Edge Matters (How sharp?)

Help EM and UK knife making and unlock loads of premium features by buying a subscription here!

  • Nice idea, but the issue would be, how do you measure it? This is still subjective as your medium sharp, might be my 5 or 6. I've had hair popping edges I would not consider scary sharp. EDIT: Scary sharp is so sharp that if you try to shave with it you cut yourself, so sharper than a new razor.


    I've been considering ways to measure sharpness, but the blade geometry and the edge angles affect each method I've ever come up with. A very thin kitchen knife that won't bite into a tomato skin will still cut most veg better than a scary sharp axe based purely on geometry.

  • Depends on the job. I like some of my EDC knives to be as sharp as I can make then, that's FUN. On the other extreme I find filleting a fish easier without too sharp an edge or point, I want the knife to follow the backbone not slice through it. Somewhere I saw someone comment that even a razor has an optimum sharpness, theoretically if too sharp it would just slice skin instead of following it.


    I think knives are an exception to the popular claim that a sharp tool is safer than a blunt one.

  • The mid range is always going to be a tricky because of the roughly y=c/x nature of edge wear, I think this is reason that actual wear resistance is hard to measure with a precise end point.


    Scary sharp is an interesting one, I think it's more to do with geometry than the edge itself.


    For example I sent a knife to Uncle Ian Longstrides for one of his famous convex edges.


    Uncle Ian is also a deer stalker so when i asked him for an edge that would stand up to this use ( bone contact on leg bones and vertebra on every deer gralloched) the edge he sent back was much more obtuse than the one he sends out to people who want a showing-off-how-sharp-it-is edge for their folder, as an example.


    Now this edge is as finely finished and as polished as any other he produces but at an included angle of around 40 degree, does not cut whilst shaving or things like that.



    With that in mind scary sharp I took to be in relation to the knife and it's usage in this context, rather than an absolute for which polished diamond at an incredibly thin angle must be 1.

  • A few accidents throughout my life with sharp knives taught me to stop short of super shaving sharp.


    I quit cutting cardboard boxes after many near misses with a super sharp S30V Spyderco Paramilitary.


    If I get them to cut paper then that is plenty enough, trying to cut hairs is just silly really.

  • To me, really sharp means being able to cut a human hair, lengthways, into three. I used to be able to do that with a cutthroat I had in my school dissection kit (those were the days - carried it to school in my bag without issue) as well as with Swan-Morton scalpel blades after I'd sharpened and honed them. But apart from slicing hairs into mini feather sticks, a talent for which there is limited call I find, such sharpness doesn't last. Certainly, dogfish skin ( the dogfish was a classic dissection for school biology back then) took the edge off the scalpel quickly!


    Today I find different sharpnesses suit different purposes. Slicing 100+ mackerel into 2cm 'chops' right through the backbone, heads as well, requires a robust approach to sharpness. A similar robust edge is on my cheapo Frost 'lenders' knife which I take on board to ensure no one asks to borrow my own, proper, knife when out sea-fishing. Even though that Frost blade has an edge like a hacksaw, it still beats most of the other lads' blades in terms of sharpness.


    For dealing with the catch (if any), I like something very sharp for filleting, robust for cutting off heads etc. and a little less sharp but slightly flexible for slicing skin off the fillet; if this blade is too sharp, it tends to cut through the skin rather than glide between it and the fish flesh, but if too blunt it tears the flesh. Once just right, it lasts for ever as it doesn't have to contend with grit, scales, bones and other stuff.


    Actually, all this is probably just an excuse for having and using more than one knife :lol:

  • I've recently taken to putting a convex on my PITS3 with my wicked edge. I start at 18deg, then 19 then 20, followed by the leather strops to soften the transitions. It stays sharp longer for utility uses.

    It's a good technique on the WE, not only does it give a good strong secondary it prolongs the life of the stones too , much less work for them .

  • I've recently taken to putting a convex on my PITS3 with my wicked edge. I start at 18deg, then 19 then 20, followed by the leather strops to soften the transitions. It stays sharp longer for utility uses.

    - a light hone on the thigh o' yer Levis too ;)

    ..


    Owning and riding a motorcycle is not a matter of life or death. It is more important than that.

  • BEst edge I’ve ever owned was a rockstead, but wouldn’t like to have put it to much use as the edge was so fine and high I’m convinced it would have chipped. Most usefully sharp knife I’ve ever had is my mason, it’s got a great slightly toothy edge that cuts effortlessly, I’ve got a s30vn sebbie and I can’t get it sharp for love nor money, I’ve stripped the daylights out of it, used stones , a Work sharp and nothing gives it a convincingly sharp edge, just given up with it as I’m a lowly wearing the blade depth away and making no progress. I’m conviced the Hearn treat is to very good on it.

  • further to the above I actually prefer steels like aus 8 or what ever the buck 110 comes in than any Gucci steels as I can easily get them frighteningly sharp with little effort. Loving my kabar dozier lock back hunter. So light weight and aus8 so really easy to sharpen

  • further to the above I actually prefer steels like aus 8 or what ever the buck 110 comes in than any Gucci steels as I can easily get them frighteningly sharp with little effort. Loving my kabar dozier lock back hunter. So light weight and aus8 so really easy to sharpen

    I'll swap an old aus8 knife I have laying around for the Sebbie you can't get on with .....





    Seriously though, I always used a Sharpmaker with my Sebbies and never had a problem :)