for $40 it isn't a bad option if you keep your blade cool. It also helps in reprofiling stuff.
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I will often go to shaving sharp with a convex edge that was thinned behind the edge.
I normally will go to 400 grit when I am in the house, but I bring a small 6" fine cut file in my hiking/camp bag. That file will get me through anything I need to and I can adjust the cut of the file (to a degree) by moderating pressure.

I also tend to carry a diamond rod from Lansky for when the inside curves on my 4 need sharpening.

neffarious said:
Shaving sharp is pretty d@#× sharp. I think that is over board. Won't that degrade against wood pretty quick?
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Shaving sharp is easiest to see that it is just the cleanliness of the apex and how accurately the sharpening was done.
I have seen 90° edges on machinery that will shave arm hair and edges under 20° that won't cut your finger being ran down it.

It is all about the actual apex of the edge.
 
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neffarious said:
Shaving sharp is pretty d@#× sharp. I think that is over board. Won't that degrade against wood pretty quick?

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Click to expand...

Not really, depends on the steel. It's really just a quick and easy test to see where the edge is. And it comes in handy if you need to carve with it too. These knives are large enough that if you really wanted to you could go with a more obtuse edge out front for chopping and have a couple inches near the handle that's thinner and could split a hair. I find that just running my large blades through a Work Sharp until I can scrape hair off my arm (doesn't have to make your arm baby-butt smooth with one pass) will hold up for a weekend in the woods without having to touch up the edge and I've never had any rolling or chipping.
 
I want my chopper's to shave cleanly, in both directions without any resistance.
 
If it won't shave, it's not sharp. After that you're just splitting hairs. ;)

But seriously, a sharp tool is s safe tool because it behaves in predictable ways.
 
Yep, its a common misconception that a "mirror edge" deforms quickly.

All a mirror finish tells you is the degree to which someone polished (ie, they used a high grit) the edge.

What it comes down to is the edge angle, and how well the edge is apexed. A wider angle will be stronger, but have more resistance to cutting, while a thin angle will cut more easily, but won't last under abuse. This is how both an axe, and a straight razor can shave hair (the apex is extremely accurate/consistent), but why one chops wood without chipping, while the other can't cut much beyond hair.

The grit used doesn't really effect how well the edge is apexed(ideally), but does change how the knife cuts. An edge sharpened on something obscenely coarse (36 grit sandpaper), will have visible grind marks on the edge, effectively creating "micro serrations" of a sort. Some people prefer a coarse edge for some tasks, usually draw cutting( hear it a fair bit on skinning knives to get through the hide). A mirror polished edge usually comes from 2000grit and above, and produces a much smoother edge. Those work better for push cutting.

A 220 grit edge done right can shave, as can a 2000 grit edge.

Since most of my cutting is push cutting, I sharpen to shaving, on the mirror side of things. Typically typically I stop around 1500 grit, then a bit of stropping with some compound, and call it good.
 
ocnLogan,

Very good explanation - even I can understand it.

This is why, when I have the time, patience and inclination - along with sufficient blade length, I like a course finish (micro serrations) where the blade draw cuts and a smoother/finer finish further where the blade sees push cutting.

These "zones" on the edge may differ from knife to knife depending on blade size and blade shape. A small section back towards the handle that is course (micro serrations) is great for rope and fibrous materials (cardboard, etc.) while further out a smoother finish push cuts better, as you so readily explained. How much real estate (blade length) is available is a factor in all of this as is whether ir not there is a re-curve to the shape. While I am not generally a fan of re-curves because they are not as easy to sharpen, they are, however, very good at getting the material into a certain spot where micro serrations (or even out and out serrations) in that spot makes short work of rope and the like. However, out further, towards the protruding belly of the re-curve is where a push cutting smoother edge makes sense.

This is more theory than actual application for me except for when I have the time, patience and inclination.
 
I wonder how long it's going to take to polish my 9s edge. Lol I just got convinced

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Can I divert this thread a little with a question about edge angles?

I have almost all my knives set at 30 degrees inclusive or less but they are not choppers. I set my BK15 at 30 degrees inclusive and will probably do the same with my BK5 once it gets here. With my BK4 and BK20 on the way as well I am trying to decide if I want to steepen them up a little as well. I was wondering if you guys all have your choppers set at around 40 degrees or if any of you have gone more acute. Will a 30 degrees edge on a chopper be durable enough or am I taking a chance doing it that way? Are most of you guys just convexing at 40 degrees and calling it good? My sharpening skills are pretty good but I am new to choppers.
 
I would go with the 30 you are comfortable at.
If it chips out, then toss on a 40° micro and convex that transition.

On my 4, I am probably around 30° if not a touch less, convexed into the flats. No chipping noticed here and I cut black locust, green not seasoned.
 
Thank you! I am pretty good with pocket stones but my muscle memory is definitely programmed for 30 degree angles. I find them easy to maintain by hand at that angle. I can maintain a 40 but I am just so used to a 30. :)
 
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