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Author Topic: tuna can test!  (Read 1465 times)
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jared williams
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« on: August 26, 2009, 08:22:00 AM »

here's a test for you guys to try out sometime.open a tuna can with your knife and watch for edge chip.
    in my line of work i spend about 18 days a month in the woods camping. because of my job i get a huge amount of knife testing done every month. a couple weeks ago i was up about 10500 ft. in the high uintas making some dinner and we didn't have a can opener so i took out my knife and went to town opening up a tuna can. the knife i carry right now is the one i posted up that had the handle break on me. the handle is holding up great now that i fixed it. but back to my test. this knife passed all my criteria for an HEPK, it edge flexed 7 times both sides and cut around 300 or so on rope...not to bad... as i was cutting open the tuna can i noticed tiny little chips coming off the edge and was completely surprised because of how well the edge flex went on the blade. i pulled out my stone and refurbished the edge to a steeper edge bevel and solved the problem....when i got home i played around a little and found that when i initially ground the edge to a zero edge it was a little to shallow of an edge and there wasn't enough meat just behind the fine edge to support it when i was cutting and cranking the knife around the can. when i open cans with a knife i push the knife into the can than i crank the knife around the lip of the can which puts a lot of force on the edge.
basically i am levering the edge of the knife on a tiny little edge created by the can lid being cut (if that makes sense).
     this week i had no problems with my edge chipping. i wondered if it was faulty testing or faulty tempering that allowed the edge to chip.after playing around i realized it was improper edge geometry for the job i was doing. one more lesson in the book. there is no one way to sharpen a knife. every knife for every job for every person needs to be sharpened for that persons need. i have no doubt that someone else could have used my knife before i opened up that can and could have opened that can without chipping the edge by his cutting technique...i custom sharpen my knives to cut for my style and use of a knife. several people i work with ask me what is the right way to sharpen a knife and i tell them to practice with what works for them and then to stick with it....there is no right way to do it there is only your own way.
     the more i do real world testing the more insight i have to put into my knives. i don't make very many knives and every knife i make i do my best to make that much better than before, and it is regular real world testing that helps me on this path....that and destroying every 10th knife i make Grin    

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Ed Fowler
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« Reply #1 on: August 27, 2009, 02:43:24 PM »

Jared: I highly applaud your evaluating your blade in a real world situation. These are the kind of tests that we as knife makers need to do and naturally share our experiences with others for this kind of experimenting leads to discussion about what really counts in knife performance.

Many consider blade geometry as three choices, hollow, flat or convex grind, this is highly simplistic. Each blade must be carefully designed to match the work it is intended to do, these considerations need a lot of input for the correct decisions on the part of the maker, as well as the client.
Thanks Friend
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