What Scientific Tests Are Useful for Knives?

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me2

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Any suggestions? I know of CATRA edge holding, Charpy Impact-notched and unnotched w/ standard or reduced sections, torsional impact, bend testing-like for weld tests, wear tests, various corrosion tests, hardness, and tensile. I recently got an add from a lab we use at work for fracture toughness testing and categorizing, but I've heard of no one using it for knife related work.
 
That depends on the test. Most of the tests listed would have to have properly shaped samples of the desired steel with the desired heat treatment.

I'm basically trying to see how many standardized tests there are that relate directly to knives, in knife like shapes. So far, only Catra and the corrosion tests of some type can use an actual knife, and I'm not even sure about the corrosion tests. There are more than one and they may rely on weight loss of standard size samples for measured values. Hardness must be done on parallel portions, which limits how close to the actual cutting edge the test can be taken. The blade could be sectioned, but then its not testing the whole knife any more.
 
You could do interesting testing with edge holding and a SEM to show the edge as it wears. Good conventional pics would be good, also. Simplest test is to show wear versus number of cuts. It is hard to quantify a picture of an edge, though a pic tells a lot.

Add scale to measure force to cut, and compare pics of edge to force to cut (both versus # of cuts).

Do the same tests adding sharpness testing via more conventional methods (CATRA sharpness test or thread test) to see how they correlate with each other and force to cut.

Make two identical blades, sharpen both to the same edge diameter, but have one at 120 grit and the other at 10,000 grit. Test them to compare force to cut different materials.

Since destruction tests seem so popular, clamp and bend blades (using the same distance between clamp and force) until bent or failure. I don't think this test is very useful, but it would generate interest....

Do an endurance test simulating batoning - do 10,000 hit trials until failure or half a million hits. Or do 10,000 hits at a stated start temp, then lower temp 5 degrees for every 10,000 hit trial until failure. Could also increase energy of each impact until failure occurs - this would be much better than a steel hammer.

Do testing with identical blades, but sharpened at varying edge angles - test using above methods and compare force to cut versus # of cuts.

Just some rough ideas for some tests that would be interesting to me. And I would want to make comparisons, so the methods would have to be repeatable.
 
I have 3 blades freshly sharpened and ready for edge holding tests. I was thinking of isolating a section of blade about 1" long and using it to cut 1" wide strips of cardboard, in a 1" of blade to 1" of cut sort of slice, then seeing how long it took to get to 500 grams on a thread cutting test. All 3 will cut the thread below 100 grams now. I have a 4th that could be used, now that I remember my Delica that I freshly sharpened then never carried. I also have a 154CM griptillian HG, a Byrd Cara Cara and my trusty sandwich damascus Food Network knife. Broos, if you have any of these, we could do a direct comparison.

I've cut cardboard on a scale to see which knives took the least amount of force to make the cut. No real surprise, the full flat ground, 1/16" thick slipjoint blade sharpened at 12 degrees per side with 15 degree Sharpmaker microbevel was the winner. One surprise is my Benchmades keep out cutting my Spyderco's. It was interesting to see that the effort went up to about 5 pounds to start the cut, then dropped to 3 to keep the cut going, essentially staying constant after the initial cut was made. That trend held for all 5 blades tested, just the loads were slightly higher.
 
You could make a trip-hammer that uses common weights for impact tests. Still think you'd need a steel striking surface, though. Nobody wants to sit around for thousands of low energy impacts that should, in reality, have little affect on a well made fixed blade and only small affect on a folder. Then, too, what are you pounding the knife into? Wood isn't consistant.

Wear tests are interesting. I suppose you could run an edge on a slow belt sander of X-grit with Y-down force to speed things up. Measure weight loss or linear loss, I suppose.

To me, the issue is time. Few are willing to take more than a few hours to perform a test.

Cutting tests only seem to be moderately popular and have/are being done. The problems are media cut, edge finish, and actual angle of the edge.

I'd like to see some folder strength tests - in the opening and closing directions as well as from the side. Maybe some twisting for those of us who sometimes "drill" with knife tips. A simple guilletine type device could be used to apply force at a set distance from the pivot.
 
At home tests are good, and I have some ideas for edge impact testing. I was really thinking of established ASTM, CATRA, ISO, etc. tests that apply to knives. The tests listed in my original post are the ones I know of, but each has its issues when applied to knives. Corrosion tests are the most straight forward. CATRA edge holding has relatively few issues. The only ones I'm aware of are questions regarding differences between a machine held blade and a hand held one. Charpy is pretty good, but there are so many variations in heat treating method that applicability is very rough at best, unless the makers do their own testing with their heat treat procedure. Even then, the scatter in the data is quite large in hardnesses used for knives.
 
Oh, man! I wish I had been a knife nut back when I was manager over a large utility's materials/products testing facility! Had an impact tester, a 10 foot hydraulic test bed, all kinds of electronic/mechanical capabilities, etc.

Lunch time could have been a blast!
 
imho, only the tests runned in a lab are useful... all the other have too many variable
 
So do you know of any labs that run edge holding tests? That is kinda the whole point of the thread. Lab tests are sometimes not that related to knife use. The ones listed above are the ones most often associated with knives, but the only one that specifically addresses cutting with knives is the catra test. Also, even ASTM standards have variables that are not accounted for during the test.
 
I'm no professional knife maker, but when I do make a knife, I do certain tests. Most of the blades I make are fairly large, over 6" blade length.

As I work the blade on my grinder after tempering, taking it to final bevel and sharpness, I keep an eye on the steel to see if there are spots which are harder or softer than elsewhere, if the steel grinds faster or slower.

Then, I hit a wooden post with the side of the knife. I slowly but surely increase the severity of the blows, until it becomes clear to me that the blade will bend and then rebound, but won't stay bent. I also look at the handle and guard, etc., to make sure this shock test hasn't loosened them.

Then, I do a chop test. Here, I chop a wooden post, slowly increasing the strength of the blows. I use the whole blade, from just in front of the handle, all the way out to the tip. All the time I'm checking the edge to see if there are any spots that seem to want to chip, roll, or dull. I also continue to check the handle and other fittings.

Then I go to batoning. I baton the blade lengthwise through a wooden post, eventually using full strength on the baton. Again, I check the handle and fittings, and check the blade for straightness, and the edge for effect, looking for any loss of sharpness or rolling or chipping.

I then stab the point of the knife into a wooden post, and pry it out sideways, to check tip strength.

If the knife passes all these tests, then I consider it a success.

This may not be exactly what you are looking for, but it works for me.

Andy
 
I don't think that destructive impact testing is of much value unless you can get a an expert to analyze the failed specimens, and/or do 10 test trials of each knife. There is large uncertainty from knife to knife, so testing only one knife is not very reliable.

I would prefer tests that test durability with impacts, like a batoning test. Or tests of strength, which would yield a more reliable measure of how much force it would take to snap or bend the knife in different axis'.

Batoning tests could give one assurance that a knife will survive years of impacts, or years of impacts at cold temps. I suspect there are knives that can be batoned forever at 40 degrees, but could break easily at -10 degrees. As someone who hunts in the frozen North, knowing my knife will survive batoning at -10 is something that would be more useful than knowing some relatively shaky measure of knife toughness (which is what you would have from even a scientific and repeatable test of one knife). Like with the charpy test, the most reliable conclusion you will be able to make from impact tests is at what temp does the steel fail in a brittle manner (or at what temp it will break while absorbing much less impact energy).

Now to know at what angle a particular knife will maintain its edge the longest cutting a given material, and at what finish it will cut with the least amount of force, would be interesting tests.
 
Given the scatter involved and the wide array of heat treatments, my feeling is that the Charpy test is somewhat over rated. From my reading and research, the torsional impact test is much more reliable, but I've only found one lab that will do it.

My slowly developing ideas for edge impact testing would only test the edge. The whole knife would not be broken, unless there really was something wrong with it.

I agree that for one knife it really wouldnt be that useful. Thicker edges and steeper bevels handle impact better than thinner/shallower ones. No mystery there. What would be useful is to test several knives of similar design and intended use. Steels, heat treatments, blade shapes and such could be different. For instance, one could test the Browning Competition knife and the Becker BK9. The relative amounts of damage could then be compared to other tests for edge holding and ease of cutting to develop a whole package. Differences in geometry, weight, steel, hardness, etc. would have to be taken into account, but each of these is part of the overall design of the knife for its intended use. This would be limited to knives that I own or use, and could be used to sort out the best of 2 or 3 different designs used for the same tasks, or to optimize each design toward its strong points or away from them to give better general performance.

As to batoning, would you do that testing with a mechanical set up, or just by hand? It becomes a personal test if by hand. We all know any knife can be broken, but can I break it? If it takes 500 ft-lbs to cause failure, but I can only get 400, I could use it without worry. Of course, if you try this yourself and break it, you're out a knife. If it doesnt break, you'll wonder if the next hit would have done it.
 
You mention damage - what would be a good material for the edge to chop into? Something that would cause a little damage to all or almost all knives maybe. One material could cause abrasive wear, another material could be hard enough to cause edge damage (edge rolling and a hard chop into seasoned hardwood has to cause blade flex) - maybe some way of intentionally chopping the edge with an off-kilter chop?


Maybe with a batoning test, because the stresses experienced by the knife should be magnitudes less than impact testing that can cause fracture emanating from a point of impact, there is a better basis to do hand testing endurance type testing? With batoning over time, would the energy of all those strikes even out more and more the longer the test goes? I can start to convince myself that this is possible, but I think that without some way to regulate impacts, the same unknowns will crop up once it comes time to explain the failure.
 
Even when of a similar shape and from the same steel, the heat treatment means that a knife that cuts brilliantly on some materials may perform poorly on others - and with other knives it's the opposite. Any cutting test would have to be over a range of different materials for meaningful comparisons

You can test some parameters but ultimately there are too many variables, not the least of which is the ergonomics - how the knife feels to the person wielding it. Not sure how you'd quantify that since there is such a huge variation in physiques, grip and usage styles.

As to batoning - how do you ensure consistency on the material you're hammering the knive into? Of what relevance is a batoning test to a dagger that's designed for stabbing?

Ultimately, knife reviews and user feedback, subjective though these be, are what we come to rely on. Hence BF Knife Reviews
 
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