Edge angles, you have nothing to worry about

PeteyTwoPointOne said:
Especially if it got the Gerald Busse protocol...;)
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well we certainly don't want this guy HT'ing a knife

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Cobalt said:
The meaning of that is lost on me. What did you mean?




or better steel and HT. like what happened above. But overall yes, you can take on damage. The difference is how much damage. The ka-bar suffered gross failure in 1/3 the time of the other two which took on moderate damage.
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I meant the broken blade would make an awesome Wharncliffe blade. I was also referring to individual blades, not when compared to others. Any given knife can cut wood at a relativity low angle. However it's not usually the wood that's the problem. The user of the knife will determine how low an angle they can go before the risk of damage is too great. For example my reground Barong was initially just a toy basically. I cut water bottles, free hanging rope, and store bought lumber. Then it started getting used for pretty rough work, like limbing, metal cutting a time or two, root cutting, clearing saplings near the ground, cutting weeds near the foundation walls of the house etc. The damage went up but I didn't want to lose the cutting ability, so I just let it go and I'm ok knowing there is always a nick or ding in the blade that will eventually sharpen out.
 
me2 said:
I meant the broken blade would make an awesome Wharncliffe blade. I was also referring to individual blades, not when compared to others. Any given knife can cut wood at a relativity low angle. However it's not usually the wood that's the problem. The user of the knife will determine how low an angle they can go before the risk of damage is too great. For example my reground Barong was initially just a toy basically. I cut water bottles, free hanging rope, and store bought lumber. Then it started getting used for pretty rough work, like limbing, metal cutting a time or two, root cutting, clearing saplings near the ground, cutting weeds near the foundation walls of the house etc. The damage went up but I didn't want to lose the cutting ability, so I just let it go and I'm ok knowing there is always a nick or ding in the blade that will eventually sharpen out.
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Lol, about the wharmcliffe. It was stupid of me to throw it away. But I was initially very disappointed with that blade.

quite true. Unfortunately, when you see people take edges down to 10-12 dps, they are not taking into account rocks or hidden nails, so you are absolutely correct. The other issue is knotts. I have cut through knotts that felt as hard as steel and some that didn't feel any harder than regular wood. Knotts are the big unknown anytime you go into them.
 
Thanks for the test cobalt!!! Please include some picks of the leaner meaner once you reprofile it!!! Im anxious to see it. Its good to know that the thin profiles still stand up to crazy test, but you are very very correct about those damn knotts.
 
Azula Gun Holsters said:
It was best that you threw it out otherwise you would be disappointed all over again every time you saw it.
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no kidding.



freehouse32 said:
Thanks for the test cobalt!!! Please include some picks of the leaner meaner once you reprofile it!!! Im anxious to see it. Its good to know that the thin profiles still stand up to crazy test, but you are very very correct about those damn knotts.
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knotts can be vicious
 
When they got it, they said it was not bad at all. the damage was between 1/16 and 3/32" deep so not bad.
 
freehouse32 said:
Wow!!! looks like nothing ever happened!!! Any luck on finding out how they repaired it?
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I don't mean to play captain obvious here, but clearly they can't add metal back into the blade, so the only other other option is that they ground the blade back beyond the depth of the deepest defect. No one can grind polish and sharpen like the Busse crew.
 
Cobalt said:
Lol, about the wharmcliffe. It was stupid of me to throw it away. But I was initially very disappointed with that blade.

quite true. Unfortunately, when you see people take edges down to 10-12 dps, they are not taking into account rocks or hidden nails, so you are absolutely correct. The other issue is knotts. I have cut through knotts that felt as hard as steel and some that didn't feel any harder than regular wood. Knotts are the big unknown anytime you go into them.
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While I agree, it's not just the edge angle while chopping wood: Low sabre grinds can also be taken down to low 10-12 degrees edge angles (especially if hollow ground), but they will generally hold up against chips better because the blade "flares" more rapidly just above the edge: This means the slightest twisting error in pulling out (which accidental twisting is almost inevitable to some degree) will have that "flare" "spreads" the wood more above the edge, and relieve the edge itself from the most pinched area into cracking a chip.

People think chips occur from a too thin edge while going in the wood: In my experience, chips in wood typically come in pairs: This means they occur as the blade is pulled out (which is always a less perfectly straight pulling motion than going in)... The pairing is because they are the outer ends of a slight twisting motion inside the most tightly "pinching" wood portions, so both outer-ends of the most pinched edge portion get chipped simultaneously.

This below occurred on a knife in 5160 at 12 degrees per side: Notice how the edge is intact near the center of the two chips, because the center of the rotation has less movement near the center, and more movement going outward from the involuntary "pivot" (the red line):

PA150197_zps1xpwron01_zpsy905dism.jpg


Another thing is that very wide (1.7" plus tall) Full Flat Grinds that also have thin edges (0.020") appear more vulnerable to chipping than sabre grinds or narrower blades, because the blades being taller they sink deeper, and pinch the edge more deeply and tightly, but, since the cross-section thickens less rapidly above the edge, they leave that edge unprotected from lateral twisting movements: Their overall thinness makes involuntary twisting easier when pulling out...

A full flat grind blade nearing two inches wide, and brought as low as 12 degrees per side, needs an edge at least 0.030" thick at the shoulders, or even more. Even just chopping wood.

And it is true knots are unpredictable, and can appear out of nowhere... They are often a complete surprise while halfway through... If you like a good slicer without chips, then it is best to start over elsewhere...

Gaston
 
mach 5 said:
I don't mean to play captain obvious here, but clearly they can't add metal back into the blade, so the only other other option is that they ground the blade back beyond the depth of the deepest defect. No one can grind polish and sharpen like the Busse crew.
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It does look obvious, but you never know when they utilize something different instead of "just" a regrind. I can do a regrind, it won't be as skilled or pretty as them but I can do one.

Everyone knows a regrind was in the picture... I was seeing what was beyond the obvious. Because even though there was damage where the chips occurred, the whole area most likely suffered some level of degradation that was not visible to the eye. That's really where I was going. What did they do if known to correct the "other than obvious" damage.
 
freehouse32 said:
.... Any luck on finding out how they repaired it?
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Looks like they had to decrease the angle of the primary grind to erase the dings.

The net result looks like it probably made it an even better slicer in addition to the more handsome grind lines. :cool:

......

Also, Gaston's observation lines up exactly with what I've experienced. Poor chopping technique leads to more edge damage than full on steel failure during reasonable use.

Getting tired, or being lazy and stirking the target with a sloppy off kilter chop has caused some dings also.

But it is surprising to some how much techinque is required to pull a blade out of a cut without chipping out the edge. "Wiggling" the blade side to side on a horizontal axis out of the cut is usually the culprit behind such damage.

Of course, hitting hidden staples, grit, or piths, and such can cause some deformation too.

Watch some of Rob Stanley's chopping vids about how to avoid chipping out your edge whilst chopping.

I've noticed he almost always works the blades out of the cut by levering it on a vertical axis, or else uses inertia of the block of wood to pull itself off the blade by banging it down on his chopping block. That is good technique. :thumbup:

And he's renowned for chopping into some exotic, very "hard" hardwoods! :eek: But I don't recall ever seeing him deform any edge during use.

But having said that, I've found INFI with substantial edges optimized for chopping, ca. 15-20 dps, will rarely show any damage at all in clear wood chopping even with the poorest of poor technique. That's just one reason why we love it! :D
 
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freehouse32 said:
It does look obvious, but you never know when they utilize something different instead of "just" a regrind. I can do a regrind, it won't be as skilled or pretty as them but I can do one.

Everyone knows a regrind was in the picture... I was seeing what was beyond the obvious. Because even though there was damage where the chips occurred, the whole area most likely suffered some level of degradation that was not visible to the eye. That's really where I was going. What did they do if known to correct the "other than obvious" damage.
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This is a good question as to whether the knife receives some kind of inspection such as eddy current testing before being returned.
 
Buyer used to do dye penetrant testing on some steels after a few blades got out with material flaws. Haven't heard of any more problems since that issue was solved
 
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