Repairing Edge Damage

S

SkepJ

Joined
Feb 1, 2005
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The search function's not working on the forums, so sorry for the new thread on this.

I was out cleaning brush today and accidentally hit my khukri's blade's edge on a large rock, which put a ding in the edge. How do I fix it? I've tried using the chakmak to burnish the bent/crushed edge back into shape before I sharpen the knife again, but I don't know if I'm using it correctly or not, since it's not working.
 
Skep, how badly is it out of line? If it's less than 1/16 inch, you have some hope of steeling it back in line. And probably not with the chakmak. The hardness of those is highly variable, mostly tending toward... soft. A butcher's steel is what I'd try, if you have one.
If it's out by more than that, or if it's crumpled (rather than out of line), you're talking steel removal (belt sander, diamond plate/stick, file...).

These are my experiences. Yes, you're not the first to hit rocks and things. Or dropping the silly thing. Umm, that's something I HEARD about, OK???
 
Aardvark said:
Skep, how badly is it out of line? If it's less than 1/16 inch, you have some hope of steeling it back in line. And probably not with the chakmak. The hardness of those is highly variable, mostly tending toward... soft. A butcher's steel is what I'd try, if you have one.
If it's out by more than that, or if it's crumpled (rather than out of line), you're talking steel removal (belt sander, diamond plate/stick, file...).

These are my experiences. Yes, you're not the first to hit rocks and things. Or dropping the silly thing. Umm, that's something I HEARD about, OK???
Click to expand...

Yeah, it's crumpled--I hit the rock dead on. Thanks, I should be able to fix it.
 
Before removing any metal, try beating the edge back into place/straight with a (small) hammer and anvil... it will help. I once hit a the edge of a steel beam with my Ganga Ram... :(


Mike
 
few years ago, repaired a BAS that had been abused. Actually ticked Bill M. off because the buyer had sent three different blades back after messing them up...no factory fault.

Here's the post on repair:

This will teach me to ask: "How hard can it be?

and thanks Bruise and ept for the kind words. I'm glad I didn't keep track of the hours working over the blade. If'd I had some 800-1200, could have brought up the mirror finish. The 600 grit did lovely, if time-consuming work.

Horn was Bag-Balmed...over and over and over. Filled with superglue in the scuffs and a crack, and then buffed with paste wax and a power buffer, steel (blade) done wet and dry, then paste waxed.

Edge? Stone, and steel and ceramic, little 600 grit to smooth the area dinged, then more stone, steel and ceramic.

Sheath didn't see much use apparently, just some neatsfoot oil to moisten it up.

It moves well in the hand. In another post, I mentioned that the AK is more blade heavy...the BAS has a better balance.

It was all, or virtually all, hand work. God love the kamis.


When you repair the blade, you may find that you feel a greater kinship to the maker. Owning, repairing, working with a tool builds trust.




Be well and safe.
Kis
 
Aardvark said:
Mike, won't that spot be inherently weak forever, though?
Click to expand...

Could be. I'm remembering Yvsa or Dave or somebody said beating an edge straight was an old trick (on a scythe?) and better than removing the metal. I could be wrong.


Mike
 
I would think that hammering the edge out at the damaged spot would weaken the steel that had been crumpled. However, I guess the alternative is to grind down the edge to flush. Either way the edge is going to be scarred or need a good bit of material taken off. It's easier said than done for me, but I would think that the best thing for a chopping blade that gets such damage would be to ignore the area and let it get sharpened out over time. A ding in the edge shouldn't affect the chopping performance. That way you don't waste a lot of good steel by grinding it off.

However, dings just bug the heck out of me.
 
Unless the steel is basically so soft it shouldnt be on a cutting edge anyways, beating a warp out of a cutting edge will almost always cause invisible cracks and stress points that will be weak. I de-warped one of my own knives a while back after an errant strike and got it back dead straight but a month later, i noticed a nice large chip out of the blade at the exact spot and shape where the bend was. It was no doubt caused by my repair. If i did it again, i would regrind the entire cutting edge PAST that bend....which would of course also require re-beveling the entire blade.

Unless you have OCD about it, I would steel off the high spot and let it be sharpened out over time....its not like youre whittling figurines with it:)
 
David Schott said:
Unless the steel is basically so soft it shouldnt be on a cutting edge anyways,
Click to expand...

that may be the case actually. the forward section of the tip and the recuve portion are sometimes as soft as the spine, depending on how the edge was hardened. almost always the tip and recurve/ricasso side of the edge is at very least noticably softer then the sweet spot, even if it was hardened tip to bolster.

just make sure that the spot thats been effected is actually an edge when your done though, not a flat spot. a flat spot will increase the speed of further damage to that area, because whatever hits it won't be cut in that spot, all the force of your swing will just transfer into the damaged/flat area. at least, it won't be cut cleanly.
 
LVC has a good point: the hardening of these edges varies greatly over the blades' length. It's at its hardest just distal to the primary curve, and softer both back toward the handle, and toward the tip. I find that the majority of my dents, dings, etc. happen out toward the tip, where the metal is softer. (I do not think this is a coincidence; the ergonomics of chopping are going to mean that the tip naturally gets a disproportionate share of such accidental contacts.) I've thus had good luck steeling near-tip dings back into shape; the biggest ones have benefited from a few light taps on an anvil with a small hammer. Now, if the damaged part is actually the main cutting portion, just tip-ward of the main curve, you've got a bigger problem. If the khukuri is properly hardened, it will be hardest, and most brittle, at that point; I've heard of Rockwell hardnesses in that part of the edge in the neighborhood of 60. You describe a crumpling, though, instead of an outright chip. If you got a mere big dent or crumple in the actual "sweet spot" main cutting area, I'd guess your khukuri somehow missed getting hardened correctly. But if you got a big dent or crumple out toward the tip, or back toward the handle, that's kind of par for the course for a heavily-used khukuri, and the hammering-and-then-steeling technique should address it well. As I understand things, this has to happen as a matter of course in the ordinary use of these knives, and I wouldn't regard the knife as very drastically damaged. Not new anymore, but I figure any "user" khukuri is going to take some hits out toward the tip, and that's the reason the tip is deliberately--even carefully--left appreciably softer than other parts.
 
Ad Astra said:
Could be. I'm remembering Yvsa or Dave or somebody said beating an edge straight was an old trick (on a scythe?) and better than removing the metal. I could be wrong.


Mike
Click to expand...

It was me, good memory Mike.;) :)

It sort of depends just where you ding the edge on a kukri. If it's further toward the tip where it's softer it can be steeled or tapped back into place and then smoothed out with a file or belt sander without any problems.
Actually by doing so the cold forming will cold harden the area just a bit. However the closer you get back to the hardened area the more likely the cold hardening will have a deleterious affect on the steel and the more chances of it being weaker in that spot.
Depending on just how bad the ding is depends on how I would fix it. If it were me I'd probably tap or steel it back in place in either case and take a chance on it.
So what if it breaks out later? You can always do what's needed to fix it to your satisfaction then. I don't like to remove steel unnecessarily.;) :p :D
 
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