How long does a hair whittling edge last?

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KennyB

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Jan 19, 2010
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Well, last night I watched a couple of videos on YouTube where the users were testing how long a hair whittling edge lasted by cutting newsprint and printer paper until it would no longer whittle hair. One test was being conducted with a Kershaw Skyline in 14C28N and the user did 15 cuts on phonebook paper, and then concluded the phonebook paper wasn't going to dull it so moved on to regular printer paper, where the ledge lost its hair-whittling sharpness 7 cuts in. Another video showed a user with a Gayle Bradely in CPM-M4 doing similar got 3 cuts into phonebook paper before it wouldn't whittle "free-hanging hair" and 7 into printer paper before it would no longer whittle hair at all.

So the point to the videos was that everyone always says, "A hair whittling edge will lose that sharpness after one cut into anything." Well, I personally didn't think the videos really disproved that because phone book and printer paper aren't exactly the most abrasive things to cut. Yeah, after time they'll dull an edge, but I think when people say "After one cut into anything," they mean something that you're actually cutting for a practical purpose, to accomplish something, i.e. real use. Now I know maybe somewhere someone's job may entail cutting up paper, but I don't think most of us can say that.

Then it struck me as I had to change my cat litter, that the bags that it comes in are these pretty thick cardboard/paper sacks and they always get really embedded with clay dust and on a few occasions a big clay particle has been there to really dull my edge. Anyway, long story short it's really nasty stuff and ever since I've made sure to give the side of the bag a good whack to knock all but the finest clay dust off, but I bet it's still plenty abrasive--way more than printer paper anyway.

So long story short, I cut open the bag across the top and my edge was still hair whittling. I'm using a Kershaw Needs work with 14C28N, finished on a 600 grit DMT hone and stropped on CrO coated MDF. I'm not going to make any direct comparisons to what was shown in the videos I mentioned, but I will say my results definitely disprove the idea that just "one" cut will remove hair whittling sharpness. So I continued on making cuts until the knife would just barely whittle hair in the last picture you see--by this point I had to hold it very close to my finger tips and really fight it to whittle, so I called it then.

Here is the knife, and the bag, after 20 cuts into the paper. The cuts were performed by plunging in with the tip, and gradually moving upward to make sure that every portion of the blade aided in each cut.

Just barely whittling still, but still plenty sharp enough to pop hairs off my arm.

hairwhittling1.jpg


And here's a picture of the bag material... Each side is actually three layers of this cardboard paper material, and the inside layer is coated with a fine powder of clay dust (that white shade you see on the inside layer of cardboard).

hairwhittling3.jpg
 
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Perhaps they were finishing theirs to a much higher grit level. Thus, it completed fewer cuts. DM
 
David Martin said:
Perhaps they were finishing theirs to a much higher grit level. Thus, it completed fewer cuts. DM
Click to expand...

:thumbup: Excellent insight David! I noticed dmt F too - very toothy ( serrated), most slice cuts won't dull the trough of serration. In my mind, the word 'whittling' go hand-in-hand with 'shaving', coincided with your higher-grit assertion.
 
David Martin said:
Perhaps they were finishing theirs to a much higher grit level. Thus, it completed fewer cuts. DM
Click to expand...
Yeah, I don't know... I had speculated about that as well, plus the idea that the 14C28N of the Skyline apparently performed better than the CPM-M4 of the Gayle Bradley. However I think there's a bunch of different variables to consider; edge angle, finish, the hair being whittled, etc. I also wondered it if was perhaps because mine was a much coarser finish, but on the other hand it could also be because the hairs used in the other videos appeared to be much finer than mine. So I pretty much ignored how much more one knife did over any other.

My main goal was just to explore the idea of "just one cut" being able to take away the hair whittling sharpness. So with that in mind, I wanted to try it on both something that I thought would be very abrasive, but also in the realm of practicality in terms of what a person might be cutting up. I really expected it to dull much quicker than it did.
 
Assuming a decent heat treat, I believe in the geometry of the finished edge more than anything, including steel type or edge finish ('toothy' vs 'polished'). If the geometry is well-suited to the steel type, edges can & will stay much sharper for longer. Fine grain is a big plus too, and that's one of the really nice attributes of 'simpler' steels, with a minimum of large carbides.

I was convinced of the above, after using an old Case 6265 SAB Folding Hunter (~1965 vintage or so) to shred some cardboard. The steel on this knife is very basic stuff (some predecessor of Case's 'CV', but not called as such at the time). I had used the secondary skinner blade to shred the cardboard, and the edge was a convex polished up through 2000+ grit (wet/dry paper). The older carbon steel knives from Case feel very 'soft' on the hones, and will abrade & sharpen up very, very quickly. I was skeptical of how long an edge would last, after sharpening mine. But this one still easily shaved/tree-topped hair from my forearm after shredding the cardboard box. That opened my eyes, and made me realize a 'supersteel' isn't needed, nor a coarse 'toothy edge'. A clean & pure apex with good supporting geometry behind it, on a blade with competent heat treat, makes 99% of the difference.

I've also noticed similar performance in Schrade's older carbon blades (1095), BTW.


David
 
Obsessed with Edges said:
Assuming a decent heat treat, I believe in the geometry of the finished edge more than anything, including steel type or edge finish ('toothy' vs 'polished'). If the geometry is well-suited to the steel type, edges can & will stay much sharper for longer. Fine grain is a big plus too, and that's one of the really nice attributes of 'simpler' steels, with a minimum of large carbides.

I was convinced of the above, after using an old Case 6265 SAB Folding Hunter (~1965 vintage or so) to shred some cardboard. The steel on this knife is very basic stuff (some predecessor of Case's 'CV', but not called as such at the time). I had used the secondary skinner blade to shred the cardboard, and the edge was a convex polished up through 2000+ grit (wet/dry paper). The older carbon steel knives from Case feel very 'soft' on the hones, and will abrade & sharpen up very, very quickly. I was skeptical of how long an edge would last, after sharpening mine. But this one still easily shaved/tree-topped hair from my forearm after shredding the cardboard box. That opened my eyes, and made me realize a 'supersteel' isn't needed, nor a coarse 'toothy edge'. A clean & pure apex with good supporting geometry behind it, on a blade with competent heat treat, makes 99% of the difference.

I've also noticed similar performance in Schrade's older carbon blades (1095), BTW.


David
Click to expand...

I've noticed neglect and time will dull a carbon steel blade more reliably than light use, assuming it isn't properly oiled.
 
Obsessed, I've owned the two knives you mention. Try cutting up 6 large cardboard boxes making 1/2"-3/4" strips out of the boxes then go to the hair whittling test. I don't doubt your test and think that it can do it after one. As those basic steels are surprising, 52100 even better. DM
 
Obsessed with Edges said:
Assuming a decent heat treat, I believe in the geometry of the finished edge more than anything, including steel type or edge finish ('toothy' vs 'polished'). If the geometry is well-suited to the steel type, edges can & will stay much sharper for longer. Fine grain is a big plus too, and that's one of the really nice attributes of 'simpler' steels, with a minimum of large carbides.

I was convinced of the above, after using an old Case 6265 SAB Folding Hunter (~1965 vintage or so) to shred some cardboard. The steel on this knife is very basic stuff (some predecessor of Case's 'CV', but not called as such at the time). I had used the secondary skinner blade to shred the cardboard, and the edge was a convex polished up through 2000+ grit (wet/dry paper). The older carbon steel knives from Case feel very 'soft' on the hones, and will abrade & sharpen up very, very quickly. I was skeptical of how long an edge would last, after sharpening mine. But this one still easily shaved/tree-topped hair from my forearm after shredding the cardboard box. That opened my eyes, and made me realize a 'supersteel' isn't needed, nor a coarse 'toothy edge'. A clean & pure apex with good supporting geometry behind it, on a blade with competent heat treat, makes 99% of the difference.

I've also noticed similar performance in Schrade's older carbon blades (1095), BTW.


David
Click to expand...

Yes, I'm starting to believe that geometry is actually superior to having a pure and refined apex as well. My hand sharpened knives are ridiculously sharp (hair whittling and all that) and they last for a while, but on the other hand I have a few knives which I sharpened with a guided system that have very nice bevels and they just seem to need far less sharpening and cut far better even though tests like "hair whittling" would suggest they're the same sharpness.

I think it's because tests like whittling hairs and all that stuff really just evaluate the refinement of the apex. They don't really do much to tell you what's going on with the rest of the edge geometry.
 
Yes, the blade geometry is the sngle most important thing in how sharp that knife is going to get, as well as how sharp it is going to stay under use. You can put a hair whittling edge on almost anything, but with the thick blade, it's going to stop cutting well and loose that hair whittling edge after a few cuts. There's a reason that a couple generations of workiing men were loyal to the point of fanatics to the old thin bladed carbon steel Schrade's and Camillus pocket knives. Now we have a generation of young guys who think they need a "hard use" knife with a blade thicker than some machete's come with.

Take a real look at some old Schrade Old Timer blade. It's a thin blade, and full flat ground all the way down to the edge. Even when it looses it's original sharpness, it will still cut. Take it and do a few swipes across some scotchbrite to dull it up, and go break down a cardboard box. You will still be able to saw through the cardboard pretty decent, or saw through a piece of rope. Try that with a modern tactical style knife.

Edge geometry is the number 1 thing in sharpness. If you have a thin blade, you can sharpen it with a rock and get it razor edge. Not so a thick blade with poor geometry.

Carl.
 
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