forging versus stock removal

R

R.C.Reichert

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Jul 26, 2008
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Hello, I have heard that forging allows the grain of the steel to run more lengthwise down the blade. Stock removal probably not so much. So question is, can a stock removal blade pass the " 90-degree flex test" the same as one that's been forged? How to they test this on a blade that is short with a thick spine? Thanks!
 
Any blade, stock removal or forged can pass the 90 degree flex, if it is differentially hardened and tempered. A forged knife will, in almost all cases out cut and flex a stock removal blade. This is of couse assuming it has been handled correctly. A forged blade has more potential, but anyone can screw anything up. Most all stock removal blades, stainless anyway, are completely hardened. The spine is as hard as the edge. This does not allow any spring or support from the spine. And wont allow it to flex. Short or long it makes no difference.
 
R.C.Reichert said:
Hello, I have heard that forging allows the grain of the steel to run more lengthwise down the blade.
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NOOOOOOOOOOOOOOoooooooo.....don't open Pandora's Box!!!!! Kevin / Mete, don't look, just walk away!!!!!

Sorry, stirring up topics like this is like poking a stick at an angry blacksmith :D
 
Sorry guys, I was just curious. After all it is a blade"smith" test, so I though it mainly pertained to blades that had been "smithed" on an anvil, not ground to shape. Sorry if that was a stupid question.
 
No, no, no, not stupid, just a "old blacksmith's tale" as it were. If you take steel as it is rolled out of a mill, it's grain runs a certain way, yes. Now, should you cut a stick of that steel off cross ways, you end up with the grain running top to bottom (spine to edge). Now, whether or not you forge or stock remove, technically that grain is still spine to edge. HOWEVER, does it matter? Probably not on anything the length of a knife. Kevin Cashen talks about this here. Feel free to read his articles section for more great legends revealed :D
 
A blade passing this test has a lot to do with the geometry of it coupled with the heat-treating.

If a blade has a nice distal taper from the ricasso on out to the tip... it's much more likely to pass this test than the same blade withOUT the taper.

I like the old "maple branch" analogy. Of course a maple branch isn't made of hardened steel, but the geometry involving tapers is there. :)

I don't think this is a stupid question, it just gets asked every week or two around here. And there's always somebody who says something like, "You crush the atomic structure of steel by forging and make a far superior blade." Which is, of course, just crazy-talk :)
 
NickWheeler said:
"You crush the atomic structure of steel by forging and make a far superior blade." Which is, of course, just crazy-talk :)
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Well, unless you're talking about carbide edge packing ;)
But that's a whole 'nother can...:eek:
 
Most of the "grain" noted in a steel is comprised of impurities stretched out during the forging process undergone by all steel stock. The myth that a forged knife is somehow superior to a stock removal blade has been passed down throughout history and accepted as fact. However, with today's foundry processes, that's not the case.

When the only steel available was smelted in a master's shop, then yes, the only way to make a knife with the resulting ingot was to forge it into a uniform and manageable mass. However, all stock removal blades are forged from the foundry in a process called "hot rolling".

The idea that a forged blade is superior to a stock removed blade is based mostly in falsities and myths. In fact, it's much, much easier to screw up a forged blade by not controlling the involved temperatures and not heat treating effectively to reduce grain size and control stress. That's why the 90 degree flex test in in the ABS testing. It's to determine if a smith can appropriately manipulate the steel using geometry, annealing, normalizing, differential hardening, etc. to accomplish a specific task. Does this mean a blade that can flex 90 degrees is desired in all cases Absolutely not! The test only tests the control of the smith over the steel and heat treating processes. The same can be done with any stock removal blade.

That being said, forging allows for decreased waste of materials, forming blades from odd shaped pieces of steel, and you get to play with fire, hammers, and glowing steel! Also, it's easier to forge in a distal taper which is often desirable for blade geometry and integrity.

It's been discussed ad nauseam in the past with excellent objective information out there. I'll see if I can find some links.

--nathan
 
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"Atomic structure" aside, once a piece of steel passed nonmagnetic, approx 1625 degrees, depending on the type, the structure will realign in its present shape. Previous "direction" has very little bearing.
 
Hot rolling is forging. Impact or not, they impart pressure to the steel. It's the same idea and why some of the best damascus makers out there forge their billets using a hydraulic press.

--nathan
 
once a piece of steel passed nonmagnetic, approx 1625 degrees, depending on the type, the structure will realign in its present shape. Previous "direction" has very little bearing.
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Hardening involves obtaining a critical temperature (A1 or austenitizing temperature) where the blade is transformed into an austenite structure and then quickly cooling to avoid forming pearlite and thus allow martensite to form. The temperature is in most cases a bit, or sometimes a good bit above curie point, and 1625 is a good bit above curie and many tool steel A1 temperatures. Too much above A1 can quickly cause grain growth and result in a weaker final product, and that temp varies depending on the steel (which you mentioned). You can correct grain size by normalizing (heat to just above curie and cool to handling temperatures).

--nathan
 
caknives said:
Hot rolling is not forging, Forging involves impact, rolling is only pressure.
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This is the kind of mis-information that ALWAYS pops up in this type of thread.

Forging is simply HOT FORMING.

It is done in a few basic forms.

- Hammer forging
- Drop forging
- Press forging
- Upset forging
- Roll forging

The different methods impart the forces in different manners, but it's all forging. :)
 
No problem :) :thumbup:

BTW, no here is trying to be a hard@$$, and I hope I'm not coming across as such. This is a great place to learn answers just like this. And the only way to get those answers is by asking. Also, google search works well (type in your query followed by site:bladeforums.com), I just wish we could make it search only the shop talk section.

caknives, welcome to the forums! This is a wonderful place full of amazing makers, and we've all learned from each other here. I know 90% of what I know because of this place!

--nathan
 
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silver_pilate said:
No problem :) :thumbup:

BTW, no here is trying to be a hard@$$, and I hope I'm not coming across as such. This is a great place to learn answers just like this. And the only way to get those answers is by asking. Also, google search works well (type in your query followed by site:bladeforums.com), I just wish we could make it search only the shop talk section.

caknives, welcome to the forums! This is a wonderful place full of amazing makers, and we've all learned from each other here. I know 90% of what I know because of this place!

--nathan
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do you mean with google, if you do then try this. i onley use google to search bladeforums and have found this to work very well.
put this whole thing into google, changing the forging to what ever you want to search for


shop talk site:http://www.bladeforums.com forging
 
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