Does previous beatings weaken the blade all around?

N

NeedItCheaper

Joined
Jun 17, 2012
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I like to test my Fix Blades heavily before I take them out.......

My question is, if I test them in hard use situations to check for proper heat treat and other issues....Does that increase the likelihood of that blade failing in the woods under similar situations(Actually I usually use my Fix Blades a LOT lighter in the woods). This is assuming of course that the blade was not heated up, or bent to the point where it did not bend back on it's own. Like a 5-10 degree bend through wood where the blade just bounce back without me having to bend it back.





Don't respond about batoning, this is not a question about batoning.
 
No. As long as you don't damage the blades during testing, you should be fine.
 
Please explain what testing under hard use situations mean exactly.
 
The thing I'd worry about is internal cracks that might come about during excessive impacts/shocks to the blade (and there's no way to tell what's 'excessive' until after the damage is done). If the blade doesn't break during testing, those cracks might not be noticed until the blade snaps under a 'light' load at the worst possible moment, when you're actually out in the woods, and need the knife the most.


David
 
Oh ye of little faith! I would just trust the MFG to produce a good knife if I was not planning to use them as hard in the woods as I would "Testing" them. Just my dos centavos worth.

Omar
 
I've seen some guys really Abuse a knife in a Test format. Trying to make it fail. Also, knife steel information found on Charpy tests may be useful before testing. DM
 
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Using someone else test loses half the value of the test in the first place. You want to know if the company gave it a poor heat treat or note. These is also a chance of a hair line fracture, and I'm sure other stuff.


I like to do batoning. To the point where the blade bends a little. Also I hack on small saplings with it.







Don't respond about batoning, this is not a question about batoning.
 
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If these 'tests' are about heat treat there are other methods for determining this. By all means enjoy yourself and please use your own knives. DM
 
I often wonder this exact question as well; I'm pretty rough on my fixed blades and don't want to get hit with an unexpected break/failure due to overworking the knife...
 
David Martin said:
If these 'tests' are about heat treat there are other methods for determining this. By all means enjoy yourself and please use your own knives. DM
Click to expand...

Actually I really am interested in this method. Care to share




Note: I'm note talking about a companies heat treat method, I'm talking about when a genuine mistake was made with the blade. Also this whole hair line fracture business, I don't even know how that can get into a blade that is unused.
 
Cutting test(cutting sisal rope) reveal much about heat treat as well as sharpening and how the burr can be removed. Also, as mentioned one can look up and read Charpy test results. Then theres cutting results based off CATRA test. These last two are far more white coat than anything we do. Just whittling hard woods (making tent stakes) will inform one about many items of the knife steels heat treat. DM
 
NeedItCheaper said:
(...) Also this whole hair line fracture business, I don't even know how that can get into a blade that is unused.
Click to expand...

It can get into a blade during testing, if the 'testing' involves any impacts/mechanical shocks to the blade. A bad heat treat or quench by the maker can also create cracks in the steel, if the hot steel cools too rapidly.


David
 
Yes and they can also be introduced From Shock. A steel cooling too rapidly is shock. But there are other forms as well. DM
 
This is a complex situation that probably doesn't have a good answer.

In general fatigue of a material takes thousands of cycles of stress. In other words you bend something, let off, bend it again, let off, eventually it initiates a fatigue crack and with more stress cycles that crack grows until you get a failure. And this can take thousands or even hundreds of thousands of stress cycles. In the worst case with materials like aluminum it takes maybe hundreds of cycles. In college I tested bolts in fatigue by bending and by stretching. We had bolts in a test machine that cycled the stress and I would check them periodically with an ultrasonic machine to map out the intiiation and growth of the cracks. But another case study involves the British Comet aircraft whose fatigue cycls involved pressurization of the cabin during takeoffs. The aircraft failed after a certain number of flights and crashed into the Atlantic Ocean, opening the way for Boeing to become the leading supplier of jet airliners.

I suspect that the stress cycles of knife testing can be higher and can lead to cracking much faster. I've watched the destruction videos on youtube from that previous knife testing site and he had knives that would fracture at fewer cycles than thousands, or maybe fewer than hundreds. I can only surmise that he had high stress levels due to shock, and stress concentrations on the blades that caused high stress levels. At knives that have sharp corners where the tangs meet the guards meet the blades, this can be a real problem and some fractures happened there.

But I have to say that the answer to the question is YES, hard testing can increase the likelihood of a blade failing in hard use. Previous to seeing the Noss tests I would have answered this differently. My experience as a structural engineer would tell me that hard testing only used up a very small percentage of the potential life of the material, but after viewing the Noss tests I have to conclude that hard use of a knife combined with the possible configuration of the knife provides a useful life that can be pretty short.
 
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