Porosity in a blade.

R

Recon Jack

Joined
Jul 10, 1999
Messages
37
I don't know if this has been done before, but I took my 18" AK (the Beast) to work with me tonight. (a die cast company) I work in Quality Control, and we have 2 x-ray machines we use for checking castings.
I put the beast in there just for the heck of it and we could find no porosity at all.
My boss said that this was unusual and we looked at the knife for quite some time. Even with the machine turned way up You could see maybe some very, very, small porosity, which my boss said would qualify as none. Just thought I'd pass this on. I have a custom Bowie that had some pretty significant porosity, but I don't think it was a forged blade.

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Jack Russell
 
Recon, maybe this is an indication of why 7 kamis working six days per week, 10 hours per day, are producing only 30 to 35 khukuris per month. It takes a lot of pounding to do the job right.

Uncle Bill
 
I agree Uncle Bill, according to my boss (we deal mostly in aluminum not steel) the steel must have been worked pretty good to remove the porosity to that level. I can see why the blades are so strong! My boss brought in a hunting knife that had snapped off about 1" of the blade. In the x-ray machine you could see lateral lines at almost regular intervals of porosity, that was bad enough to cause (I think) the blade to snap. At least I would guess it would break at those lines first. He gave me the knife so I marked the lines, and I am going to try and break it on line and between. I know this has nothing to do with My "Beast" but just want to see if I'm right. My point of posting was to point out that at least in my blade there is not porosity or impurities, which would also have showed up. And these Kami's are using, what, maybe 17th century process's? I have no idea.
Thanks Bill for putting up with my rambling.

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Jack Russell
 
Recon, to the best of my knowledge this is the first porosity test ever done on an HI khukuri but the results do not surprise me.

Just like the baker knows if he does not knead his dough enough the bread will fail, the kami knows from experience that if he does not pound and forge enough his khukuri will fail.

Your test scientifically confirms that the kamis who make the HI khukuris are certainly doing their share of pounding.

Most of the kamis who make our khukuris are using methods that have been in their families for at least 200 years -- some can trace back 400 years of knifemaking.

Uncle Bill

[This message has been edited by Bill Martino (edited 11 August 1999).]
 
Uncle Bill,
If this is the first, I think I'll take the blade to work again tonight. We have a digital camera, and I am going to take pictures of the blade on the screen and send them to you. You have my permission to do with them what you want. I'll e-mail them to you tomorrow. How's that?

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Jack Russell
 
Recon, that's great. If you could email something for comparative purposes that would add to the meaning, I think, if we decide to post anything. Not all of us are QC experts like you and need a little help with understanding.

Any side info you can send along which will help me and others to decipher the pix will be greatly appreciated by all.

Many thanks for this effort.

Uncle Bill

[This message has been edited by Bill Martino (edited 11 August 1999).]
 
Perhaps this rather simple test may solve the whole "forging vs stock removal" argument. There is often talk of grain size and alignment but not porosity when discussing blade strenth. I may be wrong, as I would have thought this test would have been more common on knives, but it seems the answer may be quite a bit simpler than we all came to expect.
 
If it rings, home I brings?

There was mention in one of Cliff's tests, about the Spec Plus Bolo singing, but it still got broke, little surprise if you follow Cliff's testing. Like the airframes sent for test to destruction, you know it will eventually fail. The question is how far you can go before it does.
 
Recon Jack,

Do the X-ray machines measure porosity on the surface only?

This is a very interesting test. Too much porosity results in weak blades just like weak castings. My guess is that porosity is cause by poor heat treat or impurities causing different shrinking rates.

With truely high quality knives it would probably be difficult to measure porosity differences.

Will

[This message has been edited by Will Kwan (edited 11 August 1999).]
 
Guys, please excuse my ignorance.Could you please give a little more detail on what your talking about? Pours or small holes in the blade?

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Bill P
 
:
Bill P:
I think the best way to describe it to us poor people that know little about such things would be to say density,or the distance between the grains of steel.
Maybe another would be to say that Pumice rock has more porosity than
solid Basalt and many times more than Obsidian which has vey little porosity.

Jack this brings a whole new area to light.
I would have never thought about doing such a thing,but then I don't and haven't worked in your field.
I agree with Yoda and Will that this could perhaps prove or disprove an age old argument,or at least begin to shed some light on it.
This may be a first as I don't recall anyone ever saying anything about such a thing before.
You could possibley wind up famous over this.
smile.gif

I wonder if it would show up any differences in cyrogenic treated and untreated steel. If I understand that right it changes the molecular structure of some of the steel.

I want to see pictures too!!


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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.
 
Everyone that responded:
I just sent some pictures to Uncle Bill and will make more, to show what porosity actually looks like. I did not realize anyone would be interested...
You will not see any steel grains in an x-ray. Imagine you have x-ray vision, and can look straight through the blade from front to back. Now the machine is set so that the part is very light colored, and fuzzy, because you are looking straight through. "Any" porosity, which is a void or gas pocket in the metal, will show up,and be very evident, as a dark area, or dot, if it is small. There is magnification in the machine so you won't miss any gas pockets. Now as far as impurities, they will show up as a light dot or area. The more that the part looks uniform the more pure it is. The x-ray machine acutally may not show surface porosity, as this would be seen by the naked eye. Surface porosity is just a hole.
The pictures will look fuzzy. That is normal because you are looking through. I will get a picture to Uncle Bill with some porosity to show the difference, and believe me it is dramatic.
Talking with some of the other experts at work, they all said that probably the hammering compresses the steel and forces the gas out.
Everyone at work agreed with me that the blade was pure and had no defects. When I told them how it was made, they could not believe it. Of course we are making aluminum castings with thousands of pounds of pressure and we can't keep all the gas out. Imagine that!
By the way, Will, I think that the less porosity, the higher quality the blade. In an x-ray porosity will show up in any blade, high quality or not.

Hope this clears things up a little.

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Jack Russell

[This message has been edited by Recon Jack (edited 12 August 1999).]
 
That really shows the excellent workmanship of HI blades.

But that doesn't make any favourable argument on forging vs stock removal thing.

That's what I understand the need of forging. In the old days, the way of obtaining iron from ores is to melt it in a open furnance. And the product is cast iron, and that thing is full of impurities and porosity. So as to purify the iron, the smiths has to forge and fold the iron in order to drive out air-pockets and impurities, in order to make usable tools....or knives.

Modern steel factories really should have very strict QC so that the steel rolled out shouldn't has any porosity. Snapping a blade will not cause too big a problem, but a weak seam in a building is.

So steel blanks from factories should be perfect, with no porosity at all. If I remembered right, heat treating will not introduce porosity.

Don't get me wrong, I am really a fans of forging. To forge out a knife esp. in charcoal of coal fire is a kind of romance to me.

I am too, anxiously waiting for the pictures.

Joe Leung
 
If I remember right, the steel used to make the blades, are made from spring steel from auto's? If that is so, some type of quality test should have been done already on the steel, or springs. It looks like when the Kami's heat the steel, that is where the porosity could enter in. I am just guessing here. I also think that the hammering is what forces the porosity out. It makes sense. My only reason for x-raying was to see if there was any voids or porosity in the metal. I think if you took the same steel and removed stock from it to make a knife.... I don't know. I would have to x-ray that knife to and see what was in there.
Has it been proven that forged knife steel is stronger that stock removed knife steel?
I have no idea.

Anybody???

You guys have me wanting to go down and x-ray every knife I have now! I have a Reeve Project I, I think it is machined from solid stock. I'll do it tonight.


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Jack Russell

[This message has been edited by Recon Jack (edited 12 August 1999).]

[This message has been edited by Recon Jack (edited 12 August 1999).]

[This message has been edited by Recon Jack (edited 12 August 1999).]
 
Jack, you obviously belong on this forum. A question comes up, and it puts a bug in your ear that won't go away til you find out and let everyone else know.
 
Recon sent me the pix and they came in as a mime file, not JPEG and I can't view them or post them -- rats! If it were not my own rule against profanity I would swear like an old sailor because I am one. I want to see the pix! Is there any among us to whom I could email this mime file and they can work it into something we can see? I am on the old win 95. Maybe win98 could solve this problem. Help anybody?

Recon called me this AM and I can guarantee you he is an HI fourmite.

Uncle Bill
 
Uncle Bill,
Keep checking your e-mail, last night I sent you BMP files. I just sent you JPEG files this morning! If that don't work I'll insert them into a word file and send them.
If you double click a BMP file Win95 should open paint and display the picture.
I'll get them to you if I have to snail mail them!

Thank You Rusty, but I am as curious as everybody else! I am learning to, I just happen to have access to some neat equipment.

Wish I had a Rockwell Hardness tester!
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Jack Russell

[This message has been edited by Recon Jack (edited 12 August 1999).]
 
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