Munk Bowie edge failure

S

Skyler R.

Joined
Dec 27, 2005
Messages
1,068
I was out doing some chopping with my Munk Bowie from DOTD 10/27. I was going though some fresh evergreen limbs that where around 2" in diameter. After I did four limbs and I went to go clean the blade, I noticed a chip in the blade. The chip is about 1/4" long and 1/8" wide. It's only on one side of the edge and does not go all the way though (split the edge in half). The area is not in the same area that I was chopping in. I also noticed two places on the edge closer to the area that I was chopping in that had good sized rolled edges.

I inspected the branches to see if something hard could of caused the rolled edges, but I could find nothing in the limbs. As for the chip, I have no clue how it happened. My best guess would be that it was a forging flaw that could not be seen with the naked eye and that it came loose due to the shock of chopping.

I inspected the knife when I received it and again before I used it and I could find nothing wrong with the knife.

Here are some pictures of what I am talking about. Maybe someone more knowledgeable may be able to explain why it happened.

DSCF0053b.jpg


DSCF0047b.jpg
 
ouch... im sorry to hear what happened :( have you contacted yangdu yet?
i'll wait also to hear what experienced members have to say on what happened :thumbup:
 
Jaiofspam said:
ouch... im sorry to hear what happened :( have you contacted yangdu yet?
i'll wait also to hear what experienced members have to say on what happened :thumbup:
Click to expand...

I am going to email Yangdu shortly. Most of the reason why I put this up was to understand better what exactly happened.



Other then this the blade is great. I am amazed how much of a beast this thing is. The weight of 34oz really feels much heavier then it does on a kuk (or at least I think it does). The blade was going though the limbs in one swing, and the damage really surprised me.
 
She'll probably get you another one. No way this should have happened. Conventional blades are supposed to be fully hardened now, but not brittle.

Well, all I can think of is what my wise Momma used to say; "this too shall pass."

(Hopefully, not pass inspection, if they're flawed!!!)


munk
 
Even if you grind it back past that spot...it'll be one heck of a chopper!

It'd make a nice recurve too...I can picture what is inside it.
 
ah, and that's the really pretty one i still regret not snagging. it's better to write yangdu first i think, have her take care of you, and then report to us :)

well, that's an odd one... evergreen is way soft usually. definitely a forging issue, possibly going as far back as the source material having a flaw - maybe they've got a bad batch of truck springs? your end product is only as good as the source materials. a light hammer test of a blade wouldn't probably found this out. 30 seconds in the shop.

i keep seeing opportunities for "fixing" :) for someone with the right gear, this could be reground i bet, and possibly something nifty could come of it. it might need a new heat treat. right up koster lane so to speak :>

bladite
 
Yes, what Hollow said. Shouldn't have chipped like that or edge rolled for that matter. That thing is a beast indeed and a few branches shouldn't have phased it. Maybe someone else can salvage it, but would have to etch it to see what hardening is there.

Let Yangdu know ASAP.

Norm
 
I emailed Yangdu after my second post, just waiting for a reply. I am sure she is probably out having fun with her father, which is great.


It would make a great knife if someone reground it, and possibly rehardened it. After I send it back to Yangdu, it would be a good chance for anyone interested to pick it up.
 
Looks like some sort of inclusion or something to my untrained eye. It wouldn't take that much work to fix it--fifteen minutes with a bastard file, followed by some cleanup work, though you'll certainly affect the blade shape a bit. My concern is that the chip is indicative of a brittle blade, and potentially further failure.
 
Josh Feltman said:
Looks like some sort of inclusion or something to my untrained eye. It wouldn't take that much work to fix it--fifteen minutes with a bastard file, followed by some cleanup work, though you'll certainly affect the blade shape a bit. My concern is that the chip is indicative of a brittle blade, and potentially further failure.
Click to expand...

15 minutes? you're the fastest in the land then :)

that's a lot of stock removal end to end, and then you've got to keep it perfectly straight, aligned, and more. doesn't include sharpening. nor addressed the heat treat or potential other issues.

bladite
 
I second the thought that there was an inclusion or flaw in the steel that it was made of. I don't feel that this was a forging a flaw, although it could be a cold shut from when they first started forging in the bevel.
 
Wow. I'm always amazed when I see stuff like this. SteveO is probably right. A small cold shut can be hard to detect.
 
Send it back to HI for replacement or refund.
Sorry
 
Looks like a second horizontal partial crack to me in the close up picture to the right of the chip.,& slightly higher.


Spiral
 
spiraltwista said:
Looks like a second horizontal partial crack to me in the close up picture to the right of the chip.,& slightly higher.


Spiral
Click to expand...


I checked that out after looking at the photo closer. It's really just oil, same with the spots to the left of the crack.


Thanks Yangdu, I will get it out today.


---Edit : After looking even closer at the area that Spiral was talking about, it's not oil like I first thought. It does seem to be another crack starting to form. Because of this I don't think that it was a problem with the steel to start with, but rather it was just over hardened. I am kind of surprised that it would be over hardened since it came from Bura, I have always found his heat treat to be great.

This still does not explain though why the edge rolled though. If it was so hard it would of cracked rather then rolling.


Maybe there was still a problem with the steel to start with, who knows (anyone?). I would be interested in seeing what someone experienced would say about it if they had it in hand and could do some tests on it.

Thanks for the explanation Flournoy.
 
My first post.
From what I can see in the photographs it appears that the blade is too hard. Possibly was not drawn back to correct temperature after hardening. Is this a laminated blade? I don't think it could be a cold shut, as someone suggested, as this can only occur when you are forge welding layers of metal into one piece and you have a spot where the weld fails.

This is not going to be a simple, quick easy fix. If this was my knife, I would remove the handle, reheat blade to a cherry red color and pack in vermiculite, wood ashes, or some type of medium to cool the blade as slowly as possible, may take more than one try. You need to get the entire blade back to a dead soft condition. When a file will readly cut any where on the blade, you can reprofile and regrind the blade. When the edge is ground, don't grind to a sharp edge. Leave the edge about the thickness of a dime. Sand blade to desired finish ,up to about 220 grit. Heat blade to nonmagnetic, about 1450 deg. F., quench in 150 deg. F., heat treat oil, this can be homemade (burnt motor oil & new oil mixture , etc.)

If this blade is 5160 (spring steel), after the above treatment it will be so hard that a NEW file will barely scratch it. This is too hard and will not make a good usable blade. This is the critical point in your heat treat. You must reheat the blade to the point where you are starting to take hardness out of the blade. The closer you heat it to 1450 deg., the softer it will be. My blades are heated to 365 deg. F., for one hour. Try the edge with a new file, if it will still not barely "grab"the cutting edge, raise your temperature another 25 deg. and try again. Continue doing this until you feel the file just beginning to cut the steel.

Now you can carefully, grind the edge to a sharp condition and test your blade on a good hard piece of wood to see how it holds up. If it is going to fail, you need to know now, before you put any more time into finishing the knife. Like I said, this is not going to be a simple 10 minute job to save this blade.

A simple regrind may or may not work. How much of the cutting edge is too hard? Was blade edge quenched or full length quenched? Is the tip too hard? I would not worry about answers to these questions and just start over again.

This is a very nice blade, beautiful fullers. I would try to save it.

I am one of the instructors at the ABS School. Passed Master Smith test in 1992. Taught numerous courses on Basic Forging, Damascus, and Handles and Guards. The above quickie explanation is exactly the way the ABS teaches beginning students heat treating. In my classes, we spend at least 2 days,trying to learn the basics of properly heat treating a blade. Not a simple task.

This is just my opinion, based on what I can see in the photos. This and a couple of bucks will get you a good hot cup of coffee at your nearest Starbucks.
 
flournoy,

Thanx for that post,
I'm a knife making n00b.
Your post explained that quicky heat treat nicely :)
 
flournoy,

Awesome first post. Stick around, we can learn stuff from you!:thumbup: :D

Regarding the Bowie, that is just too bad as that is a beautiful blade. Yangdu is making it right. Can't wait to see how the replacement blade performs.
 
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