Tang failures!

Bill Martino

Bill Martino

Joined
Mar 5, 1999
Messages
34,096
As most of you know who visit the forum and as HI customers know I am not given to hiding things or to dishonesty. I try to tell it as I see it so here's some information I am not happy to post but I feel it is part of the deal so here it is.

For 11 years the worst failure I've seen on any HI khukuri is a cracked handle. That's it. No blade failures of any type except the 1/4 inch tip lost on Julian's purple heart khukuri and that is still the case. But in the last three or four months we have experienced two tang failures and this has me totally me baffled.

The tang on a 20 inch Sirupati from shop 1 failed and the handle separated from the blade. I thought this was something that would happen only once in 11 years and maybe every five or six thousand khukuris so I wrote it off. I replaced the Sirupati with another from the same run and it has been going strong for four months and will probably keep on going. But then I got email today telling me the same thing had happened on a BAS from shop 2. Same type failure at almost the identical place. Different shop and different kami, different size and style of khukuri, but same failure.

This has me deeply concerned and absolutely puzzled so I am asking for help. Why do we go 11 years without any failure of any type and then get two almost identical tang failures in four months? Blades are fine, handles are fine, but the tang fails. What's the reason for this? I am searching for some logical explanation and I can't generate one. So if anybody has any ideas as to what could cause these tang failures let me hear them so I can pass the information back to both shops.

Of course, I am going to alert both shops to these 2 failures this weekend when I call but I have no suggestion to give them as to what to do to correct whatever it might be that they could have done wrong. I hope somebody has some ideas.

Uncle Bill


[This message has been edited by Bill Martino (edited 09 July 1999).]
 
I don't know much about the process the kamis use to make the khukris, but could it be possible that the springs had stress failures already that simply weren't reduced by the forging process? I don't know that much about steel, but it is an idea. As far as the timing, chalk it up to coincidence, I guess! Couldn't be bad karma!

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My Custom Kydex Sheath pagehttp://www.geocities.com/CollegePark/Lab/1298/knifehome.html
Palmer College of Chiropractic
On Two Wheels
 
:
Day-um Uncle Bill.
What a bummer. I have never heard of a rat tail tang failing,except when one had been welded on and the weld had an impurity in it.. Occasionally a tapered tang might fail if there is not enough material or a forging fold towards the thin end.
The odds are against it,but could there be two different Kamis in two different shops that maybe forge welded the tangs on instead of forging and drawing them from the stock material?

I think it would be difficult forge welding a rat tail to something as thick as the back of a Kuhkuri
blade.
Difference in the size of material and getting them both to the critical
forge welding temp at the same time
would be the greatest problem I would think. Then adding the possibility of dirt or slag getting in the weld under the conditions that these blades are made under..... Well...

That's one of the questions I would have anyway.
Hope this helps.

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>>>>---¥vsa---->®
The civilized man sleeps behind locked doors in the city while the naked savage sleeps (with a knife) in a open hut in the jungle.
 
It could be a scratch against the grain.I polish mainsprings lengthwise to prevent this.

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Uncle Bill, Do you know the details about the failures? What type of stress were the blades were under (prying,chopping)? This could help solve the riddle.

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Bill P
 
I was chopping a standing dead tree. It is a very hard, seasoned maple which is still verticle. I was using about 3/4 power strokes at about a 30 degree angle. I only took one or two swings before the blade separated from the tang.

My AK, village model and another custom blade have no trouble with this particular tree. (especially the AK)

I'll be sending the blade back to Uncle Bill so that a cause will be able to be determined. (hopefully!)

Mike
 
Bill,
If the failure happened at the junction of tang and blade, I'd go along with Ghostsix.
With the increased demand for the knives they may be hurring the work some and not paying so close attention to areas that don't show.
My guess would be the result of a deep grind mark or file mark.

Any stresses built up when the steel was a car spring had long since been relieved. Frankly I'm surrprised that given the size of the blades in relation to the size of the tangs that more haven't let go. Speaks volumes on behalf of the SMITHs.
Given the demand/time factor: I'd say that the safest bet would be to increase the tang size. This wouldn't change the ballance significantly, but, just doubling the cross-sectional area (not diameter) would more than quadroupal the overall strength.
Thereby reducing the failure possibilities.
So for example, a fault in a one square inch rod would cause that rod to fracture, it probably wouldn't cause failure in one that had two square inches of area, given equal stresses during use.
Dan
 
HI Bill,

The fact that both Khukuris failed in the same spot is obviously indicative (I think
smile.gif
) of the two blades having similar flaws in material,manufacturing,or both as their were only these 2 catastrophic failures so far in thousands of blades and both snapped in the same location. I believe an expert in blade craft and metallurgy like Wayne Goddard or a similar custom knifemaker with comparable expertise could ascertain said failure by examining the fracture lines for defects under magnification. Himalayan Imports excellent guarantee assures the buyer of a new khukuri and Bill Martino gets the rare failures for analysis and prevention control.

Stay safe and all the best, Phil <----<
 
Hi Uncle Bill:

Being one who has done much metal work, but little knife making, don't know if this will be much help.

I would look closely at the junction of the blade and tang. I would be looking for a sign of a small crack or spot that is a different colour from the rest of the metal at the break, indicating a manufacturing flaw in the forging.

If there is a slightly deeper grind mark and the crack originates from there I would say that this has centered the stress of the blow at that weakened point. This would be particularly true if the failure is right at the junction of the blade and tang.

smile.gif
Good luck sorting it out.
 
Dan K. came as close as we are going to come for the reason, I think.

I spend all last night pondering this and here's what I came up with for a reason. The kamis in both shops who make the HI khukuris have been under the gun for the past six months. They are busier now than they have been in 11 years. They have been behind and were getting farther behind. This is why we started shop 2. I learned they are now working 7 days per week in shop 2 rather than 6, trying to keep up. No mistakes in 11 years and then two mistakes in four months. Conclusion:

When you hurry you make mistakes.

The tangs were not welded on to the blade. They were forged from the same piece of spring so the failure was not due to a faulty weld. I have only seen one failure and it looked like a tension failure which is a bit puzzling. My guesses are 1) as stated above there could have been a deep grind mark in the wrong place. 2) the tang should be dead soft and should bend rather than break like a tension failure. Could be that in his hurry the kami accidentally or carelessly got some water on the upper part of the tang when he was quenching the blade and inadverently hardened the tang.

I called Kami last night and alerted him to the failure and he will also pass along the information to shop 1 regarding the 20 inch Sirupati. I sent a fax today with sketches of failure area and suggested increase in tang size.

Solution is to check grind marks on tang, especially at juncture of blade and tang and work out any deep grind marks. Be very careful during quencing process so as not to accidentally harden tang.

Further fix -- get more help and stop rushing. Gelbu is spending this week scouting villages for four or five more master kamis for shop 2-- plus he will pick us up some more village khukuris.

I hope this is the last we see of this problem. I realize that 2 tang failures out of six thousand khukuris is not a bad record but it is more than I want to deal with.

Many thanks for the input.

I got a coule of emails suggesting that I might be crazy to post information about failures. I replied saying I would be crazy if I didn't.

It is all perspecitive.

Uncle Bill


[This message has been edited by Bill Martino (edited 10 July 1999).]
 
:
Sounds like you have taken all the steps that will ensure the problem will be corrected Uncle Bill.

It is obvious and has been from the beginning that the H.I. Kuhkuris and you have the reputation for having the best metal and temper of all the Kuhkuris. It is a honor and a pleasure to do business with a friend and compadre.

The other thing about all of that is H.I. and you have the worlds best Kuhkuri testers. We are not going to baby these knives for fear of failure. It seems the failed tangs happened after the first few blows with the knives and I think that If they hold up after a few days use by anyone that has one,then the Kuhkuri can be counted on for no matter what.
We also know that if there is a failure that there will not be any excuses,but a search for what went wrong and the problem solved instead of just "fixed."

We know that we can pound on these with whatever is at hand,break bricks and rocks with the spine and even cut up old cars. I am waiting to find one to try mine out on.

I don't believe anyone here that know you would have expected any less than what you did by announcing the failures. The fact that you would even do such a thing shows that you have your customers and friends best interests at heart.

It is my belief that from this point on the H.I. Kuhkuris will be better than they ever were if possible.
I believe the integrity of the Kamis and the poeple of Nepal that help build these fine knives will see to that. I would imagine that each and every Kami involved or not will feel just as badly as you do about this and strive to see that there are no more problems of this kind.



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&gt;&gt;&gt;&gt;---¥vsa----&gt;®
The civilized man sleeps behind locked doors in the city while the naked savage sleeps (with a knife) in a open hut in the jungle.
 
As another said, other makers tout their 3/16ths and 1/4" blades. You give an absolute guarantee, then suggest that 3/8ths is a bit light for prying, try a thicker model if you'll be doing that often.

Murphy has apparently obtained a Nepali visa.
 
Perhaps my BAS failure was the result of an improper blessing. Shiva may be trying to weed them out!

Mike
 
It comes down to integrity.Those who have it are blessed indeed for they shall sleep at night.
 
You are right ghost. It is your Buddhist thinking. Bottom line is we must live with ourselves.

Uncle Bill
 
I must admit I was a bit shocked to hear about the tang failures. Two tang failures in four months compared to no failures in 11 years indicates a serious problem. It seems the root cause of the problem has been identified and corrective action is in progress.

The tang failures also indicate the level of skill required from the kami. If he needs to take a bit longer, impatient as I am, I would be very willing to wait for my khukhuri.

After some consideration the broken tangs do not bother me. First Uncle Bill encourages everyone to use the H.I. khukhuri's heavily and stands by them with a lifetime guantee. So anyone buying an H.I. khukhuri can verify that it will be tough enough at no risk. Second, the tang broke almost immediately rather than slowly. One serious outing with hardwood seems to be sufficient to determine if the tang will fail. I trust the khukhuri's I own not to fail me.

I will continue to buy H.I. khukhuri's. (Maybe not too many more since I own most of the ones I want.)

I am glad to see Jaeger is taking this so positively as well.

Will
 
I learned this weekend that shop 2 is now working 7 days per week rather than 6. Hurry is the problem in both shops. The answer is to get more help and slow down a bit. This is being done.

Kami's son, Gelbu, is taking a week off and scouring villages for master kamis -- and some village khukruis. Shop 1 has hired more kamis to free up all master kamis so they can devote full time to HI khukuris.

We did it right for 11 years. We can get back on track again. But the upside is Will is exactly right. If the tang is going to fail it should do it in the first 15 minutes of use. If it does send the knife back for an immediate replacement.

And, many thanks to all for such great understanding.

Uncle Bill
 
Bill :

Why do we go 11 years without any failure of any type and then get two almost identical tang failures in four months?
Click to expand...

First off you can get close runs on low probability events so I would not be jumping the gun on QC controls speculations just yet, but slowing down is always a good thing. I am sure no one would mind waiting to insure that the demand is not setting to high a workload.

As clarification, what exactly is happening? Is the blade breaking at the blade/handle juncture or is the handle just coming loose?

-Cliff
 
Yvsa has said it all - his post echoes my feelings exactly on this incident.

This post shows why Uncle Bill is not only accepted by Gurkhas and Gurkha families but also respected by them.

- Sonam



[This message has been edited by gtkguy (edited 12 July 1999).]
 
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