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#7059028 - 11/09/12 Sharpness
1234567 Offline
Campfire Guide

Registered: 11/26/07
Posts: 4320
Does anyone know how sharp you can actually get a knife edge? I am asking about steel knives.

Also, does anyone have any idea on which steel will get the sharpest.

The reason I ask is because I have read that steel has grains in it, and the finer the grain, the sharper you can hone it, but that you cannot sharpen a grain. It would seem logical, to me at least, that the finer/smaller the grain, the sharper the blade is capable of getting.

Also, I have read that about 2 or 3 microns width is about as sharp as an edge will get.

Anyone have any input on this?

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#7059115 - 11/09/12 Re: Sharpness [Re: 1234567]
mtnman1 Offline
Campfire Tracker

Registered: 12/09/03
Posts: 5545
here we go again...

Just go to this website...

http://www.catra.org/pages/products/kniveslevel1/slt.htm


Edited by mtnman1 (11/09/12)
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#7059198 - 11/09/12 Re: Sharpness [Re: mtnman1]
1234567 Offline
Campfire Guide

Registered: 11/26/07
Posts: 4320
That is not what the question was about.

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#7059399 - 11/09/12 Re: Sharpness [Re: 1234567]
mtnman1 Offline
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Registered: 12/09/03
Posts: 5545
Then I have no idea what the question is about. You asked how sharp a knife can get. I gave you the machine and the index that is used to measure it as the industry standard for 50 years. You might want to first define "Sharp"... thin doesn't necessarily mean "sharp"

Have a nice day.



Edited by mtnman1 (11/09/12)
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#7059753 - 11/09/12 Re: Sharpness [Re: 1234567]
2muchgun Offline
Campfire 'Bwana

Registered: 02/25/05
Posts: 13931
Loc: Michigun
If MM1s answer was no good, then I don't get the question either.

IME you can get just about any knife (made of decent steel) wickedly sharp. It is just that some obtain an edge easier, and some hold it longer. Other than that, wicked sharp is wicked sharp. Hard to tell which is sharper of 2 knives that will both shave hair, and at that point it really doesn't much matter, IMO.

I would say carbon steel gets sharper than stainless, in general. But that is just my opinion with no scientific research to back it up.

I would also say cold forged knives can be made very finely grained, and are capable of superior sharpness.....
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#7060060 - 11/09/12 Re: Sharpness [Re: 2muchgun]
cranky72 Offline
Campfire Regular

Registered: 12/06/11
Posts: 888
a knife can get as sharp as you can make it. 123456 have you ever seen the videos with guys whittling a single hair? 123456 how many angels can dance on the head of a pin? we did all this a few months back. cranky72

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#7060064 - 11/09/12 Re: Sharpness [Re: 2muchgun]
gotthecustombug Offline
Campfire Regular

Registered: 05/09/09
Posts: 416
Loc: Iowa, USA
I am just getting into the knife thing, as far as compostion goes. I sharpen a lot of knives though. I think one of my sharpest is a 1095 CS custom, made by bradshaw. That thing is sharp! It is a convex grind.

I have also sharpened a few stainless that realy took a keen edge. Some of the factory ones that have take a really good edge are japanese made spydercos, and some of the benchmade knives. Knives of Alaska made from D2 are usually a treat to sharpen too...end up scary sharp. There are others too, I just don't remember them all.

I sharpen almost all of them on my Edge Pro, professional, except the convex. There have been a few that I have converted to convex using my buffer...no brands mentionable, just depends on how they are.

Larry

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#7060282 - 11/10/12 Re: Sharpness [Re: gotthecustombug]
1234567 Offline
Campfire Guide

Registered: 11/26/07
Posts: 4320
Okay, I'll try again. I put the part about microns in because I thought that would more clearly explain what I am asking.

I want to know, if anyone knows, or how to find out, how many microns thick the edge would be where the angles converge to form the cutting edge. It doesn't have to be microns--it can be thousands or any measurement.

There is something about either grains or carbides and they would be lined up along the edge. I have read that these grains, or if they are carbides, will not sharpen. Supposedly, they will pull out of the matrix instead of abrading.

I am thinking that the sharpest edge would be a type of steel that has the finest carbides, or grains, whatever they are.

I have read that some type of volcanic rock, obsidian, I think, is the sharpest of any known object, but I am wanting to know about steel.

Yes, I did ask a similar question a few months ago, although I don't remember asking about Angels or pins, but no one gave a satisfactory answer.

As far as edge holding ability goes, I already know which steel that would be, and that is one of the things a Catra measures. I also know about splitting hairs. It would have to be very sharp.

What would be the thickness of the apex of the triangle where two of the sides converge on a knife blade so that it would split a hair?

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#7060883 - 11/10/12 Re: Sharpness [Re: 1234567]
cranky72 Offline
Campfire Regular

Registered: 12/06/11
Posts: 888
i'm not sure that we have an engineer that specializes in this type measurement on this forum. the sharpest apex can be measured; remember that we now have machines that can weigh a pencil mark.123456 i believe there is certainly an answer to your question but you will probably need to consult the editors of Scientific American or MIT university, another source is Cal Polytech. now my question is how this info can possibly aid your understanding of knife performance? if it's strictly academic get your self to the engineering xperts. i ca'nt possibly see how this will aid in making knives or even using them. did you count the angels yet?--cranky72

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#7060885 - 11/10/12 Re: Sharpness [Re: 1234567]
cranky72 Offline
Campfire Regular

Registered: 12/06/11
Posts: 888


Edited by cranky72 (11/10/12)

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#7061589 - 11/10/12 Re: Sharpness [Re: cranky72]
gotthecustombug Offline
Campfire Regular

Registered: 05/09/09
Posts: 416
Loc: Iowa, USA
I went looking...one fellow posted that a scalpel would measure about .001 mm across, and a razor blade would measure half that, approximately. I have a microscope I can hook up to the computer, that can measure that, maybe...if I get time, I may just mess with it a little.

Larry

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#7061679 - 11/10/12 Re: Sharpness [Re: 1234567]
JSTUART Offline
Campfire Outfitter

Registered: 06/17/07
Posts: 9552
Loc: Land of milk & honey, for some...
Originally Posted By: 1234567


Anyone have any input on this?


Yes, if you go to the campfire or hunting rifle threads and post that the .270 is better than the 30-06 you will get a longer thread, more arguments and better nudie pictures.

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#7062151 - 11/10/12 Re: Sharpness [Re: JSTUART]
1234567 Offline
Campfire Guide

Registered: 11/26/07
Posts: 4320
Cranky:

The reason I want to know is mainly because of curiosity. Usually, even when you will not put the information to use, I feel it is better to know than to not know.

That being said, the knowledge would, or could apply to surgical instruments, especially eye surgery, brain surgery, or open heat surgery, where a fine, clean cut, with no tearing, and very little pressure is required. Not that I am going to be doing any surgery.

It could also have applications in the field and also in slaughter houses where less effort would be necessary for a clean cut, without having to use too much pressure that the blade might slip and cut into a gut, or into your hand.

Another question is if there is a steel that, because of the chemical makeup, would be tough enough to hold the very sharp edge. I suppose there are steels, because of their micro and grannular structure, that can be made sharper than others.

I read where 440C was one steel that would qualify, because of the refinements made to the steel when used as surgical instruments, but I have no information to back it up.

If you could combine extreme sharpness with a steel with good toughness and abrasive resistance, I think you could make a superior blade. There might be steels available that would qualify. I just don't know what they would be.

With a surgical knife, edge holding would not be a large concern, because the blade could be replaced as soon as it got dull.

This is a serious question, at least serious to me. Not that I will ever use the information, but I would like to know, and I see no reason that technical information about how knives are made, and the materials, would be out of place on this forum.

Have you ever heard of a book titled 'Tool Steels', by three authors named Roberts, Hamaker, and Johnson?


To Larry:

Thanks for taking the time to research this. I hope you will find the time to make the measurements. I have tried with a 10X glass, but could not see it well enough to tell anything about it.

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#7062334 - 11/10/12 Re: Sharpness [Re: cranky72]
usull Offline
Campfire Regular

Registered: 06/15/11
Posts: 282
I used to touch-up Photo-masks ( by hand ) which had circuit lines which were 0.003 to 0.004 Inches wide . As I recall , that is about the width of a female human hair . Don't know much about Custom Knives , but you might be able to make some estimates of what the knife edge should be to split such a Hair . BTW , I have not been at all impressed with the few Customs I have purchased so far . They are beautiful , but NONE have been anywhere near Sharp enough to shave hand hair . With that said , I do not want to attempt Sharpening these as that would affect resale especially since I don't have a lot of experience sharpening . I'm looking for Recommendations on a Factory Knife that would fit my large hand ( maybe a drop point design , maybe not ) and be close to shaving hand hair sharp . Also as to where to buy it . TIA .

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#7062357 - 11/10/12 Re: Sharpness [Re: usull]
1234567 Offline
Campfire Guide

Registered: 11/26/07
Posts: 4320
I don't own any, but I know a person who collects those cheap knives made in China.

The ones I have handled are shaving sharp, seemingly much sharper than many of the American made knives. For a 4 or 5 dollar knife, they appear to be very well made. I don't understand how they can make a knife of that quality so cheap.

As far as how long the blade would stay sharp, I don't know. I don't know anything about the steel or the heat treatment.

As far as the sharpness of custom knives, there has been a lot written on this forum about sharpening and edge geometry and sharpness, and how much they can be used and still stay sharp.

I have made several hundred knives, and my experience, with the steel and heat treatment I use, just does not coincide with much of what I have read here.

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#7062751 - 11/10/12 Re: Sharpness [Re: 1234567]
cranky72 Offline
Campfire Regular

Registered: 12/06/11
Posts: 888
123456 you can rest assured that tn\he questions you asked have already been answered by manufacturing facilities the world round. you are wasting your time asking these questions on this forum. there have been thousands of books written on tool steels get up to modern times & research these---m390,elmax, 3v , 4v, k294. watch the videos of the chopping contests. your revelations wo'nt surprise any metallurgists of the last 20 or 30 years. i answered your question earlier.cranky72

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#7063230 - 11/11/12 Re: Sharpness [Re: cranky72]
1234567 Offline
Campfire Guide

Registered: 11/26/07
Posts: 4320
"you are wasting your time asking these questions on this forum."

If nothing else, I would have to agree with you on this. You did not answer the question. I don't think you even understand the question, and if you do, you have a funny way of answering it.

Someone said you were the expert on blade steel. I think that someone went off and neglected to tell you the truth.

Incidentally, I asked the original question because I wanted to know. I did not ask the question to listen to some of your know-nothing crap. I asked here because I thought someone with metallurgical experience might know.

Believe it or not, there are people in this world, and on this forum, who know things that you don't, and if these people do not know, they do not try to cover up their lack of knowledge by ridicule.

If you don't know the answer, why don't you admit it and say so, instead of trying to make yourself look smart and important by putting someone else down?

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#7063523 - 11/11/12 Re: Sharpness [Re: 1234567]
cranky72 Offline
Campfire Regular

Registered: 12/06/11
Posts: 888
well 123456 i can see you still have'nt counted the angels on the pinhead. your basis of knowledge has stagnated since the 60s. you are dumber than a brick but too unitelligent to realize it. my sweet potatoes have more sense than you.--cranky72

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#7064095 - 11/11/12 Re: Sharpness [Re: 1234567]
Journeyman Offline
Campfire Ranger

Registered: 11/18/03
Posts: 1559
Originally Posted By: 1234567
Does anyone know how sharp you can actually get a knife edge? I am asking about steel knives.

Also, does anyone have any idea on which steel will get the sharpest.

The reason I ask is because I have read that steel has grains in it, and the finer the grain, the sharper you can hone it, but that you cannot sharpen a grain. It would seem logical, to me at least, that the finer/smaller the grain, the sharper the blade is capable of getting.

Also, I have read that about 2 or 3 microns width is about as sharp as an edge will get.

Anyone have any input on this?


I, for one, enjoy your enthusiasm for the topic. But, with all due respect, you do seem to tend toward preconceiving the answer you wish to hear based on some limited amount of informal research. As has been said above, none of this is new.

With your keen interest you'd be well served to do more formal study, because frankly, not that many folks on a general message board are going to be that deep into the subject.

I'd suggest you get a copy of this book for starters: The Science and Engineering of Cutting

Pay particular attention to the sections on cutting edge geometry; and here's a clue: Your focus on edge thickness is off base. The grind and the angle of the edge bevel is more linearly related to your notion of "sharpness" than the edge thickness...

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#7064266 - 11/11/12 Re: Sharpness [Re: Journeyman]
cranky72 Offline
Campfire Regular

Registered: 12/06/11
Posts: 888
thanks journeyman for a courteous & intelligent input. i guess i've gotten too old to have much patience with idiots. cranky72

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#7065354 - 11/11/12 Re: Sharpness [Re: cranky72]
1234567 Offline
Campfire Guide

Registered: 11/26/07
Posts: 4320
"With your keen interest you'd be well served to do more formal study, because frankly, not that many folks on a general message board are going to be that deep into the subject."

This forum was a place to start. I thought that there might be a few engineers who are familiar with the subject and could answer my question.

Steel catalogs and web sites probably do research on what I am trying to find out, but I have never read anything in one of their catalogs about it, except for the remark I made about 440C and how it has been refined to make very sharp surgical instruments.

Look, I did not ask this question to get into a mud fight with Cranky, but it seems to be unavoidable, given his temperament. As far as being an idiot, any time he wants to compare IQs, I can do that.

Maybe we can let Mensa determine who would be the winner. I will submit my membership number, if he will submit his, if he has one.

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#7065462 - 11/11/12 Re: Sharpness [Re: 1234567]
antlers Offline
Campfire Outfitter

Registered: 06/02/08
Posts: 8537
Originally Posted By: 1234567
Maybe we can let Mensa determine who would be the winner. I will submit my membership number, if he will submit his, if he has one.

Don't bother. The fact that you guys are bickering over the schit that you are, on a forum for knife enthusiasts, would automatically disqualify either of you. No offense.
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#7065707 - 11/11/12 Re: Sharpness [Re: antlers]
cranky72 Offline
Campfire Regular

Registered: 12/06/11
Posts: 888
my 145 does'nt qualify for mensa but i can extrapolate 123456 to be about 95. i already told that idiot to call engineering at cal poly tech. he probably thinks i'm talking about dog food.--cranky72

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#7068178 - 11/12/12 Re: Sharpness [Re: antlers]
1234567 Offline
Campfire Guide

Registered: 11/26/07
Posts: 4320
Originally Posted By: antlers
Originally Posted By: 1234567
Maybe we can let Mensa determine who would be the winner. I will submit my membership number, if he will submit his, if he has one.

Don't bother. The fact that you guys are bickering over the schit that you are, on a forum for knife enthusiasts, would automatically disqualify either of you. No offense.


I agree. No offense taken.

If anyone is interested in knowing, I did find what I was originally asking about. It is one molecule, with a possibility of going on down to one atom thickness.

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