Edge failure... help

ACStudios

ACStudios

Joined
Apr 9, 2001
Messages
2,170
Hi all,

I screwed up a favorite khuk today, a Durba AK, chopping up my dog's xmas gift... a basted cow thigh bone... and wanted to see if there was any way to fix it.

I've chopped those bones several times over the years and haven't had ANY problems. This one must have been a bit harder than normal, but I wouldn't think it would damage an edge like this.

At first I thought the edge had just rolled... but then realized it had actually chipped :eek: .

edgefailure.jpg


This one was a gift.. and I don't really want to replace it. I don't have all of Wal's tools over here in Sheridan yet, but will by spring time. The chips go pretty far in on the edge.

Any ideas?
 
AC?

Looks like the damage I did on my Bura 15in AK on a deer fore-leg.

I just ground it out, and put a new profile on it. Worked very well, no noticeable loss of hardness on edge. The blade elegance was a tiny bit diminished, but nothing appreciable.

Raghorn has it now, and I think he uses it as a carry khuk.

The hardening goes up fairly high.


Shouldn't be a problem.
 
It may be just the lighting, but it almost looks hollow ground. Just needs to be reworked with a belt sander. Send it to me if you like and I'll fix it and send it back to you. It will be stronger when you get it back due to the convexing.

Merry Christmas Alan!

Don't let this little chip ruin this fine day.:) :thumbup:

Steve Ferguson
 
I would sharpen it and ignore the chips. If you smooth out the chips, you will have lost usable cutting edge. I'm cheap and don't want to waste it.

Yvsa is the bone chopping expert. I seem to recall him saying that no blade is immune to bone forever, or something like that.

Durba is not around anymore so you couldn't replace the blade easily.

munk
 
Don't worry. Some of us have done worse. This can be fixed.

Use a belt sander if you've got one (or files if you don't) and do as Kismet and Steve suggest. The hardened zone usually runs pretty far into the blade, so don't worry about breaking out of it.
 
Thanks guys. I'll see what I can do here when I get some of Wal's files back on this side of the Tetons.

Steve, if I can't get something satisfactory, I'll take you up on your offer.

Merry Christmas All!!!

Alan
 
Kismet said:
AC?

Looks like the damage I did on my Bura 15in AK on a deer fore-leg.

I just ground it out, and put a new profile on it. Worked very well, no noticeable loss of hardness on edge. The blade elegance was a tiny bit diminished, but nothing appreciable.

Raghorn has it now, and I think he uses it as a carry khuk.

The hardening goes up fairly high.


Shouldn't be a problem.
Click to expand...

I did the exact same thing to my 18" KNN AK a couple years ago (also on a deer foreleg bone). I took 1/8" off the entire edge and resharpened it. Today it performs as good as new and you can't even tell it's been reprofiled.

It was a fairly easy project, even for a neanderthal like me, Alan. Give it a shot, you'll be happy when you're done. Or if you want to, you can send it here and I'll fix it for you.

And Kismet? The Bura 15" AK is still my go-anywhere khuk. ;)
 
What the others have said. Grind it away slowly with a slow stone or a belt sander to avoid overheating the edge, reprofile, and sharpen.

Noah
 
Tools optimized to chop bone (really to crush and fracture it) have thick edges and are tempered softer than a blade intended for flesh and wood. I have two "bone cleavers" from a butchering plant. They would make lousy knives, but they do great on bone.

Poultry aside, don't chop bone with a knife. (Well, HD has his "Bone Cutter," but there is an exception to proof every rule.") Use a cheap axe.



NOMINEE FOR COMMENT OF THE DAY: "I'd give up my right arm to be ambidextrous."
 
Uwinv Alan you had just as well send it off to Steve and let him reprofile the khukuri. This happened because the edge was too hard and too thin for chopping bone. That's where an absolutely convexed edge is a must.
With the edge being that hard I'll be very surprised if a file will even cut it, probably just skate off.
The very few khuks I've had that happen too have been fine after reprofiling. Reprofiling gets rid of the too hard edge and brings the edge to otimimum, should still be too hard to file but soft enough to cut whatever you want from now on with a properly convexed edge.
 
Thomas Linton said:
Poultry aside, don't chop bone with a knife. (Well, HD has his "Bone Cutter," but there is an exception to proof every rule.") Use a cheap axe.
Click to expand...

seems i recall seeing the fiscars sport axe (small hatchet) for sale at many local stores (like wally world and target), for $20 - almost but not quite razor sharp out of the box, chops wood like crazy, and i wouldn't hesitate to chop soft wire, dirt/roots, stumping, stuff. ain't huge, but it's a champ, and at the price? what a deal. EMS or REI sells the same thing for $60-70, go figure. it's so small too, and light, that stowing one in a pack is a good thing.

sad note: it's the only axe i've seen for sale commonly that is SHARP at the get go. most everything else is utter and dangerous crap.

bladite
 
I'll put my two cents here :D I would suggest flipping your khuk over and using the spine to SMASH the bone...I've only had to whack bone once or twice-tuff s**t be better off taking a swing at a concrete block.
 
Can't you etch the blade to see how far up the hardening goes? Then make your decision on how to repair?

Thanks, Steve
 
The safest solution, honestly?

What Munk said. Fix the rolling as best you can with the chakmak or a steel, resharpen, and just keep going. Sooner or later the chips will be sharpened out.

My knowledge is limited but the only time I really get nervous is if the edge is deflected very badly (and the one time that this happened, I was able to beat it back into place with no further problems), the edge completely chips out deeply, or the chips are angular, creating stress concentrations that may possibly lead to catastrophic failure down the road.

Sometimes, for whatever reason, I hit rocks or metal or such and wind up with a chip missing, much like this one. In most cases I just ignore it. It won't affect function and it will sharpen out on its own eventually. Like Munk said, no reason to waste steel.

On a related note, the wood normally gets chopped and split in the driveway to make transportation and cleanup easier. I haven't sharpened my axe or maul in quite a while. They occasionally strike the pavement, so you can imagine what they look like. They keep working so I'll keep using them. (Although a sharpening at this point is probably a good idea, now that I think about it.)
 
munk said:
I would sharpen it and ignore the chips. If you smooth out the chips, you will have lost usable cutting edge. I'm cheap and don't want to waste it.
munk
Click to expand...

I agree with Munk. As long as you are not losing a SECTION of the edge and it's just chips I'd just sharpen it to where you have taken maybe a third of the width of the chips out and just use it.

I have a Ganga Ram beater khuk that originally rolled. I fixed it but have chipped it many times and even really burred it up when I chopped into a chainsaw chain where I was chopping a stuck chainsaw out of a log and I just took it back a little, to where it was really sharp again but where the chips were still visible and it cut fine.

Depending on what you cut, as time goes by (at least for me) you will end up completely sharpening the chips out. However like Munk said you are way better off to preserve that extra steel. I think the previously mentioned Ganga is nearly a quarter inch more narrow now after hard use and sharpening but seems harder temper wise than it was originally. However if I had completely sharpened out every chip it would be MUCH narrower
 
Hi Alan,

I think as Steve and Yvsa have said is the best advice. One of my favorite beaters is an 18" AK that Uncle Bill was selling cheap because it had a crack that went up into the edge a quater of an inch, (right in the sweet spot). I jumped on it as a chance to work over a khuk with little to loose if I screwed it up. I used layout blue on the blade,to make a visual line to follow, then reshaped the blade around what I had to grind out. The project was a great success and I think this is one of my favorite users. I reprofiled the blade following the original lines and I don't think most people could ever tell it was reworked, except I thinned out the blade to make it bite deeper with less effort. Anyway.......... I think this might be a chance for you to rework the blade and make an accident into an opportunity to explore your inner Kami!

Take are
Rick
 
Wow,

To me that is a bad heat treat. That edge was to hard. Chopping tools should be hard enough to do a good job, but not so hard as to chip like that.

The failure mode should be deformation or rolling, not chunks like that breaking off.

This is bound to happen from time to time with the "native art method" (non-scientific) heat treatment.

To me that is a blade failure and would fall under a warranty repair/replace policy. I realize that this will be a unpopular post.
 
Could be Jim, or it could be that the edge geometry was too thin for the job of chopping bones. Of course Yangdu would replace it, but as Alan stated, it was made by the kami Durba, who is no longer with us, and it was a gift. So I don't think Alan would want it to be replaced. So that's not an option.

AC, I have a Durba Chitlangi that I got from your dad. It's the lightest chit I've ever handled, and has a slightly concave, or hollow ground bevel on the blade. Maybe that was one of Durba's characteristics? I haven't been around enough to be real familiar with Durba, except to know that his blades were coveted.

As far as being unpopular, don't worry about that BigJim.

Steve
 
The edge was self-evidently too hard OR too thin -- for the material struck --with that force -- at that angle.

Buck used to demonstrate how he could drive one of his knives through a mild steel bolt -- just so. He didn't try to CHOP it in half. Tap, tap, tap with a hammer at a 90 degree angle. He told the group I was with that if the angle was "wrong" or the blows "too hard," he could be "embarassed."

There is no magic. There are trade-offs -- in design, in material, and in treatment. Railroad rail would be a better steel for a bone cutter. A thicker, convex edge would be better. RC 48 would be better.

Was the blade INTENDED to replace a bone cleaver or chisel?

Heavy bone is like concrete block - only tougher.

The "Dick" butcher's cleaver I have is almost twice as thick 1/8" behind the edge as the thickest-edged khukuri that I own. One can cut it EASILY with a file. It smashes up bone readily, but I would hate to try to cut wood with it.

And, truly, the heat treatment via the residual heat left in the blade after partial quenching is not like Paul Bros. It is craft and art rather than science.

I have a Durba AK. It has a convex edge. (I have been hiding it 'cause The Duck is known to seek out Durba khuks.)
 
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