Why isn't the entire axe head hardened?

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Well, I'm open to learnin' somethin'. Does the Collins Legitimus pictured have an eye as hard as the edge? If not, then how can one say the lower temper helped?
Well, I'm open to learnin' somethin'. Does the Collins Legitimus pictured have an eye as hard as the edge? If not, then how can one say the lower temper helped?
Some may not agree but I see a pattern that old bit up axes (ones with steel insert) are prone to have deformed eye, while those abused mono steel ones tend to be brittle around the eye and have cracks. The axe is as good as its weakest point.
 
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Some may not agree but I see a pattern that old bit up axes (ones with steel insert) are prone to have deformed eye, while those bit up mono steel ones tend to be brittle around the eye and have cracks. The axe is as good as its weakest point.
I think that is true. Those really old ones had mostly mild steel/iron bodies that were not hardened at all. Nice and stretchy, but easy to deform. Everything has a sweet spot.
 
looks like it's time to make myself a 3v axe :) ...

only kidding really, with that much 3v, I'd sooner make a kukri or waki tbh
 
Thanks to Steve we now have some definite numbers to look at:





From these two sets of data we can see that actually that USFS quoted min. hardness of Rc 45 is not at all far from the CT's stated edge-hardness of Rc 48 min.

This is important,in regards to the original question of Droppoint1 that has started this whole discussion.
Namely,it is that hardness can be a RELATIVE term,and something being "hardened",for whatever reason ,does NOT equal to being hardened excessively,or hardened insufficiently.
When we're discussing metallurgy,especially touching on specifics of someone's process,we simply must be at least somewhat cognisant of specific values .

Brian,thanks for posting those photos of the broken eye.
You're very much correct in that the grain-size in the fracture is obviously excessively enlarged(as a rule of thumb one must not be able to distinguish the individual grains).
However,your conclusion on the Hardness of that are being excessive may,or again,may Not,be right.
Personally,i'd say that there's a good chance you're right,however,without actually testing(specifically with a Rockwell tester or an analog method),we CAN'T say that,as grain enlargement does not just automatically equal excessive hardness.

I'm just all for being rational about the use of all these,sometimes tricky,terms.Otherwise things get wishy-washy quick,and all meaning gets lost.

And as a negative example i must use The Possum's mssg...

"
In the old days, the eye was soft because it was made of cheaper iron or mild steel. Good steel was so expensive, it was cheaper to forge weld just a little bit onto the cutting edge. Nowadays, I see no reason why the entire head shouldn't be heat treated. Think about it. The eye is orders of magnitude thicker than the sharp cutting edge, and doesn't take the impact directly. If a hardened eye can't stand up to the pounding, then that must also mean the edge would snap off with every swing".



sorry as i am to do so,and with all due respect,but it is exactly the sort of entirely conjectural,and based on no known metallurgical information statement...I could take an issue with about Every word in it...
However,ironically,it too has a grain of truth in it:
The entire head of any tool today IS heat-treated.
The entire head of tool at All times WAS heat-treated.(Each time you bring Ferrous alloy to A1 you're in effect heat-treating it).
The idea is to HT a tool CORRECTLY.That "correctness" is relative to the Purpose that tool is intended for.

(as usual,sorry to be a nitpicking nag...:(....it's just how i myself think about it,because i often must HT tools,And figure out how and why and wherefore et c.)

To be honest I have no real metallurgy knowledge I just know a little bit about axes. I just file tested the eye portion and pole and could tell it was all the same hardness. The second head of the same maker (I am guessing) was also the same all the way around and it had cracks on all four “corners” of the eye.
 
I think those cracked eyes give testimony to the types of forces the eyes are subjected to, and perhaps a less hard (and less brittle) eye will handle the tension stresses better, while the bit can be harder because it is subjected to mainly compressive stresses?

I think tension forces is exactly what the softer eye is designed to resist. Wedging alone puts tension on the eye.

The theory is that type of failure has to do with pressure from within the eye due to freezing water, and the weakest part if the eye lets go. Nothing to do with the use of striking wood, and not related to the bit.

Again, I think the main reason is to get the axes out the door without cracking during wedging. Resistance to the freeze/thaw cycle is just a secondary benefit.
 
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The US Forest Service seems to have relaxed their standards for axes and pulaskis, but they still insist that "within 1 inch of the eye of the tool, the steel hardness shall not exceed 45 on the Rockwell C scale."

I think it would be a shame if the high-end axe makers in the US aren't at least achieving the USFS standards for hardness.

3.2.1.2 Hardness. The ax bit shall have a hardness of 54 to 58 inclusive on the Rockwell C scale. This hardness shall extend to a distance of 1-1/4 inches ±1/4 inch back from the cutting edge. Within 1 inch of the eye of the tool, the steel hardness shall not exceed 45 on the Rockwell C scale. All hardness values shall be determined as specified in 4.5.1.2. The specified hardness shall extend through the entire thickness of the tool head steel.

https://www.fs.fed.us/t-d/programs/fire/documents/5100_9D.pdf

U.S. DEPARTMENT OF AGRICULTURE
FOREST SERVICE
SPECIFICATION
AXES: SINGLE BIT AND DOUBLE BIT
5100-9D
November, 1999
With an understanding of why the whole axe is not hardened I guess I should have worded that differently. Like, I don't no what the odds are of that causing you a problem? With that being said no %*#&'s given for what the government specifies, their study's or lab results included.
 
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