Define Sharp...a question

[kopio]

Hello All,

Ok...so in my family it has always been a matter of personal pride as to how sharp your pocketknife is. I live in the NW...what can I say.

Anyhow...I have a pocketknife that will shave the hairs right off your arm. I consider this quite sharp.

I guess I have several questions about sharpness.

I know this is sharp for a pocketknife, I would guess it's just getting started for a razor!

Could I make my pocketknife even sharper by stropping it? Would it ruin my strop?

If I can sharpen a pocket knife that sharp, is there a good chance that I can hone a straight? I know a lot of it is muscle memory, but there is also a lot of technique. I'm the guy at work that everyone always comes to when they need their knife sharpened (which is funny...I work in a grocery store...you would figure it would be the butchers they would go to)...so I'm hoping that I can take that skill set and use it as a leg up on honing.

Is my experience similiar to any of yours?

Thanks for your input. This forum has really become a great place to learn for me.

--Matt

 

[mparker762]

Razors are much sharper, but in ways that may not be immediately obvious to a knife guy.

There is the issue of objective sharpness, which I take as the distance between the two bevels where the steel becomes too thin to withstand the stresses of the hone and disintegrates. This must be as small as the steel will let you get it. For commercial blades this has been measured on scanning electron microscopes at approximately 0.38 microns, and well honed straight razors can also hit this. You cannot use the "hone to a burr" method of honing because this leaves a very wide edge, too wide to shave well. You can get an edge that will shave armhair this way, but not one that will pop armhair mid-stalk without you feeling a thing, and that's the level of sharpness we're talking about for a razor - the hair on your face is much tougher than the hair on your arm, and your face is much more sensitive.

There is also the issue of cutting friction. Knife guys usually distinguish between edges optimized for slicing vs edges optimized for push-cutting. Razors are push-cutting utensils, but the thing they are cutting has the same tensile strength as copper wire of the same diameter. Because of this, it is not sufficient to be sharp, the edge must also minimise cutting friction. Commercial blades solve this problem with teflon coatings, but straight razor shavers must solve this by polishing the bevel so it is as smooth as possible.

There is also the issue of smoothness. This is not necessarily the same thing as a polished edge - it is possible to have a very polished edge that is harsh-feeling. Partly smoothness comes from a strong edge that doesn't deform under lateral pressure, and partly it comes from having a consistent level of sharpness and polish across all areas of the edge.

All of these must come together to produce a great-shaving razor. With a knife, if you fall short of perfection then you simply have to work a little harder to cut the rope or whatever, but with a razor you are punished with nicks or razor burn, or at best embarrassing leftover stubble.

 

[Fnord5]

+1

An interesting observation of mine after honing my straights.

I re-sharpened my EDC knife, a little Victorinox officer, and before it was the sharpest thing I owned.

It is just as sharp as it ever was, but feels so incredibly dull now.

 

[kopio]

So do any of you guys use your straight razor stuff to put an even sharper edge on your knife?

 

[Fnord5]

Nope, for the simple fact that the edge is too fine to hold up for what I need a knife for. The sharper the blade, the faster it dulls, and chipping can become an issue.

 

[mparker762]

Nope, for the simple fact that the edge is too fine to hold up for what I need a knife for. The sharper the blade, the faster it dulls, and chipping can become an issue.

This. Also, knives will damage straight razor hones. They're tough enough to lap the first time, I don't want to have to do it again every time my pocketknife needs a touch-up. Oh and expensive - straight razor hones can be depressingly expensive.

I do have a hanging strop with flexcut gold on it that I use for the final edge for my kitchen knives. But that's it.

 

[tpoof]

I like the convex method of sharpening my knives.. with lesser grades of sandpaper on a mousepad... finishing with Chrome Ox paper and stropping on leather. just to get the ultimate edge.. I do not sharpen my knives with my razor stones
This will get my knives very close to shavng sharp, almost too sharp and using the finest papers will give you that edge..

 

[chess1]

i have sharpened only 1 packed knife and result was not satisfying.
1 steel are different
2 Knife sharpening is a little different . You cannot put finest edge . it will brake down as soon as it touches apple seeds. you will need to stop in some point.
hope this helps.

 

[Sticky]

If you want to use the same hones for knives and razors, 600, 1200, and 8000 mesh DMTs will do it just fine. Not all knives will take an 8k edge; a surprising number of them will.

Many users strop a knife, with and without pastes. I generally recommend keeping the razor strop seperate from the knife strop. Still, I do have one strop that I use for both.

If you can sharpen a knife, you can learn to sharpen a razor. You can "feel" what the razor is doing on the hone, as you can with a knife. I once read a Honemeister that posted: "Honing a razor is like honing a knife with training wheels". No "holding the angle" problem with a razor, just work on the light touch and even stroke along the entire edge.

Most knife guys have the most trouble with using/believing how light the finishing strokes need to be.

 

[kopio]

Wow guys....thanks for all the info and input. This has been very informative!

--Matt

 

[SavantStrike]

Razors are much sharper, but in ways that may not be immediately obvious to a knife guy.

There is the issue of objective sharpness, which I take as the distance between the two bevels where the steel becomes too thin to withstand the stresses of the hone and disintegrates. This must be as small as the steel will let you get it. For commercial blades this has been measured on scanning electron microscopes at approximately 0.38 microns, and well honed straight razors can also hit this. You cannot use the "hone to a burr" method of honing because this leaves a very wide edge, too wide to shave well. You can get an edge that will shave armhair this way, but not one that will pop armhair mid-stalk without you feeling a thing, and that's the level of sharpness we're talking about for a razor - the hair on your face is much tougher than the hair on your arm, and your face is much more sensitive.

There is also the issue of cutting friction. Knife guys usually distinguish between edges optimized for slicing vs edges optimized for push-cutting. Razors are push-cutting utensils, but the thing they are cutting has the same tensile strength as copper wire of the same diameter. Because of this, it is not sufficient to be sharp, the edge must also minimise cutting friction. Commercial blades solve this problem with teflon coatings, but straight razor shavers must solve this by polishing the bevel so it is as smooth as possible.

There is also the issue of smoothness. This is not necessarily the same thing as a polished edge - it is possible to have a very polished edge that is harsh-feeling. Partly smoothness comes from a strong edge that doesn't deform under lateral pressure, and partly it comes from having a consistent level of sharpness and polish across all areas of the edge.

All of these must come together to produce a great-shaving razor. With a knife, if you fall short of perfection then you simply have to work a little harder to cut the rope or whatever, but with a razor you are punished with nicks or razor burn, or at best embarrassing leftover stubble.

I've never had a straight sharp enough to cut arm hair mid stalk like you describe, including my one and only professionally honed razor (admittedly I only have two I consider shave ready so it's not like I've got a ton of experience ). I have had razors that are sharp enough to strip sections of my arm bare at the skin with absolutely no tugging and just that familiarly comfortable feeling of razor on skin . Am I not honing as well as I should be if I can't get mid stalk carnage?

 

[Fnord5]

I've never had a straight sharp enough to cut arm hair mid stalk like you describe, including my one and only professionally honed razor (admittedly I only have two I consider shave ready so it's not like I've got a ton of experience ). I have had razors that are sharp enough to strip sections of my arm bare at the skin with absolutely no tugging and just that familiarly comfortable feeling of razor on skin . Am I not honing as well as I should be if I can't get mid stalk carnage?

Mid stalk cutting is pretty much the same as the HHT.

I can get nearly all of mine to do it, but the ones that don't, shave just as well.

 

[Dubbya]

I borrowed this from a post by another member on another sub-forum.

On top is a Feather disposable blade(one of the sharpest available).

On the bottom is a honed and stropped Straight razor.

Just to give you an idea of what "razor sharp" means.

Feather edge at 200x

Straight edge at 200x

 

[kopio]

Wow...that's pretty cool.

 

[Dubbya]

Wow...that's pretty cool.

I thought so when I first saw it too.

 

[Seraphim]

I thought so when I first saw it too.

Thanks guys.

My definition of "sharp" is not only that it will cut arm hair mid stalk, but that it will do so without making a sound. Some HHT will pass, but with a *pop* or *ping*. Truly sharp to me is when you get it to just part in two without a sound, no pull at all, no nothing.

 

[Fnord5]

Thanks guys.

My definition of "sharp" is not only that it will cut arm hair mid stalk, but that it will do so without making a sound. Some HHT will pass, but with a *pop* or *ping*. Truly sharp to me is when you get it to just part in two without a sound, no pull at all, no nothing.

But, must you have that kind of sharpness to shave with? (you personally)

 

[Seraphim]

But, must you have that kind of sharpness to shave with? (you personally)

I think I do. I've had some less than stellar shaves when the razors don't pass my definition of sharp test. Rather, the ATG pass is usually troublesome especially on the upper lip. If it is really, really sharp, then it isn't an issue.

If BBS shaves are not your goal, then that level of sharpness probably isn't required either.

Also lately I've been working on extremely light pressure of the razor on my face, which I feel does require the ultimate in sharpness to cut the whiskers without having to bear down at all, or having the whiskers *grab* at the razor when going ATG trying to keep a light touch.

 

[Fnord5]

Interesting.
I would love to try out one of your shave ready blades.
Mine shave me well, but I have a goatee, and therefore no upper lip shaving issues.(just the jawline)

Maybe when you put up something big and wedgy on the BST, I'll have to grab it.

 

[Seraphim]

Interesting.
I would love to try out one of your shave ready blades.
Mine shave me well, but I have a goatee, and therefore no upper lip shaving issues.(just the jawline)

Maybe when you put up something big and wedgy on the BST, I'll have to grab it.

You're missing half the fun without trying the coup de maitre under the nose, and battling the barbed wire chin bristles ATG!