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#1
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destructive testing
I finally decided to make a knife to test to destruction. Now that i have my data I'm not really sure how to interpret it.
1 shaved arm hair, no problem 2 The 100 cuts through sisal rope went fine and still shaved afterwards. 3 point drove into a 2x4, and twisted out multiple times without issue 4 bailing wire chop. This is where im starting to have questions. i chopped through bailing wire at 4 points along the 4" blade. It cut through the bailing wire each time, but left a mark on the blade. looking closer it appeared that the mark was from the wire rubbing on the blade. under 100X magnification i could tell it slightly rolled the edge, the roll was very obvious under 300X. When preforming this test is a pass when no damage is visible by the naked eye or is magnification used? 5 bending in a vice, is there a typical blade thickness for this test? my knife was 3/16" thick, i got about a 30 degree bend before it snapped. The first time it snapped at the point that came in contact with the vice jaws (clamped 1/4 way up the blade). The second time it also snapped at the point that came in contact with the vice jaws (clamped at where the 1/2 way point would be prior to the 1st bend test) 6 For kicks i used the remaining knife and chopped 1/8" brass rod, 16d nails, and a 3/8" steel tent stake. The brass was no problem to cut through, but the nail and tent stake would be driven into the log before being cut through. A quick pass over the belt sander after the brass and nail got the knife to shave again but the tent stake took its toll and the knife was laid to rest. Taking the bend test and bailing wire into account would this knife make the grade? if not does anyone have any suggestions for the next destructive test knife? |
#2
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First, you forgot to tell us what steel was used. Aside from that, I'd say whatever steel it was it did pretty good.
Sounds like it did well on the bailing wire. If it had been harder it probably would have chipped. Softer, the roll would have been easily seen by the naked eye. We don't usually make knives for the purpose of cutting wire so, to me, that one performed reasonably. As for the bending, the blade pretty much always breaks at the vice jaws. This is especially true if you failed to pad the jaws with a bit of wood or Micarta which, I'm guessing, is the case here. The hard steel (or brass) edges on the jaws will cause the blade to break sooner than it would if it were bent cleanly. Bend against a piece of wood that has a gently rounded edge on it. You didn't mention is you used a breaker bar - an extension on the handle. If you did, then your blade did as well as it should against a steel vise jaw (or anything else, really). If you weren't using a bar then you probably shouldn't have been able to break the blade unless you are, literally, as strong as a gorilla. Again, without knowing the steel, what you got seems like reasonable performance under the assumed circumstances... |
#3
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The knife steel was 1075/1080 from admiral steel. I never thought to pad the jaws, and i used an 8" adjustable wrench with a pipe over the end for more leverage
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#4
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A 30? bend before breaking sounds pretty good. I know the ABS performance test says 90? but that's to test a blade that has differential hardening or tempering. I would say that your knife stood up to more than what should be expected of a knife. You didn't say what size sisal rope you cut through but 100 cuts and still shave hair would indicate good heat treatment and good geometry. I don't think that you need to find any other ways to destroy a knife.
Doug __________________ If you're not making mistakes then you're not trying hard enough |
#5
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Awesome man! I did a sillier test on a failed 1095 blade and I'm glad I did. It tought me not to take things for granted thats for sure. It failed horribly on everything but the bend test. I was able to bend it almost 180 degrees before it cracked! That's when undecided canola oil wasn't going to cut it with the steel I had.
To me (still a green horn) it sounds like its up to par that's for sure. I would rather have the edge roll like yours did rather then chip. |
#6
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Thanks for the feedback guys, its nice to feel like i am finally making progress with the HT. It has always been a point of concern for me.
I believe the sisal rope is 3/8" or 1/2" |
#7
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I was holding the HT temp a little low hoping if it didnt work it would chip so i could have another go at getting the HT temp right. I would hate for the edge to roll out bad and have to re quench and do it all over again.
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#8
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That's a good idea actually. I should try that next time.
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#9
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Sounds like a good knife to me.
The 30degrees on the bend test sounds about right for a through hardened blade. Keep in mind there are a lot of variables here. Like others mentioned wood in the vice can help you get a few more degrees before breaking...differential hardening can literally double the degrees in the bend test..a thinner/wider/longer blade will bend further than a shorter/thicker/narrow blade, etc. Of course the alloy and hardness play a huge role. WHen cutting rope there are 2 ways to do it...slicing the rope, and push cuts. Using the slicing method you can get a lot more cuts. You can also do the cuts on top of a scale and measure how many cuts before you have to push with a certain amount of force. For example see how many cuts you can do before the scale reads X amount of pounds in pushing force. Another test i like to do is hack into hardwood, then torque the blade to the side when removing it. When I get to the destructive stage I will hammer the blade into wood, then hit the side of the blade with a hammer to see if I can pop a chunk out of the edge. Hacking up cement blocks is fun. It's not the most realistic test but its fun and it can show you if your edge is too hard, too soft, or if meant for extreme hard use tasks..too thin. Some people really like batoning the knife through wood. But honestly the best test you can do is use it for its intended tasks. Bending 90degrees, cutting hundreds of pieces of rope, etc sound good on paper but you can find out a lot by just using it. |
Tags |
1095, abs, awesome, bee, blade, brass, edge, hammer, handle, horn, how to, knife, knives, make, making, man, micarta, rod, steel, vise, wood |
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