Question About Hardening Depth

[JPA88]

First I'll say I was pretty stoked at work today when I stumbled upon this barely used old 3.5# Craftsman. It was pretty rust, but at the same time covered in grease and grime. Got it home, shot it with WD40, scrubbed it, shot it again and wire wheeled it a bit.

This revealed a nice clean heat-treat line that came to about 1/8 inch of the front of the eye. I had never personally seen one that was hardened that far back from the cutting edge (I think its cool). My other various axes, including another (newer I think) Craftsman, are nowhere near that far back.

So my questions are: Do you guys see many axes hardened this far back from the edge? Theoretically, If I were to use and use and use it till it was say an inch or two from the eye (would make for a fat edge), to where the bit/cheeks are thicker, would it still be hardened all the way through? When it goes into the quench, I wonder if the middle of the thickest portion of the hardened area is cooled enough, or rapidly enough, to cause the steel to harden to it's full potential. I've heat treated knives, but they are only 1/8 inch thick.
Any experience with this stuff?

 

[Square_peg]

Very deep. I don't recall seeing one that deep before.

 

[SC T100]

Maybe a factory accident (dipped lower than usual)? Either way that's an awesome head...really high centerline too.

 

[rjdankert]

. . .
So my questions are: Do you guys see many axes hardened this far back from the edge? . . .[/URL]

Western Logger stamped axes had that:

. . . the insanely deep temper like (looks like it almost goes to the eye). . .

From: http://www.bladeforums.com/forums/showthread.php/1282434-Western-Logger-Axes?highlight=western+logger

Bob

 

[JPA88]

Maybe a factory accident (dipped lower than usual)? Either way that's an awesome head...really high centerline too.

That thought crossed my mind, too. Like maybe they had the line set up to dip a run of shorter axe heads, boys or hatchets, and didn't adjust it back when they moved to the bigger heads. Whatever the case, she's getting hung. And we have some damn nice working-in-the-garage-with-the-door-open weather rolling into IL this weekend.

 

[gben]

Depth of hardness depends on manufacturing method. Some axe manufacturers used one piece of higher grade steel for the entire axe head which would be hardened on the cutting edge and maybe the poll.

Some manufacturers "built up" the axe head using a low-carbon body with a high-carbon steel sheet wrapped around and hammer-welded to the cutting edge. A lot of times when someone sees a line on the side of an axe head, it may not have as much to do with the heat-treat as it does with being the line where two different grades of steel meet.

A one piece axe head has the potential to be through-hardened, the entire axe head could be hardened through and then it could be annealed at the eye. The built-up, hammer-welded head could only be hard where it is made of high-carbon steel.

Either method of manufacture is going to be no better than what skill is used in it's manufacture. The high-carbon part of a built-up head could be hammered to thin or installed poorly during manufacture, and a head made of one-piece of high carbon steel could be hardened or annealed poorly and be too soft or too hard in the wrong areas.

For the practical use of an old axe head which we have picked up for little or nothing, it probably does not matter.