How long should a razor edge last

[Auraria]

So how is it you did not know what the original question was?
And as to my admittedly simple answer,
Does it not depend both on the blade in question, and also how it is used?

It's a lot more complex than that.
Blade gemeotry, edge geometry, steel types, RC hardness, what type of edge is produced, ect ect ect.
It's never black and white.

 

[W.M.B.]

It's a lot more complex than that.
Blade gemeotry, edge geometry, steel types, RC hardness, what type of edge is produced, ect ect ect.
It's never black and white.

I said it depends on the blade and the use. If i understand you correctly, you seem to be saying, no, but then you go on to show that it depends on these factors about the blade.
Which sounds like yes.

 

[W.M.B.]

I said it depends on the blade and the use. If i understand you correctly, you seem to be saying, no, but then you go on to show that it depends on these factors about the blade.
Which sounds like yes.

Metallurgy is complicated, but the original question was not. The answer that I would have been happiest to give would have been in the form of time. The question was "how long..." After all. Perhaps I should have answered "indefinitely, unless you do something to dull it." But in the post following the question, the o.p. Discusses using the knives, leading to dulling, so that would have answered the original question, but not given him what he was looking for.

 

[Ankerson]

Metallurgy is complicated, but the original question was not. The answer that I would have been happiest to give would have been in the form of time. The question was "how long..." After all. Perhaps I should have answered "indefinitely, unless you do something to dull it." But in the post following the question, the o.p. Discusses using the knives, leading to dulling, so that would have answered the original question, but not given him what he was looking for.

Sure the question was simple, but the answer is much more complex than the question due to the infinite number of variables that can effect the outcome.

 

[Auraria]

He had a razor bur, that was the initial issue.
However with what you are saying, a knife can be anything, a SOG Trident Tanto like mine, isn't a tanto anymore.
Depends on factory edges, is it 50/40/30 degress? Is there a Micro bevel.
Have you personally reprofiled it.
What angle are you using.
What type of grits, what type of edge.
The thickness and grind of a specific knife come into play.
How far is the shoulder from the edge.
Thickness of the edge where it meets the shoulder.

Here in the maintenance forum I would HOPE people do NOT keep factory edges or geometries.
These ALL can affect edge retention and how sharp an edge can get SIGNIFICANTLY.

 

[W.M.B.]

Sure the question was simple, but the answer is much more complex than the question due to the infinite number of variables that can effect the outcome.

The answer you give is complicated because the question you are answering, (not the one asked) is complicated.

 

[Auraria]

The answer you give is complicated because the question you are answering, (not the one asked) is complicated.

Read my most recent post.
We answered OPs question prior, we were discussing why people were refering blade steel to hardness.

 

[W.M.B.]

Read my most recent post.
We answered OPs question prior, we were discussing why people were refering blade steel to hardness.

My responses were all related to Ankersons claim that the original question was "wtf is a hard steel?"
If you answered the original question, "how long should a razor edge last?" I missed it. How long should it last? Twenty minutes? A week? A decade?

 

[Bo T]

In science there are many models which serve to describe the same phenomena. Introductory classes expose students to the simplest models. As students advance, they are exposed to more complex models. The simple models do not work as well as the more complex models as far as, i.e. making predictions about behavior. The difficulty in using 'hard' and 'soft' is that the terms are being used to describe distinctly different properties in different models. Properties that can be related to edge retention.

So, Hard=hard to sharpen=better edge retention and soft=easy to sharpen=worse edge retention, will work to a limited extent when comparing blades. Also, the terms are used to describe other characteristics such as Rockwell and Brinell hardness which are used in different, more complex models. In contrast to Ankersons premise that 'nothing is that simple', I believe that the simple models have their place. In fairness to neophytes I believe that it should be qualified to note that these simple models do not pan out in many cases.

 

[Ankerson]

In science there are many models which serve to describe the same phenomena. Introductory classes expose students to the simplest models. As students advance, they are exposed to more complex models. The simple models do not work as well as the more complex models as far as, i.e. making predictions about behavior. The difficulty in using 'hard' and 'soft' is that the terms are being used to describe distinctly different properties in different models. Properties that can be related to edge retention.

So, Hard=hard to sharpen=better edge retention and soft=easy to sharpen=worse edge retention, will work to a limited extent when comparing blades. Also, the terms are used to describe other characteristics such as Rockwell and Brinell hardness which are used in different, more complex models. In contrast to Ankersons premise that 'nothing is that simple', I believe that the simple models have their place. In fairness to neophytes I believe that it should be qualified to note that these simple models do not pan out in many cases.

The main issues that I see in using hard or soft in describing steels in the way they seem to be used lately is it has nothing to do with RC hardness at all as it's not even referenced.

Easy to sharpen? Compared to what? And what are they using to sharpen with? How experienced are they at sharpening?

Hard to sharpen? Compared to what? And what are they using to sharpen with? How experienced are they at sharpening?

Goes dull fast etc? What are they cutting? Compared to what? What are the blade and edge specs? How was it sharpened?

Holds an edge longer? What are they cutting? Compared to what? What are the blade and edge specs? How was it sharpened?

Those are the easy questions, not even starting to get into the more complex variables and how they can effect the outcome.

NOTHING is ever that simple.........

Something like.... Oh man that's a Hard steel...... HUH? what? What? WHAT? WHAT?

 

[mako20ft]

I have no dog in this discussion but will add this. I was looking forward to some straight forward advice regarding what to reasonably expect from "How long should a razor edge last". I thought it was a simple inquiry, relative to the forum and likely, something a few other folks might want advice on.

Instead, the subject veered a bit off course and frankly, made me think I know very little of what makes a blade effective for it's intended use. Metallurgy, RC hardness, distinct characteristics of "branded steel", etc... I'm thinking the OP wasn't looking to know how much others knew about steel properties...the point was could someone impart some basic knowledge, experience, wisdom to his question?

I've been serving as a professional guide, seasoned military veteran and fun loving woods guide for nearly 40 years. Sometimes KISS works very well for regular folks that hope to have a simple answer to a polite, pertinent and simple question.

I doubt anyone's intention was to turn off a new and valued member at BF. That said, some of the responses here went more than a little ways towards doing that. It's outstanding that members take the time, energy and dedication to genuinely understand all the intricacies of making a tool "razor sharp" but frankly gentleman...many people don't care to know. Maybe, like me (again, maybe)....they just want to know what others think are good expectations once they proudly get a blade to hair shaving. No one is asking anyone to dummy it down however there is zero reason to make it more complicated than need be based on the question. Make the complexity of an answer relative to the question... If the OP follows up and is interested in diving deeper...BY ALL MEANS. You may have done the community a service and added another interested, newly enlightened member. Until then though...

It ain't Gynecology folks.

 

[Ankerson]

I have no dog in this discussion but will add this. I was looking forward to some straight forward advice regarding what to reasonably expect from "How long should a razor edge last". I thought it was a simple inquiry, relative to the forum and likely, something a few other folks might want advice on.

Instead, the subject veered a bit off course and frankly, made me think I know very little of what makes a blade effective for it's intended use. Metallurgy, RC hardness, distinct characteristics of "branded steel", etc... I'm thinking the OP wasn't looking to know how much others knew about steel properties...the point was could someone impart some basic knowledge, experience, wisdom to his question?

I've been serving as a professional guide, seasoned military veteran and fun loving woods guide for nearly 40 years. Sometimes KISS works very well for regular folks that hope to have a simple answer to a polite, pertinent and simple question.

I doubt anyone's intention was to turn off a new and valued member at BF. That said, some of the responses here went more than a little ways towards doing that. It's outstanding that members take the time, energy and dedication to genuinely understand all the intricacies of making a tool "razor sharp" but frankly gentleman...many people don't care to know. Maybe, like me (again, maybe)....they just want to know what others think are good expectations once they proudly get a blade to hair shaving. No one is asking anyone to dummy it down however there is zero reason to make it more complicated than need be based on the question. Make the complexity of an answer relative to the question... If the OP follows up and is interested in diving deeper...BY ALL MEANS. You may have done the community a service and added another interested, newly enlightened member. Until then though...

It ain't Gynecology folks.

There really isn't a simple answer to the question other than it depends..... And that would be the answer, just those two words.

Now to go deeper than that it gets more complex as the variables are taken into count.

Like I posted before the question IS simple, but the answer is much more complex.

That's if they want more than "it depends"........

And yes it can be as complicated as Gynecology depending on how deep and complete the answer has to be.

 

[Fred.Rowe]

This is a response to the original poster's question.

Everyone who sharpens knives should be able to produce a "razor" edge on a blade that is capable of carrying that acute an edge But a razor edge should not be the primary goal when sharpening a knife. You said it your self; each of these knives took a razor edge, but then what? Because an edge will whittle a hair does not mean its the best edge for a specific knife or best for it's intended use?
An edge bevel ground @ 15 degrees inclusive is an edge best sitting on a strait razor and little else.

Referencing the later banter: most talk at my shop, when a few smiths stop by, is about steel; its shape or geometry, its as quenched hardness and HRC after tempering. Its usually assumed that when we say hardness, we are speaking of the Rockwell hardness of the steel or if the numbers seem a bit odd the person may be relating to another scale for measuring the hardness of steel or another manner by which to compare steels. Talk always moves along to plasticity and deformation, along with abrasion resistance and resistance to wear. We discuss carbides and there contribution to the steel and I must agree here, that there is much to talk about when it comes to steel; but referencing the OP me thinks the answer is pretty simple.

 

[pnsxyr]

I find it hard to give actual figures here because there are so many variables that affect this. The steel itself, the heat treatment, the edge geometry, and the usage the knife sees are all major players.

Sometimes the differences between steels are not super obvious, and other times they are outright blatant. For example, I own the exact same Benchmade knife in 154CM, D2, S30V, and M390. The differences between 154CM, S30V, and D2 are there, but they are not super pronounced, especially between S30V and D2 which have a little more edge retention than 154CM. Now with M390, it's impossible to miss. I touchup the M390 knife a fraction of the others, it holds that razor fresh hone longer than the other three knives combined, it maintains that razor fresh hone even when cutting abrasive materials like cardboard, and it does this despite being at a very thin angle.

 

[neeman]

I can completely reverse their perception of what a hard and soft steel is just by changing the edge geometry and edge finish...... Using the same knife they are holding at the time.

I am sure you can change a single instance
But the general perception of the knives that the common user buys, will not change.

I write service documents to train engineers how to repair highly complex instruments
We first need to understand the basic presumtions the engineers will take
Then we can shift their thinking by planned training

The common user has their perceptions
And the knife advertising industry has no economic incentive in educating the buyers
So hard and soft remains

 

[Chris "Anagarika"]

Soft in general as in SAKs and no name steel knives factory produced will be easy to sharpen yet lose the hair whittling edge fast. Cutting paper only won't be that fast, but other more abrasive medium such as cardboard will dull it fast.

Hard in general such as S30V or M4 might hold this a bit longer. It's said hard as usually a decent maker will run it harder, nit that it can be run softer than SAK (55HRC?).

So in general: sharp will last longer if it's optimized (grit & geometry) to the task. Hair whittling? Will be lost first time the edge used to cut other than hair and air.

Hope this is simple enough an answer to OP. Not to say it isn't complex, as it is complex.

 

[KennyB]

Wow, and to think all the OP asked was how long a razor edge should last, and he got a whole dissertation on metallurgy. Talk about getting more than you bargained for.

How about instead of all this theoretically, imperical, mechanical... A little anecdotal? At the end the only way to really convey how long a certain knife of a certain steel of a certain geometry holds an edge is by actually using it and then relying on the testimonial of another person. OR you can try to find CARTA results or other tests that aim to remove the bias and partial-ness of the human factor...

Really why does it matter if people are talking about "soft steels"... Was this thread about the semantics of metallurgy or how long a razor edge should last?

 

[W.M.B.]

This is my razor. I have used this razor, and no other for more than 4 years. Sometimes I go a couple months without even using the strop. it shaves well. And it is a 10 dollar el-cheapo.