How tough is your edge really?

Hey you guys I dont think he's looking to see what knife can chop wood better I think he's just looking to help people come up with good standard tests to do on knives to know which knives will dull quicker. Some people will say I went through 2x4 blocks of wood, hundreds of sheets of paper and it's still shaving sharp. But how is that any good way to compare it to others who do similar tests but material's are different?
Example:
Person A cuts 50' feet of normal soft 2x4 wood, while the edge is still sharp.
Person B performs the same test with the same model/series/brand, but comes out with only 25 feet of wood, and the edge begins to dull. It can mislead people into thinking the blade Person A is holding is superior for edge retention, however that may not be the case. What if Person B was not cutting the same wood as Person A, what if the wood he was cutting was considerably harder?

I think what he is looking to do is add science to the testing of edge retention, something people can continually repeat with similar materials.
 
Wolfjohn said:
Why would you want to chop 2x4s with a knife?

Man, I gotta go along with this 100%. Knives are a cutting tool- period. I've seen first hand, people using a Damascus knife to pry open a paint can lid and snap the tip off a $200 plus blade. I find that totally rediculous but, short of giving an a new owner of a blade and IQ test, I guess you just shake your head and shut up because it's their investment.:confused::confused:
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Chopping is cutting. Chopping is one of the puposes of large knives. There is no other reason to make knives with 8"-13" long blades and spines over 3/16" thick. I've seen a knife take a 2x4 apart with 2 strokes. That is what that knife was made to do. Knives are for cutting, but don't presume to tell the people making them what or how they are supposed to cut. Prying is the same. Some knives are designed to pry, and I made one for myself designed for batoning. It is perfectly acceptable to both the maker and the user to use them as designed.
 
good explination luis. that is exactly what he is trying to do. find a standard item that is available anywhere like at a lumber yard or sawmill or someone sellig firewood. i have a hard oak bench in my basement that i used to cut into with the knives i make to see how well the edge holds up by making a number of cuts and seeing if the edge dulled or still shaved. i knew that if it still shaved and push cut newspaper after making 20 or 30 deep cuts it was a good edge.
 
Chopping wood is not really a edge retention test as it is a geometry and impact test. I could imagine that most edge deformation would be caused by lateral stresses from the angle of the chop and not from the abrasive qualities of the wood.

Chopping wood is not really that bad on a edge unless its really hard. Its when your here "I cut" cardboard, drywall, carpet, sod, shingles, or any obvious harsh materal "and my edge still shaved" is when the truth might be being stretched a bit. There are some things that even the best of steels won't hold up to.
 
CPM M4 is clearly the best worker steel that I've encountered. I'm pretty sure there are better steels, but I'm not willing to pay for anything better than the top notch performance of CPM M4.
It held an edge, even after stupid amounts of abuse. I've pried on it beyond a reasonable limit for my top notch chisels and it laughed at me.

I haven't met a stainless that can be misused as much as M4 and still forgive as much as M4.
 
BostonBull makes some good comments. Many knife users and quite a few knifemakers aren't interested in their knives being used hard. They will say, "that's not normal use" and avoid the exposure that would drive them to make their knives better.
There is an artcle in Blade magazine (March 2011) "It's time for new knife tests". This is what Boston is talking about. With all the advances in steel and looks the real world tests haven't kept up. When you see the knife you adored that finished gutting, quartering and legging one animal without getting dull is eclipsed by the knife that will do 12 times that much you realize you settled for too little. It is time for better tests and somebody needs to lead the way.
 
i rely on what others tell me about the knives i make. brian jones made a post about the chopper i made. i doubt he lied about what he posted :rolleyes:. i know a 1/2 micron edge would have failed doing what he did. here is what he said and the link for anyone to check out.

http://www.bladeforums.com/forums/showthread.php?t=609189&page=2

After all these years collecting and using knives hard, richardj has become my secret weapon when it comes to edge profile and heat treat. I am still trying to dull the chopper he made for me, having chopped through tons of hardwoods, and chopping through drywall to remove it in a house I am working on.

After all that, it still shaves and cut me wickedly on one of my fingers...

Richardj has hit upon some secret that I cannot explain. His knives are the "immortals" of the knife world IMHO at this point. It is uncanny and has me pleasantly mystified.
 
Guess I should clarify that my opinions are based on the results that the Spyderco GB gave me - better than my top notch chisels.
Whatever the formula is for that steel, it's a feakin' winner.

Gimme stuff that's on that par and I'm all ears.
Gimme stuff that will clearly compete with CPM M4, ala Spydie formula, and you have a cheerleader with a bionic mouth.
Guaranteed.

me - a guy that can only comment on his experience with woodworking tools
 
Still stuck on that sharp knives don't last thing huh? How do you explain the 2 micron finish you apply through the wheels, Is it too sharp? Are your edges dulling fast after being polished?
 
I think it might be somewhat useful for testing things like resistance to deformation, but wood seems a little soft even for that. I think if there actually was testing done from one edge to another, and one steel to another, and so on and so forth that there wouldn't really be that much difference in the results.

I think it would be useful to have that kind of information personally because sometimes I don't make the best cuts and accidentally run the edge into something hard, and other times it's been something random like a staple in a cardboard box.

I could see how it would be useful to take something like a rod of very hard wood, and apply pressure onto it with the knife until it it penetrates to a certain depth, then check the edge. However, in my experience metal is the most common thing that I mess my edge up on, so it seems like it would be like a better idea to use something like brass or aluminum for that.

Though, I don't know if many people would be willing to test a wide variety of steel and knives likes this since you'd probably wind up doing some pretty bad damage if you put them on aluminum or brass. On the other hand, if even super hard wood wont' do THAT much damage to a knife, then it might open up a wider widow for testing than it seems like at face value.

Still, my overall interest in it is because of clumsy cutting mistakes. I'm not really sure if there's a lot of value in trying "idiot proof" a knife, so to speak... I've still caught myself "steel shopping" for the steel that I think would hold up to those mistakes the best though.
 
termiteslayer, to Mr. richardj.

I keep hearing how refined edges don't lass and roll and was hoping for a explanation.
 
BostonBull said:
I have been reading a lot on here lately, TONS of great info! I see a lot of guys say, i cut this many ropes, or this gauge wire, or hit this many 2x4's and MY edge still cuts hair, or still push slices newspaper, or will still cut free hanging news paper hung over the blade.


Well..............
I am an Arborist. I am certified by 3 different organizations, and am a geek with all things wood and chainsaw related. I got to thinking..... When we cut different species of trees with chainsaws some dull chains a LOT faster than other species. I began to wonder if there was a standardized test of wood species and their densities?


I spoke with a well respected knife maker/sharpener on the boards here and did some research. Thats when I found the Janka hardness test. This test measures the hardness of wood. It measures the force required to embed an 11.28 mm (0.444 in) steel ball into wood to half the ball's diameter. This method leaves an indentation. It is a good measurement technique to determine the ability of a type of wood withstand denting and wear. It is also a good indicator of how resistant it is to sawing and nailing. (I pilfered this from Wikipedia) Here is a link to the USDA page about Janka tests. http://www.fpl.fs.fed.us/documnts/fplrn/fpl_rn303.pdf


I found a list of 1700+ species of wood on the Janka test scale here...... http://www.morlanwoodgifts.com/MM011.ASP?pageno=207


Here is what I am thinking. Most 2x4's are Doug Fir, Spruce, or Pine, very low density SOFT woods! How much damage is this actually doing to the blade of a knife? Its a piss poor measure of toughness in my opinion. Lets find a species on the list that rates at 2000 or higher, Apple, some hickory, dogwood, Osage Orange, etc all rate above 2000. Then let that piece dry out just like they do on the Janka tests, and then hit it with your sharpened edges. After the hitting, does it shave hair? Cut newspaper? Cut a piece of newspaper draped over the blade just by bouncing the knife?


The key here is knowing the exact species you're using. Using Latin/scientific names is the only way to go. Too many species have the same common names, and common names are misleading. If you need help identifying your species let me see the leaf and or the tree and ill key it out for you.



So lets see what your edges have!!!
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Mr. boston bull I understand exactly what you are saying. These children are just afraid that their precious knives might break or chip the blades if they cut something worthy of testing the edge besides cutting a soft conifer species of wood. I have never saw this level of disrespect mixed with imaturaty on this forum till now. I get what you are saying and I am sure all the passing grades after cutting this soft stuff would fail by cutting something harder.

I was fitting a hickory handle to a Norlund hatched head I came across. Well I took my hand made bushcraft knife to just trim the edge a bit so it would fit in the head. Well a small fracture came off the side of the blade. I could not feel this with my fingernail and when looking for it with my loup I could hardly find it. When I did find it it was just a chip off of the side and it did not even leave a indentation you could feel with your finernail.

Why did I just say all of this. Because to show these people that all you are saying is if you really want to prove your edge is tough, cut something tough. Now isn't that easy to understand.

Now if I was hacking a piece of spruce in the same manor, my knife would never have fractured the edge. The first sharpening cleaned up the look of the edge. Funny you could see it but not feel it because it came off of the side and not the edge.

I hope you can bear what these people put out. :)

Kind Regards,
Daniel
 
BostonBull said:
not asking anyone to do anything. Loads of people on here, all higly regarded makers and sharpeners already use this style of testing as a "proof" of edge retention. Why not use a dense wood, instead of a piece of soft pillowy wood?
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I think you don't understand the purpose of the test. ;)

It's not so much edge retention as it is edge Strength.

Strength means the edge doesn't chip out, roll ect, that is what they are testing for. They are testing for proper HT and tempering of the blades, there is a balance they need to meet to pass that test.

There is a difference, a big difference and yes if the knife is sharp before chopping and the edge is strong it will still be sharp after.

Wood isn't as abrasive as Sisal or Manila rope.

Edge retention is usually tested by making slicing cuts, not chopping.
 
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I think a lot of peple who replied to the OP simply missed the point, or didn't understand the question. It was a good question and worthy of discussion.

The trouble is, edge tests are like car dyno's, they are not normally reliable as a comparative measure, but very useful as a relative one.

If 2 people have a 10" wood chopper and they are on opposite sides of the country they can get an idea of how well they hold an edge by chopping wood, and harder wood will be a harder test for them.

But the results still won't tell us much about which edge was "better" for anything but that specific test.

Now if people are testing with soft woods, as they currently are, and are able to chop through those woods with no loss of edge keeness, at all (apparently) then it's self evident that BostonBull is right, it's a useless test and we need harder wood.

No one would be impressed if I said I can use my knife to slice 100 cucumbers in half and still shave after? That's not a real test, it's practically an infomercial!

Maybe that's what chopping soft 2x4's is. A waste of time?

Chopping technique will probably have more impact on the quality the egde after choping than the starting quality of the blades edge did anyway.

The rope tests that Ankerson does seem well thought out to me, that's a useful, comparative test. Of the knifes ability to cut rope. Still, better than nothing and it gives an indication.

Regarding how to test "your" knife I think Unit is right, test it by doing what you plan to do with the knife.

Chopping wood is a great way to test edge toughness on a blade that wil be used for chopping wood but you have to admit, it's a poor way to test the edge retention of a straight razor, it just wouldn't make sense.

The line between a chopper and a straight razor is a wide and blurry one. One test cannot suit all knives.

I think that a "Standardized Test" for all knife edges is based on a false premise, that it's possible to use one test for many different blade shappes/sizes/steels etc.

Still, we like to have comparative measures and we should try and make them as useful as possible, IMO.

In my experience there are 2 aspects to how tough an edge/how long it willl stay sharp for a given task. Edge geometery and level of refinement.

My thoughts on that are here.

Best regards,

Steve.
 
This is a very entertaining thread. I see the OP point and I’d like to elaborate a bit.
In the edge holding, in my opinion, user cutting technique plays a major factor. In other words, person who never used a knife before would dull a blade much faster than an experienced one. Positioning of the blade, cutting angle, pushing direction and force all affect the edge damage and effectiveness of the cut.
Also there has to be a standardized measure of sharpness. To hear someone saying “the edge is still sharp” or “it still can shave” is not a good way to determine the exact amount of damage to the edge. Something that can measure the exact amount of force needed to be applied to produce a cut.
To go further, I think the synthetic material would suit much better for cutting tests than any wood due to inconsistencies of the latter. Manila rope is used by many testers around here and I think it’s a good way to standardize the test.
There is a very expensive cut testing machine some one from this forum has access to that I read about in one of the threads. I don't know if you can get any better than that to standartize.
All steels even with a good heat treatment would lose the scary sharp edge pretty quickly, at least much quicker than I would like them to. I’m ok with this fact, after all they are not diamonds.
To sum it up I don’t think that cutting hardwoods would necessary be a good solution to standardize or to speed up the testing to compare the blades’ steels as there are many other factors involved.
 
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